The O-GlcNAc dichotomy: when does adaptation become pathological?

O-Linked attachment of β-N-acetylglucosamine (O-GlcNAc) on serine and threonine residues of nuclear, cytoplasmic, and mitochondrial proteins is a highly dynamic and ubiquitous post-translational modification that impacts the function, activity, subcellular localization, and stability of target proteins. Physiologically, acute O-GlcNAcylation serves primarily to modulate cellular signaling and transcription regulatory pathways in response to nutrients and stress. To date, thousands of proteins have been revealed to be O-GlcNAcylated and this number continues to grow as the technology for the detection of O-GlcNAc improves. The attachment of a single O-GlcNAc is catalyzed by the enzyme O-GlcNAc transferase (OGT), and their removal is catalyzed by O-GlcNAcase (OGA). O-GlcNAcylation is regulated by the metabolism of glucose via the hexosamine biosynthesis pathway, and the metabolic abnormalities associated with pathophysiological conditions are all associated with increased flux through this pathway and elevate O-GlcNAc levels. While chronic O-GlcNAcylation is well associated with cardiovascular dysfunction, only until recently, and with genetically modified animals, has O-GlcNAcylation as a contributing mechanism of cardiovascular disease emerged. This review will address and critically evaluate the current literature on the role of O-GlcNAcylation in vascular physiology, with a view that this pathway can offer novel targets for the treatment and prevention of cardiovascular diseases.

Endothelial cells differentiated from patient dermal fibroblast-derived induced pluripotent stem cells resemble vascular malformations of port-wine birthmark

Lesional induced pluripotent stem cell-derived endothelial cells can resemble pathological vascular phenotypes of port-wine birthmark (PWB). Our data demonstrate that multiple pathways, including Hippo and Wnt, NFκB, TNF, MAPK and cholesterol metabolism, are dysregulated. These data suggest new therapeutics can be developed to target such dysregulated pathways in the treatment of PWB.

Specialized Pro-resolving Mediator Improves Vascular Relaxation via Formyl Peptide Receptor-2

BACKGROUND

The resolution of inflammation is an active phenomenon important for switching off inflammatory processes once the harmful stimuli are removed and facilitate the return to homeostasis. Specialized pro-resolving mediators (SPMs), such as lipoxin A4, resolvin D1, and resolvin E1, derived from ω-3 or ω-6 polyunsaturated fatty acids, are crucial for the resolution of inflammation. We hypothesized that SPMs are decreased in hypertension which contributes to the acetylcholine-induced contraction in resistance arteries, which are well known to be mediated by leukotrienes and prostaglandins. Moreover, treatment with SPMs will decrease this contraction via formyl peptide receptor-2 (FPR-2) in resistance arteries from spontaneously hypertensive rats (SHR).

METHODS AND RESULTS

We performed a comprehensive eicosanoid lipid panel analysis, and our data showed for the first time that precursors of SPMs are decreased in SHR, limiting the production of SPMs and resolution of inflammation in vivo. This phenomenon was associated with an increase in lipid peroxidation in resistance arteries. Although SPMs did not abolish acetylcholine-induced contraction, these lipid mediators improved endothelial function in arteries from SHR via FPR-2 activation at nanomolar concentrations. SPMs also buffered TNF-α-induced reactive oxygen species generation in endothelial cells from C57Bl/6 mice.

CONCLUSIONS

We suggest that FPR-2 and SPMs could be revealed as a new target or therapeutic agent to improve vascular function in arteries from hypertensive rats.

Supporting materials: Endothelial cells differentiated from patient dermal fibroblast-derived induced pluripotent stem cells resemble vascular malformations of Port Wine Birthmark

Background

Port wine birthmark (PWB) is a congenital vascular malformation resulting from developmentally defective endothelial cells (ECs). Developing clinically relevant disease models for PWB studies is currently an unmet need.

Objective

Our study aims to generate PWB-derived induced pluripotent stem cells (iPSCs) and iPSC-derived ECs that preserve disease-related phenotypes.

Methods

PWB iPSCs were generated by reprogramming lesional dermal fibroblasts and differentiated into ECs. RNA-seq was performed to identify differentially expressed genes (DEGs) and enriched pathways. The functional phenotypes of iPSC-derived ECs were characterized by capillary-like structure (CLS) formation in vitro and Geltrex plug-in assay in vivo .

Results

Human PWB and control iPSC lines were generated through reprogramming of dermal fibroblasts by introducing the "Yamanaka factors" (Oct3/4, Sox2, Klf4, c-Myc) into them; the iPSCs were successfully differentiated into ECs. These iPSCs and their derived ECs were validated by expression of a series of stem cell and EC biomarkers, respectively. PWB iPSC-derived ECs showed impaired CLS in vitro with larger perimeters and thicker branches as compared to control iPSC-derived ECs. In the plug-in assay, perfused human vasculature formed by PWB iPSC- derived ECs showed bigger perimeters and greater densities than those formed by control iPSC- derived ECs in severe combined immune deficient (SCID) mice. The transcriptome analysis showed that dysregulated pathways of stem cell differentiation, Hippo, Wnt, and focal adhesion persisted through differentiation of PWB iPSCs to ECs. Functional enrichment analysis showed that Hippo and Wnt pathway-related PWB DEGs are enriched for vasculature development, tube morphology, endothelium development, and EC differentiation. Further, members of the zinc finger (ZNF) gene family were overrepresented among the DEGs in PWB iPSCs. ZNF DEGs confer significant functions in transcriptional regulation, chromatin remodeling, protein ubiquitination, and retinoic acid receptor signaling. Furthermore, NF-kappa B, TNF, MAPK, and cholesterol metabolism pathways were dysregulated in PWB ECs as readouts of impaired differentiation.

Conclusions

PWB iPSC-derived ECs render a novel and clinically-relevant disease model by retaining pathological phenotypes. Our data demonstrate multiple pathways, such as Hippo and Wnt, NF-kappa B, TNF, MAPK, and cholesterol metabolism, are dysregulated, which may contribute to the development of differentiation-defective ECs in PWB.

Bulleted statements

What is already known about this topic?: Port Wine Birthmark (PWB) is a congenital vascular malformation with an incidence rate of 0.1 - 0.3 % per live births.PWB results from developmental defects in the dermal vasculature; PWB endothelial cells (ECs) have differentiational impairments.Pulse dye laser (PDL) is currently the preferred treatment for PWB; unfortunately, the efficacy of PDL treatment of PWB has not improved over the past three decades.What does this study add?: Induced pluripotent stem cells (iPSCs) were generated from PWB skin fibroblasts and differentiated into ECs.PWB ECs recapitulated their pathological phenotypes such as forming enlarged blood vessels in vitro and in vivo.Hippo and Wnt pathways were dysregulated in PWB iPSCs and ECs.Zinc-finger family genes were overrepresented among the differentially expressed genes in PWB iPSCs.Dysregulated NF-kappa B, TNF, MAPK, and cholesterol metabolism pathways were enriched in PWB ECs.What is the translational message?: Targeting Hippo and Wnt pathways and Zinc-finger family genes could restore the physiological differentiation of ECs.Targeting NF-kappa B, TNF, MAPK, and cholesterol metabolism pathways could mitigate the pathological progression of PWB.These mechanisms may lead to the development of paradigm-shifting therapeutic interventions for PWB.

The janus face of ketone bodies in hypertension

Hypertension is the most important risk factor for the development of terminal cardiovascular diseases, such as heart failure, chronic kidney disease, and atherosclerosis. Lifestyle interventions to lower blood pressure are generally desirable prior to initiating pharmaceutical drug treatments, which may have undesirable side effects. Ketogenic interventions are popular but the scientific literature supporting their efficacy is specific to certain interventions and outcomes in animal models and patient populations. For example, although caloric restriction has its own inherent difficulties (e.g. it requires high levels of motivation and adherence is difficult), it has unequivocally been associated with lowering blood pressure in hypertensive patients. On the other hand, the antihypertensive efficacy of ketogenic diets is inconclusive, and this is surprising, given that these diets have been largely helpful in mitigating metabolic syndrome and promoting longevity. It is possible that side effects associated with ketogenic diets (e.g. dyslipidemia) aggravate the hypertensive phenotype. However, given the recent data from our group, and others, reporting that the most abundant ketone body, β-hydroxybutyrate, can have positive effects on endothelial and vascular health, there is hope that ketone bodies can be harnessed as a therapeutic strategy to combat hypertension. Therefore, we conclude this review with a summary of the type and efficacy of ketone supplements. We propose that ketone supplements warrant investigation as low-dose antihypertensive therapy that decreases total peripheral resistance with minimal adverse side effects.

Abstract P129: Increasing In SHR Aortic Distensibility During The Onset Of Hypertension: The Role Of Appropriate Normalization For Stress-Strain Measurements

The gold standard of arterial stiffness measurements in isolated aorta is the stress-strain (SS) relationship. Stress and strain are second-order tensors measured as newtons over the oriented area and change in length over the original length, respectfully. Wall thickness and artery diameter are variables that can change the SS curve and should be normalized to the dimensions of the subject. However, previous studies have used standard structural dimensions to calculate SS for different conditions, which may lead to conflicting data. Therefore, we hypothesized that aorta from SHR, during the onset of hypertension, will present with an increase in SS, based on their unique structural dimensions. To test this hypothesis, thoracic aorta from male Wistar (W) (3-month-old; 284±9 g) and SHR (S) (3-month-old; 458 ± 7 g) rats were cut in 2 mm segments and mounted on Tissue Puller to test SS. The rings were normalized individually (Self parameters; W and SHR-S) or using parameters from control (SHR-W). SHR rings normalized by their own parameters reduced the elastic modulus (W: 2.1 ± 0.3 vs SHR-S: 1.6 ± 0.2; p = 0.07). When the same SHR rings were normalized by W parameters, the elastic modulus increased (W: 2.1 ± 0.326 vs SHR-W: 3.3 ± 0.4; p = 0.01). Overall, these data show that the absence of individualized normalization can skew stress-strain calculations of elastic modulus. In SHR, we suggested that during the development of hypertension, there are compensatory mechanisms increasing distensibility. However, after onset, this phenomenon evolves to an increase in stiffness. These data may be absent in the literature due to the improper normalization application.

Abstract 045: Soluble Protein Oligomers Induce Endoplasmic Reticulum Stress In Endothelial Cells And Lead To Decreased Calcium Levels In The Endoplasmic Reticulum

Soluble protein oligomers (SPOs) have powerful vascular effects suggesting a link between Alzheimer’s disease (AD) and cardiovascular diseases (CVD). SPOs accumulation induces endoplasmic reticulum (ER) stress hence cell death in several CVDs. Our previous data showed that in mesenteric resistance arteries (MRA), SPOs induce ER stress leading to pathologically exacerbated endothelium-dependent vasodilation. We therefore hypothesized that the SPOs will cause ER calcium dysregulation in endothelial cells isolated from MRA. To confirm the presence of ER stress and SPO subcellular localization, endothelial cells were treated with SPOs (0.1 υM) in the presence and absence of the ER stress inhibitor 4-PBA (2 mM) and vehicle (F-12 media). Immunostaining with KDEL antibody specific for ER resident chaperones Grp78/94 was performed for 19 hr prior to visualization. Endothelial cells treated with SPOs showed increased anti-KDEL fluorescence (AU: Vehicle: 4.74 ± 0.3 vs. SPO: 15.74 ± 1.7; n= 3; p= 0.018, one-way ANOVA). This is consistent with the increased Grp78/94 protein concentration during ER stress. Interestingly, 4-PBA treated cells reduced anti-KDEL fluorescence to the same level as the control (AU: Vehicle: 4.74 ± 0.3 vs. 4-PBA: 8.74 ± 2.9; n= 3; p= 0.39; one-way ANOVA) suggesting that SPOs bind to the ER-anchored proteins during ER stress. Additionally, changes in Ca 2+ concentrations have been implicated as a mediator between ER stress and SPOs. Calcium levels in endothelial cells was investigated by transfecting a plasmid expressing a Ca 2+ indicator pCMV G-CEPIA1 er for 72 hr . Cells were treated with vehicle or SPOs in the presence or absence of 4-PBA (45 min) prior to fluorescence imaging. Cells treated with SPOs+ACh had a decreased fluorescence in the ER from the basal Ca 2+ levels (%Δ Ff-F0/F0; SPO: 53% reduction vs. vehicle), but treatment with 4-PBA+ACh did not improve this response (%Δ F f -F 0 /F 0 ; SPO+4-PBA: 48.18% reduction vs. vehicle n=2). This reveals that SPOs induce ER stress and depletion of ER calcium. However, ER stress inhibitor did not improve Ca 2+ levels. These data suggest that ER stress, is the mechanism by which SPO’s exacerbate vasodilation in the mesenteric resistance artery endothelial cells regardless of changes in Ca 2+ levels.

Abstract P058: Endothelial Dysfunction And Increased Contractility In Resistance Arteries Occurs Prior To Onset Of Hypertension In Schlager (BPH/2J) Mice

Genetically hypertensive mice (BPH/2J) were developed by Gunther Schlager more than 45 years ago, and these mice have neurogenic hypertension. Seven-weeks-old male BPH/2J mice present elevations in systolic blood pressure (SBP), and its highest value is observed in 20-weeks-old mice. Several studies have showed vascular dysfunction in these mice, but no one has demonstrated whether resistance artery dysfunction is present prior to the elevation in SBP. We hypothesized that hypercontractility and endothelial dysfunction is associated with the cause of hypertension in BPH/2J mice. We evaluated mesenteric resistance arteries (MRA) function from 5-weeks-old male BPH/2J and 9-weeks-old normotensive mice (BPN/3J), prior to the elevation of SBP. Intact-endothelium MRA were mounted in wire myographs. KCl-induced contraction (120 mM), or phenylephrine (PE) and acetylcholine (ACh) cummulative concentration curves were performed. Non-linear curve regressions were performed and maximum response (Rmax) was analyzed by Student t test ( p <0.05). BPH/2J mice presented increased KCl contraction (BPH/2J: 6.47±0.51 vs. BPN/3J: 2.95±0.13 mN/mm, n=4, p <0.05) and PE-induced contraction (Rmax: BPH/2J: 6.25±0.54 vs. BPN/3J: 4.23±0.28 mN/mm, n=4, p <0.05). ACh-dependent relaxation was decreased in BPH/2J (Rmax: BPH/2J: 76±5, n=4 vs. BPN/3J: 93±2%, n=3, p <0.05). ACh promoted contraction at high concentrations (>0.3 μM) in BPH/2J mice but not BPN/3J mice (Fig.1), suggesting increased cyclooxygenase-induced inflammation. These data reveal that vascular dysfunction contributes to the cause of hypertension in Schlager mice.

Abstract P130: Specialized Pro-resolving Mediator, Lipoxin A4, Attenuates Age-dependent Vascular Damage

Chronic, low-grade inflammation that develops with advanced age is known as inflammaging. This phenomenon is associated with large artery stiffness in age-dependent hypertension. Specialized pro-resolving mediators (SPMs), including Lipoxin A4 (LXA4) and Resolvin D1 (RD1), are derived from essential fatty acids, and they act as immunoresolvents to reduce inflammation and increase the clearance of pathogens and dying cells. However, LXA4, but not RD1, acts on formyl peptide receptor 2, which is known to modulate actin filaments and resolve inflammation. Therefore, we hypothesized that Specialized pro-resolving mediators, would restore mechanical stress and distensibility in aorta from older rats. To test this hypothesis, thoracic aortas from male Wistar rats (3 and 6 months old) were cut into 2 mm rings and incubated in the presence or absence of RD1 or LXA4; both 10 nM for 24 hours. Stress-strain curves were calculated via Tissue Puller (560TP-II, DMT). The aortic rings from 6-month-old rats presented with increased stress when compared to aortas of the 3-month-old (Maximal stress: 2749 ± 190 mN/mm 2 vs 4207 ± 242 mN/mm 2 , respectively; p=0.0015). Interestingly, LXA4 reduced stress in aorta from 6-month-old rats (Maximal stress: 2514 ± 552 mN/mm 2 , p=0.0282). No changes were observed in aorta from 3-month-old rats after LXA4 treatment. Resolvin D1 did not change vascular mechanics in aorta from 3- or 6-month-old rats. Overall, these data suggest that even modest advances in age are related with changes in vascular mechanics of large arteries and LXA4 via FPR2 can decrease inflammaging-related vascular stiffness.

Abstract P135: Specialized Pro-resolving Molecular Pathway Is Impaired In Resistance Arteries From Hypertensive Rats

Specialized pro-resolving mediators (SPMs), derived from essential fatty acids, are known to playa major role in the immune system, as immunoresolvents. SPMs reduce acute inflammatoryresponses and leads to the clearance of pathogens and dying cells. Although we have demonstratedthat lipoxin A4, biosynthesized from the 5-lipoxygenase (LOX-5), improved endothelium-dependent relaxation in resistance arteries from SHR, it is unknown if (1) SPMs molecularpathways are present in resistance arteries independent of immune system activation, and (2)whether this pathway is dysfunctional in SHR. We hypothesized that the synthesis and downstreamsignaling of LOX-5-derived SPMs are impaired in resistance arteries from SHR. Mesentericresistance arteries (MRA) from male SHR (14-weeks old, n=5) and Wistar Kyoto (WKY) (14-weeks old, n=4) were collected to assess protein expression using Western blotting analysis. SHR`sMRA showed an increase in COX-2 expression (400%) when compared to WKY (p<0.05),demonstrating an inflammatory state. However, there was a reduction in the total LOX-5expression (30%) (Fig.1). Interestingly, an 65% increase in phosphorylation of 5-LOX at Ser 271was observed in MRA from SHR (Fig. 1) Ser 271 is responsible for the pro-inflammatory effectsof LOX-5, leading to a reduction of lipoxin A4, but an increase in the synthesis of leukotrienes.Supporting our previous data, we observed that formyl peptide receptor, a receptor that recognizesSPMs, was 30% decreased in arteries from in SHR. Together, these data show that vascular tissuepresents with the “machinery” to synthesize SPMs, and the resolution of inflammation“machinery” is impaired in hypertension.

Low-dose 1,3-butanediol reverses age-associated vascular dysfunction independent of ketone body β-hydroxybutyrate

With an aging global population, identifying novel therapeutics are necessary to increase longevity and decrease the deterioration of essential end organs such as the vasculature. Secondary alcohol, 1,3-butanediol (1,3-BD), is commonly administered to stimulate the biosynthesis of the most abundant ketone body β-hydroxybutyrate (βHB), in lieu of nutrient deprivation. However, suprapharmacological concentrations of 1,3-BD are necessary to significantly increase systemic βHB, and 1,3-BD per se can cause vasodilation at nanomolar concentrations. Therefore, we hypothesized that 1,3-BD could be a novel antiaging therapeutic, independent of βHB biosynthesis. To test this hypothesis, we administered a low-dose (5%) 1,3-BD to young and old Wistar-Kyoto (WKY) rats via drinking water for 4 wk and measured indices of vascular function and metabolism posttreatment. We observed that low-dose 1,3-BD was sufficient to reverse age-associated endothelial-dependent and -independent dysfunction, and this was not associated with increased βHB bioavailability. Further analysis of the direct vasodilator mechanisms of 1,3-BD revealed that it is predominantly an endothelium-dependent vasodilator through activation of potassium channels and nitric oxide synthase. In summary, we report that 1,3-BD, at a concentration that does not stimulate βHB biosynthesis, could be a nutraceutical that can reverse the age-associated decline in vascular function. These results emphasize that 1,3-BD has multiple, concentration-dependent mechanisms of action. Therefore, we suggest alternative approaches to study the physiological and cardiovascular effects of βHB.NEW & NOTEWORTHY 1,3-Butanediol (1,3-BD) is often administered to stimulate the biosynthesis of the most abundant ketone body, β-hydroxybutyrate (βHB), and its purported salubrious effects. Here, we report that a low dose of 1,3-BD (5%) is sufficient to reverse age-associated vascular dysfunction, independent of βHB. Therefore, low-dose 1,3-BD could be a novel therapeutic to increase blood flow and improve the quality of life in the elderly.

Ketone body β-hydroxybutyrate is an autophagy-dependent vasodilator

Autophagy has long been associated with longevity, and it is well established that autophagy reverts and prevents vascular deterioration associated with aging and cardiovascular diseases. Currently, our understanding of how autophagy benefits the vasculature is centered on the premise that reduced autophagy leads to the accumulation of cellular debris, resulting in inflammation and oxidative stress, which are then reversed by reconstitution or upregulation of autophagic activity. Evolutionarily, autophagy also functions to mobilize endogenous nutrients in response to starvation. Therefore, we hypothesized that the biosynthesis of the most physiologically abundant ketone body, β-hydroxybutyrate (βHB), would be autophagy dependent and exert vasodilatory effects via its canonical receptor, Gpr109a. To the best of our knowledge, we have revealed for the first time that the biosynthesis of βHB can be impaired by preventing autophagy. Subsequently, βHB caused potent vasodilation via potassium channels but not Gpr109a. Finally, we observed that chronic consumption of a high-salt diet negatively regulates both βHB biosynthesis and hepatic autophagy and that reconstitution of βHB bioavailability prevents high-salt diet–induced endothelial dysfunction. In summary, this work offers an alternative mechanism to the antiinflammatory and antioxidative stress hypothesis of autophagy-dependent vasculoprotection. Furthermore, it reveals a direct mechanism by which ketogenic interventions (e.g., intermittent fasting) improve vascular health.

Opioids Cause Sex-Specific Vascular Changes via Cofilin-Extracellular Signal-Regulated Kinase Signaling: Female Mice Present Higher Risk of Developing Morphine-Induced Vascular Dysfunction than Male Mice

Recent studies have shown that chronic use of prescription or illicit opioids leads to an increased risk of cardiovascular events and pulmonary arterial hypertension. Indices of vascular age and arterial stiffness are also shown to be increased in opioid-dependent patients, with the effects being more marked in women. There are currently no studies investigating sex-specific vascular dysfunction in opioid use, and the mechanisms leading to opioid-induced vascular damage remain unknown. We hypothesized that exposure to exogenous opioids causes sex-specific vascular remodeling that will be more pronounced in female. Acknowledging the emerging roles of cofilins and extracellular signal-regulated kinases (ERKs) in mediating actin dynamics, we investigated the effects of morphine on these molecules. Twenty-four hour exposure to morphine increased inactivated cofilin and activated ERKs in resistance arteries from female mice, which may promote stress fiber over-assembly. We also performed continuous intraluminal infusion of morphine in pressurized resistance arteries from male and female mice using culture pressure myographs. We observed that morphine reduced the vascular diameter in resistance arteries from female, but not male mice. These results have significant implications for the previously unexplored role of exogenous opioids as a modifiable cardiovascular risk factor, especially in women.

Abstract MP59: Soluble Protein Oligomers Induce Endoplasmic Reticulum Stress In Mesenteric Resistance Arteries From Male And Female Mice

Amyloid β proteins, including toxic soluble oligomers (SPOs) are not only found in the brain duringAlzheimer’s, but also in the peripheral vascular system. The precise mechanism linking increasedcirculating levels of SPOs and vascular dysfunction remains unknown. We hypothesized that SPOslead to endoplasmic reticulum (ER) stress, further release of SPOs and vascular injury. Mesentericresistance arteries (MRAs) from 14 weeks old, male and female C57BL/6 mice were used forvascular function. Agonists were acetylcholine and phenylephrine (1nM-10mM). In acuteconditions, SPOs (0.1μM) caused pathologically exacerbated endothelium-dependent vasodilationcompared to vehicle (F12 media) [Male: EC50: SPOs: -7.0 ± 0.1 (n=4), vs. Vehicle -6.6 ± 0.1 (n=7)p=0.03; Female: EC50: SPOs: -7.3 ± 0.06 (n=5) vs. Vehicle -6.7 ± 0.1 (n=6), p=0.001]. Thisphenotype was similar to the positive control tunicamycin (5mg/ml) [Male: EC50: Tunicamycin: -7.3(n=4), vs. Vehicle -6.6 (n=7) p=0.2; Female: EC50: Tunicamycin: -7.7 (n=4) vs. Vehicle -6.8 (n=5)p=0.04]. To determine whether SPO’s cause ER stress, arteries were treated with ER stressinhibitor 4-Phenylbutyric acid (2mM). The ER stress inhibitor prevented the exacerbatedvasodilation induced by SPOs showing SPOs trigger ER stress in acute conditions independent ofsex. To determine whether SPOs are a consequence of ER stress, arteries were incubated withtunicamycin in the presence of the SPO inhibitor K01-162 (10mM). Interestingly, K01-162 did notprevent the tunicamycin-induced exacerbated vasodilation in arteries from male mice. However,this response was decreased in arteries from female mice showing that inducing ER stress leadsto the release of SPOs, escalating a feed-forward mechanism of further SPO release. There wereno changes in vascular contraction with tunicamycin or SPOs irrespective of sex. ER stress wasconfirmed with anti-KDEL antibody staining, specific for ER resident chaperones Grp78/94 andvisualized with multiphoton fluorescent confocal microscopy. These results demonstrate that SPO’sexacerbate endothelium-dependent vasodilation acutely and may contribute to brain and peripheralvascular edema and loss of autoregulation observed during cardiovascular and Alzheimer’sdisease.

Abstract MP54: Pro-resolving Lipid Mediators Ameliorate Endothelium Dysfunction In Arteries From Hypertensive Rats

Resolution of inflammation is an active phenomenon to switch off the inflammatory processes andfacilitate the return to homeostasis. Increasing the levels of pro-resolving lipid mediators topromote the resolution of inflammation is emerging as a novel therapeutic approach. Arachidonicacid (AA) and docosahexaenoic acid (DHA) are substrates to produce the pro-resolving lipidmediators lipoxin A4 (LXA4) and resolvin D1 (RvD1), respectively. However, it is unknown if thesemediators can ameliorate dysfunction in arteries from hypertensive animals. Therefore, wehypothesized that pro-resolving lipid mediators decrease acetylcholine-induced contractions inarteries from spontaneously hypertensive rats (SHR). Mesenteric resistance arteries from maleSHR and Wistar Kyoto (WKY) (14-weeks old, n=6-8) were used for vascular function via wiremyograph. MRA were incubated with either RvD1 or LXA4 (10 nM, 1 hour) or vehicle prior toconcentration response curves to acetylcholine or phenylephrine (1 nM - 3 μM). We alsoperformed lipidomic analysis on plasma from WKY and SHR. As expected, low concentrations (≤100 nM) of acetylcholine induced relaxation in arteries from both groups, however highconcentrations (≥ 1 μM) of acetylcholine induced contraction in arteries from SHR, but not in WKY[Relaxation to acetylcholine [Area Under the curve (AUC)]: WKY: 396.6 ± 17.7 vs. SHR-control:296.0 ± 26.7*, t-test *vs. WKY, p=0.03). Treatment with the mediators did not change relaxationin arteries from WKY (AUC: Vehicle: 396.6 ±17.7 vs. RvD1: 402.8 ± 18.0; LXA4: 399.0 ± 18.4,p>0.05). However, incubation with RvD1 or LXA4 reduced acetylcholine induced-contraction inarteries from SHR (AUC: Vehicle: 296.0 ± 26.7 vs. RvD1: 372.5 ± 18.5*; LXA4: 376.8 ± 23.6*, t-test *vs. vehicle, p<0.05). Lipidomic analysis showed that precursors for pro-resolving lipidmediators are decreased in SHR [DHA (pmol/mL): WKY: 5637.5 ± 275.3 vs. SHR: 4509.2 ±453.9*, AA: WKY:16018.3 ± 351.3 vs. SHR: 13928.5 ± 959.5 *vs. WKY, p<0.05]. Overall, theseresults suggest that resolution of inflammation and the pro-resolving lipid mediators, RvD1 orLXA4, may be used as a new therapeutic tool to improve vascular function in hypertension.

Ethanol: striking the cardiovascular system by harming the gut microbiota

Ethanol consumption represents a significant public health problem, and excessive ethanol intake is a risk factor for cardiovascular disease (CVD), one of the leading causes of death and disability worldwide. The mechanisms underlying the effects of ethanol on the cardiovascular system are complex and not fully comprehended. The gut microbiota and their metabolites are indispensable symbionts essential for health and homeostasis and therefore, have emerged as potential contributors to ethanol-induced cardiovascular system dysfunction. By mechanisms that are not completely understood, the gut microbiota modulates the immune system and activates several signaling pathways that stimulate inflammatory responses, which in turn, contribute to the development and progression of CVD. This review summarizes preclinical and clinical evidence on the effects of ethanol in the gut microbiota and discusses the mechanisms by which ethanol-induced gut dysbiosis leads to the activation of the immune system and cardiovascular dysfunction. The cross talk between ethanol consumption and the gut microbiota and its implications are detailed. In summary, an imbalance in the symbiotic relationship between the host and the commensal microbiota in a holobiont, as seen with ethanol consumption, may contribute to CVD. Therefore, manipulating the gut microbiota, by using antibiotics, probiotics, prebiotics, and fecal microbiota transplantation might prove a valuable opportunity to prevent/mitigate the deleterious effects of ethanol and improve cardiovascular health and risk prevention.

Guidelines for the measurement of vascular function and structure in isolated arteries and veins

The measurement of vascular function in isolated vessels has revealed important insights into the structural, functional, and biomechanical features of the normal and diseased cardiovascular system and has provided a molecular understanding of the cells that constitutes arteries and veins and their interaction. Further, this approach has allowed the discovery of vital pharmacological treatments for cardiovascular diseases. However, the expansion of the vascular physiology field has also brought new concerns over scientific rigor and reproducibility. Therefore, it is appropriate to set guidelines for the best practices of evaluating vascular function in isolated vessels. These guidelines are a comprehensive document detailing the best practices and pitfalls for the assessment of function in large and small arteries and veins. Herein, we bring together experts in the field of vascular physiology with the purpose of developing guidelines for evaluating ex vivo vascular function. By using this document, vascular physiologists will have consistency among methodological approaches, producing more reliable and reproducible results.

Macrophage-Specific Toll Like Receptor 9 (TLR9) Causes Corpus Cavernosum Dysfunction in Mice Fed a High Fat Diet

BACKGROUND

Erectile dysfunction (ED) has been shown to be related with inflammatory markers in humans. Chronic infusion of TNF-α caused ED in mice while TNF-α knockout mice exhibited improvement in the relaxation of the corpus cavernosum (CC).

AIM

Since obesity triggers an inflammatory process, we aimed to investigate the hypothesis that in obesity, Toll-like receptor 9 (TLR9) activation leads to increased TNF-α levels and impairment in CC reactivity.

METHODS

Four-week old male C57BL6 (WT) and TLR9 mutant (TLR9_MUT) mice were fed a standard chow or high fat diet (HFD) for 12 weeks. Body weight and nonfasting blood glucose were analyzed. Contractile and relaxation responses of the CC were evaluated by electrical field stimulation and concentration response curves to phenylephrine and acetylcholine. Protein expression of nNOS, TNF-α, TNF-R1, TLR9 and MyD88 were measured by western blot. Plasma levels of TNF-α were measured by ELISA.

OUTCOME

In obesity, impaired cavernosal relaxation is associated with the activation of the innate immune system, by increasing the production of TNF-α through the activation of TLR9 in the macrophages.

RESULTS

After 12 weeks of HFD both WT and TLR9_MUT mice had increased body weight and nonfasting blood glucose compared to standard chow. In the CC, acetylcholine-induced relaxation was not changed. A trend to increased contraction to phenylephrine and KCl was seen in WT HFD only. electrical field stimulation-induced relaxation of the CC was decreased in WT HFD as well as nNOS expression in the CC of WT HFD, but not in TLR9_MUT HFD. In the CC, protein expression of TLR9 and MyD88 was similar in all groups. While circulating levels of TNF-α presented only a trend to increase in mice fed HFD, the CC expression of TNF-α was increased only in WT HFD mice.

CLINICAL TRANSLATION

The innate immune system can be a target for the treatment of erectile complications in obesity.

STRENGTHS AND LIMITATIONS

This is the first study demonstrating that activation of TLR9 expressed in macrophages leads to impaired cavernosal relaxation. The main limitation of the study is the lack of understanding about the source/expression of the macrophages in the cavernous tissue. Further, herein, the experiments were performed only in isolated cavernous tissue (in vitro), thus the lack of knowledge on how the TLR9 modulates the in vivo response of the erectile tissue is another limitation of this study.

CONCLUSION

Our findings indicate that CC dysfunction observed in obesity is at least in part mediated by the production of TNF-α upon activation of TLR9 expressed in the macrophages. Priviero F, Calmasini F, Dela Justina V, et al. Macrophage-Specific Toll Like Receptor 9 (TLR9) Causes Corpus Cavernosum Dysfunction in Mice Fed a High Fat Diet. J Sex Med 2021;18:723-731.

FPR-1 (Formyl Peptide Receptor-1) Activation Promotes Spontaneous, Premature Hypertension in Dahl Salt-Sensitive Rats

[Figure: see text].

Innate Immune Cells and Hypertension: Neutrophils and Neutrophil Extracellular Traps (NETs)

Uncontrolled immune system activation amplifies end-organ injury in hypertension. Nonetheless, the exact mechanisms initiating this exacerbated inflammatory response, thereby contributing to further increases in blood pressure (BP), are still being revealed. While participation of lymphoid-derived immune cells has been well described in the hypertension literature, the mechanisms by which myeloid-derived innate immune cells contribute to T cell activation, and subsequent BP elevation, remains an active area of investigation. In this article, we critically analyze the literature to understand how monocytes, macrophages, dendritic cells, and polymorphonuclear leukocytes, including mast cells, eosinophils, basophils, and neutrophils, contribute to hypertension and hypertension-associated end-organ injury. The most abundant leukocytes, neutrophils, are indisputably increased in hypertension. However, it is unknown how (and why) they switch from critical first responders of the innate immune system, and homeostatic regulators of BP, to tissue-damaging, pro-hypertensive mediators. We propose that myeloperoxidase-derived pro-oxidants, neutrophil elastase, neutrophil extracellular traps (NETs), and interactions with other innate and adaptive immune cells are novel mechanisms that could contribute to the inflammatory cascade in hypertension. We further posit that the gut microbiota serves as a set point for neutropoiesis and their function. Finally, given that hypertension appears to be a key risk factor for morbidity and mortality in COVID-19 patients, we put forth evidence that neutrophils and NETs cause cardiovascular injury post-coronavirus infection, and thus may be proposed as an intriguing therapeutic target for high-risk individuals. © 2021 American Physiological Society. Compr Physiol 11:1575-1589, 2021.

The Obligatory Role of the Acetylcholine-Induced Endothelium-Dependent Contraction in Hypertension: Can Arachidonic Acid Resolve this Inflammation?

The endothelium produces many substances that can regulate vascular tone. Acetylcholine is a widely used pharmacological tool to assess endothelial function. In general, acetylcholine binds to G-protein coupled muscarinic receptors that mediate a transient elevation in intracellular, free calcium. This intracellular rise in calcium is responsible for triggering several cellular responses, including the synthesis of nitric oxide, endothelium- derived hyperpolarizing factor, and eicosanoids derived from arachidonic acid. Endothelial arachidonic acid metabolism is also an important signaling pathway for mediating inflammation. Therefore, in conditions with sustained and excessive inflammation such as hypertension, arachidonic acid serves as a substrate for the synthesis of several vasoconstrictive metabolites, predominantly via the cyclooxygenase and lipoxygenase enzymes. Cyclooxygenase and lipoxygenase products can then activate G-protein coupled receptors expressed on vascular smooth muscle cells to causes contractile responses. As a result, acetylcholine-induced contraction due to arachidonic acid is a commonly observed feature of endothelial dysfunction and vascular inflammation in hypertension. In this review, we will critically analyze the literature supporting this concept, as well as address the potential underlying mechanisms, including the possibility that arachidonic acid signaling is diverted away from the synthesis of pro-resolving metabolites in conditions such as hypertension.

Enterobactin induces the chemokine, interleukin-8, from intestinal epithelia by chelating intracellular iron

Iron is an indispensable nutrient for both mammals and microbes. Bacteria synthesize siderophores to sequester host iron, whereas lipocalin 2 (Lcn2) is the host defense protein that prevent this iron thievery. Enterobactin (Ent) is a catecholate-type siderophore that has one of the strongest known affinities for iron. Intestinal epithelial cells (IECs) are adjacent to large microbial population and are in contact with microbial products, including Ent. We undertook this study to investigate whether a single stimulus of Ent could affect IEC functions. Using three human IEC cell-lines with differential basal levels of Lcn2 (i.e. HT29 < DLD-1 < Caco-2/BBe), we demonstrated that iron-free Ent could induce a dose-dependent secretion of the pro-inflammatory chemokine, interleukin 8 (IL-8), in HT29 and DLD-1 IECs, but not in Caco-2/BBe. Ent-induced IL-8 secretion was dependent on chelation of the labile iron pool and on the levels of intracellular Lcn2. Accordingly, IL-8 secretion by Ent-treated HT29 cells could be substantially inhibited by either saturating Ent with iron or by adding exogenous Lcn2 to the cells. IL-8 production by Ent could be further potentiated when co-stimulated with other microbial products (i.e. flagellin, lipopolysaccharide). Water-soluble microbial siderophores did not induce IL-8 production, which signifies that IECs are specifically responding to the lipid-soluble Ent. Intriguingly, formyl peptide receptor (FPR) antagonists (i.e. Boc2, cyclosporine H) abrogated Ent-induced IL-8, implicating that such IEC response could be, in part, dependent on FPR. Taken together, these results demonstrate that IECs sense Ent as a danger signal, where its recognition results in IL-8 secretion.

Microbiota Introduced to Germ-Free Rats Restores Vascular Contractility and Blood Pressure

Commensal gut microbiota are strongly correlated with host hemodynamic homeostasis but only broadly associated with cardiovascular health. This includes a general correspondence of quantitative and qualitative shifts in intestinal microbial communities found in hypertensive rat models and human patients. However, the mechanisms by which gut microbes contribute to the function of organs important for blood pressure (BP) control remain unanswered. To examine the direct effects of microbiota on BP, we conventionalized germ-free (GF) rats with specific pathogen-free rats for a short-term period of 10 days, which served as a model system to observe the dynamic responses when reconstituting the holobiome. The absence of microbiota in GF rats resulted with relative hypotension compared with their conventionalized counterparts, suggesting an obligatory role of microbiota in BP homeostasis. Hypotension observed in GF rats was accompanied by a marked reduction in vascular contractility. Both BP and vascular contractility were restored by the introduction of microbiota to GF rats, indicating that microbiota could impact BP through a vascular-dependent mechanism. This is further supported by the decrease in actin polymerization in arteries from GF rats. Improved vascular contractility in conventionalized GF rats, as indicated through stabilized actin filaments, was associated with an increase in cofilin phosphorylation. These data indicate that the vascular system senses the presence (or lack of) microbiota to maintain vascular tone via actin polymerization. Overall, these results constitute a fundamental discovery of the essential nature of microbiota in BP regulation.

Mitophagy in Hypertension-Associated Premature Vascular Aging

Hypertension has been described as a condition of premature vascular aging, relative to actual chronological age. In fact, many factors that contribute to the deterioration of vascular function as we age are accelerated and exacerbated in hypertension. Nonetheless, the precise mechanisms that underlie the aged phenotype of arteries from hypertensive patients and animals remain elusive. Classically, the aged phenotype is the buildup of cellular debris and dysfunctional organelles. One means by which this can occur is insufficient degradation and cellular recycling. Mitophagy is the selective catabolism of damaged mitochondria. Mitochondria are organelles that contribute importantly to the determination of cellular age via their production of reactive oxygen species (ROS; Harman's free radical theory of aging). Therefore, the accumulation of dysfunctional and ROS-producing mitochondria could contribute to the acceleration of vascular age in hypertension. This review will address and critically evaluate the current literature on mitophagy in vascular physiology and hypertension.

Abstract P112: Elevated Blood Pressure In Conventionalized Germ-free Rats Is Coupled With Upregulation Of Kynurenic Pathway Metabolites And Central Immune Responses

Background: Recent evidence supports that metabolic dysfunction underlies hypertension. Injection of kynurenate, a metabolite of tryptophan pathway, into the paraventricular nucleus of the hypothalamus (PVN) lowers blood pressure (BP). Intestinal absorption and metabolism of tryptophan are impacted by gut microbiota. Since gut-brain axis contributes to gut dysbiosis-inducd hypertension, we hypothesized that gut microbiota modulates the levels of kynurenic pathway metabolites that have central impact on BP regulation.

Methods: We, for the first time, used 7 weeks old male Germ-free (GF) Spague Dawley (SD) rats (n=5) and GF rats co-housed with conventional SD rats for 10 days (GFC) (n=6). BP was measured by tail-cuff. Serum metabolites were quantified by 6495 triple quandrople mass spectrometryand data was normalized using isotoplic labelled compounds. The nucleus of the solitary tract (NTS), the principal sensory nucleus for peripheral changes, and the PVN, a relay center projecting sympathetic output based on the integrated afferent inputs from brain regions including NTS, were analyzed by microarray hybridization for mRNA expression.

Results: Compared to the GF rats, GFC rats had significantly higher systolic (139 mmHg vs 115 mmHg, p <0.05), diastolic BP (96 mmHg vs 79 mmHg, p <0.05), and serum levels of kynurenic acid (-9.76 vs -10.21, p <0.05) and 3-hydroxy kynurenine (-6.49 vs -7.34, p <0.01). Coupled with these increases in kynurenic pathway metabolites, microarray analyses demonstrated increased immune responses (e.g. Cd74, Il1b, Cxcl1, Mmp14 ) in the PVN (gene ontology analysis, p <0.001) and increased cell differentiation and synaptic plasticity (e.g. Sox11, Tp53, Cdk6, Hoxb4, Foxo4, Cyr61 ) in the NTS (gene ontology analysis, p <0.01).

Conclusion: Colonization of gut microbiota in GF rats induced increased cell differentiation and synaptic plasticity in the NTS and immune responses in the PVN, indicating the restructured sensory neurons of the NTS and enhanced sympathetic output from the PVN. These are in line with increased levels of kynurenic acid and 3-hydroxy kynurenine, and BP, respectively, suggesting that BP regulation by the gut-brain axis may be mediated by kynurenic pathway.

Abstract 22: Formyl Peptide Receptor-1 Activation Is Crucial For The Cause Of Spontaneous Hypertension In Dahl Salt Sensitive Rats

Mitochondria evolved from bacteria and use N-formylated peptides (NFPs) to synthetize protein. Bacterial and mitochondrial NFPs activate formyl peptide receptor 1 (FPR-1) and lead to vascular injury. We previously observed that Dahl Salt Sensitive rats (S) fed a low-salt (LS, 0.3% NaCl) diet presented spontaneous hypertension, vascular dysfunction, and overexpression of FPR-1 in arteries when compared to Dahl Salt Resistant (R) rats. High salt (HS, 2% NaCl) diet worsened these phenotypes in S rats. Interestingly, HS diet induced leaky gut and amoxicillin (AMO) treatment decreased BP in S-HS. Due to the dual sources of NFPs (microbiota and host mitochondria), we hypothesized that cell death-derived mitochondria and/or leaky gut-derived bacterial NFPs lead to FPR-1 activation, vascular injury and elevated BP in S rats independent of HS diet. For this, we used flow cytometry to measure cell necrosis and early and late apoptosis in kidney, bone marrow-derived macrophages and mesenteric resistance arteries (MRA) from male S and R rats (8-week old) on a LS diet. Zonulin, a biomarker for leaky gut, was measured in plasma. In another group, rats were treated with FPR-1 antagonist [Cyclosporin H (CsH), 0.3 mg/kg/day, osmotic mini-pump, 14 days], vehicle (VEH) or received water with AMO (5 mg/kg/day) for 21 days to deplete bacteria. BP was measured by telemetry and vascular function and structure were assessed in MRA. S rats presented increased kidney cell necrosis (R: 3.8±0.3 vs. S: 5.3±0.5* %). CsH decreased spontaneous elevation of BP [Diastolic: R+VEH: 77±2.7 vs. R+CsH: 81±1.2 vs. S+VEH: 126±3.0* vs. S+CsH:115±2.7 # ] and vascular hypercontractility [KCl (120mM): R+VEH: 9.4±1 vs. R+CsH: 10.2±0.4; S+VEH: 15.5±0.9* vs. S+CsH:11.7±0.8 # mN; Phenylephrine (10μM): R+VEH: 9.3±1 vs. R+CsH: 9.7±1; S+VEH: 14.5±1*vs. S+CsH: 11.4±0.6 # mN) in S-LS rats. AMO did not change vascular contraction or BP. Leaky gut was not observed in Dahl S-LS diet. In conclusion, FPR-1 can serve as a causative agent for the spontaneous elevation of BP and kidney-derived mitochondria, but not gut-derived microbiota, are the main source for NFPs.

Abstract P058: Female Rats Artificially Selected For Low Vs. High Intrinsic Aerobic Capacity Display Divergent Mechanisms In Vascular Inflammation

Hypertension is an important clinical symptom of metabolic syndrome (MetS). Rats selectively bred for low intrinsic aerobic capacity (LCR) are animal models for MetS, and present with increased blood pressure and vascular dysfunction. In contrast, rats selected for high intrinsic aerobic capacity (HCR) display reduced vascular inflammation and no metabolic abnormalities. Two important enzymes for vascular inflammation and the resolution of inflammation are cyclooxygenase (COX) and lipoxygenase (LOX), respectively; however, it is unknown whether COX and LOX play a role in the vascular function of LCR and HCR. We hypothesized that mesenteric resistance arteries (MRA) from untrained LCR present increased COX activity, while arteries from HCR show decreased COX and increased LOX activity.

Female (18-38 weeks old) LCR, HCR, and high response trained (HRT) rats, control, were used. HRT rats present higher intrinsic aerobic capacity than LCR, but lower than HCR. MRA were mounted onto a wire myograph. One-way ANOVA: p<0.05: *vs. control (HRT); # vs. HCR; & vs. absence of indomethacin (INDO), a COX inhibitor. LCR rats showed increased periovarian fat pad [HRT: 0.95±0.1 (n=7) vs. LCR: 1.80±0.1* # (n=7) vs. HCR: 1.18±0.1 (n=7) (g)]. No significant differences were observed in the KCl (120 mM), acetylcholine, and sodium-nitroprusside-induced responses. However, LCR presented a decrease in phenylephrine (PE)-induced contraction [PE: E max %: HRT: 103±3 (n=8); LCR: 74±9* # (n=11); HCR: 112±5 (n=9)]. Inhibiting COX [INDO, 10 μM] decreased contraction in HRT arteries, but had little effect on HCR arteries. Contrarily, INDO abolished contraction in MRA from LCR [PE+INDO: E max %: HRT: 31±18 & (n=7); LCR: 2±0.9 & (n=8); HCR: 77±9 (n=8)]. Lipoxin (LXA4), a LOX-derived mediator for resolution of inflammation, induced contraction in MRA from HCR, but relaxation in LCR and HRT arteries [LXA4: E max %: HRT: -69±19 (n=4); LCR: -18±9 (n=3); HCR: 11±5 (n=4)*]. Thus, HCR are unresponsive to COX inhibition, suggesting a change from a normal inflammatory state to a higher resolution state. LCR display low-grade chronic inflammation via increased COX activity. These data reveal novel, inherited mechanisms for vascular physiology in high vs. low intrinsic aerobic capacity.

Abstract MP39: Autophagy Regulates β-hydroxybutyrate Synthesis To Prevent High-salt Induced Vascular Damage

Overconsumption of dietary salt is unequivocally linked with end organ damage. We have recently observed that a high salt (HS) diet induces liver dysfunction in the form of impaired synthesis of ketone body, β-hydroxybutyrate (βOHB), in Dahl salt-sensitive rats. However, the molecular mechanisms as to why βOHB is decreased after consuming a HS diet remains unknown, as well as if it contributes to vascular dysfunction. We hypothesized that a HS diet (2%) for 8 weeks would decrease systemic levels of βOHB in Dahl salt-resistant (R) rats and this would be associated with endothelial dysfunction. Furthermore, reconstitution of βOHB bioavailability by giving 1,3-Butanediol (1,3-BD; 20% v/v ) in the drinking water would improve endothelial function in HS fed Dahl R. As hypothesized, a HS diet decreased serum concentration (mM) of βOHB [Low salt (LS), non-fasting (NF): 0.31±0.02 vs. fasting (F): 0.96±0.04*; HS, NF: 0.33±0.02 vs. F: 0.77±0.04*#, *p<0.05 vs. NF, #p<0.05 vs. LS-F]. A HS diet decreased the sensitivity of isolated mesenteric resistance arteries (MRA) to acetylcholine (ACh), and 1,3-BD treatment prevented this endothelial dysfunction (LogEC50, Dahl R-LS: -7.35±0.05 vs. Dahl R-HS: -7.19±0.07* vs. Dahl R-HS+1,3-BD: -7.42±0.10, p<0.05). Furthermore, when MRA were incubated with indomethacin, only Dahl R-HS presented with a decreased sensitivity to ACh (LogEC50, HS: -7.19±0.07 vs. HS+indomethacin: -7.66±0.08*, p<0.05), indicating that 1,3-BD treatment decreased cyclooxygenase-induced vascular inflammation (LogEC50, 1,3-BD -7.42±0.10 vs. 1,3-BD +indomethacin: -7.61±0.09, p>0.05). Evolutionarily, autophagy functions to mobilize nutrients in times of starvation, including ketone bodies such as βOHB. Therefore, we hypothesized that inhibition of autophagy would decrease βOHB. Treatment with lysosomal alkalizer chloroquine (CQ), impeded the starvation-induced increase in βOHB (NF: 0.38±0.02 vs. F: 1.11±0.09* vs. F+CQ: 0.78±0.19*#, *p<0.05 vs NF, # p<0.05 vs F). In summary, these data reveal that a HS diet decreases liver-derived βOHB, independent of high blood pressure, and is protective against HS-induced vascular damage. We suggest that autophagy could be a novel mechanism underlying the vascular protective effects of βOHB.

Abstract P149: Germ-free Rats Reveal An Obligatory Role Of Microbiota In Blood Pressure

Elevated blood pressure or hypertension is the single largest risk factor for cardiovascular diseases which are the leading cause of human deaths. Current clinical management of blood pressure is focused on restoring homeostasis of the host alone, without accounting for commensal gut microbiota. Recent evidence from the CARDIA study in humans and multiple studies using animal models suggest that development of hypertension in the host is associated with alterations in microbiotal communities. Here we examined whether microbiota is necessary for blood pressure and vascular homeostasis by functional evaluation of the gut homeostasis, hemodynamic, and vascular function of gnotobiotic rats reconstituted with microbiota to represent the complete holobiont. Gnotobiotic rats were used to represent incomplete holobionts. To reconstitute complete holobionts, gnotobiotic rats were co-housed with conventionally-raised rats. Acquisition of microbiota was evaluated through monitoring of gross ceca and fecal samples by metagenomic 16S sequencing. BP was recorded and vascular, renal, hepatic, cardiac and gut features were assessed using histology and ex vivo myography. Markers of innate immune effectors (Immune cell population, level of Lcn2, Gut permeability) were used to examine the nature and extent of host immune cell processes concomitantly occurring along with observations of host hemodynamics. Compared to the reconstituted holobiont represented by the animals exposed to microbiota, the incomplete-holobiont represented by gnotobiotic rats, had significantly lower BP (SBP of germ free:109±8 mmHg, SBP of conventionalized:138±10mmHg * ) and vascular contractility responses to phenylephrine (Emax (mN): germ-free: 6.9±1.3, GFC: 11.7±0.7*). Acute exposure of the host to microbiota reconstituted gut microbiotal communities, significantly boosted their gut epithelial cell proliferation, innate immune function and restored vascular contractility. These data indicate that in addition to the dependency of the host on microbiota for essential bodily functions such as digestion of plant-derived complex carbohydrates, the host is also dependent on microbiota for maintaining blood pressure and vascular function

Abstract P238: Bile Acid Metabolites Modulate Hypertension

Hypertension is the single prominent risk factor of epidemic proportions leading to cardiovascular disease and stroke, which comprise the top two reasons for mortality of humans in the modern age. Much of the attention for the unknown causes of hypertension was focused on genetics and dietary salt, but in recent years, host-microbiotal interaction is gaining importance. Host-microbiotal partnership is key for the generation of many bioactive molecules including bile acid (BA) metabolites. Primary bile acids are synthesized and conjugated by the host but deconjugated and further modified to secondary BA by gut commensal bacteria. BA metabolites serve as important ligands for host nuclear receptors and/or G-protein-coupled receptors. These receptors have pivotal roles in blood pressure regulation. However, the effect of the host-microorganism biliary network on blood pressure (BP) remains poorly characterized. Here we report that both dietary salt and genetic factors rewire the composition of bile acids and BP. Specific reductions in conjugated bile acids were noted in human hypertensives as well as in rats with hypertension. Conjugation of bile acids by the host alone, devoid of the deconjugation step by microbiota, was sufficient to decrease BP of germ-free rats compared to germ-free conventionalized rats. Nutritional restoration of the conjugation of bile acids with Taurine increased the availability of circulating conjugated bile acids as ligands and ameliorated host susceptibility to hypertension via BA nuclear receptors and G-protein-coupled receptors. Thus, hosts and their bacterial symbionts can control host BP homeostasis via the resulting pool of bile acid metabolites. Sources of funding: National Institutes of Health (R01HL143082).

Microbiota are critical for vascular physiology: Germ-free status weakens contractility and induces sex-specific vascular remodeling in mice

Commensal microbiota within a holobiont contribute to the overall health of the host via mutualistic symbiosis. Disturbances in such symbiosis is prominently correlated with a variety of diseases affecting the modern society of humans including cardiovascular diseases, which are the number one contributors to human mortality. Given that a hallmark of all cardiovascular diseases is changes in vascular function, we hypothesized that depleting microbiota from a holobiont would induce vascular dysfunction. To test this hypothesis, young mice of both sexes raised in germ-free conditions were examined vascular contractility and structure. Here we observed that male and female germ-free mice presented a decrease in contraction of resistance arteries. These changes were more pronounced in germ-free males than in germ-free females mice. Furthermore, there was a distinct change in vascular remodeling between males and females germ-free mice. Resistance arteries from male germ-free mice demonstrated increased vascular stiffness, as shown by the leftward shift in the stress-strain curve and inward hypotrophic remodeling, a characteristic of chronic reduction in blood flow. On the other hand, resistance arteries from germ-free female mice were similar in the stress-strain curves to that of conventionally raised mice, but were distinctly different and showed outward hypertrophic remodeling, a characteristic seen in aging. Interestingly, we observed that reactive oxygen species (ROS) generation from bone marrow derived neutrophils is blunted in female germ-free mice, but it is exacerbated in male germ-free mice. In conclusion, these observations indicate that commensal microbiota of a holobiont are central to maintain proper vascular function and structure homeostasis, especially in males.

Exposure to Amoxicillin in Early Life Is Associated With Changes in Gut Microbiota and Reduction in Blood Pressure: Findings From a Study on Rat Dams and Offspring

Background

Pediatric hypertension is recognized as an emerging global health concern. Although new guidelines are developed for facilitating clinical management, the reasons for the prevalence of hypertension in children remain unknown. Genetics and environmental factors do not fully account for the growing incidence of pediatric hypertension. Because stable bacterial flora in early life are linked with health outcomes later in life, we hypothesized that reshaping of gut microbiota in early life affects blood pressure (BP) of pediatric subjects.

Methods and Results

To test this hypothesis, we administered amoxicillin, the most commonly prescribed pediatric antibiotic, to alter gut microbiota of young, genetically hypertensive rats (study 1) and dams during gestation and lactation (study 2) and recorded their BP. Reshaping of microbiota with reductions in Firmicutes/Bacteriodetes ratio were observed. Amoxicillin treated rats had lower BP compared with untreated rats. In young rats treated with amoxicillin, the lowering effect on BP persisted even after antibiotics were discontinued. Similarly, offspring from dams treated with amoxicillin showed lower systolic BP compared with control rats. Remarkably, in all cases, a decrease in BP was associated with lowering of Veillonellaceae, which are succinate‐producing bacteria. Elevated plasma succinate is reported in hypertension. Accordingly, serum succinate was measured and found lower in animals treated with amoxicillin.

Conclusions

Our results demonstrate a direct correlation between succinate‐producing gut microbiota and early development of hypertension and indicate that reshaping gut microbiota, especially by depleting succinate‐producing microbiota early in life, may have long‐term benefits for hypertension‐prone individuals.

Toll-like receptor 9 regulates metabolic profile and contributes to obesity-induced benign prostatic hyperplasia in mice

BACKGROUND

Benign prostatic hyperplasia (BPH) is associated with obesity and prostatic inflammation. The present study investigated the participation of toll-like receptor 9 (TLR9) in obesity-induced BPH, focusing on metabolic impairments, damage-associated molecular patterns (DAMP) levels and prostatic oxidative stress generation.

METHODS

C57BL/6 (WT) and TLR9 mutant male mice were fed with regular or high-fat diet for 12 weeks. Metabolic profile, functional protocols, reactive-oxygen species (ROS) generation, prostatic histological analysis and DAMP levels were analyzed. Western blotting for prostatic TLR9 signaling pathway was also performed.

RESULTS

BPH in WT obese animals was characterized by increased prostate weight, smooth muscle hypercontractility and prostatic epithelial hyperplasia. Higher epididymal fat weight and prostatic ROS generation along with increased fasting glucose, triglyceride and circulating DAMP levels were also observed in WT obese group. Conversely, TLR9 mutant obese animals exhibited lower epididymal fat weight, fasting glucose and triglyceride levels associated with reduced prostate hypercontractility, prostatic ROS and circulating DAMP levels. However, TLR9 mutant obese mice were not protected from obesity-associated prostatic overgrowth and epithelial hyperplasia. Interestingly, TLR9 mutant lean mice exhibited augmented fasting glucose and prostatic ROS levels compared with WT lean mice. Despite increased prostatic expression of TLR9 in WT obese mice, no differences were seen in MyD88 expression between groups.

CONCLUSION

Improved obesity-induced BPH-related prostatic smooth muscle hypercontractility in TLR9 obese mice may be associated with amelioration in the metabolic profile, ROS and DAMP generation. Therefore, TLR9 could be a valuable target to improve obesity-associated metabolic disorders and prostate smooth muscle hypercontractility in BPH.

Abstract 066: Beta-Hydroxybutyrate Synthesis Contributes to the Anti-Vascular Aging Effect of Autophagy

Diminished autophagy leads to the accumulation of debris, dysfunctional organelles, and consequently, cellular aging. Premature vascular aging occurs in hypertension. In fact, many factors that contribute to the deterioration of vascular function as we age are accelerated in hypertension. Previously, we have reported decreased autophagic activity in arteries from hypertensive rats and reconstituting autophagy ameliorated several vascular aging phenotypes. However, the mechanisms by which autophagy exerts anti-vascular aging effects are still unknown. Evolutionarily, autophagy functions to mobilize micronutrients in times of starvation. As a result, autophagy has also been recognized as a mediator of fatty acid oxidation and ketogenesis, predominantly from the liver. Therefore, we hypothesized that autophagy induction by fasting would increase the expression of ketone body beta-hydroxybutyrate (βOHB) in the livers of Wistar-kyoto rats and this would be prevented by systemic inhibition autophagy (3-methyadenine). As hypothesized, fasting increased βOHB, and this was prevented by 3-methyadenine (mmol/L, non-fasting: 0.43±0.04 vs. fasting: 0.58±0.04 vs. fasting+3-methyadenine: 0.35±0.01, p<0.05). Next we questioned whether βOHB could contribute to the anti-vascular aging effect of autophagy and hypothesized that βOHB administered directly to isolated arteries would cause endothelium-dependent relaxation. To test this hypothesis, we performed concentration-response curves to βOHB in mesenteric resistance arteries from Dahl salt-sensitive rats. We observed that βOHB was a potent endothelium-dependent vasodilator (%Relaxation, βOHB+endothelium-intact: 53±6 vs. βOHB+endothelium-denuded: 24±5, p<0.05). Inhibition of endothelium-derived vasodilators revealed that this relaxation was mediated by potassium channels (%Relaxation, βOHB: 53±6 vs. βOHB+tetraethylammonium: 19±9, p<0.05), but not nitric oxide (%Relaxation, βOHB: 53±6 vs. βOHB+L-NAME: 44±15, p>0.05). Overall, these data reveal βOHB as a novel endothelium-dependent vasodilator synthesized by the liver due to induction of autophagy. We conclude that βOHB synthesis is a mechanism by which autophagy exerts anti-vascular aging effects in hypertension.

Abstract 122: Cardiac Hypertrophy and Vascular Function are Directly Proportional to Mitochondrial Variations in Intrinsic Exercise Capacity

Exercise is a primary lifestyle intervention to control cardiovascular diseases such as hypertension. Exercise capacity and its health benefits are inheritable. However, the mechanisms by which exercise capacity differences influence overall health state remain unclear. We first hypothesized that low and high intrinsic exercise capacity lead to distinct heart weight and vascular function. Animal model (male, 20-24-weeks old, n = 6): heterogeneous stock selectively bred for over 20 years to produce low-capacity running rats (LCR) and high-capacity running rats (HCR), and an intrinsic control, high response trainer rats (HRT, control). Statistics: t-test: *p<0.05. Left ventricular (LV) weight was normalized by tibia length. We observed that HCR presented with LV hypertrophy compared to LCR and control (Control: 0.0155 ± 0.0006 vs. HCR: 0.0192 ± 0.0007* vs. LCR: 0.0164 ± 0.0004). Performing wire myography with 3 rd -order mesenteric resistance arteries (MRA), we observed that LCR MRA had an impaired maximum relaxation response (E max ) to acetylcholine (ACh) compared to HCR and control (Control: 94.99 ± 1.79 vs. HCR: 93.49 ± 12.17 vs. LCR: 72.95 ± 12.40*). Next, we questioned if these differences were the result of mitochondria. We used two reciprocal conplastic strains created by utilizing maternal mitochondrial inheritance (male, 30-36-weeks old, n = 4): LCR nuclear genome with HCR mitochondria (LCR.HCR mt ) and the reciprocal HCR.LCR mt . We observed that LCR.HCR mt presented with LV hypertrophy compared to LCR (0.0195 ± 0.0002* vs 0.0164 ± 0.0004) while HCR.LCR mt abolished HCR LV hypertrophy (0.0151 ± 0.0002* vs. 0.0192 ± 0.0007). Interestingly, in a separate group of animals (n = 4 - 5), LCR had higher mean arterial pressure (MAP) compared to HCR, and LCR.HCR mt had reduced MAP compared to LCR (LCR: 119 ± 2 vs. LCR.HCR mt : 111 ± 1*). No changes were observed in HCR.LCR mt compared to HCR. Further, LCR.HCR mt MRA presented with improved E max to ACh compared to LCR MRA (LCR: 72 ± 12 vs. LCR.HCR mt : 93 ± 2*) while no changes were observed in HCR.LCR mt MRA compared to HCR MRA. Overall, we conclude that intrinsic exercise capacity is directly proportional to cardiovascular effects. Similar to the nuclear genome, mitochondria are the key to this hereditary predisposition.