The monocyte locomotion inhibitory factor inhibits the expression of inflammation‐induced cytokines following experimental contusion in rat tibia

Entamoeba histolityca produces the monocyte locomotion inhibitory factor (MLIF), a pentapeptide with powerful anti‐inflammatory properties. MLIF may regulate trauma‐induced inflammation through the effects it exerts directly or indirectly on immune cells, modulating the production and/or expression of the cytokines involved in the inflammatory processes that occur after damage. The aim of the present study was to evaluate the effect of MLIF on production of pro/anti‐inflammatory cytokines after contusion in the rat tibia. Fifty‐four Wistar rats were subjected to controlled contusion with a special guillotine‐type device, and 36 rats were injected with MLIF or tenoxicam into the tibia. Eighteen animals received saline; the animals were sacrificed 24 or 48 hours after injection. Cytokine mRNA and protein production were determined by reverse transcriptase‐polymerase chain reaction (RT‐PCR), immunofluorescence, and hematoxylin‐eosin staining was performed to visualize cellular infiltration in the rats’ injured tissue. Expression levels of the cytokines interferon gamma (IFN‐γ), tumour necrosis factor‐alpha (TNF‐α), interleukin‐6 (IL‐6) and transforming growth factor‐beta (TGF‐β) mRNA were inhibited significantly by MLIF at 24 hours post‐contusion. MLIF significantly increased the expression levels of IL‐10 at 24 hours compared with tenoxicam or the control group. These changes were associated with a significant decrease in protein production levels of TNF‐α, IFN‐γ, IL‐6 and TGF‐β at 24 hours. Histological evaluation showed the presence of infiltration by neutrophils, monocytes and leucocytes in control tissues. This infiltration was decreased after MLIF administration, and intense infiltration was observed in tenoxicam‐treated group. MLIF inhibited the expression of pro‐inflammatory cytokines and increased the expression of anti‐inflammatory cytokine IL‐10.