Oxidized Phosphatidylcholines Trigger TRPA1 and Ryanodine Receptor-dependent Airway Smooth Muscle Contraction.

Asthma pathobiology includes oxidative stress that modifies cell membranes and extracellular phospholipids. Oxidized phosphatidylcholines (OxPCs) in lung lavage from allergen-challenged human participants correlate with airway hyperresponsiveness and induce bronchial narrowing in murine thin-cut lung slices. OxPCs activate many signaling pathways, but mechanisms for these responses are unclear. We hypothesize that OxPCs stimulate intracellular free Ca2+ flux to trigger airway smooth muscle contraction. Intracellular Ca2+ flux was assessed in Fura-2-loaded, cultured human airway smooth muscle cells. Oxidized 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine (OxPAPC) induced an approximately threefold increase in 20 kD myosin light chain phosphorylation. This correlated with a rapid peak in intracellular cytoplasmic Ca2+ concentration ([Ca2+]i) (143 nM) and a sustained plateau that included slow oscillations in [Ca2+]i. Sustained [Ca2+]i elevation was ablated in Ca2+-free buffer and by TRPA1 inhibition. Conversely, OxPAPC-induced peak [Ca2+]i was unaffected in Ca2+-free buffer, by TRPA1 inhibition, or by inositol 1,4,5-triphosphate receptor inhibition. Peak [Ca2+]i was ablated by pharmacologic inhibition of ryanodine receptor (RyR) Ca2+ release from the sarcoplasmic reticulum. Inhibiting the upstream RyR activator cyclic adenosine diphosphate ribose with 8-bromo-cyclic adenosine diphosphate ribose was sufficient to abolish OxPAPC-induced cytoplasmic Ca2+ flux. OxPAPC induced ∼15% bronchial narrowing in thin-cut lung slices that could be prevented by pharmacologic inhibition of either TRPA1 or RyR, which similarly inhibited OxPC-induced myosin light chain phosphorylation in cultured human airway smooth muscle cells. In summary, OxPC mediates airway narrowing by triggering TRPA1 and RyR-mediated mobilization of intracellular and extracellular Ca2+ in airway smooth muscle. These data suggest that OxPC in the airways of allergen-challenged subjects and subjects with asthma may contribute to airway hyperresponsiveness.

Coagonist of glucagon-like peptide-1 and glucagon receptors ameliorates nonalcoholic fatty liver disease.

Nonalcoholic fatty liver disease (NAFLD) is often associated with obesity and type 2 diabetes. Coagonists of glucagon-like peptide-1 receptor (GLP-1R) and glucagon receptor (GCGR) are under clinical investigation for the treatment of obesity and type 2 diabetes. In this study, we have demonstrated the effect of a balanced coagonist in the treatment of NAFLD using mouse models. GLP-1R agonist exendin-4, glucagon, and coagonist (Aib2 C24 chimera2) were administered to C57BL6/J mice, in which NAFLD was induced by carbon tetrachloride (CCl4) treatment after high-fat diet (HFD) feeding, and choline-deficient, L-amino-acid-defined HFD (CDAHFD) feeding. Repeated dose administration of coagonist significantly attenuated liver inflammation and steatosis induced by acute and long-term treatment with CCl4 in HFD-fed mice. Coagonist markedly attenuated the CDAHFD-induced expression of TIMP-1, MMP-9, TNF-α, MCP-1, COL1A1, and α-SMA. It also inhibited progression of hepatic steatosis and fibrosis in mice. Exendin-4 was better than glucagon, but coagonist was most effective in reduction of hepatic inflammation as well as steatosis. Coagonist of GLP-1R and GCGR improved NAFLD in C57BL6/J mice. This effect is mediated by reduction in lipotoxicity and inflammation in liver.

Involvement of TACE in colon inflammation: a novel mechanism of regulation via SIRT-1 activation.

TNF-α converting enzyme (TACE) processes the membrane TNF-α to release the bioactive soluble TNF-α. Several evidences suggest the involvement of TNF-α and TACE in inflammatory bowel disease (IBD). Tissue inhibitor of metalloproteinase (TIMP)-3, an endogenous inhibitor of TACE, is positively associated with silent information regulator (SIRT)-1. We aimed to study the expression of TACE, TIMP-3 and SIRT-1 at different stages of colitis and how TACE is regulated in response to SIRT-1 activation. Acute colitis was induced by 3.5% dextran sulfate sodium (DSS) in drinking water for 5days and levels of cytokines and mRNA expression of TACE, TIMP-3 and SIRT-1 were measured in colon at different time intervals. Next, the effect of SIRT-1 activator (resveratrol) or a selective TACE inhibitor (compound 11p) treatment was evaluated. Elevated levels of TNF-α, interleukin (IL)-6, IL-1ß, interferon (IFN)-γ and IL-17 were observed during DSS exposure phase which restored to the normal level after DSS removal. A significant increase in TACE and suppression in TIMP-3 and SIRT-1 mRNA level was observed during DSS exposure phase which reverts back to normal towards the remission phase. Treatment with resveratrol significantly elevated SIRT-1 and TIMP-3 and suppressed TACE mRNA expression and was associated with amelioration of disease. Furthermore, treatment with selective TACE inhibitor significantly suppressed body weight loss, disease activity index, colonic myeloperoxidase activity and the elevated levels of cytokines after DSS challenge. These results strongly emphasize the involvement of TACE in colon inflammation and inhibition of TACE directly or indirectly via SIRT-1 activation ameliorates colitis.

Selective inhibition of tumor necrosis factor-α converting enzyme attenuates liver toxicity in a murine model of concanavalin A induced auto-immune hepatitis.

Emerging evidence suggest that tumor necrosis factor (TNF)-α plays a major role in pathogenesis of auto-immune hepatitis (AIH) induced liver injury. Blockade of TNF-α synthesis or bio-activity protects against experimental AIH. TNF-α converting enzyme (TACE) is a member of the ADAM (a disintegrin and metalloproteinase) family which processes precursor TNF-α to release soluble TNF-α. We hypothesized that selective inhibition of TACE might protect AIH. To investigate this, we studied the effects of a selective TACE inhibitor DPC-333 on murine model of liver injury and fibrosis induced with concanavalin A (Con A). Pre-treatment with DPC-333 significantly suppressed plasma alanine transaminase, aspartate transaminase and cytokines such as TNF-α, interferon (IFN)-γ, interleukin (IL)-2 and IL-6 levels due to acute Con A challenge. Interestingly; DPC-333 inhibited liver poly (ADP-ribose) polymerase (PARP)-1 activity which was associated with reduced number of necrotic hepatocytes in histological examination and mortality associated with Con A. In fibrosis study, repeated Con A administration significantly up-regulated liver collagen deposition as assessed by measurement of hydroxyproline content which was further confirmed in liver histology with Masson's trichrome staining. Treatment with 30mg/kg of DPC-333 was able to suppress liver hydroxyproline and fibrous tissue proliferation which corroborated well with inhibition in expression of pro-fibrotic genes such as tissue inhibitor of metalloproteinase (TIMP)-1 and transforming growth factor (TGF)-ß1. These observations suggest that selective TACE inhibition is an effective approach for the treatment of both immune mediated hepatic inflammation and fibrosis.