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.