Sex-Specific Regulation of Gene Expression Networks by Surfactant Protein A (SP-A) Variants in Alveolar Macrophages in Response to Klebsiella pneumoniae

Abstract

Surfactant protein A (SP-A) in addition to its surfactant-related functions interacts with alveolar macrophages (AM), the guardian cells of innate immunity in the lungs, and regulates many of its functions under basal condition and in response to various pressures, such as infection and oxidative stress. The human SPA locus consists of two functional genes, SFTPA1 and SFTPA2, and one pseudogene. The functional genes encode human SP-A1 and SP-A2 proteins, respectively, and each has been identified with several genetic variants. SPA variants differ in their ability to regulate lung function mechanics and survival in response to bacterial infection. Here, we investigated the effect of hSP-A variants on the AM gene expression profile in response to Klebsiella pneumoniae infection. We used four humanized transgenic (hTG) mice that each carried SP-A1 (6A 2 , 6A 4) or SP-A2 (1A 0 , 1A 3), and KO. AM gene expression profiling was performed after 6 h post-infection. We found: (a) significant sex differences in the expression of AM genes; (b) in response to infection, 858 (KO), 196 (6A 2), 494 (6A 4), 276 (1A 0), and 397 (1A 3) genes were identified (P < 0.05) and some of these were differentially expressed with ≥2 fold, specific to either males or females; (c) significant SP-A1 and SP-A2 variant-specific differences in AM gene expression; (d) via Ingenuity Pathway Analysis (IPA), key pathways and molecules were identified that had direct interaction with TP53, TNF, and cell cycle signaling nodes; (e) of the three pathways (TNF, TP-53, and cell cycle signaling nodes) studied here, all variants except SP-A2 (1A 3) female, showed significance for at least 2 of these pathways, and KO male showed significance for all three pathways; (f) validation of key molecules exhibited variant-specific significant differences in the expression between sexes and a similarity in gene expression profile was observed between KO and SP-A1. These results reveal for the first time a Thorenoor et al. AM Gene Regulation by SPA Variants large number of biologically relevant functional pathways influenced in a sex-specific manner by SPA variants in response to infection. These data may assist in studying molecular mechanisms of SPA mediated AM gene regulation and potentially identify novel therapeutic targets for K. pneumoniae infection.

Sex and SP-A2 Dependent NAD(H) Redox Alterations in Mouse Alveolar Macrophages in Response to Ozone Exposure: Potential Implications for COVID-19

“…Thus, the present results are consistent with a possible protective role of SP-A2 by modulating the NAD(H) redox status and the oxidative stress after ozone exposure. In fact, it has been previously postulated that SP-A has an antioxidant role in the lung by scavenging ROS [ 73 ] or possibly regulating NADPH oxidase activity in human monocyte derived macrophages [ 74 ] which may or may not capture the in vivo effect of the ozone-induced oxidative stress in the lungs. It has been shown that the tissue-specific alveolar macrophages differ from monocyte-derived macrophages in response to injury [ 75 , 76 ].…”

Impact of Surfactant Protein-A Variants on Survival in Aged Mice in Response to Klebsiella pneumoniae Infection and Ozone: Serendipity in Action

“…Infection for the young mice was performed as described previously [ 24 ] and for the aged mice as described previously [ 24 ], except a significantly higher CFU (~1800) inoculum was used for the aged mice. The higher dose was needed, because unlike the younger mice, all of the aged mice recovered if they were infected with the low CFU (~450) inoculum used for the young mice [ 39 , 40 , 60 ]. Briefly, hTG mice, SP-A1 (6A 2 , 6A 4 ), SP-A2 (1A 0 , 1A 3 ), and SP-A-KO male and female mice were anesthetized with a mixture of ketamine (Vedco.…”

“…Inc, St. Joseph, MO, USA) and xylazine (Akorn. Inc, lake forest, IL, USA) and infected with K. pneumoniae (~1800 CFU/mouse) in 50 µL of PBS delivered to oropharynx and aspirated after a brief nasal occlusion [ 60 , 81 ]. The mice were monitored for survival twice a day (morning and evening, 6–8 h difference between the two daily observations and at each observation time point, each mouse was observed for 5–10 min) for 14 days after infection.…”

“…We and others have demonstrated differences between SP-A1 and SP-A2 variants both qualitative (i.e., functional, biochemical, and/or structure) [ 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 ] and quantitative (regulatory) [ 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 ]. Moreover, SP-A1 and SP-A2 variants differ in their ability to modulate gene expression and the proteomic expression profile of AM and the AM actin cytoskeleton [ 57 , 58 , 59 , 60 ]. A single-cell analysis based on actin-staining revealed alveolar macrophage phenotypic subpopulation as well as sex- and age-related differences in KO mice in response to SP-A1 and SP-A2 proteins [ 59 ].…”

“…Sex differences in survival and lung function mechanics in response to bacterial infection between SP-A1 and SP-A2 and among variants have been observed [ 39 , 40 ]. Furthermore, the SP-A variant-dependent AM gene expression in response to infection varies in a sex-specific manner [ 60 ]. SP-A1 compared to SP-A2 exhibits a higher efficiency in pulmonary surfactant reorganization and surfactant inhibition by serum proteins [ 61 ], whereas SP-A2 exhibits higher activity in host defense-related functions [ 35 , 39 , 45 ].…”