PGC-1α ameliorates AngiotensinII-induced eNOS dysfunction in human aortic endothelial cells

Endothelial Dysfunction in Huntington's Disease: Pathophysiology and Therapeutic Implications

Huntington's disease (HD) is a progressive neurodegenerative disorder characterized by motor, cognitive, and psychiatric symptoms. While traditionally viewed through the lens of neuronal dysfunction, emerging evidence highlights the critical role of endothelial dysfunction in HD pathogenesis. This review provides a comprehensive overview of endothelial dysfunction in HD, drawing on findings from both animal models and human studies. Key features of endothelial dysfunction in HD include impaired angiogenesis, altered cerebral blood flow, compromised neurovascular coupling and cerebrovascular reactivity, and increased blood-brain barrier permeability. Genetic factors such as the mutant huntingtin protein, peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), Brain-derived neurotrophic factor (BDNF), and the adenosine A2A receptor (ADORA2A) interact to influence endothelial function in complex ways. Various therapeutic approaches targeting endothelial dysfunction, including antioxidants, nitric oxide enhancers, calcium channel blockers, statins, and metformin, have shown promise in preclinical HD models but face translational challenges, particularly regarding optimal timing of intervention and patient stratification. The implications of these findings suggest that reconceptualizing HD as a neurovascular disorder, rather than purely neuronal, could lead to more effective treatment strategies. Future research priorities should include: (1) developing validated vascular biomarkers for disease progression, (2) advancing neuroimaging techniques to monitor endothelial dysfunction in real-time. These directions will be crucial for bridging the current gap between preclinical promise and clinical success in vascular-targeted HD therapeutics.

Peroxisome proliferator‑activated receptor γ coactivator‑1α in heart disease (Review)

Heart disease (HD) is a general term for various diseases affecting the heart. An increasing body of evidence suggests that the pathogenesis of HD is closely related to mitochondrial dysfunction. Peroxisome proliferator‑activated receptor γ coactivator‑1α (PGC‑1α) is a transcriptional coactivator that plays an important role in mitochondrial function by regulating mitochondrial biogenesis, energy metabolism and oxidative stress. The present review shows that PGC‑1α expression and activity in the heart are controlled by multiple signaling pathways, including adenosine monophosphate‑activated protein kinase, sirtuin 1/3 and nuclear factor κB. These can mediate the activation or inhibition of transcription and post‑translational modifications (such as phosphorylation and acetylation) of PGC‑1α. Furthermore, it highlighted the recent progress of PGC‑1α in HD, including heart failure, coronary heart disease, diabetic cardiomyopathy, drug‑induced cardiotoxicity and arrhythmia. Understanding the mechanisms underlying PGC‑1α in response to pathological stimulation may prove to be beneficial in developing new ideas and strategies for preventing and treating HDs. Meanwhile, the present review explored why the opposite results occurred when PGC‑1α was used as a target therapy.

Mitochondrial KATP channel-mediated autophagy contributes to angiotensin II-induced vascular dysfunction in mice

BACKGROUND AND AIM

The present study aimed to investigate whether the mitochondrial KATP channel contributes to angiotensin II (Ang II)-induced vascular dysfunction, the development of hypertension, and atherosclerosis.

METHODS AND RESULTS

ApoE (-/-) mice fed a high-fat diet were chronically infused with Ang II for eight weeks and concomitantly treated with losartan (ARB), apocynin, or 5-hydroxy decanoate (5-HD), or 3-methyladenine (3-MA). Systolic blood pressure was measured, and pathological changes of aortic or liver tissue were observed. Nitric oxide (NO), superoxide dismutase 2 (SOD2) levels and vasorelaxation rate were measured, and protein and mRNA expressions were examined by western blot and RT-PCR. Ang II-induced development of hypertension was suppressed not only by ARB, and apocynin but also by 5-HD or 3-MA. Ang II infusion decreased aortic NO production and relaxation, as well as SOD2 activity in liver, which were improved by all treatments. In addition, Ang II-induced activation of autophagy was suppressed by 5-HD in aortic tissue, furthermore, Ang II increases the atherosclerotic index in plasma and exacerbates the development of atherosclerosis by increases of fat deposition in the aorta and liver. Lipid metabolism-related mRNA expressions (LXR-α, LDLR, SRBI, Acca, and FASN) were changed by Ang II. Similarly, not only ARB, and apocynin, but also 5-HD and 3-MA suppressed Ang II-induced these changes.

CONCLUSIONS

Our present findings evidence that mitochondrial KATP channel-mediated autophagy contributes to Ang II-induced vascular dysfunction, development of hypertension, and atherosclerosis.

Nanoparticle endothelial delivery of PGC-1α attenuates hypoxia-induced pulmonary hypertension by attenuating EndoMT-caused vascular wall remodeling

Pulmonary hypertension (PH) induced by chronic hypoxia is characterized by thickening of pulmonary artery walls, elevated pulmonary vascular resistance, and right-heart failure. Dysfunction of endothelial cells is the hallmark event in the progression of PH. Among various mechanisms, endothelial to mesenchymal transition (EndoMT) has emerged as an important source of endothelial cell dysfunction in PH. However, the mechanisms underlying the EndoMT in PH remain largely unknown. Our results showed that peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) expression was decreased in pulmonary arterial endothelial cells (PAECs) in PH patients and hypoxia-induced PH mouse model compared to the normal controls. Endothelial-specific overexpression of PGC-1α using nanoparticle delivery significantly attenuated the progression of PH, as shown by the significantly decreased right ventricular systolic pressure and diminished artery thickness as well as reduced vascular muscularization. Moreover, Endothelial-specific overexpression of PGC-1α blocked the EndoMT of PAECs during PH, indicating that loss of PGC-1α promotes PH development by mediating EndoMT, which damages the integrity of endothelium. Intriguingly, we found that PGC-1α overexpression rescued the expression of endothelial nitric oxide synthase in mouse lung tissues that was deceased by hypoxia treatment in vivo and in endothelial cells treated with TGF-β in vitro. Consistently, PAECs and vascular smooth muscle co-culture showed that overexpression of PGC-1α in PAECs increases nitric oxide release, which would likely diffuse to smooth muscle cells, where it activates specific protein kinases, and initiates SMC relaxation by diminishing the calcium flux. Endothelial-specific overexpression of PGC-1α also attenuated hypoxia-induced pulmonary artery stiffness which appeared to be caused by both the decreased endothelial nitric oxide production and increased vascular remodeling. Taken together, these results demonstrated that endothelial-specific delivery of PGC-1α prevents PH development by inhibiting EndoMT of PAECs and thus restoring endothelial function and reducing vascular remodeling.

The underlying mechanisms of cold exposure-induced ischemic stroke

Growing evidence suggests that cold exposure is to some extent a potential risk factor for ischemic stroke. At present, although the mechanism by which cold exposure induces ischemic stroke is not fully understood, some potential mechanisms have been mentioned. First, the seasonal and temperature variability of cerebrovascular risk factors (hypertension, hyperglycemia, hyperlipidemia, atrial fibrillation) may be involved. Moreover, the activation of sympathetic nervous system and renin-angiotensin system and their downstream signaling pathways (pro-inflammatory AngII, activated platelets, and dysfunctional immune cells) are also major contributors. Finally, the influenza epidemics induced by cold weather are also influencing factors that cannot be ignored. This article is the first to systematically and comprehensively describe the underlying mechanism of cold-induced ischemic stroke, aiming to provide more preventive measures and medication guidance for stroke-susceptible individuals in cold season, and also provide support for the formulation of public health policies.

Renin-angiotensin system and inflammation update

The most classical view of the renin-angiotensin system (RAS) emphasizes its role as an endocrine regulator of sodium balance and blood pressure. However, it has long become clear that the RAS has pleiotropic actions that contribute to organ damage, including modulation of inflammation. Angiotensin II (Ang II) activates angiotensin type 1 receptors (AT1R) to promote an inflammatory response and organ damage. This represents the pathophysiological basis for the successful use of RAS blockers to prevent and treat kidney and heart disease. However, other RAS components could have a built-in capacity to brake proinflammatory responses. Angiotensin type 2 receptor (AT2R) activation can oppose AT1R actions, such as vasodilatation, but its involvement in modulation of inflammation has not been conclusively proven. Angiotensin-converting enzyme 2 (ACE2) can process Ang II to generate angiotensin-(1-7) (Ang-(1-7)), that activates the Mas receptor to exert predominantly anti-inflammatory responses depending on the context. We now review recent advances in the understanding of the interaction of the RAS with inflammation. Specific topics in which novel information became available recently include intracellular angiotensin receptors; AT1R posttranslational modifications by tissue transglutaminase (TG2) and anti-AT1R autoimmunity; RAS modulation of lymphoid vessels and T lymphocyte responses, especially of Th17 and Treg responses; interactions with toll-like receptors (TLRs), programmed necrosis, and regulation of epigenetic modulators (e.g. microRNAs and bromodomain and extraterminal domain (BET) proteins). We additionally discuss an often overlooked effect of the RAS on inflammation which is the downregulation of anti-inflammatory factors such as klotho, peroxisome proliferator-activated receptor γ co-activator 1α (PGC-1α), transient receptor potential ankyrin 1 (TRPA1), SNF-related serine/threonine-protein kinase (SNRK), serine/threonine-protein phosphatase 6 catalytic subunit (Ppp6C) and n-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP). Both transcription factors, such as nuclear factor κB (NF-κB), and epigenetic regulators, such as miRNAs are involved in downmodulation of anti-inflammatory responses. A detailed analysis of pathways and targets for downmodulation of anti-inflammatory responses constitutes a novel frontier in RAS research.

Autophagy contributes to angiotensin II induced dysfunction of HUVECs

BACKGROUND

Signal transduction of Angiotensin II (Ang II) induced autophagy and its role in Ang II-induced dysfunction of HUVECs are still unclear.

METHODS

HUVECs are stimulated with different doses of Ang II (10-9-10-5 mol/L) for different time (6-48 hours). Autophagy-related protein markers: LC3, Beclin-1 and SQSTM1/p62 are measured by western blot.

RESULTS

Incubation with Ang II increases autophagic flux (Beclin-1, autophagosomes formation, and degradation of SQSTM1/p62, LC3-I). Increased autophagic levels are inhibited by pretreatment with Ang II type 1 receptor (AT1) blocker (Candesartan), NADPH Oxidase inhibitor (apocycin), mitochondrial K_ATP channels inhibitor (5-hydroxydecanoate, 5HD). 3-Methyladenine (inhibitors of autophagy) and rapamycin (activator of autophagy) respectively inhibits or activates Ang II-induced autophagy levels. Ang II decreases phosphorylation of endothelial nitric oxide synthase (eNOS) and NO production in HUVECs. L-NAME (NOS inhibitor) totally mimics the actions of Ang II on eNOS, NO production and autophagy levels. Rapamycin further decreases NO production combined with Ang II. Silence Atg5 completely reverses Ang II-activated autophagy levels.

CONCLUSIONS

Our results demonstrate that Ang II stimulation increases autophagy levels via AT1 receptor, NADPH oxidase, mitochondrial K_ATP channel, eNOS, Atg5 signal pathway in HUVECs, and activation of autophagy contributes to Ang II induced dysfunction of HUVECs.

Angiotensin II Decreases Endothelial Nitric Oxide Synthase Phosphorylation via AT1R Nox/ROS/PP2A Pathway

Increasing evidences suggest that angiotensin (Ang) II participates in the pathogenesis of endothelial dysfunction (ED) through multiple signaling pathways, including angiotensin type 1 receptor (AT₁R) mediated NADPH oxidase (Nox)/reactive oxygen species (ROS) signal transduction. However, the detailed mechanism is not completely understood. In this study, we reported that AngII/AT₁R-mediated activated protein phosphatase 2A (PP2A) downregulated endothelial nitric oxide synthase (eNOS) phosphorylation via Nox/ROS pathway. AngII treatment reduced the levels of phosphorylation of eNOS Ser1177 and nitric oxide (NO) content along with phosphorylation of PP2Ac (PP2A catalytic subunit) Tyr307, meanwhile increased the PP2A activity and ROS production in human umbilical vein endothelial cells (HUVECs). These changes could be impeded by AT₁R antagonist candesartan (CAN). The pretreatment of 10⁻⁸ M PP2A inhibitor okadaic acid (OA) reversed the levels of eNOS Ser1177 and NO content. Similar effects of AngII on PP2A and eNOS were also observed in the mesenteric arteries of Sprague-Dawley rats subjected to AngII infusion via osmotic minipumps for 2 weeks. We found that the PP2A activity was increased, but the levels of PP2Ac Tyr307 and eNOS Ser1177 as well as NO content were decreased in the mesenteric arteries. The pretreatments of antioxidant N-acetylcysteine (NAC) and apocynin (APO) abolished the drop of the levels of PP2Ac Tyr307 and eNOS Ser1177 induced by AngII in HUVECs. The knockdown of p22phox by small interfering RNA (siRNA) gave rise to decrement of ROS production and increment of the levels of PP2Ac Tyr307 and eNOS Ser1177. These results indicated that AngII/AT₁R pathway activated PP2A by downregulating its catalytic subunit Tyr307 phosphorylation, which relies on the Nox activation and ROS production. In summary, our findings indicate that AngII downregulates PP2A catalytic subunit Tyr307 phosphorylation to activate PP2A via AT₁R-mediated Nox/ROS signaling pathway. The activated PP2A further decreases levels of eNOS Ser1177 phosphorylation and NO content leading to endothelial dysfunction.

Roles of I2PP2A in the downregulation of eNOS Ser1177 phosphorylation by angiotensin II-activated PP2A

The chronic elevation of angiotensin II (Ang II) is an important cause of endothelial dysfunction (ED). The Ang II/type 1 receptor (AT₁R) signaling pathway can cause endothelial nitric oxide synthase (eNOS)/nitric oxide (NO) dysfunction through various mechanisms leading to ED. The modulation of eNOS phosphorylated at Ser1177 is an important mechanism upregulating eNOS activity. Protein phosphatase 2 A (PP2A) has been reported to dephosphorylate eNOS at Ser1177. The PP2A inhibitor 2 protein (I₂^PP2A) is a specific endogenous inhibitor that binds the catalytic subunit of PP2A and directly inhibits PP2A activity. Therefore, we hypothesized that Ang II might attenuate I₂^PP2A expression to activate PP2A, which downregulates eNOS Ser 1177 phosphorylation, leading to eNOS dysfunction. In our study, we used Ang II-treated human umbilical vein endothelial cells (HUVECs) and, found that the eNOS Ser1177 phosphorylation levels were downregulated, the activity of PP2A was increased, and I₂^PP2A expression was decreased. Furthermore, these effects were blocked by candesartan (CAN). The phosphorylation levels of eNOS Ser1177 were decreased after I₂^PP2A was knocked down by specific siRNA but increased after I₂^PP2A overexpression. We also found that the Ang II treatment decreased the association of I₂^PP2A with PP2A but increased the association between PP2A and eNOS. Taken together, our results suggest that Ang II activates PP2A by downregulating the I₂^PP2A expression through the AT₁R signaling pathway leading to the loss of eNOS Ser1177 phosphorylation and ED.

6-Gingerol Normalizes the Expression of Biomarkers Related to Hypertension via PPARδ in HUVECs, HEK293, and Differentiated 3T3-L1 Cells

Hypertension is a disease with a high prevalence and high mortality rates worldwide. In addition, various factors, such as genetic predisposition, lifestyle factors, and the abnormality of organs related to blood pressure, are involved in the development of hypertension. However, at present, there are few available drugs for hypertension that do not induce side effects. Although the therapeutic effects of ginger on hypertension are well established, the precise mechanism has not been elucidated. Therefore, this study was designed to evaluate the antihypertensive mechanism of 6-gingerol, one of the main ingredients of ginger, and to assist in the development of new drugs for hypertension without side effects. The antihypertensive effects and mechanism of 6-gingerol were identified through reverse transcription polymerase chain reaction (RT-PCR), western blotting, and immunocytochemical staining for biomarkers involved in hypertension in human umbilical vein endothelial cells (HUVECs), human embryonal kidney cells (HEK293 cells), and mouse preadipocytes (3T3-L1 cells). The lipid accumulation in differentiated 3T3-L1 cells was evaluated by using Oil Red O staining. 6- Gingerol increased the level of phosphorylated endothelial nitric oxide synthase (eNOS) protein but decreased that of vascular cell adhesion protein 1 (VCAM1) and tumor necrosis factor alpha (TNFα) in HUVECs. In HEK293 cells, the expression of the epithelial sodium channel (ENaC) protein was reduced by 6-gingerol. Lipid accumulation was attenuated by 6-gingerol treatment in differentiated 3T3-L1 cells. These effects were regulated via peroxisome proliferator-activated receptor delta (PPARδ). 6-Gingerol ameliorated the expression of biomarkers involved in the development of hypertension through PPARδ in HUVECs, HEK293, and differentiated 3T3-L1 cells.