Effect of sub-toxic chlorpyrifos on redox sensitive kinases and insulin signaling in rat L6 myotubes
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Sub-chronic exposures to chlorpyrifos, an organophosphorus pesticide is associated with incidence of diabetes mellitus. Biochemical basis of chlorpyrifos-induced diabetes mellitus is not known. Hence, effect of its sub-toxic exposure on redox sensitive kinases, insulin signaling and insulin-induced glucose uptake were assessed in rat muscle cell line.
In an in vitro study, rat myoblasts (L6) cell line were differentiated to myotubes and then were exposed to sub-toxic concentrations (6 mg/L and 12 mg/L) of chlorpyrifos for 18 h. Then total anti-oxidant level in myotubes was measured and insulin-stimulated glucose uptake was assayed. Assessment of activation of NFκB & p38MAPK and insulin signaling following insulin stimulation from tyrosine phosphorylation of insulin receptor substrate-1 (IRS-1) and serine phosphorylation of Akt were done in myotubes after chlorpyrifos exposure by western blot (WB) and compared with those in vehicle-treated controls.
The glucose uptake and total antioxidant level in L6-derived myotubes after sub-toxic exposure to chlorpyrifos were decreased in a dose-dependent manner. As measured from band density of WB, phosphorylation levels increased for redo-sensitive kinases (p38MAPK and IκBα component of NFκB) and decreased for IRS-1 (at tyrosine 1222) and Akt (at serine 473) on insulin stimulation following chlorpyrifos exposure as compared to those in controls.
We conclude that sub-toxic chlorpyrifos exposure induces oxidative stress in muscle cells activating redox sensitive kinases that impairs insulin signaling and thereby insulin-stimulated glucose uptake in muscle cells. This probably explains the biochemical basis of chlorpyrifos-induced insulin resistance state and diabetes mellitus.
KeywordsChlorpyrifos Type 2 diabetes mellitus Insulin signaling Insulin resistance NFκB p38MAPK
Type 2 diabetes mellitus
Insulin Receptor Substrate-1
Redox sensitive kinases
Nuclear factor kappa B
- p38 MAPK
p38 Mitogen-Activated Protein Kinase
3-(4,5-dimethylthiazol-2-yl) -2,5-diphenyltetrazolium bromide
Dulbecco'’s modified Eagle'’s medium
Fetal bovine serum
We acknowledge Science and Engineering Research Board (SERB), Department of Science and Technology (DST), Government of India (F.No. SB/SO/HS/0024/2013) for providing extramural funding to meet the expenditure of the study.
Compliance with ethical standards
Conflict of interest
The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article.
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