Objective  To investigate the therapeutic effects of β-nicotinamide mononucleotide(β-NMN) and taurine, administered in combination, on experimental silicosis in rats.

Methods  A total of 72 SPF Sprague-Dawley rats, equally divided by sex, were stratified by sex and body weight and randomly assigned into four groups(18 rats per group) using a computer-generated method, namely the blank control group(non-dust-exposed), the negative control group, the separate administration treatment group, and the simultaneous administration treatment group. A rat silicosis model was established by non-exposure tracheal instillation of 50 mg free silica dust per rat. Starting from day 4 after dust exposure, rats in the separate administration treatment group were gavaged with β-NMN solution in the morning and taurine solution in the afternoon. Rats in the simultaneous administration treatment group were gavaged with a mixture of β-NMN and taurine solution, administered twice daily in the morning and evening. The daily dose level of each drug was 300 mg per kilogram of body weight. Rats in the blank control groups and negative control group received equal volumes of ultrapure water twice daily in the morning and evening. All four groups of rats were administered the treatments for 5 days per week over a total of 6 weeks. After 6 weeks of the treatments, rats were sacrificed for evaluation. Lung hydroxyproline content, total free silica content in the lung, bronchoalveolar lavage fluid(BALF) cell counts and classifications, whole lung wet and dry weights, and organ coefficients were measured. Histopathological changes in lung tissues were also observed.

Results  In both the separate and the simultaneous administration treatment groups, lung wet weights were(2.101 ± 0.504) g and(1.916 ± 0.397) g, dry weights were(0.411 ± 0.050) g and(0.394 ± 0.047) g, lung organ coefficients were(0.675 ±0.031)% and(0.595 ± 0.034)%, and hydroxyproline contents were(0.321 ± 0.012) mg and(0.315 ± 0.011) mg, all significantly lower than those in the negative control group(P < 0.05). Cytological examination of BALF showed that in the separate and simultaneous administration groups, the total cell counts in BALF were(19.375 ± 1.815) × 10⁹ cells/L and(16.708 ± 1.317) × 10⁹cells/L, and the neutrophil proportions were(54.500 ± 3.619)% and(57.167 ± 4.215)%, all significantly lower than those in the negative control group(P < 0.05). Lung free silica content(by mass fraction) in the separate and simultaneous administration groups was(6.562 ± 0.511)% and(5.729 ± 0.601)%, respectively, significantly lower than in the negative control group(P < 0.05). The differences for any of the above indicators between the two treatment groups had no statistical significance(P > 0.05). Histopathological examination showed clearly demarcated round or oval nodules, which were phagocytic cellular nodules, with partially preserved alveolar structures in the negative control group. Similar but milder lesions were observed in both separate and simultaneous administration treatment groups compared to the negative group, and there were more intact alveolar structures.

Conclusion  Combined administration of β-nicotinamide mononucleotide and taurine exerted the therapeutic and dust-clearing effects in rats with experimental silicosis.