Pathogenic mycobacteria achieve cellular persistence by inhibiting the Niemann-Pick Type C disease cellular pathway

Abstract

Background. Tuberculosis remains a major global health concern. The ability to prevent phagosome-lysosome fusion is a key mechanism by which intracellular mycobacteria, including Mycobacterium tuberculosis, achieve long-term persistence within host cells. The mechanisms underpinning this key intracellular pro-survival strategy remain incompletely understood. Host macrophages infected with persistent mycobacteria share phenotypic similarities with cells taken from patients suffering from Niemann-Pick Disease Type C (NPC), a rare lysosomal storage disease in which endocytic trafficking defects and lipid accumulation within the lysosome lead to cell dysfunction and cell death. We investigated whether these shared phenotypes reflected an underlying mechanistic connection between mycobacterial intracellular persistence and the host cell pathway dysfunctional in NPC. Methods. The induction of NPC phenotypes in macrophages from wild-type mice or obtained from healthy human donors was assessed via infection with mycobacteria and subsequent measurement of lipid levels and intracellular calcium homeostasis. The effect of NPC therapeutics on intracellular mycobacterial load was also assessed. Results. Macrophages infected with persistent intracellular mycobacteria phenocopied NPC cells, exhibiting accumulation of multiple lipid types, reduced lysosomal Ca2+ levels, and defects in intracellular trafficking. These NPC phenotypes could also be induced using only lipids/glycomycolates from the mycobacterial cell wall. These data suggest that persistent intracellular mycobacteria inhibit the NPC pathway, likely via inhibition of the NPC1 protein, and subsequently induce altered acidic store Ca2+ homeostasis. Reduced lysosomal calcium levels may provide a mechanistic explanation for the reduced levels of phagosome-lysosome fusion in mycobacterial infection. Treatments capable of correcting defects in NPC mutant cells via modulation of host cell calcium were of benefit in promoting clearance of mycobacteria from infected host cells. Conclusion. These findings provide a novel mechanistic explanation for mycobacterial intracellular persistence, and suggest that targeting interactions between the mycobacteria and host cell pathways may provide a novel avenue for development of anti-TB therapies.

Effects of curcumin nanoformulations on cellular function in Niemann-Pick disease type C astrocytes

“…In conclusion, as NPC1 is a lipid storage disease the use of a lipidated vehicle may not be the best approach due to the possibility that the additional lipid load could alter metabolism or endocytosis and lead to further lipid storage as we have observed. Based on our evidence 2 , from this report and from others 13,14,28,29 it is perhaps the least modified forms of curcumin that appear to have the greatest benefit for NPC1 disease both in vitro and in vivo.…”

“…Unformulated curcumin has been shown to be able to ameliorate NPC disease in five separate studies 2,13,14,28,29 , whilst curcumin formulated into a lipidated vector has been shown to have little to no benefit 13 . The aim of the present study was therefore to determine whether formulated lipidated curcumin could mediate any benefit in NPC1 disease cells.…”

“…A surprising result of our work is that although all of the nanoformulations of curcumin could modulate intracellular Ca 2+ , very few actually had an impact on NPC disease lysosomal lipid storage. As unformulated curcumin has been shown in several studies to be effective 2,14,28,29 , we hypothesised that this was due in some way to the properties of the lipid carrier. Although SLN A appears to have a small benefit on some components of NPC1 lysosomal storage, no effect is seen with CGM, whilst treatment with SLN M and SLN L led to an elevation in lysosomal storage.…”

The Lysosome: A Potential Therapeutic Juncture between the COVID-19 Pandemic and Niemann-Pick Type C Disease

“…Specifically, azithromycin has been shown to block the acidification of the phagosomes containing mycobacteria, allowing the latter to escape the phagosome and multiply uncontrollably [58]. However, unlike mycobacteria, which require intact lysosomal function for containment of the infection [59,60], SARS-CoV-2, as discussed earlier, relies on an intact lysosomal function for complete entry and fusion. Thus, it is reasonable to expect that azithromycin would show efficacy against COVID-19, through a similar mechanism to chloroquinethat is, disrupting the function of lysosomal proteases.…”

Investigation of the mycobacterial enzyme HsaD as a potential novel target for anti‐tubercular agents using a fragment‐based drug design approach

“…Cholesterol has been identified as important in the infection process of M. tuberculosis (Peyron et al, ; Ouellet et al, ; Crowe et al, ; Lovewell et al, ; Fineran et al ., ) and is used as a carbon source during survival within macrophages (Van der Geize et al, ; Pandey and Sassetti, ; Rohde et al, ). In previous work, we demonstrated that an operon consisting of hsaA (Rv3567), hsaB (Rv3570), hsaC (Rv3568), hsaD (Rv3569) (Van der Geize et al, ) is involved in cholesterol metabolism.…”