In humans IL-6 is released from the brain during and after exercise and paralleled by enhanced IL-6 mRNA expression in the hippocampus of mice.

AIM: Plasma interleukin-6 (IL-6) increases during exercise by release from active muscles and during prolonged exercise also from the brain. The IL-6 release from muscles continues into recovery and we tested whether the brain also releases IL-6 in recovery from prolonged exercise in humans. Additionally, it was evaluated in mice whether brain release of IL-6 reflected enhanced IL-6 mRNA expression in the brain as modulated by brain glycogen levels. METHODS: Nine healthy male subjects completed 4 h of ergometer rowing while the arterio-jugular venous difference (a-v diff) for IL-6 was determined. The IL-6 mRNA and the glycogen content were determined in mouse hippocampus, cerebellum and cortex before and after 2 h treadmill running (N = 8). RESULTS: At rest, the IL-6 a-v diff was negligible but decreased to -2.2 ± 1.9 pg ml(-1) at the end of exercise and remained low (-2.1 ± 2.1 pg ml(-1) ) 1 h into the recovery (P < 0.05 vs. rest). IL-6 mRNA was expressed in the three parts of the brain with the lowest content in the hippocampus (P < 0.05) coupled to the highest glycogen content (3.2 ± 0.8 mmol kg(-1) ). Treadmill running increased the hippocampal IL-6 mRNA content 2-3-fold (P < 0.05), while the hippocampal glycogen content decreased to 2.6 ± 0.6 mmol kg(-1) (P < 0.05) with no significant changes in the two other parts of the brain. CONCLUSION: Human brain releases IL-6 both during and in recovery from prolonged exercise and mouse data suggest that concurrent changes in IL-6 mRNA and glycogen levels make the hippocampus a likely source of the IL-6 release from the brain.

Metal and pH dependence of heptapeptide catalysis by human matrilysin.

Human matrilysin devoid of its propeptide is expressed in Escherichia coli and purified to homogeneity by heparin chromatography after refolding of the guanidine hydrochloride solubilized protein. Matrilysin autolytically removes its N-terminal tripeptide Met-Tyr-Ser during the refolding process. The enzyme contains 1.91 +/- 0.08 zinc atoms/mol of protein and retains full activity when stored several months at 4 degrees C. It hydrolyzes the fluorescent substrate Dns-PLALWAR at the Ala-Leu bond with a kcat of 3.1 s-1 and K(m) of 1.8 x 10(-5) M at pH 7.5, 37 degrees C, values closely similar to those for the matrilysin produced by activation of the Chinese hamster ovary and E. coli-expressed promatrilysin. The properties of this form of matrilysin demonstrate that the propeptide is not essential for proper folding or stability of the enzyme but likely determines the N-terminal amino acid of the mature enzyme. The pH dependence of kcat/K(m) for Dns-PLALWAR shows that matrilysin has a broad pH optimum (5.0-9.0) and the pKa values obtained are 4.3 and 9.6 at 25 degrees C. The activity is inhibited by several metal binding agents including 1, 10-phenanthroline, OP, but not by the nonchelating isomer, 1,7-phenanthroline. OP inhibits instantaneously by likely forming a transient ternary enzyme.metal.chelator complex. The zinc atom is then removed from the protein in a time-dependent manner. In agreement with the kinetic studies, dialysis in the presence of OP and CaCl2 removes only the catalytic zinc atom. The monozinc enzyme can be reactivated to 90%, 56%, 27%, and 17% of the native activity by addition of zinc, manganese, nickel, and cobalt, respectively. Cadmium, on the other hand, forms an inactive Cd/Zn hybrid. The differences in the chelator accessibility properties of the two zinc sites can thus be exploited to yield metallohybrids of matrilysin.