Alzheimer’s disease (AD) is an increasing global healthcare crisis with few effective treatments. The accumulation of amyloid plaques and hyper-phosphorylated tau are thought to underlie the pathogenesis of AD. However, current studies have recognized a prominent role of cerebrovascular dysfunction in AD. We recently reported that SNPs in soluble epoxide hydrolase (sEH) are linked to AD in human genetic studies and that long-term administration of an sEH inhibitor attenuated cerebral vascular and cognitive dysfunction in a rat model of AD. However, the mechanisms linking changes in cerebral vascular function and neuroprotective actions of sEH inhibitors in AD remain to be determined. This study investigated the effects of administration of an sEH inhibitor, 1-(1-Propanoylpiperidin-4-yl)-3-[4-(trifluoromethoxy)phenyl]urea (TPPU), on neurovascular coupling, blood–brain barrier (BBB) function, neuroinflammation, and cognitive dysfunction in an hAPP/PS1 TgF344-AD rat model of AD. We observed predominant β-amyloid accumulation in the brains of 9–10-month-old AD rats and that TPPU treatment for three months reduced amyloid burden. The functional hyperemic response to whisker stimulation was attenuated in AD rats, and TPPU normalized the response. The sEH inhibitor, TPPU, mitigated capillary rarefaction, BBB leakage, and activation of astrocytes and microglia in AD rats. TPPU increased the expression of pre- and post-synaptic proteins and reduced loss of hippocampal neurons and cognitive impairments in the AD rats, which was confirmed in a transcriptome and GO analysis. These results suggest that sEH inhibitors could be a novel therapeutic strategy for AD.

Alzheimer's Disease and Alzheimer's Disease-related dementias (AD/ADRD) pose major global healthcare challenges, with diabetes mellitus (DM) being a key risk factor. Both AD and DM-related ADRD are characterized by reduced cerebral blood flow, although the exact mechanisms remain unclear. We previously identified compromised cerebral hemodynamics as early signs in TgF344-AD and type 2 DM-ADRD (T2DN) rat models. Genome-wide studies have linked AD/ADRD to SNPs in soluble epoxide hydrolase (sEH). This study explored the effects of sEH inhibition with TPPU on cerebral vascular function and cognition in AD and DM-ADRD models. Chronic TPPU treatment improved cognition in both AD and DM-ADRD rats without affecting body weight. In DM-ADRD rats, TPPU reduced plasma glucose and HbA1C levels. Transcriptomic analysis of primary cerebral vascular smooth muscle cells from AD rats treated with TPPU revealed enhanced pathways related to cell contraction, alongside decreased oxidative stress and inflammation. Both AD and DM-ADRD rats exhibited impaired myogenic responses and autoregulation in the cerebral circulation, which were normalized with chronic sEH inhibition. Additionally, TPPU improved acetylcholine-induced vasodilation in the middle cerebral arteries (MCA) of DM-ADRD rats. Acute TPPU administration unexpectedly caused vasoconstriction in the MCA of DM-ADRD rats at lower doses. In contrast, higher doses or longer durations were required to induce effective vasodilation at physiological perfusion pressure in both control and ADRD rats. Additionally, TPPU decreased reactive oxygen species production in cerebral vessels of AD and DM-ADRD rats. These findings provide novel evidence that chronic sEH inhibition can reverse cerebrovascular dysfunction and cognitive impairments in AD/ADRD, offering a promising avenue for therapeutic development.

Although high-throughput DNA/RNA sequencing technologies have generated massive genetic and genomic data in human disease, these findings have not been translated into new patient treatments. To address this problem, we utilized Mendelian randomization (MR) and large patient-level genetic and functional genomic data to evaluate druggable targets using Alzheimer’s disease (AD) as a prototypical example. Specifically, we applied the genetic instruments from 9 expression quantitative trait loci (eQTL) and 3 protein quantitative trait loci (pQTL) datasets across five human brain regions from three human brain biobanks and performed MR in 7 genome-wide association study (GWAS) datasets of European ancestry (EA) and African ancestry (AA), with AD cases and controls. We identified 19 drug targets, including the inflammatory target of epoxide hydrolase 2 (EPHX2) as a potent AD target. We demonstrated that a genome-wide significant and protective variant of p.Arg287Gln in EPHX2 (β = -0.096, PGWAS = 1.08 × 10-11) significantly reduced level of phosphorylated-tau (p-tau181) and the ratio of p-tau181/total tau and increased neuron clump size in patient induced Pluripotent Stem Cells (iPSC)-derived neurons, mechanistically supporting MR results. Pharmacologic inhibition of EPHX2 significantly improved cognitive behaviors in two AD transgenic rodent models (5xFAD and TgF344-AD). We further identified that 12 drugs (i.e., trazodone [ADRA1A] and baclofen [GABBR1]) harboring MR-supported targets are significantly associated with reduced incidence of AD in 111,680 mild cognitive impairment (MCI) patients from the Optum database. Using a new user active-comparator design, we found that usage of trazodone was significantly associated with 22% reduced incidence of AD (hazard ratio [HR] = 0.78, P=6.44x10-6) in people with MCI in the MarketScan database. In summary, combining genetics and real-world patient data identifies ancestry-specific therapeutic targets and medicines for AD and other neurodegenerative diseases if broadly applied.

Hypertension is a leading risk factor for the development of Alzheimer’s disease and Alzheimer’s disease-related dementia (AD/ADRD), which is closely linked with cerebral vascular inflammation and dysfunction. We previously found that high-salt-treated Dahl Salt-Sensitive (SS) rats displayed blood-brain barrier (BBB) leakage, astrocyte activation, neurodegeneration, and cognitive impairments. CD14 functions in the Toll-like receptor 4 (TLR4) complex to initiate proinflammatory signaling events in response to LPS. CD14 levels were elevated in the brains of human and animal AD/ADRD models. This study aims to explore the vascular contribution of CD14 to AD/ADRD. The expression of Cd14 was assessed through RT-PCR in primary cerebral vascular smooth muscle cells (VSMCs) isolated from TgF344-AD rats, and the results were compared to cells from control rats. The myogenic response of the middle cerebral artery (MCA) was compared between SS (SS CD14+/+ ), SS CD14-/- , and SD rats with and without the induction of hypertension with 4% NaCl diets. BBB function was detected by the leakage of injected Evans blue and fibrinogen. Brain cytokine levels were detected with Bio-Plex Rat Cytokine 23-Plex Assay. Cd14 emerged as one of the significantly upregulated top genes in high-salt-fed SS CD14+/+ rats, with a subsequent three-fold increase observed specifically in cerebral VSMCs of AD compared with control rats. Hypertensive SS CD14+/+ rats exhibited an impaired myogenic response of the MCA compared to normotensive SS CD14+/+ rats and SD rats fed with both high- and low-salt diets. Notably, the deletion of CD14 demonstrated a remarkable trend in enhancing the myogenic response of the MCA in female SS CD14-/- rats. Furthermore, high salt-fed 24-week SS CD14+/+ rats displayed BBB dysfunction. An augmented pan-cytokine panel was observed in low salt-fed 12-week SS CD14+/+ rats, and this effect was magnified in high salt-fed 24-week SS CD14+/+ rats. These results collectively point to the potential role of CD14 in influencing vascular and immune responses, suggesting a link between CD14, hypertension, and cerebrovascular pathologies, particularly in the context of AD. Additional investigations are warranted to delve into the underlying mechanisms and ascertain whether CD14 exhibits a sex-specific role in AD/ADRD.

Vascular aging influences hemodynamics, elevating risks for vascular diseases and dementia. We recently demonstrated that knockout (KO) of Dusp5 enhances cerebral and renal hemodynamics and cognitive function. This improvement correlates with elevated pPKC and pERK1/2 levels in the brain and kidneys. Additionally, we observed that Dusp5 KO modulates the passive mechanical properties of cerebral and renal arterioles, associated with increased myogenic tone at low pressure, enhanced distensibility, greater compliance, and reduced stiffness. The present study evaluates the structural and mechanical properties of the middle cerebral artery (MCA) in Dusp5 KO rats. We found that vascular smooth muscle cell layers and the collagen content in the MCA wall are comparable between Dusp5 KO and control rats. The internal elastic lamina in the MCA of Dusp5 KO rats exhibits increased thickness, higher autofluorescence intensity, smaller fenestrae areas, and fewer fenestrations. Despite an enhanced myogenic response and tone of the MCA in Dusp5 KO rats, other passive mechanical properties, such as wall thickness, cross-sectional area, wall-to-lumen ratio, distensibility, incremental elasticity, circumferential wall stress, and elastic modulus, do not significantly differ between strains. These findings suggest that while Dusp5 KO has a limited impact on altering the structural and mechanical properties of MCA, its primary role in ameliorating hemodynamics and cognitive functions is likely attributable to its enzymatic activity on cerebral arterioles. Further research is needed to elucidate the specific enzymatic mechanisms and explore potential clinical applications in the context of vascular aging.

Alzheimer’s Disease (AD) and Alzheimer’s Disease-Related Dementia (ADRD) are the primary causes of dementia that has a devastating effect on the quality of life and is a tremendous economic burden on the healthcare system. The accumulation of extracellular beta-amyloid (Aβ) plaques and intracellular hyperphosphorylated tau-containing neurofibrillary tangles (NFTs) in the brain are the hallmarks of AD. They are also thought to be the underlying cause of inflammation, neurodegeneration, brain atrophy, and cognitive impairments that accompany AD. The discovery of APP, PS1, and PS2 mutations that increase Aβ production in families with early onset familial AD led to the development of numerous transgenic rodent models of AD. These models have provided new insight into the role of Aβ in AD; however, they do not fully replicate AD pathology in patients. Familial AD patients with mutations that elevate the production of Aβ represent only a small fraction of dementia patients. In contrast, those with late-onset sporadic AD constitute the majority of cases. This observation, along with the failure of previous clinical trials targeting Aβ or Tau and the modest success of recent trials using Aβ monoclonal antibodies, has led to a reappraisal of the view that Aβ accumulation is the sole factor in the pathogenesis of AD. More recent studies have established that cerebral vascular dysfunction is one of the earliest changes seen in AD, and 67% of the candidate genes linked to AD are expressed in the cerebral vasculature. Thus, there is an increasing appreciation of the vascular contribution to AD, and the National Institute on Aging (NIA) and the Alzheimer’s Disease Foundation recently prioritized it as a focused research area. This review summarizes the strengths and limitations of the most commonly used transgenic AD animal models and current views about the contribution of Aβ accumulation versus cerebrovascular dysfunction in the pathogenesis of AD.

Alzheimer's Disease and Alzheimer's Disease-Related Dementias (AD/ADRD) is an emerging global healthcare crisis. However, underlying mechanisms have not been understood well enough to translate into precision medicine. Recent human genetic evidence indicated that soluble hydrolase (sEH) is linked to AD/ADRD. Inhibition of sEH has been reported to improve cognition in AD mice due to its anti-inflammatory and neuronal protective effects. Here, we examined whether inhibition of sEH with TPPU could reduce cognitive impairments by improving cerebral hemodynamics in 18-month-old diabetes (DM)-related ADRD rats and 6 months of TgF344-AD rats. The myogenic responses of the middle cerebral artery (MCA) were impaired in both AD and ADRD rats and were normalized with TPPU. The inner diameters of MCA increased by 49.16 ± 17.02 % in DM rats but decreased by 16.06 ± 2.46% and 11.24 ± 0.05% in age-matched control and TPPU-treated DM rats when pressure was elevated from 40 to 180 mmHg. Similarly, TPPU-treated AD rats significantly enhanced the MCA constriction by 25%. Forced dilatation occurred at pressures > 140 mmHg in MCAs in both rats and was rescued with TPPU treatment. Endothelial denuded MCAs from TPPU-treated DM rats constricted to 75.15 ± 4.25 % at a perfusion pressure of 140 mmHg and further constricted to 74.66 ± 4.01 % at 180 mmHg, compared to dilation of 155.48 ± 17.35 % and 172.78 ± 13.36 % in DM rats at the same pressures. The percentage of time spent with the novel object was 43.32 ± 8.04% and 83.23 ± 8.70% in DM and TPPU-treated DM rats, versus 75.68 ± 3.33% in non-DM rats. Impaired learning and short and long-term memory function examined with an 8-arm water maze in both DM and AD rats were rescued with TPPU treatment. These results provide the first evidence demonstrating that inhibition of sEH reverses cerebrovascular dysfunction and cognitive impairments in AD/ADRD.

Vascular aging influences hemodynamics, elevating risks for vascular diseases and dementia. We recently demonstrated that knockout (KO) of Dusp5 enhances cerebral and renal hemodynamics and cognitive function. This improvement correlates with elevated pPKC and pERK1/2 levels in the brain and kidneys. Additionally, we observed that Dusp5 KO modulates the passive mechanical properties of cerebral and renal arterioles, associated with increased myogenic tone at low pressure, enhanced distensibility, greater compliance, and reduced stiffness. The present study evaluates the structural and mechanical properties of the middle cerebral artery (MCA) in Dusp5 KO rats. We found that vascular smooth muscle cell layers and the collagen content in the MCA wall are comparable between Dusp5 KO and control rats. The internal elastic lamina in the MCA of Dusp5 KO rats exhibits increased thickness, higher autofluorescence intensity, smaller fenestrae areas, and fewer fenestrations. Despite an enhanced myogenic response and tone of the MCA in Dusp5 KO rats, other passive mechanical properties, such as wall thickness, cross-sectional area, wall-to-lumen ratio, distensibility, incremental elasticity, circumferential wall stress, and elastic modulus, do not significantly differ between strains. These findings suggest that while Dusp5 KO has a limited impact on altering the structural and mechanical properties of MCA, its primary role in ameliorating hemodynamics and cognitive functions is likely attributable to its enzymatic activity on cerebral arterioles. Further research is needed to elucidate the specific enzymatic mechanisms and explore potential clinical applications in the context of vascular aging.

Preeclampsia (PE), new-onset hypertension during pregnancy alongside organ dysfunction, is a leading cause of morbidity and mortality for the mother and fetus.PE women have activated B cells that produce agonistic autoantibodies to the angiotensin II type 1 receptor (AT1-AA).AT1-AA impairs cerebral blood flow (CBF) autoregulation during pregnancy.Although AT1-AA often remains elevated up to 8 years postpartum, AT1-AA's effect on CBF autoregulation postpartum is unknown.This study examined whether elevated AT1-AA during pregnancy impairs CBF autoregulation postpartum and if this was augmented by infusion of AT1-AA postpartum.AT1-AA was infused into 12-week-old timed-pregnant Sprague Dawley rats beginning on gestational day 14.Uterine artery resistance index (UARI) was measured on gestational day 18 as a measure of endothelial dysfunction associated with PE.Dams were allowed to deliver.One group was given a second infusion of AT1-AA (50% perinatal dose mimicking levels observed in postpartum PE women) at 9 weeks postpartum.After postpartum week 10, mean arterial pressure (MAP) was measured in conscious rats and CBF autoregulation was measured by laser Doppler flowmetry.AT1-AA during pregnancy increased UARI (P<0.05).AT1-AA during pregnancy did not affect MAP postpartum but did impair CBF autoregulation postpartum.Infusion of AT1-AA postpartum significantly elevated blood pressure (P<0.01)but did not further impair CBF autoregulation.This study demonstrates that circulating AT1-AA during pregnancy causes impairment of CBF autoregulation well into the postpartum period indicating that elevated AT1-AA leads to long-term cerebrovascular consequences.Targeting AT1-AA may prevent cerebrovascular effects associated with PE during pregnancy and postpartum.

Alzheimer's Disease (AD) and Alzheimer's Disease-Related Dementias (ADRD) are neurodegenerative disorders. Recent studies suggest that cerebral hypoperfusion is an early symptom of AD/ADRD. Dual-specificity protein phosphatase 5 (DUSP5) has been implicated in several pathological conditions, including pulmonary hypertension and cancer, but its role in AD/ADRD remains unclear. The present study builds on our previous findings, demonstrating that inhibition of ERK and PKC leads to a dose-dependent dilation of the middle cerebral artery and penetrating arteriole, with a more pronounced effect in Dusp5 KO rats. Both ERK and PKC inhibitors resulted in a significant reduction of myogenic tone in vessels from Dusp5 KO rats. Dusp5 KO rats exhibited stronger autoregulation of the surface but not deep cortical cerebral blood flow. Inhibition of ERK and PKC significantly enhanced the contractile capacity of vascular smooth muscle cells from both strains. Finally, a significant improvement in learning and memory was observed in Dusp5 KO rats 24 hours after initial training. Our results suggest that altered vascular reactivity in Dusp5 KO rats may involve distinct mechanisms for different vascular beds, and DUSP5 deletion could be a potential therapeutic target for AD/ADRD. Further investigations are necessary to determine the effects of DUSP5 inhibition on capillary stalling, blood-brain barrier permeability, and neurodegeneration in aging and disease models.

Alzheimer’s disease (AD) exerts a tremendous socio-economic burden worldwide. Although reduced cerebral blood flow is an early and persistent symptom that precedes the loss of cognitive function in AD, the underlying molecular and cellular mechanisms remain unclear. The present study investigated whether capillary endothelial inward rectifier potassium 2 (Kir2.1) expression is reduced in TgF344-AD (AD) rats and contributes to neurovascular uncoupling and cognitive deficits in AD. Three- to fourteen-month-old AD rats expressing mutant human APP and PS1 and age-matched wild-type (WT) F344 rats were studied. AD rats exhibited higher amyloid beta (Aβ) expression in the brain as early as 3 months of age and amyloid plaques by 4 months of age. Functional hyperemic responses induced by whisker stimulation were impaired at 4 months of age, which were exacerbated in 6-month- and 14-month-old AD rats. The expression of Kir2.1 protein was significantly lower in the brains of 6-month-old AD versus WT rats, and Kir2.1 coverage was lower in the cerebral microvasculature of AD than in WT rats. Aβ1–42 reduced the Kir2.1 expression in cultured capillary endothelial cells. Cerebral parenchymal arterioles with attached capillaries exhibited a reduced vasodilator in response to 10 mM K + applied to capillaries, and constricted less following administration of a Kir2.1 channel blocker, compared to WT vessels. These results indicate that capillary endothelial Kir2.1 expression is reduced and contributes to impaired functional hyperemia in AD rats at early ages, perhaps secondary to elevated Aβ expression.

Dual-specificity protein phosphatase 5 (DUSP5) is a multifunctional phosphatase that modulates signaling cascades by catalyzing the dephosphorylation of both threonine and tyrosine residues. We recently reported that KO of Dusp5 enhances cerebral and renal hemodynamics and cognitive function. This effect is associated with increased pPKC and pERK1/2 levels in arteries and arterioles of the brain and kidneys. Further, we found that KO of Dusp5 contributes to the regulation of arteriolar passive mechanical properties with higher myogenic tones, better distensibility, greater compliance, and less stiffness. The present study focuses on the structural and mechanical properties of rat middle cerebral artery (MCA) to evaluate whether it contributes to enhanced vascular and cognitive function in Dusp5 KO rats. Vascular smooth muscle cell layer numbers and collagen content in the wall of the MCA are similar in Dusp5 KO and control rats. While external elastic lamina was absent in the MCA in both strains, internal elastic lamina was thicker in the MCA of Dusp5 KO vs. control rats (2.33 ± 0.02 vs. 1.85 ± 0.03 μm) and associated with higher autofluorescence intensity (953.76 ± 10.03 vs. 737.31 ± 64.88 au), smaller fenestrae areas (51.31 ± 3.62 vs. 70.46 ± 2.24), and fewer number of fenestrations (138.19 ± 8.86 vs. 374.73 ± 17.02 μm 2 ). Even though the myogenic tone is enhanced in Dusp5 KO vs. control rats (52.37 ± 1.65 vs. 44.87 ± 2.00%), other passive mechanical properties (wall thickness, cross-sectional area, wall-to-lumen ratio, wall tension, distensibility, incremental distensibility, circumferential wall strain, circumferential wall stress, and elastin modulus) of the MCA of Dusp5 KO rats do not exhibit significant changes. The findings suggest that while Dusp5 KO has a limited impact on changing the structural and mechanical properties of the MCA, its role in enhancing hemodynamics and cognitive function is primarily attributed to its enzymatic function.

Preeclampsia (PE), new-onset hypertension during pregnancy, is the leading cause of morbidity and mortality for the mother and the fetus. A leading cause of mortality during PE is cerebrovascular disease. Women with PE have activated B cells producing agonistic autoantibodies to the angiotensin II type 1 receptor (AT1-AA) which remain elevated in maternal circulation up to 8 years postpartum (PP). AT1-AA contributes to endothelial dysfunction in the kidney, placenta, and brain during pregnancy. We believe it plays a role in the increased incidents of cardiovascular and cerebrovascular disorders in PP PE women. We have shown at AT1-AA infusion into pregnant rats results in elevated mean arterial pressure (MAP), impaired cerebral blood flow (CBF) autoregulation, and reduced pup weight. However, the effects of perinatal AT1-AA and sustained AT1-AA PP on MAP and CBF hemodynamics in the PP period is unknown. We hypothesize that AT1-AA induced hypertension during pregnancy will cause maternal hypertension and impaired maternal CBF PP.To test this hypothesis, AT1-AA (1:40) was infused into pregnant Sprague Dawley rats on gestational day (GD) 14 via a mini-osmotic pump. On GD18, uterine artery resistance index (UARI) was measured by Doppler ultrasound. Dams were allowed to deliver and pup weights were recorded within 12 hours. PP dams were aged to 9 weeks after birth and one group of AT1-AA PP dams received a second infusion of AT1-AA (1:80), to mimic the levels of AT1-AA seen in PP PE women. At 10 weeks PP, maternal MAP was measured and at 12 weeks PP, CBF autoregulation was measured by laser Doppler flowmeter.At GD 18, UARI was elevated in AT1-AA infused rats (0.610±0.080, n=7, P<0.05) compared to NP rats (0.475±0.070, n=5). At PP week 10, MAP was elevated in AT1-AA + AT1-AA (1:80) PP (129±1 mmHg, n=5, P<0.01) compared to NP (120±2 mmHg, n=5) and AT1-AA (120±1 mmHg, n=6). CBF increased by 34±4% (P<0.05, n=8) in rats with AT1-AA during pregnancy and by 39±4% (P<0.05, n=8) in rats with AT1-AA during pregnancy and (1:80) PP in response to increased MAP from 100 to 140 mmHg, versus only 4±3% (n=8) in normal pregnant controls.In conclusion, AT1-AA during pregnancy causes sustained changes in CBF hemodynamics PP. Increased AT1-AA PP also causes elevated blood pressures in association with impaired CBF. These data indicate that perinatal and PP AT1-AA cause long-term cardiovascular and cerebrovascular consequences for PE women. Targeting AT1-AA may prevent cerebral vascular and neurological defects in PE, and alleviate some of the long-term impact postpartum. This study was supported in part by NIH grants HD067541 (BL), H13865 (RJR).and P20GM121334 (BL, LA) 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.

Alzheimer's disease (AD) is a global healthcare crisis. The TgF344-AD rat is an AD model exhibiting age-dependent AD pathological hallmarks. We confirmed that AD rats developed cognitive deficits at 6 months without alteration of any other major biophysical parameters. We longitudinally characterized cerebral hemodynamics in AD rats at 3, 4, 6, and 14 months. The myogenic responses of the cerebral arteries and arterioles were impaired at 4 months of age in the AD rats. Consistent with the ex vivo results, the AD rat exhibited poor autoregulation of surface and deep cortical cerebral blood flow 2 months preceding cognitive decline. The dysfunction of cerebral hemodynamics in AD is exacerbated with age associated with reduced cerebral perfusion. Further, abolished cell contractility contributes to cerebral hemodynamics imbalance in AD. This may be attributed to enhanced ROS production, reduced mitochondrial respiration and ATP production, and disrupted actin cytoskeleton in cerebral vascular contractile cells.

Mutations in CYP4F2 (rs2108622) and CYP4A11 (rs1126742) that inhibit the production of 20-HETE have been linked to hypertension in human genetic studies. We confirmed that these same variants are associated with hypertension and cognitive dysfunction in 4,286 elderly subjects in the Atherosclerosis Risk in Communities Neurocognitive Study . These studies establish that mutations in CYP enzymes that reduce 20-HETE promote hypertension, but the mechanisms remain controversial since 20-HETE has both pro- and antihypertensive actions. To address this question, we identified a homologous genetic deficiency in the formation of 20-HETE in Dahl S (SS) rats and created SS.5 BN consomic and CYP4A transgenic SS rats to restore CYP4A expression and 20-HETE production, and CYP4A2 and CYP4A3 KO rats on the rescued SS.5 BN background. Mean arterial pressure (MAP), renal and cerebral blood flow, proteinuria, and renal injury were compared in SS versus SS.5 BN and CYP4A transgenic SS rats and in SS.5 BN versus CYP4A2 and CYP4A3 KO rats. MAP increased from 117±2 to 158±5 mmHg (n=34) in SS rats fed a high salt (HS) diet for 3 weeks. Proteinuria rose from 50±4 to 403±30 mg/day. MAP increased less, from 108 + 5 to 133 + 5 mmHg (n=7) in CYP4A1 transgenic SS rats and from 109 + 2 to 132 + 2 mmHg (n=23) in SS.5 BN rats. Proteinuria (141±15 and 169±11 mg/day), glomerular injury, and renal fibrosis were all significantly reduced in the CYP4A transgenic and SS.5 BN rats compared to SS rats. KO of CYP4A2 had no effect on MAP (134 + 2 mmHg, n=23) or proteinuria (248 + 23 mg/day) relative to SS.5 BN rats fed an HS diet for 3 weeks. In contrast, MAP and proteinuria were elevated to 148 + 3 mmHg and 350 + 23 mg/day in CYP4A3 KO rats (n=23). The myogenic response of renal and cerebral arteries and autoregulation of RBF and CBF were impaired in SS and CYP4A3 KO rats but were intact in CYP4A transgenic SS rats, SS.5 BN and CYP4A2 KO rats. These findings indicate that a deficiency in the formation of 20-HETE that impairs the myogenic response of renal and cerebral arteries, autoregulation of RBF and CBF, and increases glomerular capillary pressure, promotes the development of hypertension, proteinuria, and renal injury in genetically susceptible individuals and SS rats.

Alzheimer’s Disease (AD) is an emerging global health care crisis. However, underlying mechanisms are not understood well enough to translate to precision medicine. There is increasing evidence suggesting that AD is associated with brain hypoperfusion. However, it is unclear whether amyloid‐beta (Aβ) accumulation is a cause or consequence of AD, and how it contributes to cerebral hypoperfusion. The present study examined if Aβ accumulation induces cerebral hypoperfusion in AD by affecting cerebral vascular function via both anterograde (arteriole‐to‐capillary) and retrograde (capillary‐to‐arteriole) pathways in the TgF344‐AD rat model of Alzheimer's disease. We first confirmed that AD rats displayed hippocampal‐based cognitive dysfunction at 6 months of age using an eight‐arm water maze. We then found that AD rats exhibited impaired myogenic response (MR) of middle cerebral arteries (MCAs) and penetrating and parenchymal arterioles (PAs) two months earlier than the onset of cognitive deficits using a Living System pressure myograph. AD rats displayed poor surface and deep cortical cerebral blood flow (CBF) autoregulation recorded by laser Doppler flowmetry, and reduced functional hyperemic response induced by whisker stimulation. Moreover, cell contractile capabilities, detected by collagen gel based‐cell contraction kit, were reduced in Aβ‐treated cerebral VSMCs isolated from F344 rats, similar as seen in VSMCs isolated from AD rats. Furthermore, we found that the productions of reactive oxygen species (ROS) and mitochondrial superoxide in cerebral VSMCs isolated from AD rats were elevated using DHE staining and MitoSOX staining. Moreover, AD cells exhibited reduced mitochondrial respiration and ATP production detected by the Seahorse Cell Mito Stress Test kit. AD cerebral VSMCs also exhibited disrupted actin cytoskeleton and contractile units utilizing immunohistochemistry. Oxidative stress, mitochondrial dysfunction, and actin cytoskeleton disorganization are all factors that are associated with the reduced contractile capabilities of cerebral VSMCs mediated MR and CBF autoregulation. In other studies, we found that capillary endothelial cell‐derived inward rectifier potassium (Kir2.1) activity, which is responsible for retrograde CBF regulation, was reduced in the brain of AD rats using Western blot. PAs with capillaries isolated from AD rats dilated to a lesser degree than WT rats in response to moderately elevated extracellular K+ (10 mM) applied to capillaries. Inhibition of Kir2.1 channels with ML133 diminished the vasodilatory response to a greater extent in WT rats. These findings indicate that Aβ accumulation is associated with cerebral hypoperfusion in AD by affecting cerebral vascular function via both anterograde and retrograde pathways and provide novel insight into the vascular contribution to AD.

Diabetes, hypertension, and aging are major contributors to cardiovascular and chronic kidney disease (CKD). Sodium/glucose cotransporter 2 (SGLT2) inhibitors have become a preferred treatment for type II diabetic patients since they have cardiorenal protective effects. However, most elderly diabetic patients also have hypertension, and the effects of SGLT2 inhibitors have not been studied in hypertensive diabetic patients or animal models. The present study examined if controlling hyperglycemia with empagliflozin, or given in combination with lisinopril, slows the progression of renal injury in hypertensive diabetic rats. Studies were performed using hypertensive streptozotocin-induced type 1 diabetic Dahl salt-sensitive (STZ-SS) rats and in deoxycorticosterone-salt hypertensive type 2 diabetic nephropathy (T2DN) rats. Administration of empagliflozin alone or in combination with lisinopril reduced blood glucose, proteinuria, glomerular injury, and renal fibrosis in STZ-SS rats without altering renal blood flow (RBF) or glomerular filtration rate (GFR). Blood pressure and renal hypertrophy were also reduced in rats treated with empagliflozin and lisinopril. Administration of empagliflozin alone or in combination with lisinopril lowered blood glucose, glomerulosclerosis, and renal fibrosis but had no effect on blood pressure, kidney weight, or proteinuria in hypertensive T2DN rats. RBF was not altered in any of the treatment groups, and GFR was elevated in empagliflozin-treated hypertensive T2DN rats. These results indicate that empagliflozin is highly effective in controlling blood glucose levels and slows the progression of renal injury in both hypertensive type 1 and type 2 diabetic rats, especially when given in combination with lisinopril to lower blood pressure.

Although the causes of cognitive impairment are multifactorial, emerging evidence indicates that cerebrovascular dysfunction plays an essential role in dementia. One of the most critical aspects of cerebrovascular dysfunction is autoregulation of cerebral blood flow (CBF), mainly mediated by the myogenic response, which is often impaired in dementia individuals with comorbidities, such as diabetes and hypertension. However, many unsolved questions remain. How do cerebrovascular networks coordinately modulate CBF autoregulation in health and disease? Does poor CBF autoregulation have an impact on cognitive impairment, and what are the underlying mechanisms? This review summarizes the cerebral vascular structure and myogenic (a three-phase model), metabolic (O2, CO2, adenosine, and H+), and endothelial (shear stress) factors in the regulation of CBF; and the consequences of CBF dysautoregulation. Other factors contributing to cerebrovascular dysfunction, such as impaired functional hyperemia and capillary abnormalities, are included as well. Moreover, this review highlights recent studies from our lab in terms of novel mechanisms involved in CBF autoregulation and addresses a hypothesis that there is a three-line of defense for CBF autoregulation in the cerebral vasculature.

Diabetes mellitus (DM) is a leading risk factor for age-related dementia, but the mechanisms involved are not well understood. We previously discovered that hyperglycemia induced impaired myogenic response (MR) and cerebral blood flow (CBF) autoregulation in 18-mo-old DM rats associated with blood-brain barrier (BBB) leakage, impaired neurovascular coupling, and cognitive impairment. In the present study, we examined whether reducing plasma glucose with a sodium-glucose cotransporter-2 inhibitor (SGLT2i) luseogliflozin can ameliorate cerebral vascular and cognitive function in diabetic rats. Plasma glucose and HbA1c levels of 18-mo-old DM rats were reduced, and blood pressure was not altered after treatment with luseogliflozin. SGLT2i treatment restored the impaired MR of middle cerebral arteries (MCAs) and parenchymal arterioles and surface and deep cortical CBF autoregulation in DM rats. Luseogliflozin treatment also rescued neurovascular uncoupling, reduced BBB leakage and cognitive deficits in DM rats. However, SGLT2i did not have direct constrictive effects on vascular smooth muscle cells and MCAs isolated from normal rats, although it decreased reactive oxygen species production in cerebral vessels of DM rats. These results provide evidence that normalization of hyperglycemia with an SGLT2i can reverse cerebrovascular dysfunction and cognitive impairments in rats with long-standing hyperglycemia, possibly by ameliorating oxidative stress-caused vascular damage. NEW & NOTEWORTHY This study demonstrates that luseogliflozin, a sodium-glucose cotransporter-2 inhibitor, improved CBF autoregulation in association with reduced vascular oxidative stress and AGEs production in the cerebrovasculature of 18-mo-old DM rats. SGLT2i also prevented BBB leakage, impaired functional hyperemia, neurodegeneration, and cognitive impairment seen in DM rats. Luseogliflozin did not have direct constrictive effects on VSMCs and MCAs isolated from normal rats. These results provide evidence that normalization of hyperglycemia with an SGLT2i can reverse cerebrovascular dysfunction and cognitive impairments in rats with long-standing hyperglycemia, possibly by ameliorating oxidative stress-caused vascular damage.