ObjectiveTo investigate whether the miR-33s negatively regulates LPS-induced production of inflammatory cytokines by targeting p38 MAPK. MethodsHuman monocytes THP-1 cells were cultured in vitro and transfected with miR-33s mimic (25 nmol/L) or miR-33s inhibitor (25 nmol/L)by TransIT-X2® Dynamic Delivery System for 24 h. Then the transfected THP-1 cells were stimulated by LPS of 10.0 ng/mL for 24 h. The expression of miR-33s and p38 MAPK protein were measured by semi-quantitative RT-PCR. The concentrations of TNF-α,IL-6 and IL-1β in the cultured supernatant were assessed by ELISA. ResultsThe transfection of miR-33s mimic significantly increased the release of TNF-α,IL-6 and IL-1β(P<0.05). The expression of p38 MAPK protein was also significantly reduced(P<0.05). However,the pre-treatment of miR-33s inhibitor reversed the LPS-induced release of TNF-α,IL-6,and IL-1β,and the expression of p38 MAPK protein of THP-1 cells. ConclusionmiR-33s may play an important role in the regulation in inflammatory factors released from THP-1 cells by targeting p38 MAPK.