TRPV4 plays an important role in rat prefrontal cortex changes induced by acute hypoxic exercise

Abstract

Objective This study aims to investigate the effects of TRPV4 on acute hypoxic exercise-induced central fatigue, in order to explore the mechanism in central for exercise capacity decline of athletes in the early stage of altitude training. Methods 120 male Wistar rats were randomly divided into 12 groups: 4 normoxia groups (quiet group, 5-level group, 8-level group, exhausted group), 4 groups at simulated 2500\u202fm altitude (grouping as before), 4 groups at simulated 4500\u202fm altitude (grouping as before), 10 in each group. With incremental load movement, materials were drawn corresponding to the load. Intracellular calcium ion concentration was measured by HE staining, enzyme-linked immunosorbent assay, immunohistochemistry, RT-qPCR, Fluo-4/AM and Fura-2/AM fluorescence staining. Results (1) Hypoxic 2–5 groups showed obvious venous congestion, with symptoms similar to normoxia-8 group; Hypoxic 2–8 groups showed meningeal loosening edema, infra-meningeal venous congestion, with symptoms similar to normoxia-exhausted group and hypoxic 1-exhaused group. (2) For 5,6-EET, regardless of normoxic or hypoxic environment, significant or very significant differences existed between each exercise load group (normoxic − 5 level 20.58\u202f±\u202f0.66\u202fpg/mL, normoxic − 8 level 23.15\u202f±\u202f0.46\u202fpg/mL, normoxic - exhausted 26.66\u202f±\u202f0.71\u202fpg/mL; hypoxic1-5 level 21.72\u202f±\u202f0.43\u202fpg/mL, hypoxic1-8 level 24.73\u202f±\u202f0.69\u202fpg/mL, hypoxic 1-exhausted 28.68\u202f±\u202f0.48\u202fpg/mL; hypoxic2-5 level 22.75\u202f±\u202f0.20\u202fpg/mL, hypoxic2-8 level 25.62\u202f±\u202f0.39\u202fpg/mL, hypoxic 2-exhausted 31.03\u202f±\u202f0.41\u202fpg/mL) and quiet group in the same environment(normoxic-quiet 18.12\u202f±\u202f0.65\u202fpg/mL, hypoxic 1-quiet 19.94\u202f±\u202f0.43\u202fpg/mL, hypoxic 2-quiet 21.72\u202f±\u202f0.50\u202fpg/mL). The 5,6-EET level was significantly or extremely significantly increased in hypoxic 1 environment and hypoxic 2 environment compared with normoxic environment under the same load. (3) With the increase of exercise load, expression of TRPV4 in the rat prefrontal cortex was significantly increased; hypoxic exercise groups showed significantly higher TRPV4 expression than the normoxic group. (4) Calcium ion concentration results showed that in the three environments, 8 level group (normoxic-8 190.93\u202f±\u202f6.11\u202fnmol/L, hypoxic1-8 208.92\u202f±\u202f6.20\u202fnmol/L, hypoxic2-8 219.13\u202f±\u202f4.57\u202fnmol/L) showed very significant higher concentration compared to quiet state in the same environment (normoxic-quiet 107.11\u202f±\u202f0.49\u202fnmol/L, hypoxic 1-quiet 128.48\u202f±\u202f1.51\u202fnmol/L, hypoxic 2-quiet 171.71\u202f±\u202f0.84\u202fnmol/L), and the exhausted group in the same environment (normoxic-exhausted 172.51\u202f±\u202f3.30\u202fnmol/L, hypoxic 1-exhausted 164.54\u202f±\u202f6.01\u202fnmol/L, hypoxic 2-exhausted 154.52\u202f±\u202f1.80\u202fnmol/L) had significant lower concentration than 8-level group; hypoxic2-8 had significant higher concentration than normoxic-8. Conclusion Acute hypoxic exercise increases the expression of TRPV4 channel in the prefrontal cortex of the brain. For a lower ambient oxygen concentration, expression of TRPV4 channel is higher, suggesting that TRPV4 channel may be one important mechanism involved in calcium overload in acute hypoxic exercise.