After severe skeletal muscle damage, communication between inflammatory macrophages, myogenic cells, and modulatory secretion factors is essential to induce re-establishment of skeletal muscle structure. To analyze when characteristic gene expression of macrophages, myogenic cells, and SLPI are modulated after an exercise-induced muscle damage (EIMD) downhill protocol. Twenty-six rats were exposed to an experimental protocol of exercise and euthanized before (CTRL), immediately after (G0), and 24 (G24) and 48 (G48) hours after the exercise. After euthanasia, the Triceps brachii were dissected and analyzed by enzyme-linked immunosorbent assay and real time polymerase chain reaction. The CD68 expression was higher in the G24 when compared with all groups (p value < 0.05), whereas the CD163 was inhibited compared with G0 (p value < 0.05). MyoD and Myogenin were higher in the G24 when compared with G0 and G48 (p value < 0.05). The mRNA Secretory Leukocyte Protease Inhibitor (SLPI) was higher in the G48 when compared with the CTRL and G0 (p value < 0.05). IL-6 and TNF-α cytokines did not significantly change, but IL-10 presented a trend to be lower in the G0 when compared with G24 (p value = 0.054). A significant negative correlation was observed between CD68/CD163 (C.C = -0.71) and positive correlations between CD68/Myogenin (C.C = 0.65); MyoD/Myogenin (C.C = 0.72); IL-10/MyoD (C.C = 0.46), IL-10/MYOGENIN (C.C = 0.59); and IL-6/IL-10 (C.C = 0.64). A higher expression of CD68, concomitant with an elevation in MyoD and Myogenin 24 h after exercise, along with some correlations, suggests macrophage communication with myogenic cells independent of CD163 elevation. Additionally, the reestablishment of IL-10 in 24 h with the SLPI increased until 48 h indicate that these molecules are involved with anti-inflammatory transition after downhill exercise in the TBIH of Wistar rats.
Keywords: Downhill exercise; Macrophages; Skeletal muscle.