Synergistic action of cord factor and mycobacterial sulfatides on mitochondria.

The mechanism of a synergistic toxicity of 6,6'-dimycoloyl-alpha,alpha'-d-trehalose (cord factor) and 2,3,6,6'-tetraacyl-alpha,alpha'-d-trehalose 2'-sulfate (sulfolipid I) for mice was studied. Sulfolipid I was entirely nontoxic, but it markedly accelerated the lethal toxicity of cord factor for mice. In vivo, sulfolipid I affected neither respiration nor accompanying phosphorylation of mouse liver mitochondria, whereas in vitro, it induced a swelling and disruption of mitochondrial membranes and strongly inhibited mitochondrial oxidative phosphorylation. The effect of sulfolipid I on mitochondrial structure and function in vitro was neutralized by bovine serum albumin and various animal sera, whereas that of cord factor and cord factor plus sulfolipid I was not prevented by bovine serum albumin. The simultaneous injection of cord factor and sulfolipid I caused an intensive fragmentation of mitochondria and a marked decrease in respiratory and phosphorylative activity in mitochondria. These data indicate that sulfolipid I can achieve an effective attack on mitochondria in combination with cord factor in vivo and induces heavier damage in mitochondrial structure and function than that produced by cord factor alone.