Tetramethylpyrazine suppresses angiotensin II-induced soluble epoxide hydrolase expression in coronary endothelium via anti-ER stress mechanism

The role of Chinese herbal medicine in the regulation of oxidative stress in treating hypertension: from therapeutics to mechanisms

BACKGROUND

Although the pathogenesis of essential hypertension is not clear, a large number of studies have shown that oxidative stress plays an important role in the occurrence and development of hypertension and target organ damage.

PURPOSE

This paper systematically summarizes the relationship between oxidative stress and hypertension, and explores the potential mechanisms of Chinese herbal medicine (CHM) in the regulation of oxidative stress in hypertension, aiming to establish a scientific basis for the treatment of hypertension with CHM.

METHODS

To review the efficacy and mechanism by which CHM treat hypertension through targeting oxidative stress, data were searched from PubMed, EMBASE, the Cochrane Central Register of Controlled Trials, the Chinese National Knowledge Infrastructure, the VIP Information Database, the Chinese Biomedical Literature Database, and the Wanfang Database from their inception up to January 2024. NPs were classified and summarized by their mechanisms of action.

RESULTS

In hypertension, the oxidative stress pathway of the body is abnormally activated, and the antioxidant system is inhibited, leading to the imbalance between the oxidative and antioxidative capacity. Meanwhile, excessive production of reactive oxygen species can lead to endothelial damage and vascular dysfunction, resulting in inflammation and immune response, thereby promoting the development of hypertension and damaging the heart, brain, kidneys, blood vessels, and other target organs. Numerous studies suggested that inhibiting oxidative stress may be the potential therapeutic target for hypertension. In recent years, the clinical advantages of traditional Chinese medicine (TCM) in the treatment of hypertension have gradually attracted attention. TCM, including active ingredients of CHM, single Chinese herb, TCM classic formula and traditional Chinese patent medicine, can not only reduce blood pressure, improve clinical symptoms, but also improve oxidative stress, thus extensively affect vascular endothelium, renin-angiotensin-aldosterone system, sympathetic nervous system, target organ damage, as well as insulin resistance, hyperlipidemia, hyperhomocysteinemia and other pathological mechanisms and hypertension related risk factors.

CONCLUSIONS

CHM display a beneficial multi-target, multi-component, overall and comprehensive regulation characteristics, and have potential value for clinical application in the treatment of hypertension by regulating the level of oxidative stress.

ER stress modulates Kv1.5 channels via PERK branch in HL-1 atrial myocytes: Relevance to atrial arrhythmogenesis and the effect of tetramethylpyrazine

Endoplasmic reticulum (ER) stress is implicated in cardiac arrhythmia whereas the associated mechanisms remain inadequately understood. Kv1.5 channels are essential for atrial repolarization. Whether ER stress affects Kv1.5 channels is unknown. This study aimed to elucidate the response of Kv1.5 channels to ER stress by clarifying the unfolded protein response (UPR) branch responsible for the channel modulation. In addition, the effect of tetramethylpyrazine (TMP) on Kv1.5 channels was studied. Patch clamp and western-blot results revealed that exposure of HL-1 atrial myocytes to ER stress inducer tunicamycin upregulates Kv1.5 expression, increases Kv1.5 channel current (I Kur ) (14.91 ± 1.11 vs. 6.11 ± 1.31 pA/pF, P < 0.001), and shortened action potential duration (APD) (APD90: 82.79 ± 5.25 vs.121.11 ± 6.72 ms, P < 0.01), which could be reverted by ER stress inhibitors. Blockade of the PERK branch while not IRE1 and ATF6 branches of UPR downregulated Kv1.5 expression, accompanied by a decreased I Kur (9.03 ± 0.99 pA/pF) and a prolonged APD90 (113.69 ± 4.41 ms) (P < 0.01). PERK-mediated increases of Kv1.5 expression and I Kur were also observed in HL-1 cells incubated with thapsigargin. TMP suppressed the enhancement of I Kur (10.52 ± 0.97 vs. 17.52 ± 2.25 pA/pF, P < 0.05), prevented the shortening of APD (APD90: 110.16 ± 5.36 vs. 84.84 ± 4.58 ms, P < 0.05), and inhibited the upregulation of Kv1.5 triggered by ER stress. Our study suggests that ER stress induces upregulation and activation of Kv1.5 channels in atrial myocytes through the PERK branch of UPR. TMP prevents Kv1.5 upregulation/activation and the resultant APD shortening by inhibiting ER stress. These results may shed light on the mechanisms of atrial arrhythmogenesis and the antiarrhythmic effect of the traditional Chinese herb TMP.

Tissue-, Region-, and Gene-Specific Induction of Microsomal Epoxide Hydrolase Expression and Activity in the Mouse Intestine by Arsenic in Drinking Water

This study aimed to characterize the effects of arsenic exposure on the expression of microsomal epoxide hydrolase (mEH or EPHX1) and soluble epoxide hydrolase (sEH or EPHX2) in the liver and small intestine. C57BL/6 mice were exposed to sodium arsenite in drinking water at various doses for up to 28 days. Intestinal, but not hepatic, mEH mRNA and protein expression was induced by arsenic at 25 ppm, in both males and females, whereas hepatic mEH expression was induced by arsenic at 50 or 100 ppm. The induction of mEH was gene specific, as the arsenic exposure did not induce sEH expression in either tissue. Within the small intestine, mEH expression was induced only in the proximal, but not the distal segments. The induction of intestinal mEH was accompanied by increases in microsomal enzymatic activities toward a model mEH substrate, cis-stilbene oxide, and an epoxide-containing drug, oprozomib, in vitro, and by increases in the levels of PR-176, the main hydrolysis metabolite of oprozomib, in the proximal small intestine of oprozomib-treated mice. These findings suggest that intestinal mEH, playing a major role in converting xenobiotic epoxides to less reactive diols, but not sEH, preferring endogenous epoxides as substrates, is relevant to the adverse effects of arsenic exposure, and that further studies of the interactions between drinking water arsenic exposure and the disposition or possible adverse effects of epoxide-containing drugs and other xenobiotic compounds in the intestine are warranted. SIGNIFICANCE STATEMENT: Consumption of arsenic-contaminated water has been associated with increased risks of various adverse health effects, such as diabetes, in humans. The small intestinal epithelial cells are the main site of absorption of ingested arsenic, but they are not well characterized for arsenic exposure-related changes. This study identified gene expression changes in the small intestine that may be mechanistically linked to the adverse effects of arsenic exposure and possible interactions between arsenic ingestion and the pharmacokinetics of epoxide-containing drugs in vivo.

HMGB1-induced activation of ER stress contributes to pulmonary artery hypertension in vitro and in vivo

BACKGROUND

HMGB1 and ER stress have been considered to participate in the progression of pulmonary artery hypertension (PAH). However, the molecular mechanism underlying HMGB1 and ER stress in PAH remains unclear. This study aims to explore whether HMGB1 induces pulmonary artery smooth muscle cells (PASMCs) functions and pulmonary artery remodeling through ER stress activation.

METHODS

Primary cultured PASMCs and monocrotaline (MCT)-induced PAH rats were applied in this study. Cell proliferation and migration were determined by CCK-8, EdU and transwell assay. Western blotting was conducted to detect the protein levels of protein kinase RNA-like endoplasmic reticulum kinase (PERK), activating transcription factor-4 (ATF4), seven in absentia homolog 2 (SIAH2) and homeodomain interacting protein kinase 2 (HIPK2). Hemodynamic measurements, immunohistochemistry staining, hematoxylin and eosin staining were used to evaluate the development of PAH. The ultrastructure of ER was observed by transmission electron microscopy.

RESULTS

In primary cultured PASMCs, HMGB1 reduced HIPK2 expression through upregulation of ER stress-related proteins (PERK and ATF4) and subsequently increased SIAH2 expression, which ultimately led to PASMC proliferation and migration. In MCT-induced PAH rats, interfering with HMGB1 by glycyrrhizin, suppression of ER stress by 4-phenylbutyric acid or targeting SIAH2 by vitamin K3 attenuated the development of PAH. Additionally, tetramethylpyrazine (TMP), as a component of traditional Chinese herbal medicine, reversed hemodynamic deterioration and vascular remodeling by targeting PERK/ATF4/SIAH2/HIPK2 axis.

CONCLUSIONS

The present study provides a novel insight to understand the pathogenesis of PAH and suggests that targeting HMGB1/PERK/ATF4/SIAH2/HIPK2 cascade might have potential therapeutic value for the prevention and treatment of PAH.

Endoplasmic Reticulum Stress and Renin-Angiotensin System Crosstalk in Endothelial Dysfunction

BACKGROUND

Vascular endothelial dysfunction (VED) significantly results in catastrophic cardiovascular diseases with multiple aetiologies. Variations in vasoactive peptides, including angiotensin II and endothelin 1, and metabolic perturbations like hyperglycaemia, altered insulin signalling, and homocysteine levels result in pathogenic signalling cascades, which ultimately lead to VED. Endoplasmic reticulum (ER) stress reduces nitric oxide availability, causes aberrant angiogenesis, and enhances oxidative stress pathways, consequently promoting endothelial dysfunction. Moreover, the renin-angiotensin system (RAS) has widely been acknowledged to impact angiogenesis, endothelial repair and inflammation. Interestingly, experimental studies at the preclinical level indicate a possible pathological link between the two pathways in the development of VED. Furthermore, pharmacological modulation of ER stress ameliorates angiotensin-II mediated VED as well as RAS intervention either through inhibition of the pressor arm or enhancement of the depressor arm of RAS, mitigating ER stress-induced endothelial dysfunction and thus emphasizing a vital crosstalk.

CONCLUSION

Deciphering the pathway overlap between RAS and ER stress may open potential therapeutic avenues to combat endothelial dysfunction and associated diseases. Several studies suggest that alteration in a component of RAS may induce ER stress or induction of ER stress may modulate the RAS components. In this review, we intend to elaborate on the crosstalk of ER stress and RAS in the pathophysiology of VED.

Ligustrazine prevents coronary microcirculation dysfunction in rats via suppression of miR-34a-5p and promotion of Sirt1

INTRODUCTION

The coronary microembolization contributes to coronary microvascular dysfunction (CMD), in which miR-34a-5p may play a critical role. Ligustrazine has been reported to improve CMD. The present study was designed to discuss the role of miR-34a-5p/Sirt1 pathway in CMD and explore the underlying mechanism of ligustrazine.

METHODS

Coronary microembolization (CME) was induced by left ventricle injection of sodium laurate in rats. CME formation and cardiac function were examined by HE staining and hemodynamic tests to evaluate CMD. The expressions of miR-34a-5p, Sirt1 and the downstream proteins were detected by RT-qPCR and western blot. Dual-luciferase reporter (DLR) assay was performed to confirm the connection between miR-34a-5p and Sirt1. The blood markers of endothelial dysfunction, platelet activation and inflammation were examined with ELISA.

RESULTS

Overt CME and cardiac dysfunction as well as up-regulated miR-34a-5p and down-regulated Sirt1 were observed in CME rats. Overexpressing miR-34a-5p aggravated while silencing miR-34a-5p inhibited CME formation. DLR assay confirmed that miR-34a-5p directly inhibited Sirt1 mRNA expression. Ligustrazine pretreatment suppressed miR-34a-5p and promoted Sirt1 expression, which alleviated endothelial dysfunction, inhibited platelet activation and inflammation, and in turn reduced CME. Overexpressing miR-34a-5p diminished the positive effects of ligustrazine; while after silencing miR-34a-5p, ligustrazine failed to further promote Sirt1 expression and inhibit CME formation.

CONCLUSION

MiR-34a-5p contributes to CMD by inhibiting Sirt1 expression. Ligustrazine exerts endothelial-protective, anti-platelet and anti-inflammatory effects to prevent CMD via suppressing miR-34a-5p and promoting Sirt1.

Tetramethylpyrazine: A review on its mechanisms and functions

Ligusticum chuanxiong Hort (known as Chuanxiong in China, CX) is one of the most widely used and long-standing medicinal herbs in China. Tetramethylpyrazine (TMP) is an alkaloid and one of the active components of CX. Over the past few decades, TMP has been proven to possess several pharmacological properties. It has been used to treat a variety of diseases with excellent therapeutic effects. Here, the pharmacological characteristics and molecular mechanism of TMP in recent years are reviewed, with an emphasis on the signal-regulation mechanism of TMP. This review shows that TMP has many physiological functions, including anti-oxidant, anti-inflammatory, and anti-apoptosis properties; autophagy regulation; vasodilation; angiogenesis regulation; mitochondrial damage suppression; endothelial protection; reduction of proliferation and migration of vascular smooth muscle cells; and neuroprotection. At present, TMP is used in treating cardiovascular, nervous, and digestive system conditions, cancer, and other conditions and has achieved good curative effects. The therapeutic mechanism of TMP involves multiple targets, multiple pathways, and bidirectional regulation. TMP is, thus, a promising drug with great research potential.

Mechanisms and Efficacy of Traditional Chinese Medicine in Heart Failure

Heart failure (HF) is one of the main public health problems at present. Although some breakthroughs have been made in the treatment of HF, the mortality rate remains very high. However, we should also pay attention to improving the quality of life of patients with HF. Traditional Chinese medicine (TCM) has a long history of being used to treat HF. To demonstrate the clinical effects and mechanisms of TCM, we searched published clinical trial studies and basic studies. The search results showed that adjuvant therapy with TCM might benefit patients with HF, and its mechanism may be related to microvascular circulation, myocardial energy metabolism, oxidative stress, and inflammation.

Targeting IRE1α-JNK-c-Jun/AP-1-sEH Signaling Pathway Improves Myocardial and Coronary Endothelial Function Following Global Myocardial Ischemia/Reperfusion

Objectives: Endoplasmic reticulum (ER) stress and soluble epoxide hydrolase (sEH) upregulation/activation have been implicated in myocardial ischemia/reperfusion (I/R) injury. We previously reported that ER stress mediates angiotensin II-induced sEH upregulation in coronary endothelium, whether and how ER stress regulates sEH expression to affect postischemic cardiac function remain unexplored. This study aimed to unravel the signaling linkage between ER stress and sEH in an ex vivo model of myocardial I/R injury. Methods: Hearts from male Wistar-Kyoto rats were mounted on a Langendorff apparatus and randomly allocated to 7 groups, including control, I/R (30-min ischemia and 60-min reperfusion), and I/R groups pretreated with one of the following inhibitors: 4-PBA (targeting: ER stress), GSK2850163 (IRE1α), SP600125 (JNK), SR11302 (AP-1), and DCU (sEH). The inhibitor was administered for 15 min before ischemia with a peristaltic pump. Hemodynamic parameters including left ventricular systolic pressure (LVSP), left ventricular end-diastolic pressure (LVEDP), and maximal velocity of contraction (+dp/dt_max) and relaxation (-dp/dt_max) of the left ventricle were continuously recorded using an intraventricular balloon. Endothelial dilator function of the left anterior descending artery was studied in a wire myograph upon completion of reperfusion. The expression of ER stress molecules, JNK, c-Jun, and sEH was determined by western-blot. Results: I/R decreased LVSP (105.5±6.4 vs. 146.9±13.4 mmHg), and increased LVEDP (71.4±3.0 vs. 6.0±2.7 mmHg), with a resultant decreased LVDP (34.1±9.2 vs. 140.9±13.1 mmHg). I/R attenuated +dp/dt_max (651.7±142.1 vs. 2806.6±480.6 mmHg/s) and -dp/dt_max (-580.0±109.6 vs. -2118.0±244.9 mmHg/s) (all ps<0.001). The I/R-induced cardiac dysfunction could be alleviated by 4-PBA (LVSP 119.5±15.6 mmHg, p<0.01; LVEDP 21.2±4.2 mmHg, LVDP 98.3±12.0 mmHg, +dp/dt_max 2166.7±208.4 mmHg/s, and -dp/dt_max -1350.9±99.8 mmHg/s, all ps<0.001), GSK2850163 (LVSP 113.4±10.9 mmHg, p<0.01; LVEDP 37.1±3.1 mmHg, LVDP 76.3±13.9 mmHg, +dp/dt_max 1586.5±263.3 mmHg/s, -dp/dt_max -1127.7±159.9 mmHg/s, all ps<0.001), SP600125 (LVSP 113.9±5.6 mmHg, LVDP 40.5±3.3 mmHg, +dp/dt_max 970.1±89.8 mmHg/s, all ps<0.01), SR11302 (LVSP 97.9±7.5 mmHg, p<0.01; LVEDP 52.7±8.6mmHg, p<0.001; LVDP 45.2±9.8mmHg, p<0.05; +dp/dt_max 1231.5±196.6 mmHg/s, p<0.01; -dp/dt_max -658.3±68.9 mmHg/s, p<0.05), or DCU (LVSP 109.9±4.1 mmHg, p<0.01; LVEDP 11.7±1.8 mmHg, LVDP 98.2±4.9 mmHg, +dp/dt_max 1869.8±121.9 mmHg/s, and -dp/dt_max -1492.3±30.8 mmHg/s, all ps<0.001). The relaxant response of the coronary artery to acetylcholine was decreased after I/R in terms of both magnitude and sensitivity (p<0.001). All inhibitors improved acetylcholine-induced relaxation. Global I/R increased sEH expression and induced ER stress in both myocardium and coronary artery. Inhibition of ER stress or IRE1α downregulated I/R-induced sEH expression and inhibited JNK and c-Jun phosphorylation. Both JNK and AP-1 inhibitors lowered sEH level in myocardium and coronary artery in I/R-injured hearts. Conclusions: This study deciphered the molecular linkage between ER stress and sEH regulation in global I/R insult by uncovering a novel signaling axis of IRE1α-JNK-c-Jun/AP-1-sEH, which provided basis for future research on the therapeutic potential of targeting the IRE1α-JNK-c-Jun/AP-1-sEH axis for ischemic myocardial injury.

Protective effects of tetramethylpyrazine on dysfunction of the locus coeruleus in rats exposed to single prolonged stress by anti-ER stress mechanism

Post-traumatic stress disorder (PTSD) is a serious stress-related neuropsychiatric disorder caused by major traumatic events. Abnormal activity of the locus coeruleus (LC)-noradrenergic system is related to the development of PTSD-like symptoms. Our previous studies have indicated that endoplasmic reticulum (ER) stress induced neuronal apoptosis of LC in rats with PTSD. The purpose of this study was to further investigate the role of ER stress pathways in LC neuronal dysfunction and elucidate the effect of the bioactive component tetramethylpyrazine (TMP) against ER stress response. We used an acute exposure to single prolonged stress (SPS) to model PTSD in rats. There were higher norepinephrine (NE) levels in the brain, increased tyrosine hydroxylase expression in LC, and enhanced anxiety-like behaviors in rats exposed to SPS, which were observed by enzyme-linked immunosorbent assay, western blot analysis and elevated plus maze test, respectively. In addition, the three major pathways of ER stress were activated by SPS exposure, which may be involved in the dysregulation of the LC-noradrenergic system of rats with PTSD. Furthermore, we found that TMP administration significantly suppressed the increased responsiveness of LC-noradrenergic system, effectively reduced the anxiety response of SPS rats, and selectively attenuated the activation of pro-apoptotic ER stress pathways. The results suggest that TMP was efficient in improving the LC-NE dysfunction induced by excessive ER stress. TMP exhibited a significant neuroprotective effect and potential therapeutics on PTSD-like symptoms.

The combination of two natural medicines, Chuanxiong and Asarum: A review of the chemical constituents and pharmacological activities

Traditional Chinese medicine has been clinically used in China for many years, with experimental studies and clinical trials having demonstrated that it is safe and valid. Among many traditional natural medicines, Chuanxiong and Asarum have been proven to be effective in the treatment of relieving pain. Actually, as well as analgesic, they have common attributes, such as anti-inflammatory, cardiovascular benefits, and anticancer activities, with volatile oils being their major components. Furthermore, Chuanxiong and Asarum have been combined as drug pairs in the same prescription for thousands of years, with examples being Chuanxiong Chatiao San and Chuanxiongxixintang. More interestingly, their combination has better therapeutic effects on diseases than a single drug. After the combination of Chuanxiong and Asarum forms a blend, a series of changes take place in their chemical components, such as the contents of the main active ingredients, ferulic acid and ligustilide, increased significantly after this progress. At the same time, the pharmacological effects of the combination appearing to be more powerful, such as synergistic analgesic. This review focuses on the chemical constituents and pharmacological activities of Chuanxiong, Asarum, and Chuanxiong Asarum compositions.

Molecular mechanism of Chuanxiong Rhizoma in treating coronary artery diseases

Objective

Most of the studies on the herb Chuanxiong Rhizoma (CR) have focused on the l-arginine-nitric oxide (NO) pathway, but the nitrate-nitrite-NO (NO₃⁻–NO₂⁻–NO) pathway was rarely investigated. Therefore, the aim of this study was to evaluate the effects and mechanisms of action of CR in coronary artery disease (CAD).

Methods

The NO₃⁻, NO₂⁻ and NO levels were examined in the NO₃⁻–NO₂⁻–NO pathway. High-performance ion chromatography was used to quantify NO₃⁻ and NO₂⁻ levels. Then, NO was quantified using a multifunctional enzyme marker with a fluorescent probe. The tension of aortic rings was measured using a multi myograph system.

Results

High content of NO₃⁻ and low content of NO₂⁻ was found in CR, and which could potently convert NO₃⁻ to NO₂⁻ in the presence of endogenous reductase enzyme. Incubating human coronary artery endothelial cells (HCAECs) with CR-containing serum showed that CR significantly decreased the NO₃⁻ content and increased the levels of NO₂⁻ and NO in the cells under hypoxic conditions. In addition, CR significantly relaxed isolated aortic rings when the l-arginine –NO pathway was blocked. The optimal concentration of CR for relaxation was 200 mg/mL.

Conclusion

CR supplements large amounts of NO in cells and vessels to achieve relaxation via the NO₃⁻–NO₂⁻–NO pathway, thereby making up for the deficiency caused by the lack of NO after the l-arginine-NO pathway is suppressed. This study also supports the potential use of a traditional Chinese herb for future drug development.

Soluble epoxide hydrolase deletion attenuated nicotine-induced arterial stiffness via limiting the loss of SIRT1

Arterial stiffness, a consequence of smoking, is an underlying risk factor of cardiovascular diseases. Epoxyeicosatrienoic acids (EETs), hydrolyzed by soluble epoxide hydrolase (sEH), have beneficial effects against vascular dysfunction. However, the role of sEH knockout in nicotine-induced arterial stiffness was not characterized. We hypothesized that sEH knockout could prevent nicotine-induced arterial stiffness. In the present study, Ephx2 (the gene encodes sEH enzyme) null (Ephx2^-/-) mice and wild-type (WT) littermate mice were infused with or without nicotine and administered with or without nicotinamide [NAM, sirtuin-1 (SIRT1) inhibitor] simultaneously for 4 wk. Nicotine treatment increased sEH expression and activity in the aortas of WT mice. Nicotine infusion significantly induced vascular remodeling, arterial stiffness, and SIRT1 deactivation in WT mice, which was attenuated in Ephx2 knockout mice (Ephx2^-/- mice) without NAM treatment. However, the arterial protective effects were gone in Ephx2^-/- mice with NAM treatment. In vitro, 11,12-EET treatment attenuated nicotine-induced matrix metalloproteinase 2 (MMP2) upregulation via SIRT1-mediated yes-associated protein (YAP) deacetylation. In conclusion, sEH knockout attenuated nicotine-induced arterial stiffness and vascular remodeling via SIRT1-induced YAP deacetylation.NEW & NOTEWORTHY We presently show that sEH knockout repressed nicotine-induced arterial stiffness and extracellular matrix remodeling via SIRT1-induced YAP deacetylation, which highlights that sEH is a potential therapeutic target in smoking-induced arterial stiffness and vascular remodeling.

Potential therapeutic compounds from traditional Chinese medicine targeting endoplasmic reticulum stress to alleviate rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease which affects about 0.5-1% of people with symptoms that significantly impact a sufferer's lifestyle. The cells involved in propagating RA tend to display pro-inflammatory and cancer-like characteristics. Medical drug treatment is currently the main avenue of RA therapy. However, drug options are limited due to severe side effects, high costs, insufficient disease retardation in a majority of patients, and therapeutic effects possibly subsiding over time. Thus there is a need for new drug therapies. Endoplasmic reticulum (ER) stress, a condition due to accumulation of misfolded proteins in the ER, and subsequent cellular responses have been found to be involved in cancer and inflammatory pathologies, including RA. ER stress protein markers and their modulation have therefore been suggested as therapeutic targets, such as GRP78 and CHOP, among others. Some current RA therapeutic drugs have been found to have ER stress-modulating properties. Traditional Chinese Medicines (TCMs) frequently use natural products that affect multiple body and cellular targets, and several medicines and/or their isolated compounds have been found to also have ER stress-modulating capabilities, including TCMs used in RA treatment by Chinese Medicine practitioners. This review encourages, in light of the available information, the study of these RA-treating, ER stress-modulating TCMs as potential new pharmaceutical drugs for use in clinical RA therapy, along with providing a list of other ER stress-modulating TCMs utilized in treatment of cancers, inflammatory diseases and other diseases, that have potential use in RA treatment given similar ER stress-modulating capacity.

Endothelial Nox4 dysfunction aggravates atherosclerosis by inducing endoplasmic reticulum stress and soluble epoxide hydrolase

BACKGROUND AND AIMS

Our previous findings have demonstrated the protective effect of endothelial Nox4-based NADPH oxidase on atherosclerosis. One of the possible mechanisms is the inhibition of soluble epoxide hydrolase (sEH), a proinflammatory and atherogenic factor. Our goal was to investigate whether in vivo inhibition of sEH by 1-trifluoromethoxyphenyl-3-(1-propionylpiperidin-4-yl) urea (TPPU) alleviates endothelial Nox4 dysfunction caused atherosclerosis and the regulatory mechanism of endothelial Nox4 on sEH.

METHODS

& results: We used endothelial human Nox4 dominant-negative (EDN) transgenic mice in ApoE deficient background to mimic the dysfunction of endothelial Nox4 in atherosclerosis-prone conditions. In EDN aortic endothelium, sEH and the inflammatory marker vascular cell adhesion molecule 1 (VCAM1) were upregulated. TPPU reduced atherosclerotic lesions in EDN mice. In EDN endothelial cells (ECs), the endoplasmic reticulum (ER) stress markers (BIP, IRE1α, phosphorylation of PERK, ATF6) were upregulated, and they can be suppressed by ER stress inhibitor 4-phenyl butyric acid (4-PBA). In EDN ECs, 4-PBA downregulated the expression of sEH and VCAM1, suppressed inflammation, and its application in vivo reduced atherosclerotic lesions of EDN mice.

CONCLUSIONS

Endothelial Nox4 dysfunction upregulated sEH to enhance inflammation, probably by its induction of ER stress. Inhibition of ER stress or sEH is beneficial to alleviate atherosclerosis caused by endothelial Nox4 dysfunction.

Soluble Epoxide Hydrolase Hepatic Deficiency Ameliorates Alcohol-Associated Liver Disease

BACKGROUND & AIMS

Alcohol-associated liver disease (ALD) is a significant cause of liver-related morbidity and mortality worldwide and with limited therapies. Soluble epoxide hydrolase (sEH; Ephx2) is a largely cytosolic enzyme that is highly expressed in the liver and is implicated in hepatic function, but its role in ALD is mostly unexplored.

METHODS

To decipher the role of hepatic sEH in ALD, we generated mice with liver-specific sEH disruption (Alb-Cre; Ephx2^fl/fl). Alb-Cre; Ephx2^fl/fl and control (Ephx2^fl/fl) mice were subjected to an ethanol challenge using the chronic plus binge model of ALD and hepatic injury, inflammation, and steatosis were evaluated under pair-fed and ethanol-fed states. In addition, we investigated the capacity of pharmacologic inhibition of sEH in the chronic plus binge mouse model.

RESULTS

We observed an increase of hepatic sEH in mice upon ethanol consumption, suggesting that dysregulated hepatic sEH expression might be involved in ALD. Alb-Cre; Ephx2^fl/fl mice presented efficient deletion of hepatic sEH with corresponding attenuation in sEH activity and alteration in the lipid epoxide/diol ratio. Consistently, hepatic sEH deficiency ameliorated ethanol-induced hepatic injury, inflammation, and steatosis. In addition, targeted metabolomics identified lipid mediators that were impacted significantly by hepatic sEH deficiency. Moreover, hepatic sEH deficiency was associated with a significant attenuation of ethanol-induced hepatic endoplasmic reticulum and oxidative stress. Notably, pharmacologic inhibition of sEH recapitulated the effects of hepatic sEH deficiency and abrogated injury, inflammation, and steatosis caused by ethanol feeding.

CONCLUSIONS

These findings elucidated a role for sEH in ALD and validated a pharmacologic inhibitor of this enzyme in a preclinical mouse model as a potential therapeutic approach.

Tetramethylpyrazine reduces the consequences of nitric oxide inhibition in pregnant rats

Pre-eclampsia (PE) is closely associated with perinatal morbidity and mortality and we want to investigate tetramethylpyrazine (TMP)'s effects on PE. Pregnant Sprague-Dawley rats were randomly divided into five groups: normal pregnant (PC), PE, PE+TMP 20 mg/kg, PE+TMP 40 mg/kg, and PE+TMP 60 mg/kg group. The PE rat model was established via L-NAME treatment. Systolic blood pressures (SBP) and urinary protein concentration were detected via the tail-cuff method and CBB kit, respectively. mRNA levels of key genes were analyzed via quantitative PCR and protein levels of key genes were measured by ELISA or western blot. TMP decreased SBP and urinary protein concentration of PE rats. TMP inhibited L-NAME-induced decrease in pups alive ratio, pups weight, and the ratio of pups/placenta weight and reversed L-NAME induced changes in placental histology, whereas it had little effect on placental weight. Urinary nephrin and podocin expressions were enhanced and serum placental growth factor level was decreased in PE rats, whereas TMP inhibited the above phenomena. TMP suppressed L-NAME-induced sFlt-1 upregulation in serums and kidneys of PE rats, whereas it downregulated IL-6 and MCP-1 expression in PE rats' serums, placentas and kidneys. TMP also suppressed the increase in placental sFlt-1 and vascular endothelial growth factor level caused by L-NAME. In addition, TMP inhibited CHOP and GRP78 expressions and decreased the ratio of p-elF2α/elF2α in PE rats. TMP attenuated the consequences of NO inhibition in pregnant rats.

The histone demethylase Jarid1b mediates angiotensin II-induced endothelial dysfunction by controlling the 3'UTR of soluble epoxide hydrolase

AIM

The histone demethylase Jarid1b limits gene expression by removing the active methyl mark from histone3 lysine4 at gene promoter regions. A vascular function of Jarid1b is unknown, but a vasoprotective function to inflammatory and hypertrophic stimuli, like angiotensin II (AngII) could be inferred. This hypothesis was tested using Jarid1b knockout mice and the inhibitor PBIT.

METHODS

Mice or aortic segments were treated with AngII to induce endothelial dysfunction. Aortae from WT and Jarid1b knockout were studied in organ chambers and endothelium-dependent dilator responses to acetylcholine and endothelium-independent responses to DetaNONOate were recorded after pre-constriction with phenylephrine in the presence or absence of the NO-synthase inhibitor nitro-L-arginine. Molecular mechanisms were investigated with chromatin immunoprecipitation, RNA-Seq, RNA-3'-adaptor-ligation, actinomycin D and RNA-immunoprecipitation.

RESULTS

Knockout or inhibition of Jarid1b prevented the development of endothelial dysfunction in response to AngII. This effect was not a consequence of altered nitrite oxide availability but accompanied by a loss of the inflammatory response to AngII. As Jarid1b mainly inhibits gene expression, an indirect effect should account for this observation. AngII induced the soluble epoxide hydrolase (sEH), which degrades anti-inflammatory lipids, and thus promotes inflammation. Knockout or inhibition of Jarid1b prevented the AngII-mediated sEH induction. Mechanistically, Jarid1b maintained the length of the 3'untranslated region of the sEH mRNA, thereby increasing its stability and thus sEH protein expression. Loss of Jarid1b activity therefore resulted in sEH mRNA destabilization.

CONCLUSION

Jarid1b contributes to the pro-inflammatory effects of AngII by stabilizing sEH expression. Jarid1b inhibition might be an option for future therapeutics against cardiovascular dysfunction.

Protection of dilator function of coronary arteries from homocysteine by tetramethylpyrazine: Role of ER stress in modulation of BKCa channels

OBJECTIVES

We recently reported the involvement of ER stress-mediated BK_Ca channel inhibition in homocysteine-induced coronary dilator dysfunction. In another study, we demonstrated that tetramethylpyrazine (TMP), an active ingredient of the Chinese herb Chuanxiong, possesses potent anti-ER stress capacity. The present study investigated whether TMP protects BK_Ca channels from homocysteine-induced inhibition and whether suppression of ER stress is a mechanism contributing to the protection. Furthermore, we explored the signaling transduction involved in TMP-conferred protection on BK_Ca channels.

METHODS

BK_Ca channel-mediated relaxation was studied in porcine small coronary arteries. Expressions of BK_Ca channel subunits, ER stress molecules, and E3 ubiquitin ligases, as well as BK_Ca ubiquitination were determined in porcine coronary arterial smooth muscle cells (PCASMCs). Whole-cell BK_Ca currents were recorded.

RESULTS

Exposure of PCASMCs to homocysteine or the chemical ER stressor tunicamycin increased the expression of ER stress molecules, which was significantly inhibited by TMP. Suppression of ER stress by TMP preserved the BK_Ca β1 protein level and restored the BK_Ca current in PCASMCs, concomitant with an improved BK_Ca-mediated dilatation in coronary arteries. TMP attenuated homocysteine-induced BK_Ca β1 protein ubiquitination, in which inhibition of ER stress-mediated FoxO3a activation and FoxO3a-dependent atrogin-1 and Murf-1 was involved.

CONCLUSIONS

Reversal of BK_Ca channel inhibition via suppressing ER stress-mediated loss of β1 subunits contributes to the protective effect of TMP against homocysteine on coronary dilator function. Inhibition of FoxO3a-dependent ubiquitin ligases is involved in TMP-conferred normalization of BK_Ca β1 protein level. These results provide new mechanistic insights into the cardiovascular benefits of TMP.

Targeting vascular inflammation in ischemic stroke: Recent developments on novel immunomodulatory approaches

Ischemic stroke is a devastating and debilitating medical condition with limited therapeutic options. However, accumulating evidence indicates a central role of inflammation in all aspects of stroke including its initiation, the progression of injury, and recovery or wound healing. A central target of inflammation is disruption of the blood brain barrier or neurovascular unit. Here we discuss recent developments in identifying potential molecular targets and immunomodulatory approaches to preserve or protect barrier function and limit infarct damage and functional impairment. These include blocking harmful inflammatory signaling in endothelial cells, microglia/macrophages, or Th17/γδ T cells with biologics, third generation epoxyeicosatrienoic acid (EET) analogs with extended half-life, and miRNA antagomirs. Complementary beneficial pathways may be enhanced by miRNA mimetics or hyperbaric oxygenation. These immunomodulatory approaches could be used to greatly expand the therapeutic window for thrombolytic treatment with tissue plasminogen activator (t-PA). Moreover, nanoparticle technology allows for the selective targeting of endothelial cells for delivery of DNA/RNA oligonucleotides and neuroprotective drugs. In addition, although likely detrimental to the progression of ischemic stroke by inducing inflammation, oxidative stress, and neuronal cell death, 20-HETE may also reduce susceptibility of onset of ischemic stroke by maintaining autoregulation of cerebral blood flow. Although the interaction between inflammation and stroke is multifaceted, a better understanding of the mechanisms behind the pro-inflammatory state at all stages will hopefully help in developing novel immunomodulatory approaches to improve mortality and functional outcome of those inflicted with ischemic stroke.

Ticagrelor protects against AngII-induced endothelial dysfunction by alleviating endoplasmic reticulum stress

Ticagrelor has been reported to decrease cardiovascular mortality compared with clopidogrel. This benefit cannot be fully explained by the more efficient platelet inhibition. Many studies demonstrated that ticagrelor improved endothelial function, leaving the mechanism elusive though. The present study aims to investigate whether ticagrelor protects against endothelial dysfunction induced by angiotensinII (AngII) through alleviating endoplasmic reticulum (ER) stress. Male Sprague Dawley rats were infused with AngII or vehicle and administrated with ticagrelor or vehicle for 14 days. Reactive oxygen species (ROS) was detected. Aortas from normal mice were incubated with endoplasmic reticulum stress inducer tunicamycin with or without ticagrelor. Vasorecactivity was measured on wire myography. Rat aortic endothelial cells (RAECs) were pretreated with ticagrelor followed by AngII or tunicamycin. Endothelial nitric oxide synthase (eNOS) phosphorylation and ER stress markers were determined by western blotting. Impaired endothelial function, induction of ER stress, reduced eNOS phosphorylation and elevated ROS generation was restored by ticagrelor treatment in vivo. In addition, tunicamycin induced endothelial dysfunction was improved by ticagrelor. In vitro, the induction of ER stress and inhibited eNOS phosphorylation in REACs exposed to AngII as well as tunicamycin was reversed by co-culturing with ticagrelor. In conclusion, ticagrelor protects against AngII-induced endothelial dysfunction via alleviating ER stress.