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PubMed2026

Elevated mitochondrial superoxide promotes longevity through a mitochondria-to-nucleus kinase signaling pathway.

The reactive oxygen species superoxide is generated by mitochondria during the process of producing energy. While superoxide can cause oxidative damage to the cell, we and others have shown that a mild increase in mitochondrial superoxide extends longevity in multiple model organisms. To elucidate the molecular mechanisms involved, we identified transcriptional changes in mitochondrial superoxide dismutase deletion mutants (sod-2 worms) using RNA sequencing. sod-2 mutants exhibit a number of changes in nuclear gene expression resulting from elevated mitochondrial superoxide suggesting that mitochondria-to-nucleus signaling is contributing to their longevity. Gene ontology enrichment analysis demonstrated that genes involved in innate immunity and cuticle formation are significantly upregulated in sod-2 worms. To identify kinases involved in this lifespan-extending pathway, we completed a targeted RNA interference screen to examine the contribution of selected kinases to sod-2 longevity. From this screen, we found 25 kinases which are required for the long lifespan of sod-2 mutants including mak-2, which has a role in a kinase signaling pathway involved in axon regeneration. Disruption of mak-2 specifically reduces sod-2 lifespan but not wild-type longevity and also decreases resistance to multiple exogenous stressors. In examining other genes that act with mak-2 in established signaling pathways, we identified a SEK-3/PMK-3/MAK-2/CEBP-1 signaling pathway that is specifically required for sod-2 longevity but not wild-type lifespan. Combined these results suggest a novel role for kinases with established roles in axon regeneration in promoting longevity through a mitochondria-to-nucleus signaling pathway.

Aging↗

PubMed2018

Signaling Pathways Regulating Redox Balance in Cancer Metabolism.

The interplay between rewiring tumor metabolism and oncogenic driver mutations is only beginning to be appreciated. Metabolic deregulation has been described for decades as a bystander effect of genomic aberrations. However, for the biology of malignant cells, metabolic reprogramming is essential to tackle a harsh environment, including nutrient deprivation, reactive oxygen species production, and oxygen withdrawal. Besides the well-investigated glycolytic metabolism, it is emerging that several other metabolic fluxes are relevant for tumorigenesis in supporting redox balance, most notably pentose phosphate pathway, folate, and mitochondrial metabolism. The relationship between metabolic rewiring and mutant genes is still unclear and, therefore, we will discuss how metabolic needs and oncogene mutations influence each other to satisfy cancer cells' demands. Mutations in oncogenes, i.e., PI3K/AKT/mTOR, RAS pathway, and MYC, and tumor suppressors, i.e., p53 and liver kinase B1, result in metabolic flexibility and may influence response to therapy. Since metabolic rewiring is shaped by oncogenic driver mutations, understanding how specific alterations in signaling pathways affect different metabolic fluxes will be instrumental for the development of novel targeted therapies. In the era of personalized medicine, the combination of driver mutations, metabolite levels, and tissue of origins will pave the way to innovative therapeutic interventions.

OXPHOS↗

PubMed2026

Transcriptomic Association Between Poliovirus Receptor (PVR/CD155) and Claudin Signaling Pathways in Colorectal Cancer.

BACKGROUND/AIM: Enterotoxigenic Bacteroides fragilis promotes colorectal carcinogenesis through toxin-mediated cleavage of E-cadherin, a process facilitated by membrane-associated Claudin-4 (CLDN4). Separately, the poliovirus receptor (PVR/CD155) modulates tumor epithelial and immune dynamics. This study explored potential transcriptomic interactions and co-expression frameworks between PVR and claudin signaling pathways in colorectal cancer. MATERIALS AND METHODS: Transcriptomic and proteomic data from the The Cancer Genome Atlas-colon adenocarcinoma cohort (TCGA-COAD) were evaluated. An exploratory E-cadherin Cleavage Index was modeled to capture transcript-protein discordance. To control for tissue composition heterogeneity without mathematical circularity, a de-circularized, non-parametric partial rank residual model adjusted for independent CLDN4 expression was deployed within the stable microsatellite-stable (MSS) sub-cohort (N=473). RESULTS: Multivariable survival models showed no independent associations between overall survival and continuous PVR (p=0.79) or CLDN3 (p=0.56) expression. Robust linear modeling revealed no significant baseline interaction between PVR and CLDN4 regarding the exploratory Cleavage Index (p=0.82). However, de-circularized partial correlation analysis revealed a highly stable, positive co-expression between PVR and CLDN3 (rho=0.2459, p=3.23×10-7). Both epithelial markers retained modest inverse correlations with the infiltrating lymphocytic axis (TIGIT and CD96). CONCLUSION: Baseline PVR expression is coordinated with CLDN3 tissue programs independent of general epithelial cellularity but does not interact with the CLDN4 axis or impact overall survival in an unexposed cohort. Because TCGA lacks virome or active microbial exposure tracking, these findings serve as baseline benchmarks for future context-dependent mechanistic studies.

Bacteroides fragilis toxin↗

PubMed2026

Qingfei Dayuan granules alleviate the inflammatory response in lipopolysaccharide-induced acute lung injury mice by inhibiting the Nf-κB signaling pathway and regulating the complement pathway.

OBJECTIVES: The study aimed to explore the effects and mechanisms by which Qingfei Dayuan granules (QFDY) mitigate pulmonary inflammation in lipopolysaccharide (LPS)-induced acute lung injury (ALI). METHODS: We established an ALI mouse model by intraperitoneal injection of LPS. HE, Transmission electron microscopy, ELISA assay of inflammatory cytokines, and immunohistochemistry (IHC) were used to assess the degree of lung injury and inflammation. Utilizing network analysis and proteomics analysis, the potential targets and pathways of QFDY were identified. Western blot, IHC, and qRT-PCR analysis were used to evaluate the potential mechanism of QFDY. Additionally, the chemical composition of QFDY were performed using UPLC-MS/MS. KEY FINDINGS: QFDY reduced the pathologic changes and inflammatory cell infiltration in lung tissue inflammation. Network and proteomic analysis showed that the mechanism of QFDY protection against ALI is closely related to the Nuclear factor-kappa B (NF-κB) signaling pathway and complement pathway. Animal experiments showed that Qingfei Dayuan granules (QFDY) significantly reduced the levels of IL-1β, IL-6, TNF-α, and lung tissue F4/80-positive alveolar macrophages. Additionally, western blot and qRT-PCR analyses showed the inhibition of the NF-κB pathway. Notably, the levels of mannose-binding lectin (MBL2) were significantly increased, while complement C3a and complement C5a proteins were reduced in the QFDY group compared to the LPS group. CONCLUSIONS: QFDY suppressed the inflammation in LPS-induced ALI by inhibiting the NF-κB and complement pathway.

Animals↗

PubMed2025

EIF2B5 promotes malignant progression of hepatocellular carcinoma by activating the PI3K/AKT signaling pathway through targeting RPL6.

Hepatocellular carcinoma (HCC) is a highly aggressive malignancy with limited treatment options and poor prognosis. In this study, we demonstrated the critical role of EIF2B5 in driving HCC progression. We found EIF2B5 expression is significantly upregulated in HCC tumor tissues in several bioinformatics datasets, including The Cancer Genome Atlas, and that high expression of EIF2B5 predicts poor prognosis for HCC patients. Through a series of in vitro cell biology experiments, we found that EIF2B5 knockdown significantly attenuated Hep3B and HepG2 proliferation, migration, and invasion and increased cell cycle arrest, whereas EIF2B5 overexpression promoted HCC progression. Through mass spectrometry and immunoprecipitation validation, we found that EIF2B5 directly interacted with RPL6 and that when EIF2B5 was overexpressed in HCC cells, it promoted the expression of the downstream protein RPL6, which was able to activate the phosphatidylinositol kinase (PI3K)/serine-threonine kinase (AKT)/mammalian target of rapamycin (mTOR) pathway and thereby increase the proliferation and invasion ability of HCC cell lines, as verified by second-generation sequencing analysis and western blot. We further verified these findings using the mouse ectopic tumor assay, and the results showed that EIF2B5 knockdown significantly inhibited tumor progression in HCC mice. The present study suggests that EIF2B5 promotes malignant progression of HCC by interacting with RPL6 and activating the PI3K/AKT/mTOR signaling pathway and may serve as a potential target for the treatment of HCC.

Humans↗

PubMed1992

Internal calcium release and activation of sea urchin eggs by cGMP are independent of the phosphoinositide signaling pathway.

We show that microinjecting cyclic GMP (cGMP) into unfertilized sea urchin eggs activates them by stimulating a rise in the intracellular free calcium ion concentration ([Ca2+]i). The increase in [Ca2+]i is similar in both magnitude and duration to the transient that activates the egg at fertilization. It is due to mobilization of calcium from intracellular stores but is not prevented by the inositol trisphosphate (InsP3) antagonist heparin. Furthermore, cGMP does not stimulate the eggs Na+/H+ antiport when the [Ca2+]i transient is blocked by the calcium chelator bis-(O-aminophenoxy)-N,N,N',N'-tetraacetic acid (BAPTA), suggesting that cGMP does not activate eggs by interacting with the their phosphoinositide signaling pathway. However, the [Ca2+]i increase and activation are prevented in eggs in which the InsP3-sensitive calcium stores have been emptied by the prior microinjection of the InsP3 analogue inositol 1,4,5-trisphosphorothioate. These data indicate that cGMP activates eggs by stimulating the release of calcium from an InsP3-sensitive calcium store via a novel, though unidentified, route independent of the InsP3 receptor.

Animals↗

PubMed1992

Selective nuclear transport of the Drosophila morphogen dorsal can be established by a signaling pathway involving the transmembrane protein Toll and protein kinase A.

Establishment of dorsal-ventral polarity in the early Drosophila embryo requires a concentration gradient of the maternal morphogen dorsal (dl). This concentration gradient is established by selective nuclear transport of dl so that dl protein is present only in ventral nuclei. The activity of 11 genes is required for dl nuclear localization. One of these genes, Toll, encodes a transmembrane protein that appears to play the most direct role in regulating dl localization. We have examined the effects of Toll on dl in cotransfected Schneider cells to gain insight into the nature of the interaction between these proteins. We have found that Toll can enhance the nuclear localization of dl and, independently, the ability of dl to activate transcription once in the nucleus. We present evidence that the signaling pathway from Toll to dl involves protein kinase A (PKA) and that nuclear transport and activation of dl results from phosphorylation of dl by PKA. We discuss the significance of these results with respect both to Drosophila embryogenesis and to the regulation of the mammalian transcription factor NF-kappa B.

Animals↗

PubMed1992

N-methyl-D-aspartate antagonists block fos-like protein expression induced via multiple signaling pathways in cultured cortical neurons.

c-fos mRNA and Fos-like protein(s) (FLP) are induced in cultured cortical neurons by glutamate, high K+, phorbol ester, basic fibroblast growth factor, Zn2+, and vasoactive intestinal peptide. Glutamate induction of c-fos mRNA and FLP is blocked by noncompetitive N-methyl-D-aspartate (NMDA) antagonist, MK-801, and competitive NMDA antagonists, 4-(3-phosphonopropyl)piperazin-2-carboxylic acid and 2-amino-7-phosphonoheptanoate. These antagonists partially block high K(+)-, phorbol ester-, Zn(2+)-, and VIP-induced c-fos mRNA expression, but have no effect on bFGF-induced c-fos mRNA expression. However, both competitive and noncompetitive NMDA antagonists completely block FLP induction by all of these agents without affecting total protein synthesis. Therefore, these NMDA antagonists block FLP translation, without blocking c-fos transcription. It is hypothesized that NMDA receptor activation is required for translation of c-fos mRNA in cortical neurons after stimulation of multiple intracellular signaling pathways. It is possible that NMDA antagonists prevent cortical plasticity by blocking induction of the Fos protein that would normally be induced by neurotrophic factors, neurotransmitters, and neuromodulators.

2-Amino-5-phosphonovalerate↗

PubMed1992

Convergence of 9-cis retinoic acid and peroxisome proliferator signalling pathways through heterodimer formation of their receptors.

Peroxisomes are cytoplasmic organelles which are important in mammals in modulation of lipid homeostasis, including the metabolism of long-chain fatty acids and conversion of cholesterol to bile salts (reviewed in refs 1 and 2). Amphipathic carboxylates such as clofibric acid have been used in man as hypolipidaemic agents and in rodents they stimulate the proliferation of peroxisomes. These agents, termed peroxisome proliferators, and all-trans retinoic acid activate genes involved in peroxisomal-mediated beta-oxidation of fatty acids. Here we show that the receptor activated by peroxisome proliferators and the retinoid X receptor-alpha (ref. 6) form a heterodimer that activates acyl-CoA oxidase gene expression in response to either clofibric acid or the retinoid X receptor-alpha ligand, 9-cis retinoic acid, an all-trans retinoic acid metabolite; simultaneous exposure to both activators results in a synergistic induction of gene expression. These data demonstrate the coupling of the peroxisome proliferator and retinoid signalling pathways and provide evidence for a physiological role for 9-cis retinoic acid in modulating lipid metabolism.

Acyl-CoA Oxidase↗

PubMed2026

Dietary L-Tyrosine Sustains Egg Production and Quality by Modulating Promoter CpG Methylation, Gene Expression, and Hormone Profiles in Reproductive Signalling Pathways of Aged Laying Hens.

Managing prolactin (PRL)-mediated reproductive suppression is critical for maintaining egg production in commercial laying hens. L-tyrosine (TYR), a precursor of dopamine (DA), may counteract age-related reproductive decline by suppressing PRL, thereby sustaining productivity and egg quality in late-phase laying hens. The present study evaluated the effects of dietary L-tyrosine supplementation on laying performance, egg quality, reproductive hormone profiles, gene expression, and promoter CpG methylation in aged laying hens. A total of 180 Atak-S laying hens (71 weeks old) were randomly assigned to three dietary treatments, each with six replicates of 10 hens, and were fed a basal diet without L-tyrosine (control) or the basal diet supplemented with 0.5 g/kg (TYR0.5) or 1 g/kg (TYR1) L-tyrosine for 12 weeks. Hens in the TYR1 group exhibited higher hen-day egg production, improved feed conversion ratio, and significantly greater eggshell weight, shell thickness, Haugh unit, yolk index, and albumen index than the control group (p < 0.05). Dietary L-tyrosine increased plasma DA and serum estradiol while reducing serum PRL (p < 0.05). L-tyrosine also upregulated the expression of key dopaminergic and reproductive signalling genes, with corresponding promoter hypomethylation (p < 0.05), whereas PRL mRNA expression tended to decrease with concurrent promoter hypermethylation. A significant negative correlation was observed between target gene expression and promoter CpG methylation levels (p < 0.05). These findings indicate that dietary L-tyrosine modulates reproductive hormone profiles and molecular responses within reproductive signalling pathways, resulting in improved laying performance and egg quality. Therefore, L-tyrosine may represent a promising nutritional intervention to sustain reproductive function and productivity in late-phase laying hens.

Animals↗

PubMed1992

Phosphorylation of the MARCKS protein (P87), a major protein kinase C substrate, is not an obligatory step in the mitogenic signaling pathway of basic fibroblast growth factor in rat oligodendrocytes.

Basic fibroblast growth factor (bFGF) is a well-characterized peptide hormone that has mitogenic activity for various cell types and elicits a characteristic set of responses on the cell types investigated. In this report we confirmed that bFGF is a potent mitogen for rat brain-derived oligodendrocyte (OL) precursor cells as well as for differentiated OL in secondary culture. bFGF was shown to induce expression of the protooncogene c-fos in OL. The role of protein kinase C (PKC) in mediating bFGF-stimulated proliferation as well as c-fos expression in OL was investigated. The PKC activator phorbol 12-myristate 13-acetate (PMA) stimulated c-fos expression but did not trigger cell proliferation. When PKC was down-regulated by pretreatment of OL with PMA for 20 h, the bFGF-mediated stimulations of OL proliferation and c-fos mRNA expression were still observed, whereas the induction of c-fos mRNA by PMA was totally inhibited. These data demonstrate that the bFGF mitogenic signaling pathway in OLs does not require PKC. On the other hand, bFGF was found to stimulate specifically the phosphorylation of a limited number of PKC substrates in oligodendroglial cells, including the MARCKS protein. The bFGF-dependent phosphorylation of MARCKS protein was totally inhibited when PKC was first down-regulated, indicating that the phosphorylation of this protein is PKC dependent. Tryptic digestion of the phosphorylated MARCKS protein revealed that bFGF stimulated specifically the phosphorylation of the MARCKS protein on a single phosphopeptide. We provide evidence that bFGF also stimulated fatty acylation of the MARCKS protein, which might explain the observed specific bFGF-dependent phosphorylation of this protein in OL. We propose that bFGF-dependent fatty acylation and phosphorylation of the MARCKS protein are not essential for the transduction of the bFGF mitogenic signal but are probably linked to differentiation processes elicited by bFGF on OL.

Animals↗

PubMed1992

Transsynaptic regulation of galanin, neurotensin, and substance P in the adrenal medulla: combinatorial control by second-messenger signaling pathways.

The adrenomedullary content of neurotensin and substance P was examined 1, 6, and 12 days after hypoglycemic shock. The neurotensin content was increased 60-fold within 24 h and remained elevated for up to 12 days, whereas the substance P content was increased approximately sevenfold within 24 h of insulin treatment and returned to control levels by 12 days poststimulation. Because protein kinase A, protein kinase C, and calcium influx in the rat adrenal medulla are all stimulated following splanchnic nerve stimulation, the differential regulation of neurotensin and substance P biosynthesis following stimulation of these three pathways was examined in bovine chromaffin cells in vitro. Neurotensin levels were up-regulated by elevated potassium, forskolin, and phorbol ester in bovine chromaffin cells. Substance P levels were up-regulated by elevated potassium and forskolin but not by phorbol ester treatment. When chromaffin cells were treated with phorbol ester in combination with forskolin, neurotensin levels were increased in a synergistic fashion, whereas phorbol ester antagonized the forskolin-induced elevation of substance P levels. Earlier, it was reported that galanin biosynthesis, like neurotensin biosynthesis, is upregulated by depolarization, phorbol ester stimulation, and forskolin treatment in chromaffin cells in vitro. Here we report that galanin is also, like neurotensin, increased greater than 60-fold after stimulation of the rat adrenal medulla in vivo. Neuropeptide-specific combinatorial effects of stimulating the calcium, protein kinase A, and protein kinase C signaling pathways may underlie the quantitative differences between galanin and neurotensin compared with substance P up-regulation in rat adrenal medulla after splanchnic nerve stimulation in vivo.

Adrenal Medulla↗

PubMed1992

Terminal differentiation of mouse preadipocyte cells: the mitogenic-adipogenic role of growth hormone is mediated by the protein kinase C signalling pathway.

The role of growth hormone (GH) in the differentiation process of Ob1771 mouse preadipocyte cells has been studied under culture conditions that were serum-free and hormone-supplemented and which were previously shown to lead to terminal differentiation. In the absence of GH, a dramatic decrease in the adipogenic activity of the culture medium could be observed, as indicated 12 days after confluence by the low levels of glycerol-3-phosphate dehydrogenase activity and the sharp reduction of the number of triacylglycerol-containing cells. This decrease in adipogenic activity was accompanied by a parallel loss of the mitogenic potency of the culture medium. Determination of the half-maximal and maximal concentrations of GH required for the restoration of growth and differentiation were identical, 0.5 and 2 nM, respectively. Despite the presence of insulin-like growth factor-I (IGF-I) to substitute for supraphysiological concentrations of insulin and to saturate IGF-I receptor, GH was still required to induce terminal differentiation of a maximal number of cells. However, protein kinase C activators such as prostaglandin F2 alpha, phorbol esters and diacylglycerol were able to mimic GH in promoting a maximal mitogenic-adipogenic response, indicating that the ability of GH to induce diacylglycerol production (Doglio et al., 1989; Catalioto et al., 1990) plays a prominent role in this process. Furthermore, in agreement with the fact that the mitoses which precede terminal differentiation of Ob1771 preadipocytes are strictly controlled by cAMP and only modulated by protein kinase C, terminal differentiation of Ob1771 preadipocytes occurred in the absence of GH upon supplementation with high concentrations of carbaprostacyclin, added as a cAMP-elevating agent or with 8-Br-cAMP, added as a cAMP analogue. It is concluded that the control exerted by GH on terminal differentiation of mouse preadipocytes corresponds to a modulating mitogenic effect mediated through protein kinase C activation and leading to a potentiation of the cAMP and IGF-I mitogenic signalling pathways.

Adipose Tissue↗

PubMed1992

Ca2+ mobilization by the LH receptor expressed in Xenopus oocytes independent of 3',5'-cyclic adenosine monophosphate formation: evidence for parallel activation of two signaling pathways.

The cDNAs encoding the murine LH receptor (LHR) and the human beta 2-adrenoceptor (h beta 2AR) were cloned and RNAs complementary to their sense strands (cRNAs) were injected into defolliculated Xenopus oocytes. This led to expression, respectively, of LH- and isoproterenol-stimulable adenylyl cyclase activities, indicating that functionally active receptor cDNAs had been cloned. In oocytes injected with LHR cRNA, but not in control or h beta 2AR cRNA-injected oocytes, human CG and LH increased a Ca(2+)-activated Cl- current, as measured by the two-microelectrode voltage-clamp method. This effect was not seen with isoproterenol in control or h beta 2AR cRNA-injected oocytes, it was also not observed in response to forskolin or (Bu)2cAMP. The response to human CG could be obtained in the absence of extracellular Ca2+ but was abolished by injection of EGTA, indicating that it was caused by mobilization of Ca2+ from intracellular stores. The response was unaffected by overnight treatment with 1 microgram/ml pertussis toxin. The experiments show that a glycoprotein hormone receptor can be expressed as a functionally active molecule in Xenopus oocytes, and that the LHR has the ability of activating two separate intracellular signaling pathways: one forming the second messenger cAMP, and the other mobilizing Ca2+ from intracellular stores. It is proposed that the latter is secondary to a primary activation of phospholipase C by the LHR, which elevates intracellular Ca2+ via intermediary elevation of inositol phosphates, presumably (1,4,5)inositol trisphosphate.

Adenylyl Cyclases↗

PubMed1992

smg/rap1/Krev-1 p21s inhibit the signal pathway to the c-fos promoter/enhancer from c-Ki-ras p21 but not from c-raf-1 kinase in NIH3T3 cells.

smg/rap1A/Krev-1 p21 cDNA is known to inhibit v-Ki-ras p21-induced cell transformation in NIH3T3 cells, but the inhibitory mechanism is not clear at present. In the present study, we examined the effect of smg p21s on the c-fos promoter/enhancer linked to the luciferase reporter gene (c-fos-luciferase). After transfection of c-fos-luciferase into NIH3T3 cells constitutively expressing c-Ki-ras(val-12) p21 or activated c-raf-1 kinase, expression of c-fos-luciferase was much higher than after transfection into control NIH3T3 cells. Addition of platelet-derived growth factor (PDGF), 12-O-tetradecanoyl phorbol 13-acetate (TPA) or dibutyryl cyclic AMP (Bt2cAMP) to the control NIH3T3 cells stimulated c-fos-luciferase expression. Transfection of the smg p21 cDNAs inhibited the activated ras p21-, PDGF- or TPA-stimulated c-fos-luciferase expression, but did not inhibit the activated c-raf-1 kinase- or Bt2cAMP-stimulated reaction. These results indicate that smg p21s inhibit the signal pathways from the PDGF receptor, protein kinase C, and ras p21s to the c-fos promoter/enhancer, but not those from c-raf-1 kinase and cyclic AMP-dependent protein kinase to the c-fos promoter/enhancer.

3T3 Cells↗

PubMed2024

MONOCYTES AND B CELLS MEDIATE ALTERATIONS IN THE GENETIC ASSOCIATION BETWEEN PLATELETS AND SEPSIS VIA CLEC SIGNALING PATHWAY.

Background: Sepsis is a life-threatening condition characterized by multiple organ dysfunction. Blood cells abnormalities play a significant role in the onset and progression of sepsis; however, the potential causal relationship between platelets and sepsis remains unclear, as does whether immune cells mediate the interaction between platelets and sepsis. This study aims to explore the potential causal relationship between platelets and sepsis and analyze the mediating effect of immune cells. In addition, cell-to-cell communication was analyzed to explore the interaction between blood cells and immune cells. Material and methods: In this study, genome-wide association study data were utilized to examine the association between blood cells and sepsis. Two-sample Mendelian randomization (MR) and reverse MR were performed to investigate the potential causal relationship between blood cells and sepsis, with a specific focus on the relationship between platelets and sepsis. Subsequently, two-step MR was employed to identify the immune cells that mediate the interaction between platelets and sepsis and to assess their potential mediating effects. Cellchat software was used to analyze cell-to-cell communication. Results: The results of two-sample MR indicated that platelets were negatively correlated with sepsis (OR = 0.976, 95% CI 0.959-0.993, P = 0.005), suggesting that platelets have a protective effect against sepsis. Additionally, reverse MR demonstrated that sepsis had no significant effect on platelets (OR = 0.909, 95% CI 0.156-5.296, P = 0.916). The mediating effect analysis revealed that monocytes and B cells were important mediators in the relationship between platelets and sepsis. Notably, the correlation between platelets and sepsis shifted from negative to positive with the involvement of monocytes and B cells. The number and strength of cell-cell interactions were decreased in sepsis. Monocytes and B cells primarily regulate platelets through the CLEC signaling pathway, contributing to the pathogenesis of sepsis. Conclusion: This study confirmed the protective role of platelets in sepsis. Monocytes and B cells mediate changes in the genetic association between platelets and sepsis. Monocytes and B cells primarily interact with platelets via the CLEC pathway, thereby modulating the genetic association between platelets and sepsis. These findings indicate that thrombocytopenia, especially when accompanied by elevated monocytes and B cells, may serve as a potential marker for sepsis.

Humans↗

PubMed1992

Angiotensin II receptor recognized by DuP753 regulates two distinct guanine nucleotide-binding protein signaling pathways.

The 7315c cell, derived from a rat anterior pituitary tumor, expresses an angiotensin II (AII) receptor. [3H]AII binds to 7315c membranes specifically and saturably (Kd = 2.1 +/- 0.6 x 10(-6) M, Bmax = 282 +/- 33 fmol/mg of protein). GTP diminished the affinity of the membranes for [3H]AII (Kd = 4.1 +/- 0.4 x 10(-9) M, Bmax = 210 +/- 26 fmol/mg of protein). [3H]AII binding was displaced by AII (Ki = 1.3 +/- 0.6 x 10(-9) M), angiotensin III (AIII) (Ki = 0.9 +/- 0.4 x 10(-9) M), and the nonpeptide AII antagonist DuP753 (Ki = 1.4 +/- 0.6 x 10(-8) M). In contrast, a second nonpeptide AII ligand, PD123177, did not compete for [3H]AII binding sites. In intact cells, AII and AIII stimulated inositol trisphosphate (IP3) production (EC50 = 1.1 +/- 0.6 x 10(-8) M and 1.1 +/- 0.5 x 10(-8) M, respectively); this response to AII was antagonized by DuP753 (Ki = 1.7 +/- 0.3 x 10(-7) M). Pertussis toxin treatment failed to affect the ability of AII to stimulate IP3 production. In a crude membrane preparation, GTP was required for maximal AII-induced IP3 stimulation; guanosine thio-diphosphate abolished the agonist-GTP stimulation of IP3 production, in a concentration-dependent fashion. AII and AIII also inhibited adenylyl cyclase (EC50 = 2.9 +/- 1.1 x 10(-8) M and 6.0 +/- 1.0 x 10(-8) M, respectively). DuP753 antagonized the inhibition by AII of adenylyl cyclase (Ki = 2.8 +/- 0.4 x 10(-8) M). PD123177 failed to antagonize AII-induced cyclase inhibition. Pertussis toxin treatment abolished the AII and AIII inhibition of adenylyl cyclase. GTP was required for AII-induced inhibition of adenylyl cyclase. These data suggest that, in 7315c cells, a single subtype of AII receptor, identified by DuP753, is capable of regulating two different guanine nucleotide-binding protein (G protein) signalling pathways; one G protein, which is insensitive to pertussis toxin, stimulates IP3 production and the other G protein, which is sensitive to pertussis toxin, inhibits adenylyl cyclase.

Adenylate Cyclase Toxin↗

PubMed1992

Platelet-activating factor stimulates multiple signaling pathways in cultured rat mesangial cells.

We have previously reported that platelet-activating factor (PAF) elevates cytosolic free calcium concentration ([Ca2+]i) in fura-2-loaded glomerular mesangial cells. To confirm that this increase in [Ca2+]i is a result of receptor-mediated activation of phospholipase C, we investigated hydrolysis of phosphatidylinositol-4,5-bisphosphate (PtdIns-4,5-P2) in PAF-treated mesangial cells. PAF (10(-7) M) stimulated a rapid and transient formation of inositol trisphosphate. In concomitant experiments, PAF stimulated a biphasic accumulation of 3H-arachidonate-labeled 1,2-diacylglycerol (DAG). The secondary elevation in DAG was coincident with a rise in 3H-phosphorylcholine (PC) and 3H-phosphorylethanolamine (PE) suggesting that PAF stimulates delayed phospholipase activities which hydrolyze alternate phospholipids besides the polyphosphoinositides. This PAF-stimulated elevation in 3H-water soluble phosphorylbases was seen at 5 min but not at 15 sec suggesting that the initial rise in DAG as well as the initial elevation in [Ca2+]i are due primarily to PtdIns-4,5-P2 hydrolysis. PAF also stimulated PGE2 as well as 3H-arachidonic acid and 3H-lyso phosphatidylcholine (PtdCho) formation. We suggest that arachidonate released specifically from PtdCho via phospholipase A2 is a source of this PAF-elevated PGE2. It has been postulated that anti-inflammatory prostaglandins may antagonize the contractile and proinflammatory effects of PAF via activation of adenylate cyclase. Surprisingly, exogenous PAF reduced basal and receptor-mediated cAMP concentration indicating that PAF-stimulated transmembrane signaling pathways may oppose receptor-mediated activation of adenylyl cyclase. We have taken advantage of the different sensitivities of phospholipases A2 and C(s) to PMA, EGTA, and pertussis toxin to dissociate phospholipase A2 and C activities. Acute PMA-treatment enhanced PAF-stimulated PGE2 formation, reduced PAF-induced elevations in [Ca2+]i and had no effect upon PAF-stimulated 3H-PE. We have also demonstrated that phospholipase A2, but not PtdIns-specific phospholipase C, was sensitive to external calcium concentration. The role of a GTP-binding protein to couple PAF-receptors to the PtdIns-specific phospholipase C was confirmed as GTP gamma S synergistically elevated PAF-stimulated inositol phosphate formation. We also demonstrated that pertussis toxin ADP-ribosylates a single protein of an apparent 42 kD mass and that PAF pretreatment reduced subsequent ADP-ribosylation in a time-dependent manner. However, pertussis toxin had no effect upon phospholipase C-generated water soluble phosphorylbases or inositol phosphates. In contrast, PAF-stimulated phospholipase A2 and PAF-inhibited adenylyl cyclase activities were sensitive to pertussis toxin.(ABSTRACT TRUNCATED AT 400 WORDS)

Adenylate Cyclase Toxin↗