Pharmacological Targeting of PARP-1-NLRP3 Inflammasome Pathway in Colitis-Associated Colorectal Neoplasia: Effects of 3-aminobenzamide and Olaparib

Abstract

Colitis-associated colorectal neoplasia is the third most life-threatening consequence of prolonged ulcerative colitis. In the present investigation, we evaluated the efficacy of PARP-1 inhibitors, 3-aminobenzamide and Olaparib, in a rodent model of colitis-associated colorectal cancer (CACC) induced by azoxymethane (AOM) and Dextran sulphate sodium (DSS). For model induction, male BALB/c mice were provided DSS (3% w/v) in three cycles within drinking water following an injection of AOM (10 mg/kg, intraperitoneally). A week after the DSS treatment, 3-aminobenzamide (5, 10 and 20 mg/kg; i.p.) and Olaparib (10 mg/kg; orally) were given until sacrifice. PARP inhibitors reduced tumour progression by down-regulating mRNA expression for inflammatory markers, PARP-1, NLRP3, ASC, Caspase-1, and TNF-α. Immunoblotting showed modulation of beclin-1 expression, while transmission electron microscopy results revealed an increase in autophagosome numbers within tumour tissues. Immunofluorescence for Ki67 and immunoblotting of PCNA indicated elevated cell proliferation in the AOM/DSS group, mitigated by the treatment with 3-aminobenzamide (20 mg/kg) and Olaparib (10 mg/kg). Finally, DNA damage was also reduced by the intervention of 3-aminobenzamide and Olaparib as indicated by decrease γH2AX expression. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay and β-catenin expression suggested decrease apoptosis within tumour tissue. Both 3-aminobenzamide (20 mg/kg; i.p.) and Olaparib (10 mg/kg; orally) exhibited coloprotective effects by modulating PARP-1-NLRP3 inflammasome and autophagy pathways in a model of colitis-associated colorectal cancer.