Bleomycin-induced modulations of PARP 1 activity, NAD+ and PARG content in rat lung nuclei

Abstract

Bleomycin-induced lung pathology in rodents is a well recognized animal model widely used for evaluation of new therapeutic approaches in treatment of lung inflammation and fibrotic diseases. It is documented that poly(ADP-ribose)polymerase 1 activity has a significant role in development of inflammatory processes in the heart, liver and brain. Herein, we used biochemical and immunochemical methods for estimation of poly(ADP-ribose)polymerase 1 (PARP 1) activity, NAD+ and poly(ADP-ribose)glycohydrolase (PARG) protein content in rat lung nuclei during the inflammatory phase in a bleomycin-induced one-hit rat model. To evaluate the influence of bleomycin – induced alterations in DNA structure on regulation of poly(ADP-ribose)polymerase 1 activation pathways, we isolated DNA from nuclei of lung tissues in the phase of acute lung inflammation induced by bleomycin, and DNA melting profiles were investigated. In the present study we investigated whether naturally occurring water-soluble polyphenol tannic acid with widely accepted anti-fibrotic and anti-inflammatory effects can influence poly(ADP-ribose)polymerase 1 activity, NAD+ and poly(ADP-ribose)glycohydrolase protein content in nuclear fraction isolated from rat lung tissues in a bleomycin-induced acute lung injury model. It was demonstrated that NAD+ level and poly(ADP-ribose)glycohydrolase protein content decreased in rat lung nuclei during the inflammatory phase in the bleomycin-induced acute lung injury model. Treatment of rats with tannic acid enhanced the effects displayed by bleomycin in lung nuclei, thus indicating synergistic interaction with the drug in the field covering PARP 1 activity, poly(ADP-ribose)glycohydrolase (PARG) protein and NAD+ content in lung nuclei. We observed PARP 1 inhibition in nuclei of lung tissue during the inflammatory phase in the bleomycin-induced acute lung injury rat model, which could be coupled with the drop of NAD+ level in nuclei. In the present study we highlighted that bleomycin (BLM) can induce DNA destabilization in lung nuclei. It was proposed that bleomycin-induced modulations in DNA structure could hamper PARP 1 binding with DNA and down-regulate the enzyme activating pathway in lung nuclei. The role of poly(ADP-ribose)glycohydrolase depletion in lung nuclei and sequential accumulation of poly(ADP-ribose)polymers in lung cells, which triggers their destruction and tissues damage, was proposed. It is suggested that in the light of synergistic interaction between bleomycin and tannic acid (TA) the anti-inflammatory role of tannic acid should be repurposed.