A novel role for protein tyrosine phosphatase 1B as a positive regulator of neuroinflammation
The aim of the study was to investigate the effect of PTP1B modulation on palmitate-induced cytokine production in macrophages. Lentiviruses carrying PTP1B-shRNA or cDNA at different multiplicities of infection (MOIs) were used to decrease and increase PTP1B expression in Raw 264.7 cells, respectively. mRNA and protein levels of TNF-α and IL-6 were measured by real-time PCR and ELISA, respectively. 0.5 mM palmitate reduced PTP1B mRNA and protein levels by 25 and 19 %, respectively, compared to untreated cells. Overexpression of PTP1B decreased mRNA and protein levels of TNF-α and IL-6 in macrophages stimulated with palmitate. We found that protein and mRNA levels of cytokines significantly increased in knockdown cells stimulated by palmitate in a dose-dependent manner with increased MOI. NF-kB, JNK, p38 and ERK specific inhibitors significantly reduced the production of TNF-α and IL-6 in macrophages stimulated with palmitate and also PTP1B knockdown cells. Furthermore, inhibition of PTP1B resulted in increased phosphorylation of JNK, p38, ERK and NF-kB p65 in macrophage cells. The data of this study demonstrate that PTP1B negatively regulates palmitate-induced cytokine secretion in macrophages by mechanisms involving the activation of MAPKs and NF-kB pathways.