Effect of ageing and paracetamol on the intrinsic death pathway in Fischer 344 rat livers — The Association Specialists
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Effect of ageing and paracetamol on the intrinsic death pathway in Fischer 344 rat livers (358)

John Mach 1 2 3 , Aniko Huizer-Pajkos 1 2 , Alice Kane 1 2 3 , Brett E. Jones 3 4 , Victoria C. Cogger 3 5 , David G. Le Couteur 3 5 , Rafael de Cabo 6 , Sarah N. Hilmer 1 2 3
  1. Clinical Pharmacology and Aged Care, Royal North Shore Hospital, Sydney, NSW, Australia
  2. Laboratory of Ageing and Pharmacology, Kolling Institute of Medical Research, Sydney, NSW, Australia
  3. Sydney Medical School, University of Sydney, Sydney, NSW, Australia
  4. Department of Gastroenterology , Royal North Shore Hospital, Sydney, NSW, Australia
  5. Centre for Education and Research on Ageing and Anzac Research Institute, Concord Hospital , Sydney, NSW, Australia
  6. Laboratory of Experimental Gerontology, National Institute on Aging and Nationational Institute of Health, Baltimore, Maryland, America

Introduction. Drug-induced liver injury results in apoptosis that is regulated by mitochondria via the intrinsic death pathway. In young mice, following an acute toxic dose of paracetamol, pro-apoptotic (BID, BAX, BAK) and anti-apoptotic (Bcl-2, Bcl-Xl) proteins translocate into the mitochondrial membrane where their pivotal balance determines apoptosis. The effect of ageing on this toxicodynamic process is unknown.

Aims. To characterise the degree of hepatotoxicity and expression of the intrinsic death-associated proteins after administration of a toxic dose of paracetamol to young and old male Fischer 344 rats.

Methods. Young adult (6 ± 1 months) and old (26 ± 2 months) rats were injected intraperitoneally with 800mg/kg paracetamol (young n = 8, old n = 5) or saline (young n = 9, old n = 9) four hours prior to euthanasia. Serum ALT and liver histology indicated the degree of hepatotoxicity. Perfused liver were snap frozen for subsequent immunoblot analysis of BAX, BAK, BID, Bcl-Xl and Bcl-2 expression in the mitochondria and cytosol, Poly(ADP-ribose) polymerase 1 (PARP-1) in the nucleus and caspase-3 in cytosol.

Results. Serum ALT was elevated significantly only in paracetamol treated young rats. Paracetamol did not alter expression of the intrinsic death pathway proteins in young or old rats. In saline treated animals, cytosolic expression of pro-apoptotic BAX, BAK, BID and anti-apoptotic Bcl-Xl were decreased in old rats compared to young (p<0.05). With old age mitochondrial pro-apoptotic BAK and BID expression decreased (p<0.05), while anti-apoptotic Bcl-2 trended to decrease, and BAX and Bcl-Xl did not change. Caspase-3 activation significantly increased in old age (p<0.05) while mitochondrial BAX: Bcl-2 ratio and PARP-1 cleavage (apoptosis markers) trended to increase.

Discussion. These results suggest that in male Fischer 344 rats, the intrinsic death pathway is not activated by paracetamol toxicity and pro-apoptotic changes occur in this pathway with ageing.