Neuroprotective effect of acute prior inflammation with lipopolysaccharide for adult male rat facial motoneurones

Increases in inflammatory cytokines are reported to have both neuroprotective and neurotoxic effects depending on the type and age of neurones studied. This study aimed to determine the effect of experimental inflammation induced by Lipopolysaccharide (LPS) on the survival of injured male adult rat facial motoneurones. Time- and dose-response studies were done to optimise the LPS administration time and dose, to best correlate with inflammatory levels previously reported for aged rats. 12 cytokines were assayed through multiplex analysis. 24 h after intraperitoneal injection of 0.5 mg/kg Lipopolysaccharide in rats, IL-1β, IL-5 and IL-12p70 levels were elevated, with no observed LPS-associated sickness behaviour. In other groups of 5-6 adult rats, the facial nerve was either crushed (as mild injury) or avulsed (as severe injury) after the LPS priming injection. Stereology revealed that most motoneurones survived 28 days after nerve crush only and LPS- or saline-priming preceding nerve crush. Most motoneurones died following nerve avulsion only, whereas over half survived when LPS-priming preceded nerve avulsion. We suggest that elevated levels of experimental inflammation are neuroprotective for severely injured adult male rat facial motoneurones.