In vivo effects of the NLRP1/NLRP3 inflammasome pathway on latent respiratory virus infection

The present study aimed to investigate the effects of nucleotide-binding domain leucine-rich repeat protein (NLRP)1/NLRP3 inflammasome pathways on latent viral infection of the respiratory tract. A total of 55 BALB/c mice were assigned to the control, bleomycin (BLM)-treated, murine cytomegalovirus (MCMV), MCMV+BLM and MCMV+BLM+CD4(+) T-cell groups. The viral loads were detected in the salivary glands, kidney, liver and lung tissues via polymerase chain reaction (PCR). The weight, lung coefficient and hydroxyproline (HYP) were detected. HE and Masson staining were performed to score for alveolitis and degree of pulmonary fibrosis. Reverse transcription-quantitative PCR and western blot were applied to assess the expression levels of the NLRP inflammasome components caspase-1, interleukin (IL)-1 and IL-18. ELISA was used to evaluate the expression levels of caspase-1, tumor necrosis factor (TNF)-, IL-1 and IL-18. The weight of the mice decreased, and the lung coefficient and HYP content increased in the BLM, MCMV, MCMV+BLM and MCMV+BLM+CD4(+) T-cell groups compared with those in the control group. Compared with the control group, mice in the BLM, MCMV+BLM and MCMV+BLM+CD4(+) T-cell groups had obviously increased alveolitis and degrees of pulmonary fibrosis, increased mRNA expression levels of caspase-1, IL-1 and IL-18, and increased protein expression levels of caspase-1(p20), mature IL-1 and mature IL-18. The values in the MCMV+BLM group were also higher than those in the BLM group and those in the MCMV+BLM+CD4(+) T-cell group. The serum levels of caspase-1, TNF-, IL-1 and IL-18 in the serum of mice in the MCMV+BLM group were significantly higher than those in the BLM group. Compared with the MCMV+BLM group, the MCMV+BLM+CD4(+) T-cell group had decreased levels of caspase-1, TNF-, IL-1 and IL-18 (all P<0.05). These results demonstrated that the activation of the NLRP1 and NLRP3 inflammasome pathways may contribute to pulmonary fibrosis caused by latent MCMV infection in mice.