Annexin II-dependent actin remodelling evoked by hydrogen peroxide requires the metalloproteinase/sphingolipid pathway

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A signaling cascade mediated by ceramide, src and PDGFRβ coordinates the activation of the redox-sensitive neutral sphingomyelinase-2 and sphingosine kinase-1.

International audienceStress-inducing agents, including oxidative stress, generate the sphingolipid mediators ceramide (Cer) and sphingosine-1-phosphate (S1P) that are involved in stress-induced cellular responses. The two redox-sensitive neutral sphingomyelinase-2 (nSMase2) and sphingosine kinase-1 (SK1) participate in transducing stress signaling to ceramide and S1P, respectively; however, whether these key enzymes are coordinately regulated is not known. We investigated whether a signaling link coordinates nSMase2 and SK1 activation by H2O2. In mesenchymal cells, H2O2 elicits a dose-dependent biphasic effect, mitogenic at low concentration (5μM), and anti-proliferative and toxic at high concentration (100μM). Low H2O2 concentration triggered activation of nSMase2 and SK1 through a nSMase2/Cer-dependent signaling pathway that acted upstream of activation of SK1. Further results implicated src and the trans-activation of PDGFRβ, as supported by the blocking effect of specific siRNAs, pharmacological inhibitors, and genetically deficient cells for nSMase2, src and SK1. The H2O2-induced src/PDGFRβ/SK1 signaling cascade was impaired in nSMase2-deficient fro/fro cells and was rescued by exogenous C2Cer that activated src/PDGFRβ/SK1. Thus, the results define a nSMase2/SK1 signaling pathway implicated in the mitogenic response to low oxidative stress. On the other hand, high oxidative stress induced inhibition of SK1. The results also showed that the toxicity of high H2O2 concentration was comparable in control and nSMase2-deficient cells. Taken together the results identify a tightly coordinated nSMase2/SK1 pathway that mediates the mitogenic effects of H2O2 and may sense the degree of oxidative stress

Impact of micronutrient deficiency & malnutrition in systemic sclerosis: Cohort study and literature review

International audienceObjectives: The purpose of our study was to determine the prevalence and risk factors associated with malnutrition, and selenium (Se) and vitamin C (vitC) deficiencies in systemic sclerosis (SSc) patients.Methods: We included adult SSc patients fulfilling the 2013 ACR/EULAR criteria from the Toulouse University Hospital cohort who underwent a micronutrient workup (including vitC, Se or thiamine levels) between 2011 and 2016.Results: 82 patients were included, mostly women (76%), with a median age of 60 years. SSc was limited in 76% of the cases, with Scl-70 and centromere antibodies in 32% and 44%, respectively. Median disease duration was 7.4 years. Cardiac involvement was noticed in 19% and gastrointestinal tract in and 95%; 9% had pulmonary artery hypertension (PAH) and 63% had interstitial lung disease. Overt malnutrition was present in 14 (17%) patients. Micronutrient deficiencies included Se (35%), vitC (31%) and/or thiamine (6%). Malnourished patients had significantly a higher summed Medsger disease severity scales (7.5 vs. 5, P = .003), lower hemoglobin (10.6 vs. 12.9 g/dL, P < .0001) and vitC levels (3.6 vs. 10.6 mg/L, P = .003). Cardiac involvement was significantly associated with Se deficiency (OR 6.2, IC 95%[1.48-32.70], P = .05). The factors associated with vitC deficiency were malnutrition (OR 8.57, IC 95%[2.16-43.39], P = .003), modified Rodnan skin score ≤ 14 (OR 0.33, IC95[0.11-1], P = .05), PAH (27% in deficient vs. none in non-deficient patients, P = .0006) and esophagitis or Barrett's mucosa (OR 4.05, IC95[1.27-13.54], P = .02).Conclusions: Se testing should be considered as soon as cardiac involvement is suspected. VitC testing should be considered in malnourished SSc patients, especially if skin involvement is extensive