Regulation of the p38-MAPK pathway by hyperosmolarity and by WNK kinases

Influence and molecular mechanism of cinnamaldehyde against ventricular arrhythmia via the TAK1-p38MAPK-NLRP3 pathway

Based on the transforming growth factor β-activated kinase 1 (TAK1)-p38 mitogen-activated protein kinase (p38MAPK)-nucleotide-binding oligo-like receptor protein 3 (NLRP3) signalling pathway, the protective effect and mechanism of isoproterennaline (ISO)-induced cinnamaldehyde on inflammatory injury in ventricular rats were investigated. Fifty male SPF SD rats were randomly assigned to the normal group, model group, propranolol group, cinnamaldehyde low-dose group or cinnamaldehyde high-dose group. The ventricular arrhythmia model was constructed using the "6 + 1" ISO injection method. The rats in the propranolol group were given propranolol 15 mg·(kg d)-1, those in the low and high-dose groups were given cinnamaldehyde 20 mg·(kg d)-1 and 50 mg·(kg d)-1, respectively, and those in the control and model groups received an equal volume of 0.9% NaCl solution. Changes in the serum troponin (cTnI), creatine kinase isoenzyme (CK-MB), and interleukin-1β (IL-1β) levels in SD rats were determined by ELISA. HE staining was used to observe the tissue morphology of heart disease. The mRNA expression of IL-1β and NLRP3 was determined by RT‒PCR. Mitochondrial damage was observed by transmission electron microscopy. The expression of reactive oxygen species (ROS) was detected by immunofluorescence. Western blot or immunohistochemical detection of the protein expression of IL-1β, NLRP3, TAK1, phospho-TAK1 (p-TAK1), p38MAPK, phospho-p38MAPK (p-p38MAPK), nuclear factor-κB (NF-κB),and phospho-NF-κB (p-NF-κB) was also performed. Data analysis was performed using SPSS 25.0 software. In the control SD rats, there were no obvious ventricular arrhythmias on ECG, the cardiac tissue and mitochondria were basically normal, the serum IL-1β level was low, and the expression of myocardial IL-1β, NLRP3, ROS, p-TAK1, p-p38MAPK and p-NF-κB was weak. Compared with the control group, the model group of SD rats had significant increases in ventricular arrhythmia and arrhythmia scores according to ECG (P < 0.01). Myocardial histopathological injury, cardiac weight index (HWI) and increases in serum cTnI and CK-MB levels were detected (P < 0.01). Additionally, mitochondrial damage in myocardial tissue, increased ROS fluorescence intensity, and elevated expression of myocardial p-TAK1, p-p38MAPK and p-NF-κB were detected(P < 0.01). The protein and mRNA expression of inflammation-related factors NLRP3 and IL-1β were increased (P < 0.01 or P < 0.05). Compared with those in the model group, the arrhythmia scores were decreased in the three treatment groups (P < 0.01 or P < 0.05). Cardiac histopathological morphology was significantly improved, and HWI and myocardial injury-related indicators were decreased(P < 0.01 or P < 0.05). Damaged mitochondria were significantly improved, and the expression of ROS, p-TAK1, p-p38MAPK, and p-NF-κB were decreased. The expression of inflammation-related factors in serum and myocardial tissue was decreased (P < 0.01 or P < 0.05). TAK1-p38MAPK-NLRP3 signalling is enhanced in SD rats with ventricular arrhythmia. Cinnamaldehyde can regulate TAK1-p38MAPK-NLRP3 signalling, reduce cardiomyocyte pyroptosis, antagonize myocardial inflammatory injury and protect cardiomyocytes by inhibiting oxidative stress.

The TSC22D, WNK, and NRBP gene families exhibit functional buffering and evolved with Metazoa for cell volume regulation

The ability to sense and respond to osmotic fluctuations is critical for the maintenance of cellular integrity. We used gene co-essentiality analysis to identify an unappreciated relationship between TSC22D2, WNK1, and NRBP1 in regulating cell volume homeostasis. All of these genes have paralogs and are functionally buffered for osmo-sensing and cell volume control. Within seconds of hyperosmotic stress, TSC22D, WNK, and NRBP family members physically associate into biomolecular condensates, a process that is dependent on intrinsically disordered regions (IDRs). A close examination of these protein families across metazoans revealed that TSC22D genes evolved alongside a domain in NRBPs that specifically binds to TSC22D proteins, which we have termed NbrT (NRBP binding region with TSC22D), and this co-evolution is accompanied by rapid IDR length expansion in WNK-family kinases. Our study reveals that TSC22D, WNK, and NRBP genes evolved in metazoans to co-regulate rapid cell volume changes in response to osmolarity.

Advances of the MAPK pathway in the treatment of spinal cord injury

Spinal cord injury (SCI) represents a complex pathology within the central nervous system (CNS), leading to severe sensory and motor impairments. It activates various signaling pathways, notably the mitogen-activated protein kinase (MAPK) pathway. Present treatment approaches primarily focus on symptomatic relief, lacking efficacy in addressing the underlying pathophysiological mechanisms. Emerging research underscores the significance of the MAPK pathway in neuronal differentiation, growth, survival, axonal regeneration, and inflammatory responses post-SCI. Modulating this pathway post-injury has shown promise in attenuating inflammation, minimizing apoptosis, alleviating neuropathic pain, and fostering neural regeneration. Given its pivotal role, the MAPK pathway emerges as a potential therapeutic target in SCI management. This review synthesizes current knowledge on SCI pathology, delineates the MAPK pathway's characteristics, and explores its dual roles in SCI pathology and therapeutic interventions. Furthermore, it addresses the existing challenges in MAPK research in the context of SCI, proposing solutions to overcome these hurdles. Our aim is to offer a comprehensive reference for future research on the MAPK pathway and SCI, laying the groundwork for targeted therapeutic strategies.

Isoform-independent promotion of contractility and proliferation, and suppression of survival by with no lysine/K kinases in prostate stromal cells

With no lysine/K kinases (WNKs) promote vasocontraction and vascular smooth muscle cell proliferation. In the prostate, smooth muscle contraction and growth may be critical for the development and medical treatment of voiding symptoms in benign prostatic hyperplasia. Here, we examined the effects of isoform-specific WNK silencing and of the WNK inhibitor WNK463 on growth-related functions and contraction in prostate stromal cells, and in human prostate tissues. Impacts of WNK silencing by transfection of cultured stromal cells with isoform-specific siRNAs were qualitatively and quantitatively similar for each WNK isoform. Effects of silencing were largest on cell death (3-5 fold increase in annexin V-positive/7-AAD-positive cells), on proliferation rate, Ki-67 mRNA expression and actin organization (reduced around two-thirds). Contraction in matrix contraction assays and viability were reduced to a lower degree (approximately half), but again to a similar extent for each WNK isoform. Effects of silencing were quantitatively and qualitatively reproduced by 10 μM WNK463, while 1 μM still induced cell death and breakdown in actin organization, without affecting proliferation or viability. Using 500 nM and 10 μM, WNK463 partly inhibited neurogenic and U46619-induced contractions of human prostate tissues (around half), while inhibition of α1-adrenergic contractions (around half) was limited to 10 μM. All four WNK isoforms suppress cell death and promote proliferation in prostate stromal cells. WNK-driven contraction of stromal cells appears possible, even though to a limited extent. Outcomes of isoform-specific WNK silencing can be fully reproduced by WNK463, including inhibition of smooth muscle contraction in human prostate tissues, but require high concentrations.

The in vitro cytotoxic effects of natural (fibrous epsomite crystals) and synthetic (Epsom salt) magnesium sulfate

Exposure to mineral fibers represents an occupational and environmental hazard since particulate inhalation leads to several health disorders. However, few data are available on the effect of fibers with high solubility like natural epsomite, a water-soluble fiber with an inhalable size that allows it to penetrate biological systems, with regard to the respiratory tract. This study evaluated the natural (fibrous epsomite) and synthetic (Epsom salt) magnesium sulfate pathogenicity. Investigations have been performed through morpho-functional and biochemical analyses, in an in vitro cell model that usually grows as monocytes, but that under appropriate conditions differentiates into macrophages. These latter, known as alveolar macrophages, if referred to lungs, represent the first line of defense against harmful inhaled stimuli. Morphological observations reveal that, if Epsom salt induces osmotic stress on cell culture, natural epsomite fibers lead to cellular alterations including thickening of the nuclear envelope and degenerated mitochondria. Moreover, the insoluble fraction (impurities) internalized by cells induces diffuse damage characterized at the highest dosage and exposure time by secondary necrosis or necrotic cell death features. Biochemical analyses confirm this mineral behavior that involves MAPK pathway activation, resulting in many different cellular responses ranging from proliferation control to cell death. Epsom salt leads to MAPK/ERK activation, a marker predictive of overall survival. Unlike, natural epsomite induces upregulation of MAPK/p38 protein involved in the phosphorylation of downstream targets driving necrotic cell death. These findings demonstrate natural epsomite toxicity on U937 cell culture, making the inhalation of these fibers potentially hazardous for human health. RESEARCH HIGHLIGHTS: Natural epsomite and synthetic Epsom salt effects have been evaluated in U937 cell model. Epsom salt induces an osmotic cellular stress. Natural epsomite fibers lead to cellular damage and can be considered potentially dangerous for human health.

Involvement of CCL2 in Salivary Gland Response to Hyperosmolar Stress Related to Sjögren's Syndrome

In primary Sjögren's syndrome (pSS) patients, salivary gland (SG) epithelial cells (SGECs) could be exposed to chronic hyperosmotic stress (HOS), consecutive to their destruction and deregulation, that exacerbates an inflammatory response. The aims of this study were to assess the mechanism accounting for C-C motif chemokine ligand 2 (CCL2) expression in an immortalized human salivary gland epithelial acinar cell line (NS-SV-AC) subjected to HOS, as well as the involvement of CCL2 in pSS. CCL2 mRNA and protein levels were determined via RT-qPCR and ELISA. Reporter plasmids and a promoter pull-down assay were used to identify transcription factors associated with CCL2 mRNA increase. Our data showed that HOS-induced CCL2 mRNA increase was independent of the nuclear factor of activated T-cells 5 (NFAT5) and nuclear factor-kappa B (NFkB) but involved Kruppel-like factor 5 (KLF5). CCL2 protein levels, quantified by enzyme-linked immunosorbent assay (ELISA) in sera samples from pSS patients, correlated with the European Alliance of Associations for Rheumatology's Sjogren's syndrome disease activity index (ESSDAI) score for systemic activity. In addition, CCL2 protein levels were higher in patients with biological activity, cutaneous manifestations, and ESSDAI score superior or equal to five. Our data suggest that chronic HOS could exacerbate pSS disease by contributing to the inflammatory process induced by the expression and secretion of CCL2.

Mechanisms underlying sensing of cellular stress signals by mammalian MAP3 kinases

Cellular homeostasis is continuously challenged by environmental cues and cellular stress conditions. In their defense, cells need to mount appropriate stress responses that, dependent on the cellular context, signaling intensity, and duration, may have diverse outcomes. The stress- and mitogen-activated protein kinase (SAPK/MAPK) system consists of well-characterized signaling cascades that sense and transduce an array of different stress stimuli into biological responses. However, the physical and chemical nature of stress signals and how these are sensed by individual upstream MAP kinase kinase kinases (MAP3Ks) remain largely ambiguous. Here, we review the existing knowledge of how individual members of the large and diverse group of MAP3Ks sense specific stress signals through largely non-redundant mechanisms. We emphasize the large knowledge gaps in assigning function and stress signals for individual MAP3K family members and touch on the potential of targeting this class of proteins for clinical benefit.

WNK kinases sense molecular crowding and rescue cell volume via phase separation

When challenged by hypertonicity, dehydrated cells must recover their volume to survive. This process requires the phosphorylation-dependent regulation of SLC12 cation chloride transporters by WNK kinases, but how these kinases are activated by cell shrinkage remains unknown. Within seconds of cell exposure to hypertonicity, WNK1 concentrates into membraneless condensates, initiating a phosphorylation-dependent signal that drives net ion influx via the SLC12 cotransporters to restore cell volume. WNK1 condensate formation is driven by its intrinsically disordered C terminus, whose evolutionarily conserved signatures are necessary for efficient phase separation and volume recovery. This disorder-encoded phase behavior occurs within physiological constraints and is activated in vivo by molecular crowding rather than changes in cell size. This allows kinase activity despite an inhibitory ionic milieu and permits cell volume recovery through condensate-mediated signal amplification. Thus, WNK kinases are physiological crowding sensors that phase separate to coordinate a cell volume rescue response.