Effects of bacterial lysates on immune function in elderly mice with pulmonary fibrosis / 中华老年医学杂志

ABSTRACT

Objective:To investigate the correlation between immune function and age-related pulmonary fibrosis, as well as the potential impact of bacterial lysates on this condition.Methods:Twenty-four healthy male C57BL/6 mice, aged 24, were randomly divided into three groups: a control group(Group N), a pulmonary fibrosis group(Group M), and a pulmonary fibrosis+ bacterial lysis product intervention group(Group P). Mice in Groups M and P were intratracheally injected with bleomycin(5 mg/kg)to induce a mouse pulmonary fibrosis model, while mice in Group N were injected with saline.After modeling, mice in Group P were orally administered 0.4 ml of a bacterial lysis product once a day.After 28 days, lung tissue and blood samples were collected for analysis.Pathological changes in lung tissue were assessed using hematoxylin and tosin staining(HE)and Masson staining and the Ashcroft score.The expression of CD4+ and CD8+ in lung tissue was evaluated using immunohistochemistry.The levels of serum interferon-γ(INF-γ), interleukin-3(IL-13), and immunoglobulin A(IgA)protein were measured using Enzyme-linked Immuno Sorbent Assay(ELISA). The levels of INF-γ and IL-13 mRNA in lung tissue were determined using Real-Time Quantitative Transcription PCR(RT-qPCR). Additionally, the protein expression levels of matrix metalloprotein-9(MMP-9)and tissue inhibitor of metalloproteincise 1(TIMP-1)in lung tissue were assessed using blot analysis.Results:The degree of lung fibrosis was significantly reduced in mice in group P compared with group M when treated with bacterial lysis products.Group M showed a significant decrease in the expression of CD4+ T cells and an increase in the expression of CD8+ T cells( P<0.05)compared to group N. Additionally, the content of IgA was decreased( P<0.05)in group M. On the other hand, group P showed a significant increase in the expression of CD4+ T cells and a decrease in the expression of CD8+ T cells( P<0.05)compared to group M. Furthermore, the content of IgA was elevated( P<0.05)in group P. After bacterial lysis product intervention, mRNA and protein expression levels of IFN-γ were elevated( P<0.05), while mRNA and protein expression levels of IL-13 were reduced( P<0.05). Moreover, protein expression of MMP-9 and TIMP-1 was significantly up-regulated in group M compared with group N( P<0.05), and decreased after bacterial lysis product intervention( P<0.05). Conclusions:It is well-known that immune mechanisms play a crucial role in the development of pulmonary fibrosis.The use of bacterial lysates has been found to effectively regulate immune balance and mitigate the severity of pulmonary fibrosis in elderly mice.