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Background and Purpose: Human malignant hyperthermia (MH) syndrome is induced by volatile anaesthetics and involves increased levels of cystathionine β-synthase (CBS)-derived H 2 S within skeletal muscle. This increase contributes to skeletal muscle hypercontractility. K v 7 channels, expressed in skeletal muscle, may be a molecular target for H 2 S. Here, we have investigated the role of K v 7 channels in MH., Experimental Approach: Skeletal muscle biopsies were obtained from MH-susceptible (MHS) and MH-negative (MHN) patients. Immunohistochemistry, RT-PCR, Western blot, and in vitro contracture test (IVCT) were carried out. Development and characterization of primary human skeletal muscle cells (PHSKMC) and evaluation of cell membrane potential were also performed. The persulfidation state of K v 7 channels and polysulfide levels were measured., Key Results: K v 7 channels were similarly expressed in MHN and MHS biopsies. The IVCT revealed an anomalous contractility of MHS biopsies following exposure to the K v 7 channel opener retigabine. Incubation of negative biopsies with NaHS, prior to retigabine addition, led to an MHS-like positive response. MHS-derived PHSKMC challenged with retigabine showed a paradoxical depolarizing effect, compared with the canonical hyperpolarizing effect. CBS expression and activity were increased in MHS biopsies, resulting in a major polysulfide bioavailability. Persulfidation of K v 7.4 channels was significantly higher in MHS than in MHN biopsies., Conclusions and Implications: In skeletal muscle of MHS patients, CBS-derived H 2 S induced persulfidation of K v 7 channels. This post-translational modification switches the hyperpolarizing activity into depolarizing. This mechanism can contribute to the pathological skeletal muscle hypercontractility typical of MH syndrome., Linked Articles: This article is part of a themed section on Hydrogen Sulfide in Biology & Medicine. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.4/issuetoc., (© 2019 The British Pharmacological Society.)

Background and Purpose: Hydrogen sulphide (H(2)S), considered as a novel gas transmitter, is produced endogenously in mammalian tissue from L-cysteine by two enzymes, cystathionine β-synthase and cystathionine γ-lyase. Recently, it has been reported that H(2)S contributes to the local and systemic inflammation in several experimental animal models. We conducted this study to investigate on the signalling involved in H(2)S-induced inflammation., Experimental Approach: L-cysteine or sodium hydrogen sulphide (NaHS) was injected into the mouse hind paw and oedema formation was evaluated for 60 min. In order to investigate H(2)S-induced oedema formation, we used 5-HT and histamine receptor antagonists, and inhibitors of K(ATP) channels or arachidonic acid cascade. Prostaglandin levels were determined in hind paw exudates by radioimmunoassay. Paws injected with L-cysteine or NaHS were examined by histological methods., Key Results: Both NaHS and L-cysteine caused oedema characterized by a fast onset which peaked at 30 min. This oedematogenic action was not associated with histamine or 5-HT release or K(ATP) channel activation. However, oedema formation was significantly inhibited by the inhibition of cyclooxygenases and selective inhibition of phospholipase A(2). Prostaglandin levels were significantly increased in exudates of hind paw injected with NaHS or L-cysteine. The histological examination clearly showed an inflammatory state with a loss of tissue organization following NaHS or L-cysteine injection., Conclusions and Implications: Phospholipase A(2) and prostaglandin production are involved in pro-inflammatory effects of H(2)S in mouse hind paws. The present study contributes to the understanding of the role of L-cysteine/H(2)S pathway in inflammatory disease., (© 2010 The Authors. British Journal of Pharmacology © 2010 The British Pharmacological Society.)

1. Several thrombin cellular effects are dependent upon stimulation of proteinase activated receptor-1 (PAR-1) localized over the cellular surface. Following activation by thrombin, a new N-terminus peptide is unmasked on PAR-1 receptor, which functions as a tethered ligand for the receptor itself. Synthetic peptides called thrombin receptor activating peptides (TRAPs), corresponding to the N-terminus residue unmasked, reproduce several thrombin cellular effects, but are devoid of catalytic activity. We have evaluated the bronchial response to intravenous administration of human alpha-thrombin or a thrombin receptor activating peptide (TRAP-9) in anaesthetized, artificially ventilated guinea-pigs. 2. Intravenous injection of thrombin (100 microkg(-1)) caused bronchoconstriction that was recapitulated by injection of TRAP-9 (1 mg kg(-1)). Animal pretreatment with the thrombin inhibitor Hirulog (10 mg kg(-1) i.v.) prevented thrombin-induced bronchoconstriction, but did not affect bronchoconstriction induced by TRAP-9. Both agents did not induce bronchoconstriction when injected intravenously to rats. 3. The bronchoconstrictor effect of thrombin and TRAP-9 was subjected to tolerance; however, in animals desensitized to thrombin effect, TRAP-9 was still capable of inducing bronchoconstriction, but not vice versa. 4. Depleting animals of circulating platelets prevented bronchoconstriction induced by both thrombin and TRAP-9. 5. Bronchoconstriction was paralleled by a biphasic change in arterial blood pressure, characterized by a hypotensive phase followed by a hypertensive phase. Thrombin-induced hypotension was not subject to tolerance and was inhibited by Hirulog; conversely, hypertension was subject to tolerance and was not inhibited by Hirulog. Hypotension and hypertension induced by TRAP-9 were neither subject to tolerance nor inhibited by Hirulog. 6. Our results indicate that thrombin causes bronchoconstriction in guinea-pigs through a mechanism that requires proteolytic activation of its receptor and the exposure of the tethered ligand peptide. Platelet activation might be triggered by the thrombin effect.