Dual Role of TRPV1 Channels in Cerebral Stroke: An Exploration from a Mechanistic and Therapeutic Perspective

Transient receptor potential vanilloid subfamily member 1 (TRPV1) has been strongly implicated in the pathophysiology of cerebral stroke. However, the exact role and mechanism remain elusive. TPRV1 channels are exclusively present in the neurovascular system and involve many neuronal processes. Numerous experimental investigations have demonstrated that TRPV1 channel blockers or the lack of TRPV1 channels may prevent harmful inflammatory responses during ischemia-reperfusion injury, hence conferring neuroprotection. However, TRPV1 agonists such as capsaicin and some other non-specific TRPV1 activators may induce transient/slight degree of TRPV1 channel activation to confer neuroprotection through a variety of mechanisms, including hypothermia induction, improving vascular functions, inducing autophagy, preventing neuronal death, improving memory deficits, and inhibiting inflammation. Another factor in capsaicin-mediated neuroprotection could be the desensitization of TRPV1 channels. Based on the summarized evidence, it may be plausible to suggest that TPRV1 channels have a dual role in ischemia-reperfusion-induced cerebral injury, and thus, both agonists and antagonists may produce neuroprotection depending upon the dose and duration. The current review summarizes the dual function of TRPV1 in ischemia-reperfusion-induced cerebral injury models, explains its mechanism, and predicts the future.

LncRNA SNHG1 alleviates myocardial ischaemia-reperfusion injury by regulating the miR-137-3p/KLF4/TRPV1 axis

AIMS

Myocardial ischaemia-reperfusion injury (MIRI) contributes to serious myocardial injury and even death. Long non-coding RNAs (lncRNAs) have been reported to play pivotal roles in the occurrence and development of MIRI. Here, the detailed molecular mechanism of lncRNA SNHG1 in MIRI was explored.

METHODS AND RESULTS

A cell model of MIRI was established through hypoxia/reoxygenation (H/R) stimulation. Cell viability and pyroptosis were evaluated utilizing MTT, PI staining, and flow cytometry. Interleukin (IL)-1β and IL-18 secretion levels were examined by ELISA. The gene and protein expression were detected by RT-qPCR and western blot, respectively. Dual luciferase reporter gene, RIP and ChIP assays were performed to analyse the molecular interactions. The results showed that lncRNA SNHG1 overexpression alleviated H/R-induced HL-1 cell pyroptosis (all P < 0.05). LncRNA SNHG1 promoted KLF4 expression by sponging miR-137-3p. miR-137-3p silencing alleviated H/R-induced pyroptosis in HL-1 cells (all P < 0.05), which was abolished by KLF4 knockdown (all P < 0.05). KLF4 activated the AKT pathway by transcriptionally activating TRPV1 in HL-1 cells (all P < 0.05). TRPV1 knockdown reversed the alleviation of SNHG1 upregulation on H/R-induced pyroptosis in HL-1 cells (all P < 0.05).

CONCLUSIONS

These results showed that lncRNA SNHG1 assuaged cardiomyocyte pyroptosis during MIRI progression by regulating the KLF4/TRPV1/AKT axis through sponging miR-137-3p. Our findings may provide novel therapeutic targets for MIRI.

Lysophosphatidic acid contributes to myocardial ischemia/reperfusion injury by activating TRPV1 in spinal cord

Lysophosphatidic acid (LPA) is a bioactive phospholipid that plays a crucial role in cardiovascular diseases. Here, we question whether LPA contributes to myocardial ischemia/reperfusion (I/R) injury by acting on transient receptor potential vanilloid 1 (TRPV1) in spinal cord. By ligating the left coronary artery to establish an in vivo I/R mouse model, we observed a 1.57-fold increase in LPA level in the cerebrospinal fluid (CSF). The I/R-elevated CSF LPA levels were reduced by HA130, an LPA synthesis inhibitor, compared to vehicle treatment (4.74 ± 0.34 vs. 6.46 ± 0.94 μg/mL, p = 0.0014). Myocardial infarct size was reduced by HA130 treatment compared to the vehicle group (26 ± 8% vs. 46 ± 8%, p = 0.0001). To block the interaction of LPA with TRPV1 at the K710 site, we generated a K710N knock-in mouse model. The TRPV1K710N mice were resistant to LPA-induced myocardial injury, showing a smaller infarct size relative to TRPV1WT mice (28 ± 4% vs. 60 ± 7%, p < 0.0001). Additionally, a sequence-specific TRPV1 peptide targeting the K710 region produced similar protective effects against LPA-induced myocardial injury. Blocking the K710 region through K710N mutation or TRPV1 peptide resulted in reduced neuropeptides release and decreased activity of cardiac sensory neurons, leading to a decrease in cardiac norepinephrine concentration and the restoration of intramyocardial pro-survival signaling, namely protein kinase B/extracellular regulated kinase/glycogen synthase kinase-3β pathway. These findings suggest that the elevation of CSF LPA is strongly associated with myocardial I/R injury. Moreover, inhibiting the interaction of LPA with TRPV1 by blocking the K710 region uncovers a novel strategy for preventing myocardial ischemic injury.

Distribution and morphology of calcitonin gene-related peptide (CGRP) innervation in flat mounts of whole rat atria and ventricles

Calcitonin gene-related peptide (CGRP) is widely used as a marker for nociceptive afferent axons. However, the distribution of CGRP-IR axons has not been fully determined in the whole rat heart. Immunohistochemically labeled flat-mounts of the right and left atria and ventricles, and the interventricular septum (IVS) in rats for CGRP were assessed with a Zeiss imager to generate complete montages of the entire atria, ventricles, and septum, and a confocal microscope was used to acquire detailed images of selected regions. We found that 1) CGRP-IR axons extensively innervated all regions of the atrial walls including the sinoatrial node region, auricles, atrioventricular node region, superior/inferior vena cava, left pre-caval vein, and pulmonary veins. 2) CGRP-IR axons formed varicose terminals around individual neurons in some cardiac ganglia but passed through other ganglia without making appositions with cardiac neurons. 3) Varicose CGRP-IR axons innervated the walls of blood vessels. 4) CGRP-IR axons extensively innervated the right/left ventricular walls and IVS. Our data shows the rather ubiquitous distribution of CGRP-IR axons in the whole rat heart at single-cell/axon/varicosity resolution for the first time. This study lays the foundation for future studies to quantify the differences in CGRP-IR axon innervation between sexes, disease models, and species.

Transient Receptor Potential (TRP) Channels in Pain, Neuropsychiatric Disorders, and Epilepsy

Pharmacomodulation of membrane channels is an essential topic in the study of physiological conditions and disease status. Transient receptor potential (TRP) channels are one such family of nonselective cation channels that have an important influence. In mammals, TRP channels consist of seven subfamilies with a total of twenty-eight members. Evidence shows that TRP channels mediate cation transduction in neuronal signaling, but the full implication and potential therapeutic applications of this are not entirely clear. In this review, we aim to highlight several TRP channels which have been shown to mediate pain sensation, neuropsychiatric disorders, and epilepsy. Recent findings suggest that TRPM (melastatin), TRPV (vanilloid), and TRPC (canonical) are of particular relevance to these phenomena. The research reviewed in this paper validates these TRP channels as potential targets of future clinical treatment and offers patients hope for more effective care.

Electroacupuncture Pretreatment Attenuates Cerebral Ischemia-Reperfusion Injury in Rats Through Transient Receptor Potential Vanilloid 1-Mediated Anti-apoptosis via Inhibiting NF-κB Signaling Pathway

Our previous study showed that electroacupuncture (EA) pretreatment elicited protective effect on cerebral ischemia-reperfusion injury (CIRI) in rats, at least partly, which was associated with transient receptor potential vanilloid 1 (TRPV1)-regulated anti-oxidant stress and anti-inflammation. In this study, we further investigated the possible contribution of TRPV1-mediated anti-apoptosis in EA pretreatment-evoked neuroprotection in CIRI. After EA pretreatment at Baihui (GV20), bilateral Shenshu (BL23) and Sanyinjiao (SP6) acupoints, transient focal cerebral ischemia was induced by middle cerebral artery occlusion (MCAO) for 2 h followed by reperfusion for 6 h in rats. Then, infarct volume, nerve cell injury, neuronal apoptosis, NF-κB signaling activation, and expression of TRPV1 were evaluated by TTC staining, Hematoxylin-Eosin staining, transmission electron microscopy, immunochemistry, immunofluorescence, and Western blot, respectively. The presented data showed that EA pretreatment significantly reduced infarct volume, relieved nerve cell injury, decreased the expression of pro-apoptotic proteins Bax and cleaved caspase-3, increased the level of anti-apoptotic protein Bcl-2, inhibited NF-κB (p65) transcriptional activity, and curbed TRPV1 expression in MCAO rats. By contrast, enhancement of TRPV1 expression accompanying capsaicin application, the specific TRPV1 agonists, markedly accelerated nerve cell damage, aggravated neuronal apoptosis, prompted nuclear translocation of NF-κB (p65), resulting in the reversion of EA pretreatment-evoked neuroprotective effect in MCAO rats. Thus, we conclude that EA pretreatment-induced downregulation of neuronal TRPV1 expression plays an anti-apoptosis role through inhibiting NF-κB signaling pathway, thereby protecting MCAO rats from cerebral ischemia-reperfusion injury.

Transient Receptor Potential Vanilloid in the Brain Gliovascular Unit: Prospective Targets in Therapy

The gliovascular unit (GVU) is composed of the brain microvascular endothelial cells forming blood–brain barrier and the neighboring surrounding “mural” cells (e.g., pericytes) and astrocytes. Modulation of the GVU/BBB features could be observed in a variety of vascular, immunologic, neuro-psychiatric diseases, and cancers, which can disrupt the brain homeostasis. Ca²⁺ dynamics have been regarded as a major factor in determining BBB/GVU properties, and previous studies have demonstrated the role of transient receptor potential vanilloid (TRPV) channels in modulating Ca²⁺ and BBB/GVU properties. The physiological role of thermosensitive TRPV channels in the BBB/GVU, as well as their possible therapeutic potential as targets in treating brain diseases via preserving the BBB are reviewed. TRPV2 and TRPV4 are the most abundant isoforms in the human BBB, and TRPV2 was evidenced to play a main role in regulating human BBB integrity. Interspecies differences in TRPV2 and TRPV4 BBB expression complicate further preclinical validation. More studies are still needed to better establish the physiopathological TRPV roles such as in astrocytes, vascular smooth muscle cells, and pericytes. The effect of the chronic TRPV modulation should also deserve further studies to evaluate their benefit and innocuity in vivo.

12(S)-HETE mediates diabetes-induced endothelial dysfunction by activating intracellular endothelial cell TRPV1

Patients with diabetes develop endothelial dysfunction shortly after diabetes onset that progresses to vascular disease underlying the majority of diabetes-associated comorbidities. Increased lipid peroxidation, mitochondrial calcium overload, and mitochondrial dysfunction are characteristics of dysfunctional endothelial cells in diabetic patients. We here identified that targeting the lipid peroxidation product 12(S)-hydroxyeicosatetraenoic acid-induced [12(S)-HETE-induced] activation of the intracellularly located cation channel transient receptor potential vanilloid 1 (TRPV1) in endothelial cells is a means to causally control early-stage vascular disease in type I diabetic mice. Mice with an inducible, endothelium-specific 12/15-lipoxygenase (12/15Lo) knockout were protected similarly to TRPV1-knockout mice from type 1 diabetes-induced endothelial dysfunction and impaired vascular regeneration following arterial injury. Both 12(S)-HETE in concentrations found in diabetic patients and TRPV1 agonists triggered mitochondrial calcium influx and mitochondrial dysfunction in endothelial cells, and 12(S)-HETE effects were absent in endothelial cells from TRPV1-knockout mice. As a therapeutic consequence, we found that a peptide targeting 12(S)-HETE-induced TRPV1 interaction at the TRPV1 TRP box ameliorated diabetes-induced endothelial dysfunction and augmented vascular regeneration in diabetic mice. Our findings suggest that pharmacological targeting of increased endothelial lipid peroxidation can attenuate diabetes-induced comorbidities related to vascular disease.

TRPV1 activation inhibits phenotypic switching and oxidative stress in vascular smooth muscle cells by upregulating PPARα

The proliferation and migration of vascular smooth muscle cells (VSMCs) is one of main reasons of vascular remodeling and is the pathogenesis of atherosclerosis and other vascular diseases. Transient receptor potential vanilloid 1 (TRPV1) is the specific receptor of capsaicin. TRPV1 has been previously reported to inhibit proliferation, migration and phenotypic switching, but the regulatory mechanisms and relevant signalling pathways are not clear. The aim of this study was to investigate the effects of capsaicin-activated TRPV1 on VSMC phenotypic switching. In this study, oxidized low density lipoprotein (ox-LDL) was used to induce the proliferation and migration of VSMCs. Our data showed that the VSMC proliferation induced by ox-LDL was dependent on the concentration of ox-LDL. Nevertheless, the data showed that capsaicin activated TRPV1 significantly decreased ox-LDL-induced superoxide anion generation. Phenotypic switching of VSMCs was inhibited by the activation of TRPV1. Furthermore, capsaicin decreased ox-LDL-induced superoxide anion generation by activating peroxisome proliferator activated receptor α (PPARα). TRPV1 inhibited VSMC phenotypic switching via upregulated expression of PPARα. It may be considered a useful target for the treatment of vascular remodeling.

Role of Bile Acids and Bile Salts in Acute Pancreatitis: From the Experimental to Clinical Studies

ABSTRACT

Acute pancreatitis (AP) is one of the most common gastroenterological disorders leading to hospitalization. It has long been debated whether biliary AP, about 30% to 50% of all cases, is induced by bile acids (BAs) when they reach the pancreas via reflux or via the systemic blood circulation.Besides their classical function in digestion, BAs have become an attractive research target because of their recently discovered property as signaling molecules. The underlying mechanisms of BAs have been investigated in various studies. Bile acids are internalized into acinar cells through specific G-protein-coupled BA receptor 1 and various transporters. They can further act via different receptors: the farnesoid X, ryanodine, and inositol triphosphate receptor. Bile acids induce a sustained Ca2+ influx from the endoplasmic reticulum and release of Ca2+ from acidic stores into the cytosol of acinar cells. The overload of intracellular Ca2+ results in mitochondrial depolarization and subsequent acinar cell necrosis. In addition, BAs have a biphasic effect on pancreatic ductal cells. A more detailed characterization of the mechanisms through which BAs contribute to the disease pathogenesis and severity will greatly improve our understanding of the underlying pathophysiology and may allow for the development of therapeutic and preventive strategies for gallstone-inducedAP.

A Potential Involvement of Anandamide in the Modulation of HO/NOS Systems: Women, Menopause, and "Medical Cannabinoids"

Endocannabinoids and their receptors are present in the cardiovascular system; however, their actions under different pathological conditions remain controversial. The aim of our study was to examine the effects of anandamide (AEA) on heme oxygenase (HO) and nitric oxide synthase (NOS) systems in an estrogen-depleted rat model. Sham-operated (SO) and surgically induced estrogen-deficient (OVX) female Wistar rats were used. During a two-week period, a group of OVX rats received 0.1 mg/kg estrogen (E₂) per os, while AEA-induced alterations were analyzed after two weeks of AEA treatment at the dose of 1.0 mg/kg. At the end of the experiment, cardiac activity and expression of HO and NOS enzymes, content of cannabinoid 1 receptor, as well as concentrations of transient potential vanilloid 1 (TRPV1) and calcitonin gene-related peptide (CGRP) were measured. Our results show that estrogen withdrawal caused a significant decrease in both NOS and HO systems, and a similar tendency was observed regarding the TRPV1/CGRP pathway. Two weeks of either AEA or E₂ treatment restored the adverse changes; however, the combined administration of these two molecules did not result in a further improvement. In light of the potential relationship between AEA and HO/NOS systems, AEA-induced upregulation of HO/NOS enzymes may be a therapeutic strategy in estrogen-deficient conditions.

Effect and Molecular Mechanisms of Collateral Vessel Growth Mediated by Activation of Transient Receptor Potential Vanilloid Type 1

Information on the function of transient receptor potential vanilloid 1 (TRPV1) in arteriogenesis is limited. We aimed to verify whether TRPV1 is involved in collateral vessel growth in rat hind limbs and elucidate the possible subcellular action mechanisms. Adult Sprague Dawley rats were chosen to establish the hind limb ischemic model and treatment with capsaicin. Angiographies were performed, and tissue was isolated for immunohistochemistry. In vitro, rat aortic endothelial cells (RAECs) were treated with capsaicin and antagonist capsazepine. The RAEC proliferation was determined, and the protein and mRNA levels of Ca2+-dependent transcription factors were assessed. In vivo, the collateral vessels exhibited positive outward remodeling characterized by enhanced inflammatory cell/macrophage accumulation in the adventitia and activated cell proliferation in all layers of the vascular wall and elevated endothelial NO synthetase expression in the rats with hind limb ligation. In RAECs, TRPV1 activation-induced Ca2+-dependent transcriptional factors, nuclear factor of activated T cells 1, calsenilin and myocyte enhancer factor 2C increase, and augmented RAEC proliferation could be a subcellular mechanism for TRPV1 in endothelial cells and ultimately contribute to collateral vessel growth. TRPV1, a novel candidate, positively regulates arteriogenesis, meriting further studies to unravel the potential therapeutic target leading to improved collateral vessel growth for treating ischemic diseases.

Endothelial TRPV1 as an Emerging Molecular Target to Promote Therapeutic Angiogenesis

Therapeutic angiogenesis represents an emerging strategy to treat ischemic diseases by stimulating blood vessel growth to rescue local blood perfusion. Therefore, injured microvasculature may be repaired by stimulating resident endothelial cells or circulating endothelial colony forming cells (ECFCs) or by autologous cell-based therapy. Endothelial Ca²⁺ signals represent a crucial player in angiogenesis and vasculogenesis; indeed, several angiogenic stimuli induce neovessel formation through an increase in intracellular Ca²⁺ concentration. Several members of the Transient Receptor Potential (TRP) channel superfamily are expressed and mediate Ca²⁺-dependent functions in vascular endothelial cells and in ECFCs, the only known truly endothelial precursor. TRP Vanilloid 1 (TRPV1), a polymodal cation channel, is emerging as an important player in endothelial cell migration, proliferation, and tubulogenesis, through the integration of several chemical stimuli. Herein, we first summarize TRPV1 structure and gating mechanisms. Next, we illustrate the physiological roles of TRPV1 in vascular endothelium, focusing our attention on how endothelial TRPV1 promotes angiogenesis. In particular, we describe a recent strategy to stimulate TRPV1-mediated pro-angiogenic activity in ECFCs, in the presence of a photosensitive conjugated polymer. Taken together, these observations suggest that TRPV1 represents a useful target in the treatment of ischemic diseases.

TRPV2 channel as a possible drug target for the treatment of heart failure

Heart transplantation is currently the only viable option available for the treatment of severe heart failure conditions such as dilated cardiomyopathy. Hence, novel drugs for treating such conditions need to be developed urgently. Recent studies suggest that Ca²⁺ overload is involved in the onset and progression of dilated cardiomyopathy, and thus heart failure. The expression and activation of the Ca²⁺ permeable channel, transient receptor potential vanilloid 2 (TRPV2) channel have been found to play an essential role in sustained intracellular Ca²⁺ concentration increase, leading to heart failure. However, since there have been no TRPV2-specific inhibitors available until recently, the effect of TRPV2 inhibition on the pathology has not been clearly elucidated. Recent reports show that inhibiting TRPV2 activity effectively improves cardiac function, suppressing myocardial fibrosis and ameliorating the prognosis in animal models of cardiomyopathy with heart failure. In addition to that, inflammation is reported to be involved in the development of heart failure. Here, we review the recent findings on TRPV2 in cardiomyocytes and immune cells involved in the development of heart failure and discuss the current progress of drug development for the treatment of heart failure via targeting TRPV2.

TRPV1 translocated to astrocytic membrane to promote migration and inflammatory infiltration thus promotes epilepsy after hypoxic ischemia in immature brain

BACKGROUND

Neonatal hypoxic-ischemic brain damage (HIBD), a leading cause of neonatal mortality, has intractable sequela such as epilepsy that seriously affected the life quality of HIBD survivors. We have previously shown that ion channel dysfunction in the central nervous system played an important role in the process of HIBD-induced epilepsy. Therefore, we continued to validate the underlying mechanisms of TRPV1 as a potential target for epilepsy.

METHODS

Neonatal hypoxic ischemia and oxygen-glucose deprivation (OGD) were used to simulate HIBD in vivo and in vitro. Primarily cultured astrocytes were used to assess the expression of TRPV1, glial fibrillary acidic protein (GFAP), cytoskeletal rearrangement, and inflammatory cytokines by using Western blot, q-PCR, and immunofluorescence. Furthermore, brain electrical activity in freely moving mice was recorded by electroencephalography (EEG). TRPV1 current and neuronal excitability were detected by whole-cell patch clamp.

RESULTS

Astrocytic TRPV1 translocated to the membrane after OGD. Mechanistically, astrocytic TRPV1 activation increased the inflow of Ca²⁺, which promoted G-actin polymerized to F-actin, thus promoted astrocyte migration after OGD. Moreover, astrocytic TRPV1 deficiency decreased the production and release of pro-inflammatory cytokines (TNF, IL-6, IL-1β, and iNOS) after OGD. It could also dramatically attenuate neuronal excitability after OGD and brain electrical activity in HIBD mice. Behavioral testing for seizures after HIBD revealed that TRPV1 knockout mice demonstrated prolonged onset latency, shortened duration, and decreased seizure severity when compared with wild-type mice.

CONCLUSIONS

Collectively, TRPV1 promoted astrocyte migration thus helped the infiltration of pro-inflammatory cytokines (TNF, IL-1β, IL-6, and iNOS) from astrocytes into the vicinity of neurons to promote epilepsy. Our study provides a strong rationale for astrocytic TRPV1 to be a therapeutic target for anti-epileptogenesis after HIBD.

TRPV1 mediates astrocyte activation and interleukin-1β release induced by hypoxic ischemia (HI)

BACKGROUND

Hypoxic-ischemic encephalopathy (HIE) is a serious birth complication with high incidence in both advanced and developing countries. Children surviving from HIE often have severe long-term sequela including cerebral palsy, epilepsy, and cognitive disabilities. The severity of HIE in infants is tightly associated with increased IL-1β expression and astrocyte activation which was regulated by transient receptor potential vanilloid 1 (TRPV1), a non-selective cation channel in the TRP family.

METHODS

Neonatal hypoxic ischemia (HI) and oxygen-glucose deprivation (OGD) were used to simulate HIE in vivo and in vitro. Primarily cultured astrocytes were used for investigating the expression of glial fibrillary acidic protein (GFAP), IL-1β, Janus kinase 2 (JAK2), signal transducer and activator of transcription 3 (STAT3), and activation of the nucleotide-binding, oligomerization domain (NOD)-like receptor pyrin domain-containing protein 3 (NLRP3) inflammasome by using Western blot, q-PCR, and immunofluorescence. Brain atrophy, infarct size, and neurobehavioral disorders were evaluated by Nissl staining, 2,3,5-triphenyltetrazolium chloride monohydrate (TTC) staining and neurobehavioral tests (geotaxis reflex, cliff aversion reaction, and grip test) individually.

RESULTS

Astrocytes were overactivated after neonatal HI and OGD challenge. The number of activated astrocytes, the expression level of IL-1β, brain atrophy, and shrinking infarct size were all downregulated in TRPV1 KO mice. TRPV1 deficiency in astrocytes attenuated the expression of GFAP and IL-1β by reducing phosphorylation of JAK2 and STAT3. Meanwhile, IL-1β release was significantly reduced in TRPV1 deficiency astrocytes by inhibiting activation of NLRP3 inflammasome. Additionally, neonatal HI-induced neurobehavioral disorders were significantly improved in the TRPV1 KO mice.

CONCLUSIONS

TRPV1 promotes activation of astrocytes and release of astrocyte-derived IL-1β mainly via JAK2-STAT3 signaling and activation of the NLRP3 inflammasome. Our findings provide mechanistic insights into TRPV1-mediated brain damage and neurobehavioral disorders caused by neonatal HI and potentially identify astrocytic TRPV1 as a novel therapeutic target for treating HIE in the subacute stages (24 h).

Kcne4 deletion sex dependently inhibits the RISK pathway response and exacerbates hepatic ischemia-reperfusion injury in mice

Activation of antiapoptotic signaling cascades, such as the reperfusion injury salvage kinase (RISK) and survivor activating factor enhancement (SAFE) pathways, is protective in a variety of tissues in the context of ischemia-reperfusion (IR) injury. Hepatic IR injury causes clinically significant hepatocellular damage in surgical procedures, including liver transplantation and hepatic resection, increasing associated morbidity and mortality. We previously found that the cardiovascular-expressed K⁺ voltage-gated channel ancillary subunit KCNE4 sex specifically influences the cardiac RISK/SAFE pathway response to IR and that Kcne4 deletion testosterone dependently exacerbates cardiac IR injury. Here, we discovered that germline Kcne4 deletion exacerbates hepatic IR injury damage in 13-mo-old male mice, despite a lack of Kcne4 expression in male mouse liver. Examining RISK/SAFE pathway induction, we found that Kcne4 deletion prevents the hepatic ERK1/2 phosphorylation response to IR injury. Conversely, in 13-mo-old female mice, Kcne4 deletion increased both baseline and post-IR GSK-3β inhibitory phosphorylation, and pharmacological GSK-3β inhibition was hepatoprotective. Finally, castration of male mice restored normal hepatic RISK/SAFE pathway responses in Kcne4^-/- mice, eliminated Kcne4 deletion-dependent serum alanine aminotransferase elevation, and genotype independently augmented the hepatic post-IR GSK-3β phosphorylation response. These findings support a role for KCNE4 as a systemic modulator of IR injury response and uncover hormonally influenced, sex-specific, KCNE4-dependent and -independent RISK/SAFE pathway induction.

Transient Receptor Potential Vanilloid 1 Expression Mediates Capsaicin-Induced Cell Death

The transient receptor potential (TRP) ion channel family consists of a broad variety of non-selective cation channels that integrate environmental physicochemical signals for dynamic homeostatic control. Involved in a variety of cellular physiological processes, TRP channels are fundamental to the control of the cell life cycle. TRP channels from the vanilloid (TRPV) family have been directly implicated in cell death. TRPV1 is activated by pain-inducing stimuli, including inflammatory endovanilloids and pungent exovanilloids, such as capsaicin (CAP). TRPV1 activation by high doses of CAP (>10 μM) leads to necrosis, but also exhibits apoptotic characteristics. However, CAP dose-response studies are lacking in order to determine whether CAP-induced cell death occurs preferentially via necrosis or apoptosis. In addition, it is not known whether cytosolic Ca²⁺ and mitochondrial dysfunction participates in CAP-induced TRPV1-mediated cell death. By using TRPV1-transfected HeLa cells, we investigated the underlying mechanisms involved in CAP-induced TRPV1-mediated cell death, the dependence of CAP dose, and the participation of mitochondrial dysfunction and cytosolic Ca²⁺ increase. Together, our results contribute to elucidate the pathophysiological steps that follow after TRPV1 stimulation with CAP. Low concentrations of CAP (1 μM) induce cell death by a mechanism involving a TRPV1-mediated rapid and transient intracellular Ca²⁺ increase that stimulates plasma membrane depolarization, thereby compromising plasma membrane integrity and ultimately leading to cell death. Meanwhile, higher doses of CAP induce cell death via a TRPV1-independent mechanism, involving a slow and persistent intracellular Ca²⁺ increase that induces mitochondrial dysfunction, plasma membrane depolarization, plasma membrane loss of integrity, and ultimately, cell death.

FOXO1 targeting by capsaicin reduces tissue damage after testicular torsion

Testicular torsion-related oxidative stress causes a sequential chain of DNA damage, lipid peroxidation and cell death that leads to the derangement in the sperm functions and infertility. Capsaicin that has been applied for pain relief and cancer prevention possesses antioxidant properties which can be exploited to confer cell survival under ischaemic testis damage. Wistar male rats weighing 150-200 g were randomly divided into four groups: (i) sham group (all procedures except torsion of testis), (ii) ischaemia group (TT group), (iii) three TT groups treated with different dose of capsaicin (TT + different doses of Cap) and (iv) three control groups treated with different doses of capsaicin (100, 500 and 1000 ug/ml). Capsaicin administration significantly decreased the expression of pro-apoptotic factors and increased the expression of anti-apoptotic factors. Likewise, the expression of FOXO1 is significantly increased by higher doses of the capsaicin. Histological assessment by H&E and TUNEL method also exhibited an improved testicular morphology and decreased apoptosis in testes. These results suggested clinical potential for capsaicin in treatment of testicular torsion by targeting FOXO1 and apoptotic pathways.