Noncleavable poly(ADP-ribose) polymerase-1 regulates the inflammation response in mice

Abstract

Poly(ADP-ribosyl)ation is rapidly formed in cells following DNA damage and is regulated by poly(ADPribose) polymerase-1 (PARP-1). PARP-1 is known to be involved in various cellular processes, such as DNA repair, genomic stability, transcription, and cell death. During apoptosis, PARP-1 is cleaved by caspases to generate 89-kDa and 24-kDa fragments, a hallmark of apoptosis. This cleavage is thought to be a regulatory event for cellular death. In order to understand the biological significance of PARP-1 cleavage, we generated a PARP-1 knockin (PARP-1 KI/KI ) mouse model, in which the caspase cleavage site of PARP-1, DEVD 214 , was mutated to render the protein resistant to caspases during apoptosis. While PARP-1 KI/KI mice developed normally, they were highly resistant to endotoxic shock and to intestinal and renal ischemia-reperfusions, which were associated with reduced inflammatory responses in the target tissues and cells due to the compromised production of specific inflammatory mediators. Despite normal binding of NF-κB to DNA, NF-κB-mediated transcription activity was impaired in the presence of caspase-resistant PARP-1. This study provides a novel insight into the function of PARP-1 in inflammation and ischemia-related pathophysiologies. IntroductionUpon DNA damage, poly(ADP-ribose) polymerase-1 (PARP-1, EC 2.4.2.30) is activated and catalyzes the formation of poly(ADPribose) (PAR) chains by transferring (ADP-ribose) from β-NAD + onto itself and nuclear acceptor proteins (1). PARP-1 is known to be involved in various cellular processes including DNA repair, recombination, genomic stability, transcription regulation, and cell death (1-3). In addition, massive poly(ADP-ribosyl)ation induced by acute DNA damage results in rapid depletion of cellular NAD + and ATP pools, which, if not regulated, can lead to cellular dysfunction and cell death (4). Involvement of PARP-1 in cell death is also speculated based on the prominent phenomenon that during apoptosis, PARP-1 is cleaved by caspases at the conserved site DEVD 214 , generating 24-kDa and 89-kDa fragments, a hallmark of apoptosis.Mice lacking PARP-1 develop normally and PARP-1 -/-fibroblasts and lymphoid cells display a normal apoptotic response after treatment with various apoptotic inducers, such as anti-Fas antibody, TNF-α, γ-radiation, and dexamethasone, which demonstrates that PARP-1 per se is dispensable for apoptosis, at least in these cell types (5, 6). However, inactivation of PARP-1 by chemical inhibitors and genetic means protects mice from endotoxic shock and other disease models related to inflammation, such as diabetes, stroke, and myocardial reperfusion (7-12). In addition, PARP inhibitors protect rats from renal and intestinal ischemia-

Autophagy Contributes to Caspase-independent Macrophage Cell Death

“…PARP-1 is known to be involved in various cellular processes, such as DNA repair and transcription, so the in vivo role of PARP-1 in macrophage death could be very complicated. Since both PRAP-1 knock-out mice and non-cleavable PARP-1 knockin mice are resistant to endotoxic shock, it is possible that the caspase cleavage products of PARP-1 are important in regulating inflammatory response in vivo (42,57).…”

Caspase substrates

“…The enhanced activity results from interactions between the large subunit of caspase-7 with poly(ADP-ribose) that are not present with caspase-3, 61 hinting at an exosite interaction. Mice expressing a transgenic PARP caspase cleavage site mutant (DEVN 213 kG) develop normally, but resist endotoxic shock and intestinal and renal ischemia-reperfusion in vivo, 62 indicating that failure to cleave the protein has similar tissue-restricted effects to mice defective in caspasemediated RB cleavage (see above).…”

Differential expression in lupus-associated IL-10 promoter single-nucleotide polymorphisms is mediated by poly(ADP-ribose) polymerase-1

“…This cleavage is important for the regulation of inflammatory responses by PARP-1. 54 It has been shown that the 24-kDa fragment can act to compete against the full-length PARP-1 and inhibit DNA repair, ADP-ribose polymer formation and damagedependent upregulation of transcription. 55,56 We investigated the direct role of PARP-1 in the regulation of IL-10 gene transcription by using a chemical inhibitor of PARP-1 activity, 3-aminobenzamide (3-AB) 57 and by overexpressing PARP-1.…”

“…The biological significance of PARP-1 cleavage is shown in a PARP-1 knockin (PARP-1(KI/KI)) mouse model, in which the caspase cleavage site of PARP-1, DEVD(214), was mutated to render the protein resistant to caspases during apoptosis. 54 Although PARP-1(KI/KI) mice developed normally, they were highly resistant to endotoxic shock and to intestinal and renal ischemiareperfusions, which were associated with reduced inflammatory responses in the target tissues and cells due to the compromised production of specific inflammatory mediators.…”