Differential Impact of Co-expressed SP-A1/SP-A2 Protein on AM miRNome; Sex Differences

Abstract

In humans there are two surfactant protein A (SP-A) functional genes SFTPA1 and SFTPA2 encoding innate immune molecules, SP-A1 and SP-A2, respectively, with numerous genetic variants each. SP-A interacts and regulates many of the functions of alveolar macrophages (AM). It is shown that SP-A variants differ in their ability to regulate the AM miRNome in response to oxidative stress (OxS). Because humans have both SP-A gene products, we were interested to determine the combined effect of co-expressed SP-A1/SP-A2 (co-ex) in response to ozone (O 3 ) induced OxS on AM miRNome. Human transgenic (hTG) mice, carrying both SP-A1/SP-A2 (6A 2 /1A 0 , co-ex) and SP-A- KO were utilized. The hTG and KO mice were exposed to filtered air (FA) or O 3 and miRNA levels were measured after AM isolation with or without normalization to KO. We found: (i) The AM miRNome of co-ex males and females in response to OxS to be largely downregulated after normalization to KO, but after Bonferroni multiple comparison analysis only in females the AM miRNome remained significantly different compared to control (FA); (ii) The targets of the significantly changed miRNAs were downregulated in females and upregulated in males; (iii) Several of the validated mRNA targets were involved in pro-inflammatory response, anti-apoptosis, cell cycle, cellular growth and proliferation; (iv) The AM of SP-A2 male, shown, previously to have major effect on the male AM miRNome in response to OxS, shared similarities with the co-ex, namely in pathways involved in the pro-inflammatory response and anti-apoptosis but also exhibited differences with the cell-cycle, growth, and proliferation pathway being involved in co-ex and ROS homeostasis in SP-A2 male. We speculate that the presence of both gene products vs. single gene products differentially impact the AM responses in males and females in response to OxS.

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

“…The underlying mechanisms and whether it is due to gender and/or sex differences is not known at this time. Given the sex-specific and the SP-A genotype specific outcomes in animal models [ 41 , 42 , 79 , 86 , 88 ] and the important role of innate immunity in providing the first line of defense, it is highly likely that the genetics of the innate immunity molecule, SP-A, contribute to and/or may partly explain the differential outcome in COVID-19 patients under different lung microenvironments [ 89 , 90 ]. The genotype- and sex-dependent effect of SP-A on NAD(H) redox status and oxidative stress/inflammatory pathways may be of clinical relevance in COVID-19 patients and SP-A may be considered as a potential therapy.…”

“…The genotype- and sex-dependent effect of SP-A on NAD(H) redox status and oxidative stress/inflammatory pathways may be of clinical relevance in COVID-19 patients and SP-A may be considered as a potential therapy. The rationale for this potential therapy is based on the information where SP-A is shown to modulate pathways either under baseline conditions [ 32 , 40 ] or in response to infection and/or ozone exposure [ 43 , 86 , 88 ] that are deemed important in COVID-19 disease [ 91 ]. These include, among others, the Nrf2 and the acute phase response that includes NF-κB and the IL-6.…”

The Importance of Redox Status in the Frame of Lifestyle Approaches and the Genetics of the Lung Innate Immune Molecules, SP-A1 and SP-A2, on Differential Outcomes of COVID-19 Infection

“…The coding variants hold the potential for functional differences among themselves. In fact, a considerable body of research has shown this to be the case in both host defense and surfactant-related functions [8][9][10][11][12][117][118][119][120][121][122][123][124][125][126]. Although in terms of host defense, the mechanistic details of SP-A1/SP-A2 binding to alveolar macrophages to bring about the observed differential outcomes are not known, the B max of SP-A2 binding to alveolar macrophage is 2-3 times higher than that of SP-A1 [127].…”

“…SP-A1 and SP-A2 variants differentially affect alveolar macrophage function (i.e., its ability to produce proinflammatory cytokines and carry out bacterial phagocytosis) [8][9][10]130,131]. Mouse models, where each mouse line carries and expresses a different human SP-A1 or SP-A2 variant or both, showed a differential impact on the bronchoalveolar lavage proteome [118], as well as the alveolar macrophage proteome [121,124], miRNome [117,119], and gene expression [132] under baseline conditions and in response to ozone-induced oxidative stress (OxS) or infection, and these responses were sex-specific. Furthermore, SP-A1 and SP-A2 variants have also been shown to differentially affect the epithelial type II cell miRNome in a sex-specific manner [120].…”

“…In summary, the available data together indicate: (a) the importance of SP-A in lung health; (b) that the differential effect of SP-A genetic variants on the proteome of the bronchoalveolar lavage and on the alveolar cells (function and regulation) may create a variable alveolar microenvironment that is SP-A genotype-dependent; (c) that the SP-A variant-dependent changes in the collective microenvironment (cellular and the surrounding hypophase/liquid) are sex-specific [11,12,[117][118][119][120][121]126] and SP-A-concentration dependent [124]; (d) in a large number of pulmonary diseases, susceptibility and severity have been associated with SP-A genetic variants [122,123,125]. Moreover, although it is known that SP-A1 and SP-A2 are differentially regulated [114,[135][136][137][138][139][140][141], it is currently unknown how this regulation may be further altered in the presence, for example, of infection.…”