Search Results (72)

Carbon monoxide (CO) is a gasotransmitter generated by heme oxygenase (HO) isoforms during heme catabolism. The inducible HO-1 produces CO under conditions of redox imbalance, such as oxidative stress and inflammation. On the other hand, HO-2 constitutively generates CO, primarily during the physiological turnover of heme. Extensive evidence indicates that CO exerts autocrine effects by targeting hemoproteins, including soluble guanylyl cyclase, cyclooxygenase, and cytochromes. Furthermore, CO regulates many biological processes within the brain, including mitochondrial biogenesis, potassium channel activity, mitogen-activated protein kinase and phosphatidylinositol-3-kinase/Akt signaling. It also controls the activity of transcription factors, such as hypoxia-inducible factor-1 and peroxisome proliferator-activated receptor-γ. Through these mechanisms, CO modulates inflammatory gene expression, promotes anti-apoptotic signaling, and contributes to local stress responses. Conversely, CO produced in the hypothalamus inhibits the stress-induced release of corticotropin-releasing hormone and arginine vasopressin under pro-inflammatory conditions, resulting in reduced adrenocorticotropin hormone release and cortisol secretion from the anterior pituitary and adrenal cortex, respectively. Moreover, hypothalamic CO acts in a paracrine manner to modulate glucocorticoid release during psychological stress, including restraint or water deprivation. Together, these findings support the view that endogenous CO is a key modulator of the stress axis, exerting pleiotropic effects that integrate neuroendocrine, immune, and metabolic responses. Full article

Sepsis is a life-threatening syndrome driven by a dysregulated host response to infection and is frequently complicated by sepsis-associated encephalopathy (SAE), which contributes to long-term cognitive and neuropsychiatric sequelae. Despite advances in critical care, effective targeted therapies for SAE remain limited. Aquaporin-4 (AQP4), the predominant astrocytic water channel, plays a central role in cerebral water homeostasis, neuroinflammatory signaling, and blood–brain barrier integrity, suggesting its potential involvement in sepsis-induced cerebral dysfunction and neurorepair processes. Polymicrobial sepsis was induced in C57BL/6J mice using the cecal ligation and puncture (CLP) model. AQP4 activity was pharmacologically modulated through either inhibition or facilitation following sepsis induction. Disease severity was assessed using physiological parameters and a modified murine sepsis score. Neurological outcomes were evaluated through standardized behavioral tests assessing locomotor activity, motor coordination, cognitive performance, and depressive-like behavior. Neuroinflammatory and neuronal changes were examined by immunohistochemical analyses of microglial activation (Iba1), astroglial reactivity (GFAP), neuronal integrity (NeuN), and AQP4 expression. Compared with AQP4 facilitation, pharmacological inhibition of AQP4 was associated with a more favorable clinical recovery profile, reflected by lower sepsis severity scores and a more favorable body weight trajectory during the recovery phase. Behavioral analyses demonstrated preserved cognitive function, enhanced motor coordination, and reduced depressive-like behavior in AQP4 inhibitor-treated mice compared with animals receiving AQP4 facilitation. At the histological level, the inhibitor-treated group showed lower microglial and astroglial activation and better preservation of neuronal markers than the facilitator-treated group, whereas AQP4 facilitation exacerbated neuroinflammatory responses and neuronal alterations. These findings highlight a dual, context-dependent role of AQP4 in sepsis-associated cerebral dysfunction. These findings suggest that AQP4 modulation influences sepsis-associated cerebral dysfunction in a context-dependent manner. Within our experimental design, AQP4 facilitation was associated with worse outcomes, whereas AQP4 inhibition was associated with a comparatively more favorable neurobehavioral and histological profile. Full article

The aquaporin 0 (AQP0)/major intrinsic protein of eye lens (MIP) cDNA was cloned and sequenced. Initial studies of the tissue distribution of mRNA expression proved to be incorrect. Subsequent experiments showed that AQP0 mRNA is expressed strongly in the eye with moderately strong expression in the kidneys and some expression was seen in the brain and muscle tissue, and very low expression in the esophagus/fundic stomach. Another set of PCR reactions with five times the amount of cDNA additionally showed mRNA/cDNA expression in the liver, rectal gland, and a very low level in the intestine. Sporadic expression of different pieces of AQP0 cDNA was seen in various experiments in gill and pyloric stomach. A custom polyclonal antibody was produced against a region near the C-terminal end of the AQP0 protein sequence. The antibody gave a band of around the correct size (for the AQP0 protein) on the Western blot, which also showed a few other higher-molecular-weight bands. The antibody was also used in immunohistochemistry, and in the kidney, it showed staining in the proximal II (PII), intermediate segment I (IS I), and late distal tubule (LDT) parts of the sinus zone region of nephrons as well as some staining in the bundle zone tubule segments, suggesting a role for AQP0 as a water channel. In the rectal gland, the antibody showed weak apical membrane staining in a few secretory tubules near the duct, but also somewhat stronger staining in cells appearing to connect various secretory tubules, suggesting a role in cell–cell adhesion. In the spiral valve intestine side wall and valve flap, after signal amplification, weak antibody staining was seen in the apical and lateral membranes of epithelial cells adjacent to the luminal surface. There was also some staining in the intestinal muscle. In the rectum/colon, staining was seen in a layer of cells underlying the epithelium and in some muscle layers. In the gill, there was very weak staining in secondary lamellae epithelial cells and in connective tissue surrounding blood vessels and blood sinuses. The low level of transcript expression in the rectal gland, gill, and intestinal tissues suggests caution in the interpretation of the immunohistochemical staining in these tissues. Full article

Depression represents a leading cause of global disability, yet its pathogenesis remains incompletely understood. This review synthesizes emerging evidence highlighting the multifaceted role of Aquaporin-4 (AQP4), the central nervous system’s predominant water channel, in the pathophysiology of depression. Preclinical studies frequently report AQP4 dysregulation in depression models, characterized by reduced perivascular expression and impaired polarization in mood-relevant brain circuits. We delineate how AQP4 impairment is implicated in depression through several interconnected mechanistic pathways: (1) exacerbating glutamate excitotoxicity by disrupting astrocytic glutamate clearance; (2) impairing monoaminergic neurotransmission and synaptic plasticity; (3) potentiating neuroinflammatory cascades; (4) inducing mitochondrial functional impairment and oxidative stress; and (5) participating in hypothalamic–pituitary–adrenal (HPA) axis dysregulation by disrupting perineuronal osmotic and ionic homeostasis in response to arginine vasopressin (AVP) signaling. Furthermore, we explore the therapeutic relevance of AQP4, noting that diverse antidepressant treatments appear to partly exert their effects by modulating AQP4 expression and function. Collectively, the evidence positions AQP4 not as a solitary causative factor, but as a critical contributing component within the broader astrocyte–neuron–immune network. We therefore propose AQP4 as a promising node for therapeutic intervention, whose modulation may help counteract core pathophysiological processes in depression, offering a potential avenue for novel treatment development. Full article

Water deprivation triggers coordinated physiological responses to preserve body fluid balance, yet the molecular mechanisms that regulate aquaporin-mediated water transport under dehydration remain incompletely understood. Aquaporin-4 (AQP4), the main water channel in the brain and a basolateral water pathway in the kidney collecting duct, exists in multiple isoforms, including the translational readthrough variant AQP4ex, whose regulatory role is only beginning to be defined. Here, we investigated the effects of acute water deprivation (6–12 h) on AQP4 isoform expression and phosphorylation in a mouse kidney and brain. While total AQP4 and AQP4ex protein levels remained largely unchanged in both tissues, dehydration induced a marked and divergent regulation of the phosphorylated form of AQP4ex. Levels increased in the kidney medulla, consistent with enhanced antidiuretic water transport, but decreased in the cerebral cortex, suggesting a protective reduction in perivascular water permeability. No changes were detected in the cerebellum. These findings identify phosphorylation of AQP4ex as a rapid, tissue-specific regulatory mechanism that adjusts water flux according to the physiological needs of each organ, revealing an additional layer of control in systemic water homeostasis and highlighting AQP4ex as a potential target in dehydration-related and osmotic disorders. Future studies could explore the signaling pathways regulating AQP4ex phosphorylation and investigate its potential involvement in pathological conditions, such as diabetes insipidus or cerebral edema. Full article

Epilepsy is a prevalent neurological disorder characterized by spontaneous recurrent seizures (SRS). Epileptogenesis is a multifaceted pathophysiological process that transforms a normal brain into one prone to chronic seizures. Targeting epileptogenesis is a compelling line of epilepsy therapy. Thus, discovering new drugs that oppose, mitigate, or modify epileptogenesis is a significant challenge in modern neuroscience. Our previous work demonstrated that, in a kainic acid (KA)-induced post-status epilepticus model, 28 days myo-inositol (MI) treatment reduces frequency and duration of motor and electrographic SRS even following cessation of treatment, for the following 4 weeks and identified MI as a promising antiepileptogenic compound To further evaluate the dose-dependent efficacy of MI, we applied the same experimental model using 30 mg/kg (dose used in earlier studies), 60 mg/kg, and 120 mg/kg to assess effects on hippocampal electrographic and motor SRS, as well as KA-induced spatial learning and memory impairment in a Morris water maze test. We found that MI had long-lasting, dose-dependent suppressive effects on behavioral and electrographic manifestations of epileptogenesis and ameliorated spatial learning and memory deficit induced by SE, with 60 mg/kg emerging as the most effective dose. Furthermore, we investigated transcriptomic and epigenetic alterations associated with the optimal MI dose and identified multiple affected pathways in the hippocampus. Interestingly, MI treatment resulted in transcriptomic upregulation and prevention of downregulation of several ion channel subunits, including GRIK3 and GRIN3A (kainate and NMDA receptor subunits) and the sodium channel subunit SCNB4. The obtained data highlight new molecular targets for epilepsy therapy and support the translational potential of MI. Full article

Subarachnoid hemorrhage (SAH), often resulting from aneurysmal rupture, remains a life-threatening cerebrovascular disorder with high morbidity and mortality. While previous research has focused primarily on cerebral damage and neurological outcomes, growing evidence suggests that SAH also causes systemic complications, including pulmonary dysfunction. The underlying mechanisms linking SAH to lung injury, however, are not fully understood. The glymphatic system, a perivascular network that facilitates the clearance of cerebrospinal fluid (CSF) and interstitial waste from the brain, plays a critical role in maintaining central nervous system (CNS) homeostasis. Aquaporin-4 (AQP4) water channels, predominantly expressed in astrocytic end feet, are essential for efficient glymphatic flow. Emerging studies have shown that SAH impairs glymphatic function by disrupting AQP4 polarity and CSF circulation, resulting in the accumulation of neurotoxic substances and neuroinflammation. Recent findings further suggest that glymphatic dysfunction may exert systemic effects beyond the CNS, contributing to a breakdown of the brain–lung axis. The release of pro-inflammatory cytokines, blood degradation products, and damage-associated molecular patterns (DAMPs) into systemic circulation can promote pulmonary endothelial injury and trigger immune responses in the lungs. This phenomenon is exacerbated by impaired clearance via the glymphatic system, amplifying systemic inflammation and increasing the risk of acute lung injury (ALI) or neurogenic pulmonary edema (NPE). This review proposes a novel perspective linking glymphatic impairment with pulmonary complications after SAH. Understanding this connection could open new therapeutic avenues—such as targeting AQP4 function, enhancing CSF circulation, or modulating the inflammatory response—to mitigate both neurological and respiratory sequelae in SAH patients. Full article

Stroke is a leading global cause of mortality and long-term disability, with cerebral edema constituting a major contributor to early neurological deterioration and poor outcomes. Aquaporin-4 (AQP4), the predominant water channel in the central nervous system, plays a paradoxical role in stroke-related brain edema, facilitating both the formation and clearance of excess fluid depending on the pathological context. This review explores the biphasic function of AQP4 across cytotoxic and vasogenic edema, emphasizing its dynamic regulation, subcellular localization, and implications for therapeutic intervention. Evidence from rodent models shows that AQP4 exacerbates cytotoxic edema in acute ischemia by promoting intracellular water influx into astrocytes, whereas in vasogenic edema, it supports fluid reabsorption and glymphatic clearance, thereby alleviating brain swelling. Human studies corroborate AQP4 upregulation in infarcted regions and suggest a potential role for AQP4 polymorphisms and circulating levels as biomarkers of stroke severity and outcome, although larger cohorts and more robust methodological designs are needed. This review also discusses emerging pharmacological strategies to modulate AQP4 activity, including inhibitors, trafficking modulators, and gene-targeted delivery systems, while highlighting challenges in achieving phase-specific modulation. Given its central role in both injury and recovery, AQP4 emerges as a promising yet complex therapeutic target for personalized management of stroke-induced brain edema. Future directions include real-time imaging of AQP4 function, genotype-stratified clinical trials, and integration of AQP4 modulation with current stroke treatment protocols. Full article

Attraction of glioblastoma cells to potassium was suspected when glioblastoma cells clustered around dying cells and migrated towards serum (high [K⁺]) and increased potassium. Potassium channel proteins (KCN family, 90 members) mediating alterations in the transmembrane flux may provide K⁺ that releases H⁺ bound to inner membranes in cancer cells for cytosolic proton transfer, possibly conformational in water (Grotthuss), to extrusion sites. Cell settling and migration assay results led to collecting 70 studies, unbiased by the authors for inclusion of KCN genes, that detected KCN differentially expressed genes (DEGs). Of 53 KCN DEGs found among 29 malignancies, 62.3% encoded H⁺-sensitive proteins. KCN DEGs encoding H⁺-sensitive proteins were more prevalent in 50 studies involving one or more categories (seven oncogenes and histone/DNA modifiers) versus those with none; p = 0.0325. Pertinent genes for lactate outflow, etc., had relatively normal levels of expression. Brain tumors in REMBRANDT (database) showed altered expression of KCN genes encoding H⁺-sensitive proteins in glioblastomas versus less invasive oligodendrogliomas of patients on anti-seizure medications, with less KCNJ16/Kir5.1; p = 5.32 × 10⁻⁸ in glioblastomas. Altered H⁺-sensitive potassium flux via the KCN family, downstream of oncogenes and histone/DNA modifiers, putatively incites proton transfers for H⁺ release during pH reversal (pHi > pHe) in cancer. Full article

Thirst is usually characterized as an unpleasant sensation provoking drinking of water. The purpose of the present review is to draw attention to the importance of thirst in overall regulation of body fluid homeostasis in health and pathology. Intensity of thirst is determined by signals generated in multiple groups of osmosensitive neurons engaged in dipsogenic and antidipsogenic activities, which are located in the brain cortex, the insula, the amygdala, the median preoptic area, the hypothalamic nuclei and the organum vasculosum laminae terminalis. Water ingestion is also influenced by signals generated in the cardiovascular system, the gastrointestinal system, the pancreas, the liver and the kidney and by changes of body temperature. Regulation of thirst engages the autonomic nervous system and several neuroactive factors synthetized in the brain and the peripheral organs. Among them are components of the renin–angiotensin system, vasopressin, atrial natriuretic peptide, cholecystokinin, ghrelin, gaseous transmitters, cytokines and prostaglandins. Experimental studies provide evidence that elevation of fluid osmolality, which is the most frequent cause of thirst, influences function of the voltage-gated sodium channel and calcium-dependent kinase II subunit alpha. Regulation of thirst may be inappropriate in old age and under some pathological conditions including infections, heart failure, diabetes insipidus, diabetes mellitus, and psychogenic disorders. The molecular background of the abnormal regulation of thirst in the clinical disorders is not yet sufficiently recognized and requires further examination. Full article

Aquaporins (AQPs) are a family of transmembrane water channel proteins facilitating the transport of water and, in some cases, small solutes such as glycerol, lactate, and urea. In the central nervous system (CNS), several aquaporins play crucial roles in maintaining water homeostasis, modulating cerebrospinal fluid (CSF) circulation, regulating energy metabolism, and facilitating neuroprotection under pathological conditions. Among them, AQP2, AQP4, AQP9, and AQP11 have been implicated in traumatic and non-traumatic brain injuries. The most abundant aquaporin (AQP) in the brain, AQP4, is essential for fluid regulation, facilitating water transport across the blood–brain barrier and glymphatic clearance. AQP2 is primarily known for its function in the kidneys, but it is also expressed in brain regions related to vasopressin signaling and CSF dynamics. AQP9 acts as a channel for glycerol and lactate, thus playing a role in metabolic adaptation during brain injury. AQP11, an intracellular aquaporin, is involved in oxidative stress responses and cellular homeostasis, with emerging evidence suggesting its role in neuroprotection. Aquaporins play a dual role in brain injury; while they help maintain homeostasis, their dysregulation can exacerbate cerebral edema, metabolic dysfunction, and inflammation. In traumatic brain injury (TBI), aquaporins regulate the formation and resolution of cerebral edema. In non-traumatic brain injuries, including ischemic stroke, aneurysmal subarachnoid hemorrhage (aSAH), and intracerebral hemorrhage (ICH), aquaporins influence fluid balance, energy metabolism, and oxidative stress responses. Understanding the specific roles of AQP2, AQP4, AQP9, and AQP11 in these brain injuries may lead to new therapeutic strategies to mitigate secondary damage and improve neurological outcomes. This review explores the function of the above aquaporins in both traumatic and non-traumatic brain injuries, highlighting their potential and limitations as therapeutic targets for neuroprotection and recovery. Full article

Purinergic P2X receptors (P2X) are ATP-gated ion channels that are broadly expressed in the brain, particularly in the hypothalamus. As ionic channels with high permeability to calcium, P2X play an important and active role in neural functions. The hypothalamus contains a number of small nuclei with many molecularly defined types of peptidergic neurons that affect a wide range of physiological functions, including water balance, blood pressure, metabolism, food intake, circadian rhythm, childbirth and breastfeeding, growth, stress, body temperature, and multiple behaviors. P2X are expressed in hypothalamic neurons, astrocytes, tanycytes, and microvessels. This review focuses on cell-type specific expression of P2X in the most important hypothalamic nuclei, such as the supraoptic nucleus (SON), paraventricular nucleus (PVN), suprachiasmatic nucleus (SCN), anteroventral periventricular nucleus (AVPV), anterior hypothalamic nucleus (AHN), arcuate nucleus (ARC), ventromedial hypothalamic nucleus (VMH), dorsomedial hypothalamic nucleus (DMH), tuberomammillary nucleus (TMN), and lateral hypothalamic area (LHA).> The review also notes the possible role of P2X and extracellular ATP in specific hypothalamic functions. The literature summarized here shows that purinergic signaling is involved in the control of the hypothalamic-pituitary endocrine system, the hypothalamic–neurohypophysial system, the circadian systems and nonendocrine hypothalamic functions. Full article

The piperazine derivative N-(2,6-difluorophenyl)-2-(4-phenylpiperazin-1-yl)propanamide (cmp2) has emerged as a potential transient receptor potential cation channel, subfamily C, member 6 (TRPC6) modulator, offering a promising pathway for Alzheimer’s disease (AD) therapy. Our recent findings identify cmp2 as a novel compound with synaptoprotective effects in primary hippocampal cultures and effective blood–brain barrier (BBB) penetration. In vivo studies demonstrate that cmp2 (10 mg/kg, intraperitoneally) restores synaptic plasticity deficits in 5xFAD mice. This study further shows cmp2’s selectivity towards tetrameric TRPC6 channel in silico. Acute administration of cmp2 is non-toxic, with no indications of chronic toxicity, and Ames testing confirms its lack of mutagenicity. Behavioral assays reveal that cmp2 improves cognitive functions in 5xFAD mice, including increased novel object recognition, better passing of the Morris water maze, and improved fear memory, as well as upregulation of motor function in beam walking tests. These findings suggest that cmp2 holds promise as a candidate for AD treatment. Full article

The glymphatic system, an analog of the peripheral lymphatic system in the brain, and the meningeal lymphatic system are critical to central nervous system health. The glymphatic system functions to distribute cerebrospinal fluid and important compounds throughout the brain and to remove metabolic waste. The flow of cerebrospinal fluid through this system is affected by changes in cerebral blood flow, intracranial pressure, and vascular tone. Cetaceans experience profound cardiorespiratory alterations while diving that can directly affect cerebrospinal fluid and blood flow and, thus, glymphatic function. Our goal was to investigate glymphatic and lymphatic system structures, including perivascular spaces, aquaporin-4 water channels, meningeal lymphatic, and dural venous sinus vessels in the common dolphin (Delphinus delphis), using immunofluorescent labeling, histochemical staining, and postmortem computed tomography (CT) angiography. We highlight perivascular spaces and aquaporin-4 water channels surrounding blood vessels in the parenchyma and demonstrate evidence of meningeal lymphatic vessels and associated dural venous sinuses. These results demonstrate that common dolphins possess the key anatomical structures required for functional glymphatic and meningeal lymphatic systems. Future studies can build upon these anatomical discoveries to study the function and role of these systems in brain health in this species. Full article

The response of ryanodine receptor (RyR) channels to increases in free cytoplasmic calcium concentration ([Ca²⁺]) is tuned by several mechanisms, including redox signaling. Three different responses to [Ca²⁺] have been described in RyR channels, low, moderate and high activity responses, which depend on the RyR channel protein oxidation state. Thus, reduced RyR channels display the low activity response, whereas partially oxidized channels display the moderate response and more oxidized channels, the high activity response. As described here, RyR channels from rat brain cortices or hippocampi displayed aged-related marked changes in the distribution of these channel responses; RyR channels from aged rats displayed reduced fraction of low activity channels and increased fraction of high activity channels, which would favor Ca²⁺-induced Ca²⁺ release. In addition, compared with young rats, aged rats displayed learning and memory defects, with lower hit rates when tested in the Oasis maze, a dry version of the Morris water maze. Previous oral administration of N-acetylcysteine for 3 weeks prevented both the age-dependent effects on RyR channel activation by [Ca²⁺], and the learning and memory defects. Based on these results, it is proposed that redox-sensitive neuronal RyR channels partake in the mechanism underlying the learning and memory disruptions displayed by aged rats. Full article