The aetiology and pathogenesis of Reye's syndrome (RS) are incompletely understood. A number of environmental toxins and biological agents, including viruses, have been postulated to cause RS, either acting alone or synergistically. Most investigations have suggested that the primary insult is in the liver mitochondria, leading to a complex biochemical catastrophe, with death from encephalopathy. Margosa oil (MO), a long-chain fatty acid compound, has been shown to cause a Reye-like syndrome with death from hepatoencephalopathy, in children in Malaysia and India. The present time-course study performed in MO-administered mice showed the development of hepatic lesions with many features of RS. MO acts rapidly, within 30 min, on the nuclei of hepatocytes inducing mitoses and binucleated cells. This is followed by mitochondrial injury, with swelling, rarefaction of matrix, loss of dense bodies, pleomorphism, and loss of ribosomes starting at 60 min. There is loss of liver glycogen, and proliferation and hypertrophy of the endoplasmic reticulum (ER), followed by the presence of lipid droplets in the hyaloplasm, and globules within dilated cisterns of the ER. Additional fatty acids from lipolysis of body adipocytes, and fat globules from intestinal MO ingestion further aggravate the liver fatty change. There is evidence of fat globule ingestion by endocytosis into hepatocytes at the level of the sinusoids. The development of microvesicular liver steatosis and glycogen depletion due to involvement of liver cell organelles occur rapidly as in RS.
Margosa oil (MO), a fatty acid-rich extract of the seeds of the neem tree and a reported cause of Reye's syndrome, has been used in the induction of an experimental model of Reye's syndrome in rats. It has been reported that MO causes a decrease in in vivo mitochondrial enzyme activity similar to that seen in Reye's syndrome. We have attempted to uncover some of the biochemical mechanisms of MO's toxicity by examining its effect in vitro on isolated rat liver mitochondria. Male rat liver mitochondria were isolated by centrifugation; oxygen uptake, reduced forms of cytochrome b, c + c1, a + a3, and flavoprotein, intramitochondrial concentrations of acetyl coA, acid-soluble coA, acid-insoluble coA, and ATP content were measured after incubation with and without MO. Our results reveal that MO is a mitochondrial uncoupler. State 4 respiration was increased while the respiratory control ratio was decreased. The intramitochondrial content of ATP was also decreased. There were substantial changes in the reduction of the respiratory chain components after incubation of mitochondria with MO. This decelerative effect on mitochondrial electron transport was alleviated by the addition of coenzyme Q and/or carnitine. These effects of MO on mitochondrial respiration may be due to changes in fatty acid metabolism caused by MO as MO caused a shift in the proportion of acid-soluble or acid-insoluble coA esters. Supplementary therapy with L-carnitine and coenzyme Q may be useful in the management of MO-induced Reye's syndrome.