Potassium-Channel Openers KMUP-1 and Pinacidil Prevent Subarachnoid Hemorrhage–Induced Vasospasm by Restoring the BKCa-Channel Activity

Electrolyte Imbalance in Acute Traumatic Brain Injury: Insights from the First 24 h

BACKGROUND/OBJECTIVES

Electrolyte disturbances are common in patients with traumatic brain injury (TBI), particularly affecting sodium, potassium, chloride, and calcium levels. This study aims to provide insights into these disturbances within the first 24 h post-injury.

METHODS

We conducted a cross-sectional analysis of 50 TBI patients, excluding those with conditions affecting electrolyte balance. Electrolyte levels were measured, and correlations with demographic data, trauma mechanisms, imaging findings, and Glasgow Coma Scale (GCS) scores were analyzed.

RESULTS

The results indicated that chloride levels inversely correlated with GCS scores (ρ = -0.515; p = 0.002), suggesting that elevated chloride may indicate severe neurological impairment. Potassium levels were significantly associated with subdural hematoma (p = 0.032) and subarachnoid hemorrhage (p = 0.043), highlighting their potential as markers for severe brain injuries. No significant associations were found between sodium or calcium levels and the studied variables.

CONCLUSIONS

These findings underscore the importance of early monitoring of chloride and potassium levels in TBI patients to improve management and outcomes. Future research should focus on larger, multi-center studies to validate these findings and develop comprehensive guidelines for managing electrolyte imbalances in TBI patients.

The Xanthine Derivative KMUP-1 Inhibits Hypoxia-Induced TRPC1 Expression and Store-Operated Ca2+ Entry in Pulmonary Arterial Smooth Muscle Cells

Exposure to hypoxia results in the development of pulmonary arterial hypertension (PAH). An increase in the intracellular Ca2+ concentration ([Ca2+]i) in pulmonary artery smooth muscle cells (PASMCs) is a major trigger for pulmonary vasoconstriction and proliferation. This study investigated the mechanism by which KMUP-1, a xanthine derivative with phosphodiesterase inhibitory activity, inhibits hypoxia-induced canonical transient receptor potential channel 1 (TRPC1) protein overexpression and regulates [Ca2+]i through store-operated calcium channels (SOCs). Ex vivo PASMCs were cultured from Sprague-Dawley rats in a modular incubator chamber under 1% O2/5% CO2 for 24 h to elucidate TRPC1 overexpression and observe the Ca2+ release and entry. KMUP-1 (1 μM) inhibited hypoxia-induced TRPC family protein encoded for SOC overexpression, particularly TRPC1. KMUP-1 inhibition of TRPC1 protein was restored by the protein kinase G (PKG) inhibitor KT5823 (1 μM) and the protein kinase A (PKA) inhibitor KT5720 (1 μM). KMUP-1 attenuated protein kinase C (PKC) activator phorbol 12-myristate 13-acetate (PMA, 1 μM)-upregulated TRPC1. We suggest that the effects of KMUP-1 on TRPC1 might involve activating the cyclic guanosine monophosphate (cGMP)/PKG and cyclic adenosine monophosphate (cAMP)/PKA pathways and inhibiting the PKC pathway. We also used Fura 2-acetoxymethyl ester (Fura 2-AM, 5 μM) to measure the stored calcium release from the sarcoplasmic reticulum (SR) and calcium entry through SOCs in hypoxic PASMCs under treatment with thapsigargin (1 μM) and nifedipine (5 μM). In hypoxic conditions, store-operated calcium entry (SOCE) activity was enhanced in PASMCs, and KMUP-1 diminished this activity. In conclusion, KMUP-1 inhibited the expression of TRPC1 protein and the activity of SOC-mediated Ca2+ entry upon SR Ca2+ depletion in hypoxic PASMCs.

Impact of human serum albumin level on symptomatic cerebral vasospasm in patients with aneurysmal subarachnoid hemorrhage

OBJECTIVE

To investigate the impact of human serum albumin (HSA) levels on symptomatic cerebral vasospasm (SCVS) in patients with aneurysmal subarachnoid hemorrhage (aSAH).

METHODS

We retrospectively reviewed the medical records. SCVS was defined as the development of a new neurological deterioration when the cause was considered to be ischemia attributable to vasospasm after other possible causes of worsening had been excluded. The aSAH patients were divided into two groups: those with SCVS (group 1) and those without SCVS (group 2). The HSA level data on the 1st, 2nd, and 3rd day after admission was collected. Multivariate logistical regression and receiver operating characteristic (ROC) analysis were performed to evaluate the ability of HSA level to predict the development of SCVS.

RESULTS

A total of 270 patients were included in our study, of which 74 (27.4%) developed SCVS. The average and lowest HSA levels were lower in group 1 (P < 0.001). In univariate logistic regression, white blood cell count, neutrophil count, and average and lowest HSA levels were associated with SCVS. After adjustment for age, CT Fisher grade, Hunt-Hess grade, and WFNS grade, both the average and lowest HSA levels remained independent predictors of SCVS (P < 0.001). The CT Fisher grade was confirmed to be an independent predictor of SCVS across each model. ROC analysis revealed that the lowest HSA level was a better predictor for SCVS than average HSA level and CT Fisher grade.

CONCLUSION

Clinicians are encouraged to measure HSA levels for the first 3 days after admission to predict the occurrence of SCVS after aSAH.

The blood-brain barrier and the neurovascular unit in subarachnoid hemorrhage: molecular events and potential treatments

The response of the blood-brain barrier (BBB) following a stroke, including subarachnoid hemorrhage (SAH), has been studied extensively. The main components of this reaction are endothelial cells, pericytes, and astrocytes that affect microglia, neurons, and vascular smooth muscle cells. SAH induces alterations in individual BBB cells, leading to brain homeostasis disruption. Recent experiments have uncovered many pathophysiological cascades affecting the BBB following SAH. Targeting some of these pathways is important for restoring brain function following SAH. BBB injury occurs immediately after SAH and has long-lasting consequences, but most changes in the pathophysiological cascades occur in the first few days following SAH. These changes determine the development of early brain injury as well as delayed cerebral ischemia. SAH-induced neuroprotection also plays an important role and weakens the negative impact of SAH. Supporting some of these beneficial cascades while attenuating the major pathophysiological pathways might be decisive in inhibiting the negative impact of bleeding in the subarachnoid space. In this review, we attempt a comprehensive overview of the current knowledge on the molecular and cellular changes in the BBB following SAH and their possible modulation by various drugs and substances.

BKCa Channel Inhibition by Peripheral Nerve Injury Is Restored by the Xanthine Derivative KMUP-1 in Dorsal Root Ganglia

This study explored whether KMUP-1 improved chronic constriction injury (CCI)-induced BKCa current inhibition in dorsal root ganglion (DRG) neurons. Rats were randomly assigned to four groups: sham, sham + KMUP-1, CCI, and CCI + KMUP-1 (5 mg/kg/day, i.p.). DRG neuronal cells (L4-L6) were isolated on day 7 after CCI surgery. Perforated patch-clamp and inside-out recordings were used to monitor BKCa currents and channel activities, respectively, in the DRG neurons. Additionally, DRG neurons were immunostained with anti-NeuN, anti-NF200 and anti-BKCa. Real-time PCR was used to measure BKCa mRNA levels. In perforated patch-clamp recordings, CCI-mediated nerve injury inhibited BKCa currents in DRG neurons compared with the sham group, whereas KMUP-1 prevented this effect. CCI also decreased BKCa channel activity, which was recovered by KMUP-1 administration. Immunofluorescent staining further demonstrated that CCI reduced BKCa-channel proteins, and KMUP-1 reversed this. KMUP-1 also changed CCI-reduced BKCa mRNA levels. KMUP-1 prevented CCI-induced neuropathic pain and BKCa current inhibition in a peripheral nerve injury model, suggesting that KMUP-1 could be a potential agent for controlling neuropathic pain.

Activation of endothelial NO synthase by a xanthine derivative ameliorates hypoxia-induced apoptosis in endothelial progenitor cells

OBJECTIVES

Endothelial damage is strongly associated with cardiovascular diseases such as atherosclerosis, thrombosis and hypertension. Endothelial progenitor cells (EPCs) are primitive bone marrow (BM) cells that possess the capacity to mature into endothelial cells and play a role in neovascularization and vascular remodelling. This study aimed to investigate whether KMUP-1, a synthetic xanthine-based derivative, atorvastatin and simvastatin, can prevent endothelial dysfunction and apoptosis induced by hypoxia and to elucidate the underlying mechanisms.

METHODS

Mononuclear cells were separated and were induced to differentiate into EPCs. KMUP-1, atorvastatin or simvastatin were administered prior to hypoxia.

KEY FINDINGS

We found that EPCs exposed to hypoxia increased apoptosis as well as diminished proliferation. Pretreatment with KMUP-1, atorvastatin and simvastatin significantly prevented hypoxia-induced EPCs death and apoptosis, with associated increased of the Bcl-2/Bax ratio, and reduced caspase-3 and caspase-9 expression. We also assessed the nitrite production and Ser(1177)-phospho-eNOS expression and found that KMUP-1, atorvastatin and simvastatin not only increased the secretion of NO compared with the hypoxia group but also upregulated the eNOS activation.

CONCLUSIONS

KMUP-1 inhibited hypoxia-induced dysfunction and apoptosis in EPCs, which may be mediated through suppressing oxidative stress, upregulating eNOS and downregulating the caspase-3 signalling pathway.

Phosphodiesterase inhibitor KMUP-3 displays cardioprotection via protein kinase G and increases cardiac output via G-protein-coupled receptor agonist activity and Ca(2+) sensitization

KMUP-3 (7-{2-[4-(4-nitrobenzene) piperazinyl]ethyl}-1, 3-dimethylxanthine) displays cardioprotection and increases cardiac output, and is suggested to increase cardiac performance and improve myocardial infarction. To determine whether KMUP-3 improves outcomes in hypoperfused myocardium by inducing Ca(2+) sensitization to oppose protein kinase (PK)G-mediated Ca(2+) blockade, we measured left ventricular systolic blood pressure, maximal rates of pressure development, mean arterial pressure and heart rate in rats, and measured contractility and expression of PKs/RhoA/Rho kinase (ROCK)II in beating guinea pig left atria. Hemodynamic changes induced by KMUP-3 (0.5-3.0 mg/kg, intravenously) were inhibited by Y27632 [(R)-(+)-trans-4-1-aminoethyl)-N-(4-Pyridyl) cyclohexane carboxamide] and ketanserin (1 mg/kg, intravenously). In electrically stimulated left guinea pig atria, positive inotropy induced by KMUP-3 (0.1-100μM) was inhibited by the endothelial NO synthase (eNOS) inhibitors N-nitro-l-arginine methyl ester (L-NAME) and 7-nitroindazole, cyclic AMP antagonist SQ22536 [9-(terahydro-2-furanyl)-9H-purin-6-amine], soluble guanylyl cyclase (sGC) antagonist ODQ (1H-[1,2,4] oxadiazolo[4,3-a] quinoxalin-1-one), RhoA inhibitor C3 exoenzyme, β-blocker propranolol, 5-hydroxytryptamine 2A antagonist ketanserin, ROCK inhibitor Y27632 and KMUP-1 (7-{2-[4-(2-chlorobenzene) piperazinyl]ethyl}-1, 3-dimethylxanthine) at 10μM. Western blotting assays indicated that KMUP-3 (0.1-10μM) increased PKA, RhoA/ROCKII, and PKC translocation and CIP-17 (an endogenous 17-kDa inhibitory protein) activation. In spontaneous right atria, KMUP-3 induced negative chronotropy that was blunted by 7-nitroindazole and atropine. In neonatal myocytes, L-NAME inhibited KMUP-3-induced eNOS phosphorylation and RhoA/ROCK activation. In H9c2 cells, Y-27632 (50μM) and PKG antagonist KT5823 [2,3,9,10,11,12-hexahydro-10R- methoxy-2,9-dimethyl-1-oxo-9S,12R-epoxy-1H-diindolo(1,2,3-fg:3',2',1'-kl) pyrrolo(3,4-i)(1,6)benzodiazocine-10-carboxylic acid, methyl ester] (3μM) reversed KMUP-3 (1-100μM)-induced Ca(2+)-entry blockade. GPCR agonist activity of KMUP-3 appeared opposed to KMUP-1, and increased cardiac output via Ca(2+) sensitization, and displayed cardioprotection via cyclic GMP/PKG-mediated myocardial preconditioning in animal studies.

Pinacidil protects osteoblastic cells against antimycin A-induced oxidative damage

The present study aimed to investigate the protective effect of a non-selective mitochondrial adenosine triphosphate (ATP)-sensitive potassium channel (mito-KATP) opener, pinacidil, on antimycin A-induced oxidative damage in osteoblastic MC3T3-E1 cells. Antimycin A inhibits mitochondrial electron transport by binding to complex III. Osteoblastic MC3T3-E1 cells were treated with antimycin A in the presence or absence of pinacidil and markers of mitochondrial function and oxidative stress were subsequently examined. The effects of pinacidil on the activation of phosphoinositide 3-kinase (PI3K), Akt and cyclic adenosine monophosphate‑responsive element-binding protein (CREB) were also examined. In osteoblastic MC3T3-E1 cells exposed to antimycin A, pinacidil inhibited antimycin A-induced cell death. The protective effects of pinacidil on cell survival were prevented by the addition of LY294002 (a PI3K inhibitor), an Akt inhibitor or auranofin [a thioredoxin reductase (TrxR) inhibitor], but not by KATP channel inhibitor glibenclamide. Pinacidil inhibited antimycin A-induced inactivation of PI3K and Akt as well as phosphorylation of CREB and TrxR. Furthermore, pinacidil prevented antimycin A-induced mitochondrial superoxide release, mitochondrial membrane potential dissipation, reduced ATP synthesis and intracellular [Ca2+] elevation. In conclusion, these results suggested that pinacidil may rescue osteoblastic cells from antimycin A-induced cellular damage, potentially via antioxidant activity and restoration of mitochondrial function, which are mediated in part by the PI3K/Akt/CREB signaling pathway.

Xanthine derivative KMUP-1 reduces inflammation and hyperalgesia in a bilateral chronic constriction injury model by suppressing MAPK and NFκB activation

Neuropathic pain is characterized by spontaneous pain, hyperalgesia, and allodynia. The aim of this study was to investigate whether KMUP-1 (7-[2-[4-(2-chlorobenzene)piperazinyl]ethyl]-1,3-dimethylxanthine) could improve pain hypersensitivity and reduce inflammatory mediators, and also explore possible mechanisms in the rat sciatic nerve using bilateral chronic constriction injury (CCI) to induce neuropathic pain. Sprague-Dawley rats were randomly divided into four groups: Sham, Sham+KMUP-1, CCI, and CCI+KMUP-1. KMUP-1 (5 mg/kg/day) was injected intraperitoneally starting at day 1 after surgery. Mechanical and thermal responses were assessed before surgery and at days 3, 7, and 14 after CCI. Sciatic nerves around the injury site were isolated for Western blots and enzyme-linked immunosorbent assay to analyze protein and cytokine levels. The results show that thermal hyperalgesia and mechanical allodynia were reduced in the KMUP-1 treated group as compared to that in the CCI group. Inflammatory proteins (COX2, iNOS, and nNOS) and proinflammatory cytokines (TNF-α and IL-1β) induced by CCI were decreased in the KMUP-1 treated group at day 7 after surgery. KMUP-1 also inhibited neuropathic pain-related mechanisms, including p38 and ERK activation, but not JNK. Furthermore, KMUP-1 blocked IκB phosphorylation (p-IκB) and phospho-nuclear factor κB (p-NF-κB) translocation to nuclei. Double immunofluorescent staining further demonstrated that p-IκB (an indicator of activated NFκB) and p-NFκB proteins were almost abolished by KMUP-1 in peripheral macrophages and spinal microglia cells at day 7 after surgery. On the basis of these findings, we concluded that KMUP-1 has antiinflammatory and antihyperalgesia properties in CCI-induced neuropathic pain via decreases in MAPKs and NF-κB activation.

A xanthine-derivative K(+)-channel opener protects against serotonin-induced cardiomyocyte hypertrophy via the modulation of protein kinases

This study investigated whether KMUP-1, a xanthine-derivative K⁺ channel opener, could prevent serotonin-induced hypertrophy in H9c2 cardiomyocytes via L-type Ca²⁺ channels (LTCCs). Rat heart-derived H9c2 cells were incubated with serotonin (10 μM) for 4 days. The cell size increased by 155.5%, and this was reversed by KMUP-1 (≥1 μM), and attenuated by the LTCC blocker verapamil (1 μM) and the 5-HT_2A antagonist ketanserin (0.1 μM), but unaffected by the 5-HT_2B antagonist SB206553. A perforated whole-cell patch-clamp technique was used to investigate Ca²⁺ currents through LTCCs in serotonin-induced H9c2 hypertrophy, in which cell capacitance and current density were increased. The LTCC current (I_Ca,L) increased ~2.9-fold in serotonin-elicited H9c2 hypertrophy, which was attenuated by verapamil and ketanserin, but not affected by SB206553 (0.1 μM). Serotonin-increased I_Ca,L was reduced by KMUP-1, PKA and PKC inhibitors (H-89, 1 μM and chelerythrine, 1 μM) while the current was enhanced by the PKC activator PMA, (1 μM) but not the PKA activator 8-Br-cAMP (100 μM), and was abolished by KMUP-1. In contrast, serotonin-increased I_Ca,L was blunted by the PKG activator 8-Br-cGMP (100 μM), but unaffected by the PKG inhibitor KT5823 (1 μM). Notably, KMUP-1 blocked serotonin-increased I_Ca,L but this was partially reversed by KT5823. In conclusion, serotonin-increased I_Ca,L could be due to activated 5-HT_2A receptor-mediated PKA and PKC cascades, and/or indirect interaction with PKG. KMUP-1 prevents serotonin-induced H9c2 cardiomyocyte hypertrophy, which can be attributed to its PKA and PKC inhibition, and/or PKG stimulation.

NO donor KMUP-1 improves hepatic ischemia-reperfusion and hypoxic cell injury by inhibiting oxidative stress and pro-inflammatory signaling

This study investigates whether KMUP-1 improves hepatic ischemia-reperfusion (I/R) and hypoxic cell injury via inhibiting Nox2- and reactive oxygen species (ROS)-mediated pro-inflammation. Rats underwent ischemia by occlusion of the portal vein and hepatic artery for 45 minutes. Reperfusion was allowed for 4 h. Serum was used for analysis of aspartate aminotransferase (AST) and alanine aminotransferase (ALT). DNA extracted from liver homogenate was analyzed by electrophoresis to observe the fragmentation. Lipid peroxidation (LPO) was evaluated by measuring thiobarbituric acid-reactive substances (TBARS). NO and ROS contents were measured using Griess reagent and 2′-7′-dichlorofluorescein, respectively. Proteins levels were visualized by Western blotting. Liver damage was observed under a microscope. Intravenous KMUP-1 (0.25, 0.5 and 1 mg/kg) reduced I/R-induced ALT and AST levels, DNA fragmentation, ROS and malondialdehyde (MDA) and restored the NO levels of I/R rats. KMUP-1 protected the liver architecture from worsening of damage and focal sinusoid congestion, increased endothelium NO synthase (eNOS), guanosine 3', 5'cyclic monophosphate (cGMP), protein kinase G (PKG) and the B-cell lymphoma 2/Bcl-2-associated X protein (Bcl-2/Bax) ratio, attenuated phosphodiesterase 5A (PDE-5A) and cleaved caspase-3 expression in I/R-liver. In hypoxic HepG2 cells, KMUP-1 increased cGMP/PKG, restored peroxisome proliferator-activated receptor-gamma (PPAR-gamma) and decreased matrix metalloproteinases-9 (MMP-9), Rho kinase II (ROCK II), hypoxia-inducible factor-1alpha (HIF-1alpha) and vascular endothelium growth factor (VEGF). KMUP-1 protects liver from I/R-injury and hypoxic hepatocytes from apoptosis-associated free radical generation and pro-inflammation by restoring/increasing NO/cGMP/PPAR-gamma, reducing ROS/Nox2 and inhibiting ROCKII/MMP-9.

Cyclic guanosine monophosphate-enhancing reduces androgenic extracellular regulated protein kinases-phosphorylation/Rho kinase II-activation in benign prostate hyperplasia

OBJECTIVES

To investigate whether 7-[2-[4-(2-chlorophenyl) piperazinyl] ethyl]-1,3-di-methylxanthine (KMUP-1) inhibits the effects of testosterone on the development of benign prostatic hyperplasia and sensitizes prostate contraction.

METHODS

A benign prostatic hyperplasia animal model was established by subcutaneous injections of testosterone (3 mg/kg/day, s.c.) for 4 weeks in adult male Sprague-Dawley rats. Animals were divided into six groups: control, testosterone, testosterone with KMUP-1 (2.5, 5 mg/kg/day), sildenafil (5 mg/kg/day) or doxazosin (5 mg/kg/day). After 4 weeks, the animals were killed, and prostate tissues were prepared for isometric tension measurement and western blotting analysis. KMUP-1, Y27632, zaprinast, doxazosin or tamsulosin were used at various concentrations to determine the contractility sensitized by phenylephrine (10 μmol/L).

RESULTS

KMUP-1 inhibited testosterone-induced phosphorylation of extracellular signal-regulated phosphorylated protein kinase and mitogen-activated protein kinase kinase and Rho kinase-II activation. Sildenafil and doxazosin significantly decreased benign prostatic hyperplasia-induced mitogen-activated protein kinase kinase and Rho kinase-II activation. The decreased expressions of soluble guanylate cyclase α1 was reversed by KMUP-1, doxazosin and sildenafil. Soluble guanylate cyclase β1 and protein kinase G were increased by KMUP-1, doxazosin, and sildenafil in the testosterone-treated benign prostatic hyperplasia group. Phosphodiesterase-5A was increased by testosterone and inhibited by KMUP-1 (5 mg/kg/day) or sildenafil (5 mg/kg/day). KMUP-1 inhibited phenylephrine-sensitized prostate contraction of rats treated with testosterone.

CONCLUSIONS

Mitogen-activated protein kinase 1/extracellular regulated protein kinases kinase, soluble guanylate cyclase/cyclic guanosine monophosphate, protein kinase/protein kinase G and Rho kinase-II are related to prostate smooth muscle tone and proliferation induced by testosterone. KMUP-1 inhibits testosterone-induced prostate hyper-contractility and mitogen-activated protein kinase 1/extracellular regulated protein kinases kinase-phosphorylation, and it inactivates Rho kinase-II by cyclic guanosine monophosphate, protein kinase and α1A-adenergic blockade. Thus, KMUP-1 might be a beneficial pharmacotherapy for benign prostatic hyperplasia.