Hot water immersion elevates interleukin-6 in persons with cervical spinal cord injury

Abstract

Core temperature elevations can impact positively on immunity, potentially due to increases of catecholamines acting on immune cells’ adrenergic receptors. The dysfunctional sympathetic nervous system in individuals with cervical spinal cord injury (CSCI) impairs adrenergic responses and may contribute to depressed immunity and the occurrence of low-grade systemic inflammation related disorders. However, some immune markers improve following exercise in CSCI, even though the positive effects are often blunted. Non-exercise induced body temperature manipulations have yet to be investigated in CSCI. Seven male participants with a motor complete CSCI and 8 male able-bodied controls were immersed for 60 min in water set at a temperature 2 C above the individuals’ resting oesophageal temperature. Blood was collected before, during, and every hour up to 4 h after immersion and analyzed for interleukin-6 (IL-6). Hot water immersion increased IL-6 in both groups ( P < 0.001). IL-6 plasma concentrations were higher in CSCI, but it was not significant. Possibly, the reduced active muscle mass in CSCI does not allow for sufficient core temperature elevations during exercise to increase these cytokines. Together with the lower catecholamine levels usually found in CSCI, this may explain the blunted exercise response on some aspects of immunity. This seems especially concerning as higher average levels of IL-6 support the indication of chronic low-grade systemic inflammation in CSCI. This is the first study to show an acute cytokine response induced by hot water immersion in CSCI. Passive elevation of core temperature may help to improve the cytokine profile in CSCI.