MODULATION BY DANTROLENE OF ENDOTOXIN-INDUCED INTERLEUKIN-10, TUMOR-NECROSIS-FACTOR-ALPHA AND NITRIC-OXIDE PRODUCTION IN-VIVO AND IN-VITRO

1 Intracellular calcium has been suggested to be an important mediator of the cellular response in endotoxaemia and shock. Dantrolene is an agent that interferes with intracellular calcium fluxes resulting in a decreased availability of calcium in the cytoplasm. Here we have inve stigated the effect of dantrolene on lipopolysaccharide (LPS)-induced production of interleukin-10 (IL-10), tumour necrosis factor-alpha (TN F-alpha), and nitric oxide (NO) in mice and in cultured RAW 264.7 macr ophages in vitro. 2 In BALB/c mice, LPS-induced plasma IL-10 levels we re significantly enhanced by pretreatment with dantrolene (20 mg kg(-1 ), i.p.) (P<0.005 at the 90 min time-point). On the other hand, dantro lene pretreatment suppressed circulating TNF-alpha and nitrite/nitrate (breakdown products of NO) concentrations. However, dantrolene had no effect on LPS-induced plasma interleukin-6 (IL-6) levels (67.22 +/- 5 .51 ng ml(-1) in vehicle-pretreated mice and 62.22 +/- 3.66 ng ml(-1) in dantrolene-pretreated mice, n = 9). 3 Dantrolene inhibited TNF-alph a and NO production in C57BL/6 IL-10(+/+) mice, as well as in their IL -10 deficient counterparts (C57BL/6 IL-10(0/0)). 4 In RAW 264.7 macrop hages, dantrolene (10-300 mu M) reduced IL-10, TNF-alpha, and nitrite (breakdown product of NO) production elicited by LPS (10 mu g ml(-1)). Dantrolene (300 mu M) did not affect the LPS-induced nuclear transloc ation of transcription factor nuclear factor kappa B in these cells. 5 Although LPS failed to alter the intracellullar concentration of calc ium in single macrophages loaded with Fura-2, dantrolene caused a sign ificant decrease of the basal calcium level as determined 30 min after dantrolene treatment (P<0.005). ATP (1 mM) caused a rapid rise in int racellular calcium levels in both dantrolene-pretreated and vehicle-pr etreated cells. 6 These results indicate that unlike the secretion of TNF-alpha and NO, IL-10 production is differentially regulated in vitr o and in vivo. The decrease of plasma levels of the pro-inflammatory m ediators TNF-alpha and NO, and increase in circulating IL-10 concentra tions by dantrolene suggest that this drug might offer a new therapeut ic approach in inflammatory diseases and septic shock.