Acquired tick resistance (ATR) is well characterized in tick-exposed animals, compromising tick fitness through antibody-mediated activation of basophils. Yet, anti-tick vaccines inducing ATR have had limited success. Here, we describe a neuroimmune event preceding ATR that leads to rapid host-mediated tick removal. Tick-sensitized guinea pigs mechanically remove ticks within 3-6 hours via an acquired neuroimmune-induced itch response that correlates with increased dermal expression of itch-associated genes like OSM and skin infiltration by T cells and macrophages, independently of IgG and IgE antibodies. When we expose humans to ticks, a similar immune response is observed. Blocking T cells before tick sensitization prevents immune cell infiltration to bite sites and abrogates scratching and tick removal. This neuroimmune response is independent of Trpv1 as tick-sensitized guinea pigs treated with resiniferatoxin remove ticks effectively. Itch-induced tick removal or IITR offers a novel approach to tick-borne disease prevention through early tick detection and removal.

Introduction Sickle cell disease is a monogenic blood disorder prevalent in Africa, where malaria poses a health risk for affected individuals. Individuals with sickle cell disease are susceptible to malaria, which can be complicated by vaso-occlusive episodes, severe anaemia and death. Understanding the intersection of malaria and sickle cell disease in African countries with high co-prevalence is essential for developing effective management and prevention strategies, including clinical guidelines on the use of malaria chemoprophylaxis in this population. This study will determine the monthly incidence of malaria in children living with sickle cell disease in each of two clusters of African countries.Methods and analysis This 1-year observational study will enrol 2808 children with sickle cell disease, aged 6 months to 17 years, at Sickle Pan-African Research Consortium clinical sites in Ghana, Mali, Nigeria (West), Tanzania, Uganda, Zimbabwe and Zambia (East-South). Malaria infection will be assessed at monthly visits and unscheduled sick visits over 12 months. Data collected will include socio-demographic characteristics, beta-globin genotype, medical history, clinical symptoms and malaria blood smear or rapid diagnostic test results. The primary outcome is monthly incidence of clinical malaria; a secondary outcome is incidence of asymptomatic malaria.Ethics and dissemination This study was developed with input from patients with sickle cell disease and their caregivers. The study will be conducted according to the principles of the Declaration of Helsinki. Written informed consent from guardians and assent from child participants age 7 or above will be provided before enrolling in the study. This protocol has been reviewed and approved by local and national ethics committees at each study site. The findings of this study will be provided to participants and the general public through presentations at the annual Sickle Cell Day community events at each study site, local media and open access publication in peer-reviewed journals.The full names of the ethics committees are as follows. Ghana: Komfo Anokye Teaching Hospital Institutional Review Board; Mali: Ethics Committee of the University of Sciences, Techniques and Technologies of Bamako; Nigeria: National Health Research Ethics Committee of Nigeria; Tanzania: Muhimbili University of Health and Allied Sciences Research Ethics Committee and National Health Research Ethics Committee; Uganda: Makerere School of Medicine Research and Ethic Committee; Zambia: National Health Research Authority and Excellence in Research Ethics and Science Converge Institutional Review Board; and Zimbabwe: Joint Research Ethics Committee and the Medical Research Council of Zimbabwe.

OBJECTIVE: Constriction of vascular smooth muscle cells evokes a counterbalancing dilatory signal from endothelium, a phenomenon called feedback vasodilation. Ex vivo studies have identified nitric oxide and endothelium-derived hyperpolarizing factor as key signals mediating feedback vasodilation. However, to study this mechanism in vivo, we need non-invasive approaches to quantify responses to vasoconstrictive stimuli in humans. We hypothesized that standing, hand grip exercise, or cold exposure would raise blood pressure (BP) in healthy volunteers. METHODS: BP was recorded continuously with theHuman Non-Invasive BP Nano (ADInstruments) while three vasoconstrictive stimuli were performed: standing from a supine position, isometric hand grip exercise, and immersion of one hand in cold water. Renal artery Doppler ultrasound was performed with the exercise and cold stimuli. The primary outcome measures were the changes in BP and renal vascular conductance (RVC, velocity/BP) before and after each stimulus. Data are presented as mean ± standard error. Repeated measures one-way ANOVA with Dunnett’s post hoc test was used to compare BP during stimulation against baseline. To assess inter-day reproducibility, each visit was repeated at least 48 hours later, and paired t-test and Pearson’s correlation were applied. RESULTS: 9 participants (6 women and 3 men) aged 30.2 ± 5.2 years participated. On first visits, standing from supine raised systolic BP by 12.1 ± 3.0 mmHg (p = 0.0065) and diastolic BP by 13.2 ± 1.7 mmHg (p < 0.0001). Handgrip at 100% effort raised systolic BP by 15.2 ± 4.6 mmHg (p = 0.0445) and diastolic BP by 11.5 ± 2.5 mmHg (p = 0.0098). Handgrip decreased RVC by 0.26 ± 0.06 cm/s/mmHg (p = 0. 0119) during systole and by 0.24 ± 0.07 cm/s/mmHg (p = 0.0591) during diastole. Cold exposure increased systolic BP by 29.4 ± 3.9 mmHg (p = 0.0002) and diastolic BP by 24.7 ± 2.8 mmHg (p < 0.0001). Cold decreased RVC by 0.42 ± 0.09 mmHg (p = 0.0065) during systole and by 0.33 ± 0.11 mmHg (p = 0.0464) during diastole. While the BP and RVC responses were similar from visit one to visit two at a group level, intra-individual correlations were not statistically significant. CONCLUSIONS: Standing, exercise, and cold each induced vasoconstriction in healthy volunteers as demonstrated by increases in BP and decreases in RVC. The magnitude and variation of these responses, along with inter-day differences, facilitate sample size estimation for studies to investigate medical, genetic, or pharmacologic determinants of feedback vasodilation in humans. Funded by the Intramural Research Program of the National Institutes of Allergy and Infectious Diseases. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.

Recent studies have identified the expression and function of hemoglobin-α subunit in mouse resistance arteries. Our latest research extends these findings by demonstrating the presence of tetrameric hemoglobin (comprising both α and β subunits) in human resistance arteries, where it regulates nitric oxide (NO) mediated endothelial feedback. However, the size range of human blood vessels expressing hemoglobin remains unclear. To elucidate the distribution of hemoglobin within the human vascular network, we hypothesized that hemoglobin is preferentially expressed in smaller resistance arteries (<200 µm) compared to medium-sized (200–600 µm) and larger (600–1000 µm) arteries. To test this hypothesis, we micro-dissected arteries of varying diameters from human omental tissues, collecting approximately 10–15 segments for each size group, and processed them for analysis. We employed multi-photon imaging to detect autofluorescence signals representing hemoglobin protein, and digital droplet PCR to quantify endothelial expression of target hemoglobin genes, such as HBA1 (hemoglobin-α1), HBA2 (hemoglobin-α2), HBB (hemoglobin-β), along with NOS3 (eNOS), MYLK (myosin light-chain kinase) and CYGB (cytoglobin). One-way ANOVA with trend test was performed in statistical analysis of gene expression data. Imaging findings suggest a differential expression pattern of hemoglobin, with higher expression observed in smaller segments. Supporting this, gene expression analysis demonstrates that the expression of hemoglobin genes is elevated in smaller arteries. Specifically, the expression levels (normalized to GAPDH, mean ±SEM, p represents value for linear trend, with n=3 individuals except for HBA1 in large with n=2) are as follows: HBA1 in large (1.3±0.2), medium (4.8±1.7), and small (7.7±1.3), p=0.003; HBA2 in large (10.6±5.9), medium (15.3±4.7), and small (23.2±3.1), p=0.010; HBB in large (7.5±4.0), medium (11.9±4.6), and small (15.3±3.2), p=0.002; NOS3 in large (26.8±10.7), medium (39.3±15.1), and small (43.0±7.0), p=0.076; MYLK in large (958.7±63.1), medium (797.8±61.7, 797.8±61.7) and small (836.0±154.6), p=0.382; CYGB in large (18.43±4.1), medium (22.7±1.7) and small (21.3±0.8), p=0.353. These data indicate a significant trend in the expression of HBA1, HBA2, and HBB, but not in NOS3, MYLK, or CYGB genes, suggesting higher hemoglobin expression in small resistance arteries, while providing new insights into its distribution along the vascular network. This raises the possibility that increased hemoglobin expression may contribute to the resistance exerted by these arteries. NIH Intramural Research Program This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.

Background Addressing sickle cell disease (SCD) is crucial for achieving health-related Sustainable Development Goals, particularly in Africa. The region is significantly affected, with 78.7% of patients with SCD residing in sub-Saharan Africa and over 515 000 newborns diagnosed annually. Historically, African health systems have struggled to provide optimal care for patients with SCD, resulting in high under-5 mortality and severe childhood morbidity. Scientific innovations and stakeholder engagement offer hope for improving SCD outcomes.Objective To explore the role of high-level partnerships and scientific innovation in advancing SCD care and research in Africa, focusing on the contributions and strategic engagements of the SickleInAfrica, as highlighted at the 77th United Nations General Assembly (UNGA) and the US-Africa Leaders’ Summit.Approach SickleInAfrica, comprising eight countries, leverages a robust infrastructure for SCD research and care. The consortium has established a comprehensive SCD database and a patient registry in each of the consortium sites that includes demographic details, clinical diagnosis, management details and follow-ups/visits. Currently, over 34 000 patients with SCD are enrolled, making it the largest globally. It has also contextually adapted clinical guidelines for managing SCD for all levels of care. The high-level engagements at the 77th UNGA held in September 2022 in New York and the US-Africa Leaders’ Summit held in December 2022 in Washington DC promoted SCD awareness and partnerships. The UNGA session emphasised biomedical science, implementation research and partnerships in therapeutic development, while the US-Africa Leaders’ Summit session focused on Global Partnerships for SCD: Advancing Science and Technology for Health in Africa.Conclusions High-level engagements facilitate cross-border dialogues, underscoring the importance of partnerships from grassroots to global alliances. Key outcomes include increased awareness, policy advocacy and the establishment of SCD Centres of Excellence and genomics capacity-building initiatives. Sustainable efforts require robust partnerships, government involvement, community awareness and equitable access to advanced therapies.

Introduction: Mice with experimental cerebral malaria (ECM) exhibit reduced nitric oxide (NO) bioavailability, loss of vascular integrity, and impaired cerebral microcirculatory blood flow in vivo, but ex vivo, cerebral arteries behave normally. We hypothesized that plasma factors explain the discrepancy between in vivo and ex vivo arterial vasoreactivity in ECM. Methods: Wire myography was used to assess reactivity of aortic rings to plasma from healthy or ECM mice. L-NAME, nifedipine, EGTA, and ketanserin were used to assess NO synthase (NOS), calcium, and serotonin effects, respectively. To compare luminal against abluminal stimulation, mesenteric arteries were cannulated and exposed to 3% plasma or 1 μM serotonin on the luminal and then abluminal sides of the vessels. Results (mean ± SD) were expressed as force (g) differences from baseline for wire myography (n = 4-6) and as changes in diameter from baseline (% or μm) for pressure myography (n = 2-5). Linear regression was used to quantify dose-response relationships; repeated measures one-way ANOVA was used to assess changes before and after exposures. Results: Healthy and ECM plasma induced dose-dependent increases in aortic ring tension: m = 0.12 ± 0.07 g/M, p < 0.0001, and m = 0.08 ± 0.04 g/M, p < 0.0001, respectively; the effect of healthy or ECM plasma was similar (p = 0.17). L-NAME increased tension by 0.52 ± 0.24 g (p = 0.003) in arteries exposed to healthy plasma and by 0.58 ± 0.32 g in those exposed to ECM plasma (p = 0.008). Nifedipine decreased tension to 0.08 ± 0.07 g (p = 0.0007) and 0.13 ± 0.16 g (p = 0.002) respectively; EGTA further decreased tension to baseline (-0.003 ± 0.06 g, p = 0.0001, and 0.04 ± 0.02 g, p = 0.0003). In rings pre-treated with L-NAME, ketanserin decreased tension by 60 ± 6 % in rings stimulated with healthy plasma (p = 0.0007), and by 57 ± 7 % in rings stimulated with ECM plasma (p = 0.006).Serotonin elicited a greater vasoconstrictive response when applied to the abluminal vs luminal surfaces of cannulated arteries (-43 ± 27 vs -5.2 ± 7 µm, p = 0.01), an effect that was recapitulated by 3% plasma (-45 ± 6 vs -0.7 ± 8 µm, p = 0.2). Conclusion: Serotonin is the primary factor in plasma responsible for constriction of aortic rings. This vasoconstriction is calcium-dependent and partially counterbalanced by NOS. Studies of intact arteries revealed plasma serotonin must reach the abluminal surface to induce vasoconstriction. Thus, loss of vascular integrity, accompanied by extravasation of plasma into smooth muscle, may contribute to vascular dysfunction in cerebral malaria. Funded by CNPq, CAPES, IOC-Fiocruz, NIAID This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.

BACKGROUND:Severe malaria is associated with impaired nitric oxide (NO) synthase (NOS)-dependent vasodilation, and reversal of this deficit improves survival in murine models. Malaria might have selected for genetic polymorphisms that increase endothelial NO signaling and now contribute to heterogeneity in vascular function among humans. One protein potentially selected for is alpha globin, which, in mouse models, interacts with endothelial NOS (eNOS) to negatively regulate NO signaling. We sought to evaluate the impact of alpha globin gene deletions on NO signaling and unexpectedly found human arteries use not only alpha but also beta globin to regulate eNOS. METHODS:The eNOS-hemoglobin complex was characterized by multiphoton imaging, gene expression analysis, and coimmunoprecipitation studies of human resistance arteries. Novel contacts between eNOS and hemoglobin were mapped using molecular modeling and simulation. Pharmacological or genetic disruption of the eNOS-hemoglobin complex was evaluated using pressure myography. The association between alpha globin gene deletion and blood pressure was assessed in a population study. RESULTS:Alpha and beta globin transcripts were detected in the endothelial layer of the artery wall. Imaging colocalized alpha and beta globin proteins with eNOS at myoendothelial junctions. Immunoprecipitation demonstrated that alpha globin and beta globin form a complex with eNOS and cytochrome b5 reductase. Modeling predicted negatively charged glutamic acids at positions 6 and 7 of beta globin to interact with positively charged arginines at positions 97 and 98 of eNOS. Arteries from donors with a glutamic acid-to-valine substitution at beta globin position 6 (sickle trait) exhibited increased NOS-dependent vasodilation. Alpha globin gene deletions were associated with decreased arterial alpha globin expression, increased NOS-dependent vasodilation, and lower blood pressure. Mimetic peptides that targeted the interactions between hemoglobin and eNOS recapitulated the effects of these genetic variants on human arterial vasoreactivity. CONCLUSIONS:Alpha and beta globin subunits of hemoglobin interact with eNOS to restrict NO signaling in human resistance arteries. Malaria-protective genetic variants that alter the expression of alpha globin or the structure of beta globin are associated with increased NOS-dependent vasodilation. Targeting the hemoglobin-eNOS interface could potentially improve NO signaling in diseases of endothelial dysfunction such as severe malaria or chronic cardiovascular conditions.

Malaria causes hundreds of thousands of deaths each year in children, and many survivors are left with lasting neurological injury. While we have effective parasite-killing drugs, we need treatments that target disease mechanisms to improve outcomes. Bond et al. recently reported uric acid as a potential target for anti-disease therapy.

COVID-19 causes more severe and frequently fatal disease in patients with pre-existing comorbidities such as hypertension and heart disease. SARS-CoV-2 virus enters host cells through the angiotensin-converting enzyme 2 (ACE2), which is fundamental in maintaining arterial pressure through the renin-angiotensin system (RAS). Hypertensive patients commonly use medications such as angiotensin-converting enzyme inhibitors (ACEi), which can modulate the expression of ACE2 and, therefore, potentially impact the susceptibility and severity of SARS-CoV-2 infection. Here we assessed whether treatment of ACE2-humanized (K18-hACE2) mice with the ACEi Lisinopril affects lung ACE2 levels and the outcome of experimental COVID-19. K18-hACE2 mice were treated for 21 days with Lisinopril 10 mg/kg and were then infected with 105 PFU of SARS-CoV-2 (Wuhan strain). Body weight, clinical score, respiratory function, survival, lung ACE2 levels, viral load, lung histology, and cytokine (IL-6, IL-33, and TNF-α) levels were assessed. Mice treated with Lisinopril for 21 days showed increased levels of ACE2 in the lungs. Infection with SARS-CoV-2 led to massive decrease in lung ACE2 levels at 3 days post-infection (dpi) in treated and untreated animals, but Lisinopril-treated mice showed a fast recovery (5dpi) of ACE2 levels. Higher ACE2 levels in Lisinopril-treated mice led to remarkably higher lung viral loads at 3 and 6/7dpi. Lisinopril-treated mice showed decreased levels of the pro-inflammatory cytokines IL-6 and TNF-α in the serum and lungs at 6/7dpi. Marginal improvements in body weight, clinical score and survival were observed in Lisinopril-treated mice. No differences between treated and untreated infected mice were observed in respiratory function and lung histology. Lisinopril treatment showed both deleterious (higher viral loads) and beneficial (anti-inflammatory and probably anti-constrictory and anti-coagulant) effects in experimental COVID-19. These effects seem to compensate each other, resulting in marginal beneficial effects in terms of outcome for Lisinopril-treated animals.

Sickle cell nephropathy (SCN) is a leading cause of morbidity and mortality in sickle cell disease (SCD). Early intervention is crucial for mitigating its effects. However, current diagnostic methods rely on generic tests and may not detect SCN until irreversible renal damage occurs. Therefore, specific biomarkers for early diagnosis of SCN are needed. Urinary exosomes, membrane-bound vesicles secreted by renal podocytes and epithelial cells, contain both common and cell type-specific membrane and cytosolic proteins, reflecting the physiologic and pathophysiologic states of the kidney. Using proteomics, we analyzed the proteomes of urinary exosomes from humanized SCD mice at 2 months (without albuminuria) and 4 months (with albuminuria) of age. Excretion of 164 proteins were significantly increased and 176 proteins was significantly decreased in the exosomes when mice developed albuminuria. Based on the relevance to SCD, chronic kidney disease and Western blot confirmation in mice, we analyzed protein abundance of heparanase, cathepsin C, α2-macroglobulin and sarcoplasmic endoplasmic Ca2+ ATPase-3 (SERCA3) in the urinary exosomes and urine of 18 SCD subjects without albuminuria and 12 subjects with albuminuria using Western blot analyses. Both male and female subjects increased or tended to increase the excretion of these proteins in their urinary exosomes upon developing albuminuria, but female subjects demonstrated stronger correlations between the excretion of these proteins and urine albumin creatinine ratio (UACR) compared to male subjects. In contrast, exosomal excretion of Tamm-Horsfall protein, β-actin and SHP-1 was independent of albuminuria. These findings provide a foundation for a time-course study to determine whether increases in the levels of these proteins precede the onset of albuminuria in patients, which will help determine the potential of these proteins as biomarkers for early detection of SCN.

Globin proteins interact with endothelial nitric oxide synthase at the myoendothelial junctions of resistance arteries to regulate nitric oxide signaling between endothelium and smooth muscle. Human resistance arteries express both alpha and beta globin to form heterotetrameric hemoglobin (α2β2). To better understand the role of hemoglobin in human resistance arteries, we need to identify an animal model in which both alpha and beta globin are expressed in the resistance vasculature. To identify potential candidates, we used microscopy to survey a range of mammalian laboratory animals for hemoglobin in the artery wall. We isolated arteries (100-200 μm in diameter) from mesenteric tissue collected from human patients undergoing clinically-indicated surgery and from the following laboratory animals: mouse ( Mus musculus, C57BL/6 strain), rat ( Rattus norvegicus, CD strain), African thicket rat ( Grammomys surdaster), guinea pig ( Cavia porcellus), New Zealand white rabbit ( Oryctolagus cuniculus), Beagle dog ( Canis lupus familiaris), and cynomolgus macaque ( Macaca fascicularis) after they underwent euthanasia on approved animal study protocols. We leveraged the autofluorescence of heterotetrameric hemoglobin under multiphoton excitation to visualize hemoglobin in the wall of intact, unstained, paraformaldehyde-fixed artery segments. Autofluorescent puncta representing tetrameric hemoglobin were observed in the wall of resistance arteries from the human patients, non-human primate, and canines, but not from rabbit nor any of the rodent species. The ability of beta globin to restrict endothelial NO signaling was confirmed in canine arteries ex vivo by testing a beta globin mimetic peptide that inhibited vasoconstriction to phenylephrine. In conclusion, primates and canines appear to have tetrameric hemoglobin in the resistance artery wall, whereas rodents and rabbits do not. This study highlights differences in vascular globin expression between humans and rodents and extends the recent discovery of hemoglobin in resistance arteries of humans to two additional mammalian species that may serve as models for studying the unique activities of tetrameric hemoglobin in the resistance vasculature. Funding: Intramural Research program, NIAID, NIH This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Brain swelling is associated with death from cerebral malaria, but it is unclear whether brain swelling is caused by cerebral edema or vascular congestion-two pathological conditions with distinct effects on tissue hemoglobin concentrations. We used near-infrared spectroscopy (NIRS) to noninvasively study cerebral microvascular hemoglobin concentrations in 46 Malawian children with cerebral malaria. Cerebral malaria was defined by the presence of the malaria parasite Plasmodium falciparum on a blood smear, a Blantyre coma score of 2 or less, and retinopathy. Children with uncomplicated malaria (n = 33) and healthy children (n = 29) were enrolled as comparators. Cerebral microvascular hemoglobin concentrations were higher among children with cerebral malaria compared with those with uncomplicated malaria [median (25th, 75th): 145.2 (95.2, 190.0) μM versus 82.9 (65.7, 105.4) μM, P = 0.008]. Cerebral microvascular hemoglobin concentrations correlated with brain swelling score determined by MRI (r = 0.37, P = 0.03). Fluctuations in cerebral microvascular hemoglobin concentrations over a 30-min time period were characterized using detrended fluctuation analysis (DFA). DFA determined self-similarity of the cerebral microvascular hemoglobin concentration signal to be lower among children with cerebral malaria compared with those with uncomplicated malaria [0.63 (0.54, 0.70) versus 0.91 (0.82, 0.94), P < 0.0001]. The lower self-similarity of the hemoglobin concentration signal in children with cerebral malaria suggested impaired regulation of cerebral blood flow. The elevated cerebral tissue hemoglobin concentration and its correlation with brain swelling suggested that excess blood volume, potentially due to vascular congestion, may contribute to brain swelling in cerebral malaria.

Introduction The genetic determinants of fractional exhalation of nitric oxide (FeNO), a marker of lung inflammation, are understudied in Black individuals. Alpha globin (HBA) restricts nitric oxide signalling in arterial endothelial cells via interactions with nitric oxide synthase; however, its role in regulating the release of NO from respiratory epithelium is less well understood. We hypothesised that an HBA gene deletion, common among Black individuals, would be associated with higher FeNO.Methods Healthy Black adults were enrolled at four study sites in North Carolina from 2005 to 2008. FeNO was measured in triplicate using a nitric oxide analyzer. The −3.7 kb HBA gene deletion was genotyped using droplet digital PCR on genomic DNA. The association of FeNO with HBA copy number was evaluated using multivariable linear regression employing a linear effect of HBA copy number and adjusting for age, sex and serum immunoglobulin-E levels. Post-hoc analysis employing a recessive mode of inheritance was performed.Results 895 individuals were in enrolled in the study and 720 consented for future genetic research; 643 had complete data and were included in this analysis. Median (25th, 75th) FeNO was 20 (13, 31) ppb. HBA genotypes were: 30 (4.7%) -a/-a, 197 (30.6%) -a/aa, 405 (63%) aa/aa and 8 (1.2%) aa/aaa. Subjects were 35% male with median age 20 (19, 22) years. Multivariable linear regression analysis revealed no association between FeNO and HBA copy number (β=−0.005 (95% CI −0.042 to 0.033), p=0.81). In the post-hoc sensitivity analysis, homozygosity for the HBA gene deletion was associated with higher FeNO (β=0.107 (95% CI 0.003 to 0.212); p=0.045).Conclusion We found no association between HBA copy number and FeNO using a prespecified additive genetic model. However, a post hoc recessive genetic model found FeNO to be higher among subjects homozygous for the HBA deletion.

Background Alpha globin is expressed in the endothelial cells of human resistance arteries where it binds to endothelial nitric oxide synthase and limits release of the vasodilator nitric oxide. Genomic deletion of the alpha globin gene (HBA) is common among Black Americans and could lead to increased endothelial nitric oxide signaling and reduced risk of hypertension. Methods Community-dwelling US adults aged 45 years or older were enrolled and examined from 2003 to 2007, followed by telephone every 6 months, and reexamined from 2013 to 2016. At both visits, trained personnel performed standardized, in-home blood pressure measurements and pill bottle review. Prevalent hypertension was defined as systolic blood pressure ≥ 140mmHg or diastolic blood pressure ≥ 90mmHg or anti-hypertensive medication use. Droplet digital PCR was used to determine HBA copy number. The associations of HBA copy number with prevalent hypertension, resistant hypertension, and incident hypertension were estimated using multivariable regression. Results Among 9,684 Black participants, 7,439 (77%) had hypertension at baseline and 1,044 of those had treatment-resistant hypertension. 1,000 participants were not hypertensive at baseline and participated in a follow up visit; 517 (52%) developed hypertension over median 9.2 years follow-up. Increased HBA copy number was not associated with prevalent hypertension (PR = 1.00; 95%CI 0.98,1.02), resistant hypertension (PR = 0.95; 95%CI 0.86,1.05), or incident hypertension (RR = 0.96; 95%CI 0.86,1.07). Conclusions There were no associations between increased HBA copy number and risk of hypertension. These findings suggest that variation in alpha globin gene copy number does not modify the risk of hypertension among Black American adults.

To successfully feed on blood, hematophagous arthropods must combat the host's natural hemostatic and inflammatory responses. Salivary proteins of blood-feeding insects such as mosquitoes contain compounds that inhibit these common host defenses against blood loss, including vasoconstriction, platelet aggregation, blood clotting, pain, and itching. The D7 proteins are some of the most abundantly expressed proteins in female mosquito salivary glands and have been implicated in inhibiting host hemostatic and inflammatory responses. Anopheles gambiae, the primary vector of malaria, expresses three D7 long-form and five D7 short-form proteins. Previous studies have characterized the AngaD7 short-forms, but the D7 long-form proteins have not yet been characterized in detail. Here, we characterized the A. gambiae D7 long-forms by first determining their binding kinetics to hemostatic agonists such as leukotrienes and serotonin, which are potent activators of vasoconstriction, edema formation, and postcapillary venule leakage, followed by ex vivo functional assays. We found that AngaD7L1 binds leukotriene C4 and thromboxane A2 analog U-46619; AngaD7L2 weakly binds leukotrienes B4 and D4; and AngaD7L3 binds serotonin. Subsequent functional assays confirmed AngaD7L1 inhibits U-46619-induced platelet agserotonin-induced platelet aggregation and vasoconstriction. It is therefore possible that AngaD7L proteins counteract host hemostasis by scavenging these mediators. Finally, we demonstrate that AngaD7L2 had a dose-dependent anticoagulant effect via the intrinsic coagulation pathway by interacting with factors XII, XIIa, and XI. The uncovering of these interactions in the present study will be essential for compreinterface.

Angiotensin-converting enzyme 2 (ACE2) is the established cellular receptor for SARS-CoV-2. However, it is unclear whether ACE1 inhibitors (e.g., lisinopril) or angiotensin receptor blockers (e.g., losartan) alter tissue ACE2 expression. This study sought to determine whether lisinopril or losartan, as monotherapies or in combination, changes tissue levels of ACE2 in healthy male and female mice. Mice received lisinopril (10 mg/kg/day), losartan (10 mg/kg/day), or both for 21 days via drinking water. A control group received water without drug. The ACE2 protein index (ACE2 protein/total protein) was determined on the small intestine, lung, kidney, and brain. Oral lisinopril increased the ACE2 protein index across all tissues (p < 0.0001 vs. control). In contrast, the combination of lisinopril plus losartan did not increase ACE2 levels in any tissue (p = 0.89 vs. control) and even decreased tissue expression of the Ace2 gene (p < 0.001 vs. control). Tissue ACE2 remained elevated in the mice 21 days after cessation of lisinopril (p = 0.02). Plasma ACE2 did not correlate with the ACE2 protein index in any tissue. A sex difference was observed: kidney ACE2 levels were higher in male than in female mice (p < 0.0001). Oral lisinopril increases ACE2, the cellular receptor for SARS-CoV-2, in tissues that are relevant to the transmission and pathogenesis of COVID-19. Remarkably, the addition of losartan prevented lisinopril-induced increases in ACE2 across tissues. These results suggest that ACE inhibitors and angiotensin receptor blockers interact to determine tissue levels of ACE2.

Resistance artery vasodilation in response to hypoxia is essential for matching tissue oxygen and demand. In hypoxia, erythrocytic hemoglobin tetramers produce nitric oxide through nitrite reduction. We hypothesized that the alpha subunit of hemoglobin expressed in endothelium also facilitates nitrite reduction proximal to smooth muscle. Here, we create two mouse strains to test this: an endothelial-specific alpha globin knockout (EC Hba1Δ/Δ) and another with an alpha globin allele mutated to prevent alpha globin’s inhibitory interaction with endothelial nitric oxide synthase (Hba1WT/Δ36–39). The EC Hba1Δ/Δ mice had significantly decreased exercise capacity and intracellular nitrite consumption in hypoxic conditions, an effect absent in Hba1WT/Δ36–39 mice. Hypoxia-induced vasodilation is significantly decreased in arteries from EC Hba1Δ/Δ, but not Hba1WT/Δ36–39 mice. Hypoxia also does not lower blood pressure in EC Hba1Δ/Δ mice. We conclude the presence of alpha globin in resistance artery endothelium acts as a nitrite reductase providing local nitric oxide in response to hypoxia.

Saliva from mosquitoes contains vasodilators that antagonize vasoconstrictors produced at the bite site. Sialokinin is a vasodilator present in the saliva of Aedes aegypti. Here, we investigate its function and describe its mechanism of action during blood feeding. Sialokinin induces nitric oxide release similar to substance P. Sialokinin-KO mosquitoes produce lower blood perfusion than parental mosquitoes at the bite site during probing and have significantly longer probing times, which result in lower blood feeding success. In contrast, there is no difference in feeding between KO and parental mosquitoes when using artificial membrane feeders or mice that are treated with a substance P receptor antagonist, confirming that sialokinin interferes with host hemostasis via NK1R signaling. While sialokinin-KO saliva does not affect virus infection in vitro, it stimulates macrophages and inhibits leukocyte recruitment in vivo. This work highlights the biological functionality of salivary proteins in blood feeding.

BACKGROUND Cerebral malaria is a lethal complication of Plasmodium falciparum infections in need of better therapies. Previous work in murine experimental cerebral malaria (ECM) indicated that the combination of artemether plus intraperitoneal whole blood improved vascular integrity and increased survival compared to artemether alone. However, the effects of blood or plasma transfusion administered via the intravenous route have not previously been evaluated in ECM.OBJECTIVES To evaluate the effects of intravenous whole blood compared to intravenous plasma on hematological parameters, vascular integrity, and survival in artemether-treated ECM. METHODS Mice with late-stage ECM received artemether alone or in combination with whole blood or plasma administered via the jugular vein. The outcome measures were hematocrit and platelets; plasma angiopoietin 1, angiopoietin 2, and haptoglobin; blood-brain barrier permeability; and survival.FINDINGS Survival increased from 54% with artemether alone to 90% with the combination of artemether and intravenous whole blood. Intravenous plasma lowered survival to 18%. Intravenous transfusion provided fast and pronounced recoveries of hematocrit, platelets, angiopoietins levels and blood brain barrier integrity.MAIN CONCLUSIONS The outcome of artemether-treated ECM was improved by intravenous whole blood but worsened by intravenous plasma. Compared to prior studies of transfusion via the intraperitoneal route, intravenous administration was more efficacious.

Globin proteins exist in every cell type of the vasculature, from erythrocytes to endothelial cells, vascular smooth muscle cells, and peripheral nerve cells. Many globin subtypes are also expressed in muscle tissues (including cardiac and skeletal muscle), in other organ-specific cell types, and in cells of the central nervous system (CNS). The ability of each of these globins to interact with molecular oxygen (O2) and nitric oxide (NO) is preserved across these contexts. Endothelial α-globin is an example of extraerythrocytic globin expression. Other globins, including myoglobin, cytoglobin, and neuroglobin, are observed in other vascular tissues. Myoglobin is observed primarily in skeletal muscle and smooth muscle cells surrounding the aorta or other large arteries. Cytoglobin is found in vascular smooth muscle but can also be expressed in nonvascular cell types, especially in oxidative stress conditions after ischemic insult. Neuroglobin was first observed in neuronal cells, and its expression appears to be restricted mainly to the CNS and the peripheral nervous system. Brain and CNS neurons expressing neuroglobin are positioned close to many arteries within the brain parenchyma and can control smooth muscle contraction and thus tissue perfusion and vascular reactivity. Overall, reactions between NO and globin heme iron contribute to vascular homeostasis by regulating vasodilatory NO signals and scavenging reactive species in cells of the mammalian vascular system. Here, we discuss how globin proteins affect vascular physiology, with a focus on NO biology, and offer perspectives for future study of these functions.