The Secretory Leukocyte Protease Inhibitor mRNA expression is involved with inflammatory control after downhill exercise in the triceps brachii intermediary head in Wistar rats

Abstract

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.

Skeletal muscles induce recruitment of Ly6C+macrophage subtypes and release inflammatory cytokines 3 days after downhill exercise

“…Furthermore, we also demonstrated that on D2 and D3, the Ly6C ϩ macrophage elevation occurred roughly at the same time point where others show the increase of macrophage type 2 markers, such as CD163 (40,68). However, besides these studies with individual evidence, we understand that this elevation of CD163 may not represent an increase of other macrophage populations, as suggested in other studies (15,16,40,41,58,68), instead of a functional transition of the macrophage itself.…”

“…First, downhill exercise does not induce an extensive damage process, which would require massive renovation of myogenic stem cells (1,40,41,47,57,58,67). Second, our histological parameters did not identify a degeneration process in R602 muscles as did other severe damage models (2,5,30,43); rather, we observed an increase in CSA on D3.…”

“…In this sense, instead of inducing the full replacement of cells as the severe damage process, moderate EIMD protocols as downhill exercise tend to stimulate the recruitment of macrophages and myogenic cell manifestation in the first 2 days after exercise (D2), which could lead to the formation of new growth fibers related to skeletal muscle adaption after acute exercise (40,41,47,58,67,68).…”

“…With some limitations, after the moderate EIMD protocols, there is the involvement of two distinct macrophage subtypes, which are related to the secretion of proinflammatory cytokines and myogenic cell proliferation 48 h after. However, the previous analysis of the macrophage subtypes was limited once the analysis conducted was poorly explored with a few numbers of receptor markers (e.g., CD68 and CD163), which also can be present in other cell types (1,27,40,41,58,68).…”

“…Nevertheless, despite some studies attempting to analyze the participation of macrophage subtypes, only few of them have investigated a link between its distinct population and the secretion of cytokines that can influence the myogenesis after exercise (33,40,41,68). Based on this information, this study aimed to evaluate two classic macrophage subtypes, and some inflammatory cytokines might involve the muscle adaption process after exercise.…”