RATIONALE: Pulmonary hypertension (PH) is a progressive condition associated with significant morbidity and mortality. Although various inflammatory pathways and mediators have been implicated in PH pathogenesis, little is known about the role of triggering receptor expressed on myeloid cells-1 (TREM-1) in PH or its tissue localization. TREM-1 stimulates pro-inflammatory cytokine and chemokine release, is activated by hypoxia in vitro, and is implicated in cardiac remodeling following myocardial ischemia. Taken with our previous observations that systemic TREM-1 inhibition attenuates hypoxia-induced hemodynamic changes, we hypothesize that pulmonary vascular cells express TREM-1 and contribute to PH pathogenesis in hypoxic conditions. METHODS: Age-matched male C57Bl/6 mice were exposed to 3 weeks of hypoxia (10% O2); or to 3 months of air or cigarette smoke followed by 3 weeks of normoxia (21% O2) or hypoxia to induce emphysema and PH. Right heart catheterization (RHC) was used to assess in vivo pressure changes with a Millar catheter system. Mouse lungs were either lavaged with PBS then flash-frozen, or inflated with formalin for immunohistology. Human pulmonary vascular smooth muscle cells (hPASMCs) and microvascular endothelial cells (hPMVECs) were exposed to 24 hrs of hypoxia or normoxia for measurement of soluble TREM-1 (sTREM-1) in cell lysate. Plasma was collected from patients with or without PH (N=34) and patients with or without COPD but no PH (N=51). Markers of cardiac remodeling and disease, including sTREM-1, were measured in mouse serum and bronchoalveolar lavage fluid (BALF), and human plasma. RESULTS: Hypoxia increased pulmonary sTREM-1 in the BALF of mice without preliminary cigarette smoke exposure (p<0.05). Immunofluorescence staining demonstrated higher TREM-1 levels in both pulmonary vascular ECs and SMCs in mice following hypoxia. This was supported by elevated sTREM-1 in hypoxia-exposed hPASMCs compared to normoxia controls (p<0.01); however, there was no such induction of TREM-1 in hPMVECs. Plasma sTREM-1 was elevated in COPD patients requiring long-term oxygen compared to those without (p<0.05), and in COPD patients with PH (p<0.05) compared to non-COPD, non-PH controls. CONCLUSIONS: Hypoxia induces TREM-1 in murine SMCs and ECs, and increases sTREM-1 in cell-free BALF. However, in vitro, hypoxia increased sTREM-1 levels in human PASMCs only, suggesting that SMCs play a more direct role in hypoxic PH pathogenesis. Furthermore, circulating sTREM-1 was elevated in plasma from COPD patients needing long-term oxygen without comorbid PH, as well as in those with PH. These data support TREM-1 as a biomarker and potential therapeutic target in PH and hypoxic lung disease.

Introduction: Classically, vulnerable plaques at risk for acute coronary syndrome (ACS) have been defined by cellular architecture. However, contemporary imaging studies have shed light into new mechanisms of ACS (e.g., plaque erosion), challenging plaque rupture as the sole mechanism of disease. Furthermore, mechanisms within the vascular microenvironment that may modulate these disease phenotypes are poorly understood. Our objective was to examine differential programming of smooth muscle and macrophage cells amongst patients with stable and unstable plaques using spatial transcriptomics. Methods: Autopsy-derived coronary arteries were reviewed by an independent pathologist and segregated into stable (N=8) and unstable (defined by the presence of CD68+ cells and a large lipid core, N=8) plaques for spatial profiling. In combination with immunofluorescent histology, our approach enabled cell-specific, spatially resolved transcriptional profiling of plaques with mapping of cell populations via gene expression patterns. Results: We observed unique spatial and cell-specific transcriptional signatures for stable and unstable plaques including regional differences in the tunica intima and media. These regions differentially expressed pro-inflammatory (e.g., IFN-gamma, MHC Class II, pro-inflammatory cytokines) and pro-thrombotic signaling pathways. Cell-type-specific expression analysis using spatial deconvolution revealed heterogeneous CD68+ cell populations which shared gene signatures with endothelial, smooth muscle, and myeloid cells. Conclusion: Our results highlight cell-specific and regional pro-inflammatory and coagulation transcriptional changes within unstable coronary arterial plaques and supports the idea of cellular dedifferentiation and intra-plaque plasticity as a contributor to plaque instability. These findings may help to identify novel mediators of ACS and potential therapeutic targets.

Prior studies have suggested a role for TGF-β in the generation of hypertension in SS rats. We have shown that production of MCP-1 (CCL-2) and TGF-β1 increase in the vasculature of hypertensive SS rats. This study aims to explore novel mechanisms of hypertension development. We hypothesize that TGF-β1 regulated the production of MCP-1 by VSMCs in the setting of cyclic strain. Primary cultures of SS aortic VSMCs in early (<6) passages were grown in standard fashion in Dulbecco’s Modified Eagle’s Medium supplemented with 10% fetal bovine serum. Cultured cells were identified as smooth muscle cells by their characteristic morphology and positive immunostaining for α-smooth muscle actin. In the first study, VSMCs were treated with recombinant active TGF-β1 (1 ng/mL and 10 ng/mL) for 6 h, then harvested for MCP-1 mRNA quantification by SYBR green qPCR. Medium was also collected to determine MCP-1 levels using ELISA. TGF-β1 increased MCP-1 mRNA expression by 2.0- and 3.1-fold in VSMC incubated in medium containing 1 ng/mL and 10 ng/mL of TGF-β1, respectively. In a second series of studies, VSMCs were seeded onto 6-well BioFlex plates. Some cells were pre-treated with 10 μmol/mL of an ALK4/5 inhibitor. Cyclic strain, an in vitro model of hypertension, was performed using the FlexCell 6000 and a standardized regimen (8 h, 15% elongation @ 1 Hz). Cells and medium were then harvested for mRNA analyses and determination of MCP-1 levels. When compared with expression by VSMCs maintained under static condition, cyclic strain increased (p<0.05) MCP-1 mRNA expression 4.2-fold and TGF-β1 mRNA 1.93-fold. Cyclic strain also increased (p<0.01) MCP-1 protein in the medium (static condition vs cyclic strain, 112.6 ± 7.1 pg/mL vs 222.5 ± 6.5 pg/mL, n=6). Pre-treatment of VSMC with the ALK4/5 inhibitor reduced mRNA expression of MCP-1 mediated by cyclic strain (Cyclic strain vs Cyclic strain + AKL4/5 inhibitor, 4.5 ± 1.06 vs 2.88 ± 0.47, n=6, P < 0.01). Thus, cyclic strain promotes MCP-1 production by VSMCs through the TGF-β pathway. The data support the need for further study of this interaction as well as a potential role in arterial hypertension in this rodent model. Department of Veterans Affairs Basic Sciences R&D (BSRD) Service (1 I01 BX005640) National Institutes of Health (P30 DK079337). This is the full abstract presented at the American Physiology Summit 2024 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.

ObjectivesOur objective was to examine coronary endothelial and myocardial programming in patients with severe COVID-19 utilizing digital spatial transcriptomics. BackgroundSevere acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has well-established links to thrombotic and cardiovascular events. Endothelial cell infection was initially proposed to initiate vascular events; however, this paradigm has sparked growing controversy. The significance of myocardial infection also remains unclear. MethodsAutopsy-derived cardiac tissue from control (n = 4) and COVID-19 (n = 8) patients underwent spatial transcriptomic profiling to assess differential expression patterns in myocardial and coronary vascular tissue. Our approach enabled transcriptional profiling in situ with preserved anatomy and unaltered local SARS-CoV-2 expression. In so doing, we examined the paracrine effect of SARS-CoV-2 infection in cardiac tissue. ResultsWe observed heterogeneous myocardial infection that tended to colocalize with CD31 positive cells within coronary capillaries. Despite these differences, COVID-19 patients displayed a uniform and unique myocardial transcriptional profile independent of local viral burden. Segmentation of tissues directly infected with SARS-CoV-2 showed unique, pro-inflammatory expression profiles including upregulated mediators of viral antigen presentation and immune regulation. Infected cell types appeared to primarily be capillary endothelial cells as differentially expressed genes included endothelial cell markers. However, there was limited differential expression within the endothelium of larger coronary vessels. ConclusionOur results highlight altered myocardial programming during severe COVID-19 that may in part be associated with capillary endothelial cells. However, similar patterns were not observed in larger vessels, diminishing endotheliitis, and endothelial activation as key drivers of cardiovascular events during COVID-19.

This study tested if matrix metalloproteinase (MMP)-9 promoted microvascular pathology that initiates hypertensive (HT) kidney disease in salt-sensitive (SS) Dahl rats. SS rats lacking Mmp9 (Mmp9-/-) and littermate control SS rats were studied after one week on a normotensive 0.3% sodium chloride (Pre-HT SS and Pre-HT Mmp9-/-) or a hypertension-inducing diet containing 4.0% sodium chloride (HT SS and HT Mmp9-/-). Telemetry-monitored blood pressure of both the HT SS and HT Mmp9-/-rats increased and did not differ. Kidney microvessel transforming growth factor-beta 1 (Tgfb1) mRNA did not differ between Pre-HT SS and Pre-HT Mmp9-/-rats, but with hypertension and expression of Mmp9 and Tgfb1 increased in HT SS rats, along with phospho-Smad2 labeling of nuclei of vascular smooth muscle cells, and with peri-arteriolar fibronectin deposition. Loss of MMP-9 prevented hypertension-induced phenotypic transformation of microvascular smooth muscle cells and the expected increased microvascular expression of pro-inflammatory molecules. Loss of MMP-9 in vascular smooth muscle cells in vitro prevented cyclic strain-induced production of active TGF-b1 and phospho-Smad2/3 stimulation. Afferent arteriolar autoregulation was impaired in HT SS rats but not in HT Mmp9-/-rats or the HT SS rats treated with doxycycline, an MMP inhibitor. HT SS but not HT Mmp9-/-rats showed decreased glomerular Wilms Tumor 1 protein-positive cells (a marker of podocytes) along with increased urinary podocin and nephrin mRNA excretion, all indicative of glomerular damage. Thus, our findings support an active role for MMP-9 in a hypertension-induced kidney microvascular remodeling process that promotes glomerular epithelial cell injury in SS rats.

Inflammation facilitates kidney ischemia-reperfusion (I/R) injury. Endothelial cells (ECs) that were modified to overexpress (C-X-C motif) chemokine receptor (CXCR)1/2 (CXCR1/2-ECs) were injected immediately following kidney I/R injury. The interaction of CXCR1/2-ECs, but not ECs transduced with an empty adenoviral vector, with injured kidney tissue preserved kidney function and reduced production of inflammatory markers, capillary rarefaction, and interstitial fibrosis. The study highlights a functional role for the C-X-C chemokine pathway in kidney damage following I/R injury.

Introduction: Patients with chronic obstructive pulmonary disease (COPD) often develop cardiovascular disorders such as right ventricular hypertrophy (RVH) and pulmonary hypertension (PH). We hypothesized that the neutrophil chemoattractant proline-glycine-proline (PGP), generated by the stepwise proteolytic cleavage of collagen by matrix metalloproteinases and prolyl endopeptidase (PE), would be involved in ongoing PH pathogenesis. Methods: Mice were administered with acetylated PGP (Ac-PGP) (250 µg/dose) intratracheally for 6 and 10 weeks or exposed to cigarette smoke for 6 weeks to evaluate lung inflammation and RVH. To further elucidate the impact of PGP on pulmonary vascular remodeling, the PE inhibitor benzyloxycarbony-proline-prolinal (ZPP) was intratracheally administered in a 6-week smoking model. Results: In mice treated with Ac-PGP at 6 weeks and 10 weeks, there was increased right ventricular systolic pressures (RVSP) when compared to the control group. The average ratio of RV/(LV+S) also showed significant increase with Ac-PGP administration. Ac-PGP levels in the blood was significantly increased after 6 weeks of smoke exposure. Treating the mice with ZPP intratracheally prior to smoke exposure significantly decreased inflammation in the lungs and prevented mice from developing PH. Furthermore, nitrite and nitrate levels in blood were elevated after smoke exposure and the nitrite/nitrate ratio returned to baseline levels after ZPP treatment, suggesting reduced oxidative stress. Conclusion: These results demonstrate that Ac-PGP induced the development of PH and that targeting of PGP peptides in a smoke model affects the development of RVH and PH.

Rationale: Idiopathic Pulmonary Arterial Hypertension (IPAH) is a progressive disorder with limited therapeutic options and excessive morbidity and mortality. IPAH is characterized by abnormal vasoconstriction and remodeling of the pulmonary arteries driven by apoptotic-resistant endothelial and smooth muscle cells. Alpha-B crystallin (CRYAB) is implicated in angiogenesis, cell survival, and apoptotic resistance in cancer. Here, we hypothesize that CRYAB contributes to abnormal vascular remodeling and apoptotic resistance in IPAH. Methods: siRNA transfection was utilized to knock out CRYAB protein in pulmonary arterial smooth muscle cells (PASMCs) cultured from IPAH individuals. At 72 hrs post siRNA transfection, cells were treated with staurosporine and caspase 3 activity was measured. Immunohistochemical staining of CRYAB protein was performed on lung sections from age-matched IPAH and control subjects. RNA isolated from partially muscularized pulmonary vessels obtained by laser capture microdissection was sequenced and underwent Ingenuity pathway analysis. Results: CRYAB siRNA transfection reduced CRYAB protein level in PASMCs by ~70%. Staurosporine-induced caspase 3 activity was enhanced by 1.6-fold in cells transfected with CRYAB siRNA compared to scramble siRNA. CRYAB protein staining was increased in pulmonary vascular smooth muscle in IPAH. CRYAB mRNA was highly differentially expressed in IPAH pulmonary vessels compared to control. Conclusions: These results suggest that CRYAB prevents apoptosis in PASMCs and its dysregulation may contribute to the development of IPAH. Therefore, further studies targeting CRYAB may provide novel therapeutic strategies for IPAH treatment.

Introduction: Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is linked to thrombotic and cardiovascular events. Endothelial cell infection was initially proposed to initiate vascular events; however, this has sparked growing controversy. Significance of myocardial infection also remains unclear. Hypothesis: Our objective was to examine coronary endothelial and myocardial programming in patients with severe COVID-19 with digital spatial transcriptomics. Methods: Autopsy-derived cardiac tissue from control (n = 4) and COVID-19 (n = 8) patients underwent spatial transcriptomic profiling to assess differential expression patterns in myocardial and coronary vascular tissue. Our approach enabled transcriptional profiling in situ with preserved anatomy and unaltered local SARS-CoV-2 expression. In so doing, we examined paracrine effect of SARS-CoV-2 infection in cardiac tissue. Results: We observed heterogeneous myocardial infection that tended to colocalize with CD31 positive cells within coronary capillaries. Despite these differences, COVID-19 patients displayed a uniform and unique myocardial transcriptional profile independent of local burden. Segmentation of tissues directly infected with SARS-CoV-2 showed unique, pro-inflammatory expression profiles including upregulated mediators of viral antigen presentation and immune regulation. Infected cell types appeared to primarily be capillary endothelial cells as differentially expressed genes included endothelial cell markers (Figure 1). However, there was limited differential expression within the endothelium of larger coronary vessels. Conclusions: Our results highlight altered myocardial programming during severe COVID-19 that may be associated with capillary endothelial cells. However, similar patterns were not observed in larger vessels, diminishing endotheliitis and endothelial activation as key drivers of cardiovascular events during COVID-19.

Prevention of phenotype switching of vascular smooth muscle cells is an important determinant of normal vascular physiology. Hydrogen peroxide (H2O2) promotes osteogenic differentiation of vascular smooth muscle cells through expression of Runt related transcription factor 2 (Runx2). In this study, an increase in dietary NaCl increased endothelial H2O2 generation through NOX4, a NAD(P)H oxidase. The production of H2O2 was sufficient to increase Runx2, osteopontin and osteocalcin in adjacent vascular smooth muscle cells from control littermate mice but was inhibited in mice lacking endothelial Nox4. A vascular smooth muscle cell culture model confirmed the direct involvement of the activation of protein kinase B (Akt) with inactivation of FoxO1 and FoxO3a observed in the control mice on the high NaCl diet. The present study also showed a reduction of catalase activity in aortas during high NaCl intake. The findings demonstrated an interesting cell-cell communication in the vascular wall that was initiated with H2O2 production by endothelium and was regulated by dietary NaCl intake. A better understanding of how dietary salt intake alters vascular biology may improve treatment of vascular disease that involves activation of Runx2.

Altered inflammation and tissue remodeling are cardinal features of cardiovascular disease and cardiac transplant rejection. Neutrophils have increasingly been understood to play a critical role in acute rejection and early allograft failure; however, discrete mechanisms that drive this damage remain poorly understood. Herein, we demonstrate that early acute cardiac rejection increases allograft prolyl endopeptidase (PE) in association with de novo production of the neutrophil proinflammatory matrikine proline-glycine-proline (PGP). In a heterotopic murine heart transplant model, PGP production and PE activity were associated with early neutrophil allograft invasion and allograft failure. Pharmacologic inhibition of PE with Z-Pro-prolinal reduced PGP, attenuated early neutrophil graft invasion, and reduced proinflammatory cytokine expression. Importantly, these changes helped preserve allograft rejection-free survival and function. Notably, within 2 independent patient cohorts, both PGP and PE activity were increased among patients with biopsy-proven rejection. The observed induction of PE and matrikine generation provide a link between neutrophilic inflammation and cardiovascular injury, represent a potential target to reduce allogenic immune responses, and uncover a mechanism of cardiovascular disease that has been previously unrecognized to our knowledge.

Introduction: Patients with chronic obstructive pulmonary disease (COPD) are at increased risk of coronary artery disease (CAD). Proline-glycine-proline (PGP) is an extracellular matrix-derived chemokine ( matrikine ) that is increased in COPD and known to promote neutrophil chemotaxis, endothelial dysfunction, and vascular inflammation through activation of the CXC Chemokine Receptor 2 (CXCR2). Despite these observations, no study has examined PGP as a marker of CAD within COPD patients. Hypothesis: We hypothesized that circulating PGP is associated with comorbid CAD amongst COPD patients. Methods: Current and former smokers with COPD enrolled in the UAB P rospective R epository for coupling EVE nts to N ovel pa T hways in COPD (PREVENT COPD) cohort underwent phlebotomy and spirometry. Cardiovascular diagnoses were adjudicated by two physician reviewers with access to medical records. CAD was defined as a composite of prior myocardial infarction, coronary revascularization, or by physician diagnosis of CAD. Plasma PGP was measured using a solid-phase extraction method coupled with tandem mass spectrometry. Other known CXCR2 ligands (e.g. GRO alpha, IL-8) were measured by multiplex protein assay. SPSSv27 was used for logistic regression models to measure associations between plasma biomarkers and the presence of CAD. Results: The 104 participants were 60±9 years old, 50% male, and 50% Black race. CAD was prevalent in 21 (21%) of the cohort. Plasma PGP was detectable for all participants (0.05 - 15.1 ng/mL). Participants with CAD had higher PGP concentrations compared to participants without CAD (1.26 vs. 0.52 ng/mL, p=0.042). Similarly, PGP was increased among participants with prior coronary revascularization (p<0.01). Associations between plasma PGP and CAD remained significant after adjustment for FEV1 % predicted and smoking status (OR 1.62, 95%CI 1.02-2.56). Concentrations of other CXCR2 ligands were low and not associated with CAD. Conclusions: Our results highlight PGP as a potentially novel biomarker of CAD among individuals with COPD. Future studies are needed to assess whether plasma PGP is predictive of CAD outcomes in COPD, as well as determine the significance of endothelial CXCR2 activation on the development of atherosclerosis.

BACKGROUND:Pulmonary artery (PA) enlargement, defined as pulmonary artery to ascending aorta diameter ratio (PA:A)>1 on computed tomography (CT), is a marker of pulmonary vascular disease in chronic lung diseases. PA enlargement is prevalent in cystic fibrosis (CF), but its relationship to hemodynamics and prognostic utility in severe CF are unknown. We hypothesized that the PA:A would have utility in identifying pulmonary hypertension (PH) in severe CF and that PA enlargement would be associated with reduced transplant-free survival. METHODS:We conducted a retrospective study of adults with CF undergoing lung transplant evaluation at a single center between 2000 and 2015. CT, right heart catheterization (RHC), and clinical data were collected. The PA:A was measured from a single CT slice. We measured associations between PA:A and invasive hemodynamic parameters including PH defined as a mPAP ≥25mmHg using adjusted linear and logistic regression models. Kaplan-Meier and adjusted Cox regression models were used to measure associations between PA:A>1, RHC-defined PH, and transplant-free survival in severe CF. RESULTS:We analyzed 78 adults with CF that had CT scans available for review, including 44 that also had RHC. RHC-defined PH defined as a mPAP ≥25mmHg was present in 36% of patients with CF undergoing transplant evaluation. The PA:A correlated with mPAP (r = 0.73; 95% CI 3.87-7.80; p<0.001) and PVR (r = 0.42, p = 0.005) and the PA:A>1 was an independent predictor of PH (aOR 4.50; 95% CI 1.05-19.2; p = 0.042). PA:A>1 was independently associated with increased hazards for death or transplant (aHR 2.69; 95% CI 1.41-5.14; P = 0.003). The presence of mPAP ≥25mmHg was independently associated with decreased survival in this cohort. CONCLUSIONS:PA enlargement is associated with pulmonary hemodynamics and PH in severe CF. PA enlargement is an independent prognostic indicator of PH and decreased survival in this population.

The chemokine receptors CXCR1/2 and CCR2/5 play a critical role in neutrophil and monocyte recruitment to sites of injury and/or inflammation. Neutrophil-mediated inflammation and endothelial cell (EC) injury are unifying factors in the pathogenesis of the acute respiratory distress syndrome. This study tested the hypothesis that systemic administration of rat-induced pluripotent stem cell (iPS)-derived ECs (iPS-ECs) overexpressing CXCR1/2 or CCR2/5 attenuates lipopolysaccharide (LPS)-induced acute lung injury. Rat iPS-ECs were transduced with adenovirus containing cDNA of CXCR1/2 or CCR2/5. Ovariectomized Sprague-Dawley rats (10 wk old) received intraperitoneal injection of LPS and intravenous infusion of 1) saline vehicle, 2) AdNull-iPS-ECs (iPS-ECs transduced with empty adenoviral vector), 3) CXCR1/2-iPS-ECs (iPS-ECs overexpressing CXCR1/2), or 4) CCR2/5-iPS-ECs (iPS-ECs overexpressing CCR2/5) at 2 h post-LPS. Rats receiving intraperitoneal injection of saline served as sham controls. Later (4 h), proinflammatory cytokine/chemokine mRNA and protein levels were measured in total lung homogenates by real-time RT-PCR and Luminex multiplex assays, and neutrophil and macrophage infiltration in alveoli was measured by immunohistochemical staining. Pulmonary microvascular permeability was assessed by the Evans blue technique, and pulmonary edema was estimated by wet-to-dry lung weight ratios. Albumin levels and neutrophil counts were assessed in bronchoalveolar lavage fluid at 24 h post-LPS. Both CXCR1/2-iPS-ECs and CCR2/5-iPS-ECs significantly reduced LPS-induced proinflammatory mediator expression, neutrophil and macrophage infiltration, pulmonary edema, and vascular permeability compared with controls. These provocative findings provide strong evidence that targeted delivery of iPS-ECs overexpressing CXCR1/2 or CCR2/5 prevents LPS-induced acute lung injury.NEW & NOTEWORTHY We have developed a novel approach to address neutrophil-mediated inflammation and endothelial damage by targeted delivery of rat-induced pluripotent stem cell (iPS)-derived endothelial cell (ECs)overexpressing chemokine receptors CXCR1/2 and CCR2/5 in injured lung tissue in a model of acute lung injury. We have demonstrated that intravenously transfused CXCR1/2-iPS-ECs and CCR2/5-iPS-ECs are recruited to lipopolysaccharide-injured lungs and attenuate lipopolysaccharide-induced parenchymal lung injury responses, including inflammatory mediator expression, inflammatory cell infiltration, and vascular leakage compared with controls.

Prior studies reported that haploinsufficiency of the transcription factor ETS-1 is renoprotective in Dahl salt-sensitive rats, but the mechanism is unclear. Here, we tested whether ETS-1 is involved in hypertension-induced renal microvascular pathology and autoregulatory impairment. Hypertension was induced in salt-sensitive rats and salt-sensitive rats that are heterozygous with 1 wild-type or reference allele of Ets1 (SSEts1+/-) by feeding a diet containing 4% sodium chloride for 1 week. Increases in blood pressure did not differ. However, phosphorylated ETS-1 increased in afferent arterioles of hypertensive salt-sensitive rats, but not in hypertensive SSEts1+/- rats. Afferent arterioles of hypertensive salt-sensitive rats showed increased monocyte chemotactic protein-1 expression and infiltration of CD68 positive monocytes/macrophages. Isolated kidney microvessels showed increased mRNA expression of vascular cell adhesion molecule, intercellular adhesion molecule, P-selectin, fibronectin, transforming growth factor-β, and collagen I in hypertensive salt-sensitive rats compared with hypertensive SSEts1+/- rats. Using the in vitro blood-perfused juxtamedullary nephron preparation, pressure-mediated afferent arteriolar responses were significantly blunted in hypertensive salt-sensitive rats compared to hypertensive SSEts1+/- rats. Over a 65-170 mm Hg pressure range tested baseline arteriolar diameters averaged 15.1 μm and remained between 107% and 89% of baseline diameter in hypertensive salt-sensitive rats vs. 114% and 73% in hypertensive SSEts1+/- rats (significantly different). Thus, ETS-1 participates in renal arteriolar pathology and autoregulation and thereby is involved in hypertension-mediated kidney injury in salt-sensitive rats.