Activating transcription factor 3 regulates chemokine expression in contracting C2C12 myotubes and in mouse skeletal muscle after eccentric exercise

Abstract

a b s t r a c tActivating transcription factor (ATF) 3 regulates chemokine expression in various cell types and tissues. Herein, we studied this regulation in contracting muscle cells in vitro, and in skeletal muscle after muscle-damaging exercise in vivo. C 2 C 12 myotubes with normal or low ATF3 levels (atf3_siRNA) were electrically stimulated (EPS). Also, ATF3-knockout (ATF3-KO) and control mice ran downhill until exhaustion, and muscles were analyzed post-exercise. EPS increased ATF3 levels in myotubes (P < 0.01). Chemokine C-C motif ligand (ccl) 2 mRNA increased post-EPS, but atf3_siRNA attenuated the response (P < 0.05). Atf3_siRNA up-regulated ccl6 basal mRNA, and down-regulated ccl9 and chemokine C-X-C motif ligand (cxcl) 1 basal mRNAs. Post-exercise, ATF3-KO mice showed exacerbated mRNA levels of ccl6 and ccl9 in soleus (P < 0.05), and similar trends were observed for ccl2 and interleukin (il) 1b (P < 0.09). In quadriceps, il6 mRNA level increased only in ATF3-KO (P < 0.05), and cxcl1 mRNA showed a similar trend (P ¼ 0.082). Cluster of differentiation-68 (cd68) mRNA, a macrophage marker, increased in quadriceps and soleus independently of genotype (P < 0.001). Our data demonstrate that ATF3 regulates chemokine expression in muscle cells in vitro and skeletal muscle in vivo, but the regulation differs in each model. Cells other than myofibers may thus participate in the response observed in skeletal muscle. Our results also indicate that ATF3-independent mechanisms would regulate macrophage infiltration upon muscledamaging exercise. The implications of chemokine regulation in skeletal muscle remain to be determined.

A novel voluntary weightlifting model in mice promotes muscle adaptation and insulin sensitivity with simultaneous enhancement of autophagy and mTOR pathway

“…49 Finally, a robust upregulation of Atf3 mRNA (8-fold) was observed following weightlifting (Figure 2D). Upregulation of Atf3 gene, which was induced by eccentric contractions, 50 has anti-inflammatory roles by inhibiting chemokine and cytokine expression. 51 These findings support that acute weightlifting elicits transcriptome responses as an early step in skeletal muscle adaptation to resistance exercise, laying a foundation for future dissection of molecular mechanisms underlying structural and functional adaptations to resistance training.…”

Protective role of activating transcription factor 3 against neuronal damage in rats with cerebral ischemia

“…Therefore, we wonder whether ATF3 could also regulate the transcription of a gene to participate in cerebral ischemia. Postexercise, ATF3‐knockout mice showed exacerbated mRNA levels of CCL2 and interleukin (IL)‐1β (Fernandez‐Verdejo et al., 2017 ), indicating the possible connection between ATF3 and CCL2. Furthermore, CCL2 is involved in the signaling pathways recruiting microglia after repetitive head impacts and may serve as a future therapeutic target in chronic traumatic encephalopathy (Cherry et al., 2020 ).…”

Characteristics of the Protocols Used in Electrical Pulse Stimulation of Cultured Cells for Mimicking In Vivo Exercise: A Systematic Review, Meta-Analysis, and Meta-Regression

“…Two main groups of cell types were used in the included studies: a. cell lines and b. biopsies from humans and mice ( Table S2 ). More specifically, 30 of the eligible studies used cell lines: 24 studies employed the C2C12 cell line [ 16 , 17 , 26 , 28 , 30 , 31 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 ], a mouse myoblast cell line; while one study used the L6 cell line [ 55 ], a rat myoblast cell line; one used primary human cells [ 13 ]; and one the H-2kb muscle cells (a mouse myoblast cell line) [ 56 ]. Of the remaining eligible studies, 12 used human skeletal muscle biopsies [ 18 , 19 , 20 , 21 , 23 , 24 , 25 , 29 , 50 , 57 , 58 , 59 , 60 ] from different sites, such as vastus lateralis, satellite cells, and rectus abdominis, obtained from healthy ( n = 64), lean ( n = 32), obese ( n = 20), and diabetic donors ( n = 4).…”

“…The protocol used by Breton et al [ 24 ] was the only one where we detected linking both acute (30 min stimulation) and chronic (3 day stimulation) protocols to resistance training in vitro. Furthermore, three studies [ 39 , 52 , 60 ] identified their EPS model as “endurance training”, either establishing the optimal conditions for EPS to mimic endurance training in vitro (60 min, 11.5 V, 10 Hz) or using an already established protocol (240 min, 20 V, 1 Hz) that was previously proven to mimic endurance exercise in vitro [ 62 ].…”