Background: Toll-like receptors (TLRs) are emerging as immunometabolic receptors and nutrient sensors. In obese and T2D patients, oxidative stress acts as a critical early-trigger of altered pathophysiology. In immune cells, it remains unclear whether the oxidative stress can modulate expression of the receptors. We assessed the expression of TLR2 and TLR4 in the peripheral blood mononuclear cells (PBMCs) following H2O2 treatment.
Methods: Human PBMCs were isolated from healthy donors and were subjected to oxidative stress by H2O2 with or without antioxidants or ROS inhibitors. Using qRT-PCR and flow cytometry, the gene expression of TLR2 and TLR4 was determined, Moreover, expression of the phosphorylated c-Jun, ERK1/2, p38, and NF-?B signaling proteins was determined.
Results: TLR2 and TLR4 gene and protein expression was elevated in PBMCs following induction of oxidative stress compared to controls (P<0.001); and this induction was abrogated by cell pre-treatment with apocynin or N-acetyl cysteine (P<0.05). Treatments with palmitate or LPS, in the presence of oxidative stress, further promoted the TLR2 and TLR4 expression. Oxidative stress also upregulated the expression of MyD88, IRF3, IRF5, and FOXO1 in PBMC. Both the MAPK and NF-?B signaling pathways were involved in H2O2-mediated TLR2 and TLR4 upregulation. Oxidative stress also increased the gene expression of proinflammatory IL-1β, IL-6, TNF-α, IFN-γ and MCP-1 (P<0.001).
Conclusion: Taken together, oxidative stress upregulates the TLR2 and TLR4 expression in PBMC through the MAPK/NF-?B dependent mechanism in parallel with increased expression of proinflammatory cytokines/chemokine. We speculate that TLR2/TLR4 suppression by ROS-inhibition or antioxidant strategies may alleviate metabolic inflammation.
S.T. Sindhu: None. A. Al Madhoun: None. N. Akhter: None. F. Al-Mulla: None. R. Ahmad: None.
Kuwait Foundation for the Advancement of Sciences; Dasman Diabetes Institute