KATP Channel Expression Research Articles

Loss of ATP-Sensitive Potassium Channel Expression and Function in the Nervous System Decreases Opioid Sensitivity in a High-Fat Diet-Fed Mouse Model of Diet-Induced Obesity.

During diabetes progression, β-cell dysfunction due to loss of potassium channels sensitive to ATP, known as KATP channels, occurs contributing to hyperglycemia. The aim of this study is to investigate if KATP channel expression or activity in the nervous system was altered in a high-fatdiet-( HFD) fed mouse model of diet-induced obesity. Expression of two KATP channel subunits, Kcnj11 (Kir6.2) and Abcc8 (SUR1), were decreased in the peripheral and central nervous system in HFD mice, which is significantly correlated with mechanical paw withdrawal thresholds. HFD mice had decreased antinociception to systemic morphine compared to control diet (CON) mice, which was expected as KATP channels are downstream targets of opioid receptors. Mechanical hypersensitivity in HFD mice was exacerbated after systemic treatment with glyburide or nateglinide, KATP channel antagonists clinically used to control blood glucose levels. Upregulation of SUR1 and Kir6.2, through an adenovirus delivered intrathecally, increased morphine antinociception in HFD mice,. These data present a potential link between KATP channel function and neuropathy during early stages of diabetes. There is a need for increased knowledge in how diabetes affects structural and molecular changes in the nervous system, including ion channels, to lead to the progression of chronic pain and sensory issues.

The impact of ATP-sensitive potassium channel modulation on mitochondria in a Parkinson’s disease model using SH-SY5Y cells depends on their differentiation state

Inward rectifying potassium channels sensitive to ATP levels (KATP) have been the subject of investigation for several decades. Modulators of KATP channels are well-established treatments for metabolic as well as cardiovascular diseases. Experimental studies have also shown the potential of KATP modulation in neurodegenerative disorders. However, to date, data regarding the effects of KATP antagonists/agonists in experiments related to neurodegeneration remain inconsistent. The main source of confusion in evaluating available data seems to be the choice of experimental models. The present study aims to provide a comprehensive understanding of the effects of both opening and blocking KATP channels in two forms of SH-SY5Y cells. Our results offer valuable insights into the significance of metabolic differences between differentiated and non-differentiated SH-SY5Y cells, particularly in the context of glibenclamide and diazoxide effects under normal conditions and during the initiation of pathological events simulating Parkinson’s disease in vitro. We emphasize the analysis of mitochondrial functions and changes in mitochondrial network morphology. The heightened protein expression of KATP channels identified in non-differentiated SH-SY5Y cells seems to be a platform for a more significant impact of KATP modulators in this cell type. The efficiency of rotenone treatment in inducing morphological changes in the mitochondrial network depends on the differentiation status of SH-SY5Y cells.

SAT083 Comparing Grit, Anxiety, And Social Responsiveness In KCNJ11-NDM And Their Sibling Controls

Abstract Disclosure: J. Desai: None. L. Letourneau-Freiberg: None. M. Msall: None. M. Scott: None. R.N. Naylor: None. L. Philipson: None. S.W. Greeley: None. Background: Neonatal diabetes mellitus (NDM), diabetes with onset before 6-12 months of age, is most commonly caused from mutations in the ATP-dependent Potassium (KATP) channel genes: KCNJ11 (KCNJ11-NDM) or ABCC8. Because of brain expression of mutant KATP channels, a spectrum of neurodevelopmental difficulties have been described, such as developmental delay, epilepsy, and neonatal diabetes (DEND) syndrome, learning disorders, and Attention-deficit/hyperactivity disorder (ADHD). In order to understand more about specific challenges, we compared self- and parent/caregiver-reported grit, anxiety, and social responsiveness among participants with KCNJ11 mutations and their sibling controls. Methods: We recruited 12 families (12 KCNJ11-NDM participants and 10 sibling controls) through the University of Chicago Monogenic Diabetes Registry (www.monogenicdiabetes.org). Affected participants and sibling controls, and in some cases their parent/caregiver, completed the SCARED/SCAARED (anxiety), SRS-2 (social responsiveness) and Grit Scale (grit) surveys. Nonparametric analyses were performed using the Mann-Whitney U-test for group comparisons. Results: Individuals with KCNJ11-NDM had significantly worse social responsiveness scores compared to sibling controls in both Total Social Responsiveness and 4/5 subscales including Social Awareness, Cognition, Communication, and Restricted Interests and Repetitive Behavior (p<0.05), but no difference for Motivation. In terms of deficits in social interaction, 20% of KCNJ11-NDM participants had total SRS-2 T-scores in the mild range, 30% with scores in the moderate range, and 40% with scores in the severe range. 80% of control participants had total SRS-2 T-scores in normal range. Grit results were not significantly different between groups. Total anxiety scores and anxiety subscale scores were not significantly different between groups. Nevertheless, both participants with KCNJ11-NDM and sibling controls revealed greater levels of anxiety as a whole; 50% of KCNJ11-NDM participants (n=6) and 40% of unaffected controls (n=4) had mean total anxiety scores ≥ 25, indicating the possible presence of a clinical anxiety disorder. Conclusion: The prevalence of social interaction challenges was high among KCNJ11-NDM participants, highlighting the importance of early clinical assessment and support for such problems. Results of the SRS-2 Motivation subscale and Grit, which measure more intrinsic levels of personality, may suggest that individuals with KCNJ11-NDM exhibit intrinsic motivation and grit. Elevated overall anxiety levels in both KCNJ11-NDM participants and sibling controls suggest the need for early assessment and supportive interventions for families affected by KCNJ11-NDM. Presentation: Saturday, June 17, 2023

1539-P: Effects of Free Fatty Acids (FFA) on Central Regulation of Glucose Metabolism

Activation of hypothalamic KATP channels reduces endogenous glucose production (EGP) in nondiabetic rodents and humans, but this response is lost in T2D. Lowering FFA with nicotinic acid (NA) restored central regulation of EGP in T2D subjects (Diabetes 2019; 1799P). High FFA levels, typical of T2D, may increase endoplasmic reticulum (ER) stress and thereby impair hypothalamic control of EGP. To explore how increased FFA might impact central regulation of EGP, we harvested hypothalamic wedges from n=10 Zucker Diabetic Fatty (ZDF) rats (glucose ~ 370 mg/dL) following infusion of NA or saline (Alzet minipump) for 18 h. Nondiabetic rats (n=5) were studied as controls. Gene expression of KATP channel subunit Kir6.2 was decreased in ZDF rats. Upon lowering FFA with NA, hypothalamic expression of this major subunit was restored (Fig 1a). Conversely, increased expression of genes regulating ER stress was reversed by NA (Fig 1b). Directly treating ZDF rat brain slices with NA did not alter the expression of these genes, suggesting that NA's effects were mediated by lowering FFA (Fig 1c). In conclusion, hypothalamic effects of elevated FFA include reduced KATPchannel expression and increased expression of ER stress genes, both of which may contribute reversibly to the loss of central regulation of EGP in T2D. These findings are consistent with our observations in humans noted above, suggesting that FFA could be a therapeutic target in T2D. Disclosure M. Nogueira Cordeiro: None. V.H. Routh: None. A. Manavalan: None. P.M. Mathias: None. C.E. Boyle: None. A.C. Rios Chen: None. N. Jiang: None. N. Friedman: None. Y. Demirhan: None. M. Hawkins: None. K. Zhang: None. Funding American Diabetes Association (7-08-CR-28 to M.H.); National Institutes of Health (R01DK069861); Diabetes Action Research and Education Foundation

KATP channel mutations in congenital hyperinsulinism: Progress and challenges towards mechanism-based therapies.

Congenital hyperinsulinism (CHI) is the most common cause of persistent hypoglycemia in infancy/childhood and is a serious condition associated with severe recurrent attacks of hypoglycemia due to dysregulated insulin secretion. Timely diagnosis and effective treatment are crucial to prevent severe hypoglycemia that may lead to life-long neurological complications. In pancreatic β-cells, adenosine triphosphate (ATP)-sensitive K+ (KATP) channels are a central regulator of insulin secretion vital for glucose homeostasis. Genetic defects that lead to loss of expression or function of KATP channels are the most common cause of HI (KATP-HI). Much progress has been made in our understanding of the molecular genetics and pathophysiology of KATP-HI in the past decades; however, treatment remains challenging, in particular for patients with diffuse disease who do not respond to the KATP channel activator diazoxide. In this review, we discuss current approaches and limitations on the diagnosis and treatment of KATP-HI, and offer perspectives on alternative therapeutic strategies.

Upregulation of ATP-Sensitive Potassium Channels as the Potential Mechanism of Cardioprotection and Vasorelaxation Under the Action of Pyridoxal-5-Phosphate in Old Rats.

Background: The aging process is accompanied by the weakening of the protective systems of the organism, in particular by the decrease in the expression of ATP-sensitive potassium (KATP) channels and in the synthesis of H2S. The aim of our work was to investigate the role of KATP channels in the cardioprotection induced by pyridoxal-5-phosphate (PLP) in aging. Methods: Experiments were performed on adult and old (aged 24 months) male Wistar rats, which were divided into 3 groups: adults, old, and old PLP-treated rats. PLP was administered orally once a day for 14 days at a dose of 0.7 mg/kg. The levels of mRNA expression of subunits KATP channels were determined by reverse transcription and real-time polymerase chain reaction analysis. Protein expression levels were determined by the Western blot. Cardiac tissue morphology was determined using transverse 6 μm deparaffinized sections stained with picrosirius red staining. Vasorelaxation responses of isolated aortic rings and the function of Langendorff-perfused isolated hearts during ischemia-reperfusion, H2S levels, and markers of oxidative stress were also studied. Results: Administration of PLP to old rats reduces cardiac fibrosis and improves cardiac function during ischemia-reperfusion and vasorelaxation responses to KATP channels opening. At the same time, there was a significant increase in mRNA and protein expression of SUR2 and Kir6.1 subunits of KATP channels, H2S production, and reduced markers of oxidative stress. The specific KATP channel inhibitor-glibenclamide prevented the enhancement of vasodilator responses and anti-ischemic protection in PLP-treated animals. Conclusions: We suggest that this potential therapeutic effect of PLP in old animals may be a result of increased expression of KATP channels and H2S production.

Glutathione Upregulates the Expression of KATP Channels and Vasorelaxation Responses and Inhibits mPTP Opening and Oxidative Stress in the Heart Mitochondria of Old Rats.

In the present work, we investigated the effect of exogenous glutathione in old rats on the expression of ATP-sensitive potassium (KATP) channels, the mitochondrial permeability transition pore (mPTP) opening in the heart, and the vasorelaxation responses of isolated aortic rings to activation of KATP channels. Experiments were performed on adult (6 months) and old (24 months) male Wistar rats, which were divided into three groups: adult, old, and glutathione-treated old rats. Glutathione was injected intraperitoneally at a dose of 52 mg/kg 1 hour before the studies. The mRNA expression of KATP channels was determined using reverse transcription and real-time polymerase chain reaction analysis. The effect of glutathione administration on mPTP opening, relaxation responses of isolated aortic rings, and oxidative stress markers was studied. It was shown that the expression levels of Kir6.1, Kir6.2, and SUR1 subunits of KATP channels and levels of reduced glutathione were significantly increased in glutathione-treated old rats (by 8.3, 2.8, 13.1, and 1.5-fold, respectively), whereas the levels of oxidative stress markers (hydrogen peroxide, diene conjugates, malondialdehyde, and rate of superoxide generation) in heart mitochondria and mPTP opening were significantly reduced. Relaxation of aortic rings was significantly increased in response to the actions of KATP channel openers flocalin and pinacidil in glutathione-treated animals, which was prevented by glibenclamide. Thus, the administration of exogenous glutathione to old rats resulted in a significant increase in the expression levels of the Kir6.1, Kir6.2, and SUR1 subunits of KATP channels and a decrease in oxidative stress. This was accompanied by inhibition of mPTP opening and enhancement of vasorelaxation responses to activation of KATP channels.

The reversible effects of free fatty acids on sulfonylureas-stimulated insulin secretion are related to the expression and dynamin mediated endocytosis of KATP channels in pancreatic β cells.

Lipotoxicity-induced pancreatic β cells-dysfunction results in decreased insulin secretion in response to multiple stimulus. In this study, we investigated the reversible effects of palmitate (PA) or oleate (OA) on insulin secretion and the relationship with pancreatic β cell ATP-sensitive potassium (KATP) channels. MIN6 cells were treated with PA and OA for 48 hr and then washed out for 24 hr to determine the changes in expression and endocytosis of the KATP channels and insulin secretion under glucose- (GSIS) and sulfonylureas-stimulated (SUs-SIS). MIN6 cells exposed to PA or OA showed both impaired GSIS and SUs-SIS, the former was not restorable, while the latter was reversible with wash out of PA or OA. Decreased expressions of both total and surface Kir6.2 and SUR1 and endocytosis of KATP channels were observed which were also recoverable after washed out. When MIN6 cells exposed to FFAs were cotreated with AICAR or dynasore, we found that endocytosis of KATP channels did not change significantly by AICAR, but was almost completely blocked by dynasore. Meanwhile, the inhibition of endocytosis of KATP channels after washed out could be activated by PIP2. The recovery of SUs-SIS after washed out was significantly weakened by PIP2, but the decrease of SUs-SIS induced by FFAs was not alleviated by dynasore. FFAs can cause reversible impairment of SUs-SIS on pancreatic β cells. The reversibility of the effects is partial because of the changes of expression and endocytosis of Kir6.2 and SUR1 which was mediated by dynamin.

Rab35 GTPase positively regulates endocytic recycling of cardiac KATP channels

ABSTRACT ATP-sensitive K+ (KATP) channel couples membrane excitability to intracellular energy metabolism. Maintaining KATP channel surface expression is key to normal insulin secretion, blood pressure and cardioprotection. However, the molecular mechanisms regulating KATP channel internalization and endocytic recycling, which directly affect the surface expression of KATP channels, are poorly understood. Here we used the cardiac KATP channel subtype, Kir6.2/SUR2A, and characterized Rab35 GTPase as a key regulator of KATP channel endocytic recycling. Electrophysiological recordings and surface biotinylation assays showed decreased KATP channel surface density with co-expression of a dominant negative Rab35 mutant (Rab35-DN), but not other recycling-related Rab GTPases, including Rab4, Rab11a and Rab11b. Immunofluorescence images revealed strong colocalization of Rab35-DN with recycling Kir6.2. Rab35-DN minimized the recycling rate of KATP channels. Rab35 also regulated KATP channel current amplitude in isolated adult cardiomyocytes by affecting its surface expression but not channel properties, which validated its physiologic relevance and the potential of pharmacologic target for treating the diseases with KATP channel trafficking defects.

Subcellular trafficking and endocytic recycling of KATP channels.

Sarcolemmal/plasmalemmal ATP-sensitive K+ (KATP) channels have key roles in many cell types and tissues. Hundreds of studies have described how the KATP channel activity and ATP sensitivity can be regulated by changes in the cellular metabolic state, by receptor signaling pathways and by pharmacological interventions. These alterations in channel activity directly translate to alterations in cell or tissue function, that can range from modulating secretory responses, such as insulin release from pancreatic β-cells or neurotransmitters from neurons, to modulating contractile behavior of smooth muscle or cardiac cells to elicit alterations in blood flow or cardiac contractility. It is increasingly becoming apparent, however, that KATP channels are regulated beyond changes in their activity. Recent studies have highlighted that KATP channel surface expression is a tightly regulated process with similar implications in health and disease. The surface expression of KATP channels is finely balanced by several trafficking steps including synthesis, assembly, anterograde trafficking, membrane anchoring, endocytosis, endocytic recycling, and degradation. This review aims to summarize the physiological and pathophysiological implications of KATP channel trafficking and mechanisms that regulate KATP channel trafficking. A better understanding of this topic has potential to identify new approaches to develop therapeutically useful drugs to treat KATP channel-related diseases.

KATP Channels Function in the Peripheral and Central Nervous Systems in a Mouse Model of Type 2 Diabetes

Over 50% of individuals with type 2 diabetes eventually develop diabetic neuropathy. There is a need for increased knowledge in how diabetes affects structural and molecular changes in the nervous system, and how current diabetes interventions affect the progression of chronic pain. Loss of KATP channel activity or function could cause nerve fiber hypersensitivity and consequently increased pain sensitivity due to neuron depolarization. Diabetic neuropathy was induced in male and female C57Bl6 mice over a total of 16 weeks by feeding the animals a high-fat diet (HFD) or corresponding control diet (12330 and 12328, Research Diets Inc., New Brunswick, NJ) for over 16 weeks. Mice on the HFD for at longer than 8 weeks have significantly lower mechanical thresholds and compared to control diet mice. Decreased expression of KATP channel subunits in the spinal cord, and dorsal root ganglia were correlated with decreased mechanical paw withdrawal thresholds. Mice fed a HFD also have decreased analgesia to systemic morphine (0-20 mg/kg, s.c.), which is exacerbated after systemic treatment with glyburide or nateglinide for four weeks, (KATP channel antagonist, glyburide or nateglinide, 50 mg/kg/day, IP or vehicle, 5% DMSO + 0.5% Tween). Upregulation of KATP channels using a viral vector strategy increased paw withdrawal thresholds to systemic morphine. Diabetes affects many adults including those with prediabetes and new-onset diabetes. It is clear that novel biomarkers and pharmaceutical targets are needed in order to (1) confront the demand for new treatments that better manage and (2) identify patients that may develop diabetic neuropathy. Further investigation of KATP channel expression and function during chronic pain syndromes, including diabetic neuropathy, may help to find sufficient treatment options for patients. This work was supported through a University of Minnesota Academic Health Center Faculty Development Grant to AHK and MLG. Funding also provided by the NIH: K01 DA042902, R01 DA051876, and UL1TR002494 (AHK).

Effect of visfatin on KATP channel upregulation in colonic smooth muscle cells in diabetic colon dysmotility.

The mechanisms of diabetes-related gastrointestinal dysmotility remains unclear. This study aimed to investigate the effect and mechanisms of proinflammatory adipokine visfatin (VF) in the contractile dysfunction of diabetic rat colonic smooth muscle. Twenty Sprague-Dawley rats were randomly divided into control and type 2 diabetes mellitus groups. VF levels in the serum and colonic muscle tissues were tested, the time of the bead ejection and contractility of colonic smooth muscle strips were measured, and the expression of ATP-sensitive potassium (KATP) channels in the colonic muscle tissues was analyzed. In vitro, we tested VF’s effects on intracellular reactive oxygen species (ROS) levels, NF-κB’s nuclear transcription, KATP channel expression, intracellular Ca2+ concentrations, and myosin light chain (MLC) phosphorylation in colonic smooth muscle cells (CSMCs). The effects of NAC (ROS inhibitor) and BAY 11-7082 (NF-κB inhibitor) on KATP expression were also tested. Diabetic rats showed elevated VF levels in serum and colonic muscle tissues, a delayed distal colon ejection response time, weakened contractility of colonic smooth muscle strips, and increased KATP channel expression in colonic muscle tissues. VF significantly inhibited the contractility of colonic smooth muscle strips from normal rats. In cultured CSMCs, VF caused ROS overload, increased NF-κB nuclear transcription activity and increased expression of Kir6.1, eventually reducing intracellular Ca2+ levels and MLC phosphorylation. NAC and BAY 11-7082 inhibited the VF–induced Kir6.1 upregulation. In conclusion, VF may cause contractile dysfunction of CSMCs by upregulating the expression of the Kir6.1 subunit of KATP channels via the ROS/NF-κB pathway and interfering with Ca2+ signaling.

A co-expression vector for baculovirus-mediated protein expression in mammalian cells

BacMam system utilizes baculovirus to deliver exogenous genes into mammalian cells and is extensively used for recombinant production of eukaryotic proteins. Here, we described the development of a BacMam vector (pBMCL1), which allows convenient tracing of virus production, provides higher infection efficiency towards mammalian cells, minimizes unwanted transcription of toxic genes in insect cells, and provides the capability for co-expression of multiple proteins via a single virus. We demonstrate the successful application of the pBMCL1 vector for the expression of homo-tetrameric human TRPC3 channel and hetero-octameric KATP channel.

Smooth muscle ATP-sensitive potassium channels mediate migraine-relevant hypersensitivity in mouse models.

Opening of KATP channels by systemic levcromakalim treatment triggers attacks in migraine patients and hypersensitivity to von Frey stimulation in a mouse model. Blocking of these channels is effective in several preclinical migraine models. It is unknown in what tissue and cell type KATP-induced migraine attacks are initiated and which KATP channel subtype is targeted. In mouse models, we administered levcromakalim intracerebroventricularly, intraperitoneally and intraplantarily and compared the nociceptive responses by von Frey and hotplate tests. Mice with a conditional loss-of-function mutation in the smooth muscle KATP channel subunit Kir6.1 were given levcromakalim and GTN and examined with von Frey filaments. Arteries were tested for their ability to dilate ex vivo. mRNA expression, western blotting and immunohistochemical stainings were made to identify relevant target tissue for migraine induced by KATP channel opening. Systemic administration of levcromakalim induced hypersensitivity but central and local administration provided antinociception respectively no effect. The Kir6.1 smooth muscle knockout mouse was protected from both GTN and levcromakalim induced hypersensitivity, and their arteries had impaired dilatory response to the latter. mRNA and protein expression studies showed that trigeminal ganglia did not have significant KATP channel expression of any subtype, whereas brain arteries and dura mater primarily expressed the Kir6.1 + SUR2B subtype. Hypersensitivity provoked by GTN and levcromakalim in mice is dependent on functional smooth muscle KATP channels of extracerebral origin. These results suggest a vascular contribution to hypersensitivity induced by migraine triggers.

KATP and TRPM2-like channels couple metabolic status to resting membrane potential of octopus neurons in the mouse ventral cochlear nucleus

ATP-sensitive potassium (KATP) channels and transient receptor potential melastatin 2 (TRPM2) channels are commonly expressed both pre- and postsynaptically in the central nervous system (CNS). We hypothesized that KATP and TRPM2 may couple metabolic status to the resting membrane potential of octopus neurons of the mouse ventral cochlear nucleus (VCN).Therefore, we studied the expression of KATP channels and TRPM2 channels in octopus cells by immunohistochemical techniques and their contribution to neuronal electrical properties by the electrophysiological patch clamp technique.In immunohistochemical staining of octopus cells, labelling with Kir6.2 and SUR1 antibodies was strong, and labelling with the SUR2 antibody was moderate, but labelling with Kir6.1 was very weak. Octopus cells had intense staining with TRPM2 antibodies.In patch clamp recordings, bath application of KATP channel agonists H2O2 (880 μM), ATZ (1 mM), cromakalim (50 μM), diazoxide (200 μM), NNC 55-0118 and NN 414 separately resulted in hyperpolarizations of resting potential to different extents. Application of 8-Bro-cADPR (50 μM), a specific antagonist of TRPM2 channels, in the presence of H2O2 (880 μM) resulted in further hyperpolarization by approximately 1 mV. The amplitudes of H2O2-induced outward KATP currents and ADPR-induced inward currents were 206.1 ± 31.5 pA (n = 4) and 136.8 ± 22.4 pA, respectively, at rest. Their respective reversal potentials were -77 ± 2.6 mV (n = 3) and -6.3 ± 2.9 (n = 3) and -6.3 ± 2.9 (n = 3).In conclusion, octopus cells appear to possess both KATP channels and TRPM2-like channels. KATP might largely be constituted by SUR1–Kir6.2 subunits and SUR2–Kir6.2 subunits. Both KATP and TRPM2-like channels might have a modulatory action in setting the membrane potential.

Novel cholesterol-dependent regulation of cardiac KATP subunit expression revealed using histone deacetylase inhibitors.

We recently discovered that the histone deacetylase inhibitor, trichostatin A (TSA), increases expression of the sulfonylurea receptor 2 (SUR2; Abcc9) subunit of the ATP‐sensitive K+ (KATP) channel in HL‐1 cardiomyocytes. Interestingly, the increase in SUR2 was abolished with exogenous cholesterol, suggesting that cholesterol may regulate channel expression. In the present study, we tested the hypothesis that TSA increases SUR2 by depleting cholesterol and activating the sterol response element binding protein (SREBP) family of transcription factors. Treatment of HL‐1 cardiomyocytes with TSA (30 ng/ml) caused a time‐dependent increase in SUR2 mRNA expression that correlates with the time course of cholesterol depletion assessed by filipin staining. Consistent with the cholesterol‐dependent regulation of SREBP increasing SUR2 mRNA expression, we observe a significant increase in SREBP cleavage and translocation to the nucleus following TSA treatment that is inhibited by exogenous cholesterol. Further supporting the role of SREBP in mediating the effect of TSA on KATP subunit expression, SREBP1 significantly increased luciferase reporter gene expression driven by the upstream SUR2 promoter. Lastly, HL‐1 cardiomyocytes treated with the SREBP inhibitor PF429242 significantly suppresses the effect of TSA on SUR2 gene expression. These results demonstrate that SREBP is an important regulator of KATP channel expression and suggest a novel method by which hypercholesterolemia may exert negative effects on the cardiovascular system, namely, by suppressing expression of the KATP channel.

Beneficial Effects of Spirulina Aqueous Extract on Vasodilator Function of Arteries from Hypertensive Rats.

Hypertension is a multifactorial disorder considered one of the major causes of premature death worldwide. This pathology is associated with vascular functional/structural alterations in which nitric oxide (NO) and oxygen reactive species participate. On the other hand, the use of microalgae extracts in the treatment of cardiovascular diseases is increasing. Based on the antioxidant and antihypertensive properties of Spirulina, this study aims to investigate the effect of an aqueous extract of Spirulina on the vasodilator function of the aorta from spontaneously hypertensive rats (SHR), analyzing the functional role of NO. For this, aortic segments from male SHR were divided into two groups, one control and the other exposed to an Spirulina aqueous extract (0.1% w/v, for 3 hours), to analyze (i) the production of NO, superoxide anion, and hydrogen peroxide; (ii) the vasodilator response induced by acetylcholine (ACh), by the NO donor and sodium nitroprusside (SNP), and by the KATP channel opener and pinacidil; and (iii) the expression of the p-Akt, p-eNOS, and HO-1 proteins. The results showed that the aqueous Spirulina extract (i) increased the production of NO, did not significantly modify that of superoxide, while decreased that of hydrogen peroxide; (ii) increased the vasodilatory responses induced by ACh, NPS, and pinacidil; and (iii) increased the expression of p-Akt and HO-1. These results suggest that incubation with the aqueous Spirulina extract improves the vascular function of arteries from SHR by increasing the release/bioavailability/function of NO. Increased KATP channel activation and expression of pAkt and HO-1 appear to be participating in these actions.

The baroreflex afferent pathway plays a critical role in H2S-mediated autonomic control of blood pressure regulation under physiological and hypertensive conditions.

Hydrogen sulfide (H2S), which is closely related to various cardiovascular disorders, lowers blood pressure (BP), but whether this action is mediated via the modification of baroreflex afferent function has not been elucidated. Therefore, the current study aimed to investigate the role of the baroreflex afferent pathway in H2S-mediated autonomic control of BP regulation. The results showed that baroreflex sensitivity (BRS) was increased by acute intravenous NaHS (a H2S donor) administration to renovascular hypertensive (RVH) and control rats. Molecular expression data also showed that the expression levels of critical enzymes related to H2S were aberrantly downregulated in the nodose ganglion (NG) and nucleus tractus solitarius (NTS) in RVH rats. A clear reduction in BP by the microinjection of NaHS or L-cysteine into the NG was confirmed in both RVH and control rats, and a less dramatic effect was observed in model rats. Furthermore, the beneficial effects of NaHS administered by chronic intraperitoneal infusion on dysregulated systolic blood pressure (SBP), cardiac parameters, and BRS were verified in RVH rats. Moreover, the increase in BRS was attributed to activation and upregulation of the ATP-sensitive potassium (KATP) channels Kir6.2 and SUR1, which are functionally expressed in the NG and NTS. In summary, H2S plays a crucial role in the autonomic control of BP regulation by improving baroreflex afferent function due at least in part to increased KATP channel expression in the baroreflex afferent pathway under physiological and hypertensive conditions.

Glibenclamide restores dopaminergic reward circuitry in obese mice through interscauplar brown adipose tissue

BackgroundObesity, a critical feature in metabolic disorders, is associated with medical depression. Recent evidence reveals that brown adipose tissue (BAT) activity may contribute to mood disorders, Adenosine triphosphate (ATP)-sensitive K+ (KATP) channels regulate BAT sympathetic nerve activity. However, the mechanism through which BAT activity affects mood control remains unknown. We hypothesized the BAT is involved in depressive-like symptoms regulation by trafficking KATP channels. MethodsEight-week-old male B6 mice fed with a high-fat diet (HFD) for 12 weeks exhibited characteristics of metabolic disorders, including hyperglycemia, hyperinsulinemia, and hyperlipidemia, as well as depressive symptoms. In this study, we surgically removed interscapular BAT in mice, and these mice exhibited immobility in the forced swim test and less preference for sugar water compared with other mice. To delineate the role of KATP channels in BAT activity regulation, we implanted a miniosmotic pump containing glibenclamide (GB), a KATP channel blocker, into the interscapular BAT of HFD-fed mice. ResultsGB infusion improved glucose homeostasis, insulin sensitivity, and depressive-like symptoms. KATP channel expression was lower in HFD-fed mice than in chow-fed mice. Notably, GB infusion in HFD-fed mice restored KATP channel expression. ConclusionKATP channels are functionally expressed in BAT, and inhibiting BAT-KATP channels improves metabolic syndromes and reduces depressive symptoms through beta-3-adrenergic receptor-mediated protein kinase A signaling.

Ankyrin-G Mediates Targeting of both Na+ and KATP Channels to the Cardiac Intercalated Disc

Na+ channels and KATP channels are both enriched at the intercalated disk (ICD) of cardiomyocytes. Targeting of Na+ channels to the ICD is relatively well described. A Brugada-associated mutation in Nav1.5 has revealed a key role for Ankyrin G (AnkG). Here, we investigate whether a relationship exists between Na+ and KATP channel expression and targeting mechanisms to the ICD. We found that Na+ and KATP channels reciprocally negatively regulate each other's surface density. Physiological relevance is demonstrated since adenoviral delivery of Kir6.2 into cardiomyocytes reduces native INa.