{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,15]],"date-time":"2026-09-15T12:31:43Z","timestamp":1789475503490,"version":"build-2803163510"},"reference-count":39,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2024,4,30]],"date-time":"2024-04-30T00:00:00Z","timestamp":1714435200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Florida legislative grant","award":["2014-2024"],"award-info":[{"award-number":["2014-2024"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Nutrients"],"abstract":"<jats:p>Background: Vitamin D plays a vital role in modulating both innate and adaptive immune systems. Therefore, vitamin D deficiency has been associated with higher levels of autoimmune response and increased susceptibility to infections. CYP27B1 encodes a member of the cytochrome P450 superfamily of enzymes. It is instrumental in the conversion of circulating vitamin D (calcifediol) to active vitamin D (calcitriol). This is a crucial step for macrophages to express Cathelicidin Anti-microbial Peptide (CAMP), an anti-bacterial factor released during the immune response. Our recent study indicated that a Crohn\u2019s disease (CD)-associated pathogen known as Mycobacterium avium paratuberculosis (MAP) decreases vitamin D activation in macrophages, thereby impeding cathelicidin production and MAP infection clearance. The mechanism by which MAP infection exerts these effects on the vitamin D metabolic axis remains elusive. Methods: We used two cell culture models of THP-1 macrophages and Caco-2 monolayers to establish the effects of MAP infection on the vitamin D metabolic axis. We also tested the effects of Calcifediol, Calcitriol, and SB203580 treatments on the relative expression of the vitamin D metabolic genes, oxidative stress biomarkers, and inflammatory cytokines profile. Results: In this study, we found that MAP infection interferes with vitamin D activation inside THP-1 macrophages by reducing levels of CYP27B1 and vitamin D receptor (VDR) gene expression via interaction with the TLR2-dependent p38\/MAPK pathway. MAP infection exerts its effects in a time-dependent manner, with the maximal inhibition observed at 24 h post-infection. We also demonstrated the necessity to have toll-like receptor 2 (TLR2) for MAP infection to influence CYP27B1 and CAMP expression, as TLR2 gene knockdown resulted in an average increase of 7.78 \u00b1 0.88 and 13.90 \u00b1 3.5 folds in their expression, respectively. MAP infection also clearly decreased the levels of p38 phosphorylation and showed dependency on the p38\/MAPK pathway to influence the expression of CYP27B1, VDR, and CAMP which was evident by the average fold increase of 1.93 \u00b1 0.28, 1.86 \u00b1 0.27, and 6.34 \u00b1 0.51 in their expression, respectively, following p38 antagonism. Finally, we showed that calcitriol treatment and p38\/MAPK blockade reduce cellular oxidative stress and inflammatory markers in Caco-2 monolayers following macrophage-mediated MAP infection. Conclusions: This study characterized the primary mechanism by which MAP infection leads to diminished levels of active vitamin D and cathelicidin in CD patients, which may explain the exacerbated vitamin D deficiency state in these cases.<\/jats:p>","DOI":"10.3390\/nu16091358","type":"journal-article","created":{"date-parts":[[2024,4,30]],"date-time":"2024-04-30T04:01:52Z","timestamp":1714449712000},"page":"1358","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":10,"title":["Mycobacterium avium paratuberculosis Infection Suppresses Vitamin D Activation and Cathelicidin Production in Macrophages through Modulation of the TLR2-Dependent p38\/MAPK-CYP27B1-VDR-CAMP Axis"],"prefix":"10.3390","volume":"16","author":[{"given":"Muna M.","family":"Talafha","sequence":"first","affiliation":[{"name":"Division of Molecular Microbiology, Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL 32816, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3740-6963","authenticated-orcid":false,"given":"Ahmad","family":"Qasem","sequence":"additional","affiliation":[{"name":"Division of Molecular Microbiology, Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL 32816, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9222-4527","authenticated-orcid":false,"given":"Saleh A.","family":"Naser","sequence":"additional","affiliation":[{"name":"Division of Molecular Microbiology, Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL 32816, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2024,4,30]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Giustina, A., and Bilezikian, J.P. 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