Fig. 6: NMN supplementation alleviates pathological phenotypes of MASCp36-induced pneumonia.

a Schematic diagram of experimental design for NMN and NAD⁺ supplementation in MASCp36-infected aged mice. b H&E staining results of lung sections from saline-, NMN-, and NAD⁺-administered MASCp36-infected aged mice. Green arrowhead: inflammatory cell aggregates. Scale bars, 100 μm. c Survival of saline (n = 10) and NMN (n = 10) administered MASCp36-infected aged mice. d Immunostaining results with SARS-CoV-2 nucleocapsid (green) and macrophage marker (CD68, red) antibodies of two adjacent lung sections for each group. Scale bars, 100 μm. e Quantification of the density of CD68⁺ cells of lung sections from saline-, NMN-, and NAD⁺-administered MASCp36-infected aged mice. t-test. n = 3 mice per group. f, g qPCR results of relative expression levels of CD400 receptor genes, Cd200r3 (f) and Cd200r4 (g). t-test. n = 6 mice for saline group and n = 3 mice for NMN and NAD⁺ groups. Exact P values are indicated. h Immunostaining results with SARS-CoV-2 nucleocapsid (green) and Cas3 (red) antibodies of two adjacent lung sections for each group. Scale bars, 100 μm. i Quantification of the ratio of Cas3⁺ cells to infected cells of saline-, NMN-, and NAD⁺-administered MASCp36-infected aged mice. Mann–Whitney test. n = 3 mice per group. j qPCR results of relative expression levels of apoptosis protease activating factor gene, Apaf1. t-test. n = 6 mice for saline group and n = 3 mice for NMN and NAD⁺ groups. Exact P values are indicated. All quantification data are shown as means ± SEM. ***P < 0.001, ****P < 0.0001.