Immunomodulatory effects of atorvastatin on peripheral blood mononuclear cells infected with Mycobacterium tuberculosis

Solima Sabeel^1,2,3Bongani Motaung^1,2Mumin Ozturk^1,2Trevor S Mafu¹Robert Wilkinson^4,5Friedrich Thienemann^6,7,8*Reto Guler^1,2,9*

• ¹Department of Pathology, Division of Immunology, Institute of Infectious Diseases and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, Western Cape, South Africa
• ²Cape Town Component, International Centre for Genetic Engineering and Biotechnology (ICGEB), Cape Town, South Africa
• ³Division of Experimental Medicine, Department of Medicine, Zuckerberg San Francisco General Hospital, University of California, San Francisco, United States
• ⁴Faculty of Health Sciences, Wellcome Centre for Infectious Diseases Research in Africa, Institute of Infectious Disease and Molecular Medicine, University of Cape Town, Cape Town, Western Cape, South Africa
• ⁵NW1 1AT, The Francis Crick Institute, London, England, United Kingdom
• ⁶General Medicine & Global Health (GMGH), Department of Medicine and Cape Heart Institute, Faculty of Health Science, University of Cape Town, Cape Town, South Africa
• ⁷Department of Internal Medicine, University Hospital Zürich, University of Zürich, Zürich, Switzerland
• ⁸Cape Universities Body Imaging Centre, University of Cape Town, Cape Town, South Africa
• ⁹Wellcome Centre for Infectious Diseases Research in Africa, Institute of Infectious Disease and Molecular Medicine, University of Cape Town, Cape Town, Western Cape, South Africa

Background: Tuberculosis (TB) remains a major global health threat, contributing substantially to high morbidity and mortality rates. This underscores the urgent need for more effective interventions. Recent studies highlight the potential of host-directed therapy approaches to enhance immune defences against TB. Atorvastatin, recognized for both its lipid-lowering properties and its immunomodulatory effects, has emerged as a compelling candidate for host-directed therapy against TB. Here, we investigated the ex vivo efficacy of atorvastatin in inducing immunomodulatory activities (phagosome maturation, autophagy, and apoptosis) and enhancing the mycobacterial killing capacity in Mycobacterium tuberculosis (Mtb)-infected peripheral blood mononuclear cells (PBMCs).Method: Blood samples from healthy donors were collected for PBMC isolation. PBMCs were then treated overnight with or without atorvastatin, followed by infection with Mtb strains (H37Rv, HN878, and CDC1551) to evaluate intracellular mycobacterial growth by colony-forming units enumeration. Furthermore, co-localization of late endosomal marker (Rab-7), lysosomal markers (Cathepsin-D and LAMP-3), and autophagy marker (LC3B) with GFP-Mtb was investigated in infected PBMCs using laser scanning confocal microscopy. Moreover, multiple apoptotic assays were performed, including the TUNEL assay for DNA fragmentation, quantification of caspase-3 activity, and the expression levels of the pro-apoptotic gene (Bax) and anti-apoptotic gene (Bcl2).Results: Treatment with atorvastatin significantly reduced intracellular mycobacterial replication compared to untreated controls in Mtb-infected PBMCs. Moreover, atorvastatin enhanced colocalization between Mtb and late endosomal marker (Rab-7), lysosomal markers (Cathepsin-D and LAMP-3), and autophagy marker (LC3B) in Mtb-infected PBMCs. Furthermore, atorvastatin robustly promoted apoptosis in Mtb-infected PBMCs, as demonstrated by TUNEL assay and caspase-3 activation.Our findings highlight atorvastatin's potential as a crucial modulator of the immune response in Mtb-infected PBMCs, supporting its role in host-directed therapy.