Modulation by dantrolene of endotoxin-induced interleukin-10, tumour necrosis factor-α 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 investigated the effect of dantrolene on lipopolysaccharide (LPS)-induced production of interleukin-10 (IL-10), tumour necrosis factor-alpha (TNF-alpha), and nitric oxide (NO) in mice and in cultured RAW 264.7 macrophages in vitro. 2 In BALB/c mice, LPS-induced plasma IL-10 levels were 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, dantrolene 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-alpha 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 macrophages, 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 translocation of transcription factor nuclear factor kappa B in these cells. 5 Although LPS failed to alter the intracellullar concentration of calcium in single macrophages loaded with Fura-2, dantrolene caused a significant decrease of the basal calcium level as determined 30 min after dantrolene treatment (P<0.005). ATP (1 mM) caused a rapid rise in intracellular calcium levels in both dantrolene-pretreated and vehicle-pretreated cells. 6 These results indicate that unlike the secretion of TNF-alpha and NO, IL-10 production is differentially regulated in vitro and in vivo. The decrease of plasma levels of the pro-inflammatory mediators TNF-alpha and NO, and increase in circulating IL-10 concentrations by dantrolene suggest that this drug might offer a new therapeutic approach in inflammatory diseases and septic shock.