Role of PARP on iNOS pathway during endotoxin-induced acute lung injury.

Objective: Excessive nitric oxide (NO) and especially peroxynitrite may cause pulmonary tissue damage, e.g., through lipid peroxidation and/or exhaustion of cellular energy depletion induced by activation of poly (ADP-ribose) polymerase (PARP). Furthermore, PARP seems to aggravate tissue destruction by regulating the expression of respective genes.

Design: Prospective animal study.

Setting: University research laboratory.

Intervention: We investigated the effect of competitive PARP inhibition by 3-aminobenzamide (3-AB) on the pulmonary iNOS pathway after infusion of lipopolysaccharide (LPS).

Measurements And Results: The pretreatment of rabbits with 3-AB attenuated the LPS-induced iNOS mRNA and protein expression analyzed by RT-PCR and Western blot, and plasma nitrite concentrations quantified by Griess reaction (71+/-6%, 93+/-6% vs baseline). Electromobility shift assay showed an enhanced NF-kappaB and attenuated AP-1 activation after 3-AB vs LPS alone. Lipid peroxidation determined as levels of thiobarbituric acid reactive substances in plasma and lung tissue was reduced by 50% in the LPS+3-AB in comparison to LPS alone. Simultaneously, 3-AB was able to inhibit correspondingly the LPS-induced extravasation of gold-labeled albumin and increase of alveolo-arterial oxygen difference.

Conclusion: PARP regulates the pulmonary NO pathway during endotoxemia via AP-1 and not NF-kappaB. Thus, pharmacological inhibition of PARP might be an effective intervention to prevent endotoxin-induced lung injury, interrupting the vicious circle of NO production and PARP activation.