Investigation of wild-type and mycolactone-negative mutantMycobacterium ulceranson skeletal muscle: IGF-1 protects against mycolactone-induced muscle catabolism

Abstract

Dufresne SS, Frenette J. Investigation of wild-type and mycolactone-negative mutant Mycobacterium ulcerans on skeletal muscle: IGF-1 protects against mycolactone-induced muscle catabolism. Buruli ulcer (BU), which is caused by Mycobacterium ulcerans (MU), is an endemic and neglected tropical disease that affects mostly subcutaneous tissues. Skeletal muscle under infected skin is also subject to serious dysfunctions and contractures. The goal of this study was to investigate the effects of an infection with the wild-type M. ulcerans (WT-MU) or the mycolactone-negative Mycobacterium ulcerans (M neg -MU) mutant strains on myotubes or fully differentiated skeletal muscles. WT-MU infection decreased by 22% and 29% the maximal muscle force at days 7 and 42 postinfection, respectively, while M neg -MU induced no decrease at day 7 postinfection and a small but significant 13% decrease in muscle force at day 42. A 13.2-fold and 4.3-fold increase in neutrophil and macrophage concentrations, respectively, was observed on day 42 following the injection of WT-MU. However, the increases in neutrophil and macrophage concentrations were 2.4-fold and 5.5-fold in M neg -MU. Myoblast proliferation decreased by 20%, myotube diameter by 45%, MyHC levels by 32%, while MuRF-1 levels increased by 22.8% when C2C12 cells and WT-MU were cocultured for 48 h at a multiplicity of infection of 5:1. In contrast, M neg -MU had no significant effect. Interestingly, the addition of 1,000 ng/ml of IGF-1 to the WT-MU/C2C12 coculture significantly improved all of these biological parameters. The present investigation clearly established that muscle dysfunction and chronic inflammation in the presence of WT-MU are largely caused by the release of mycolactone, and the addition of recombinant IGF-1 was sufficient to alleviate some of the antiproliferative and atrophic effects of mycolactone.Buruli ulcer; insulin-like growth factor-1; muscle dysfunction; Mycobacterium ulcerans; mycolactone BURULI ULCER (BU), WHICH IS caused by Mycobacterium ulcerans (MU) infections, is a disease of wet tropical and subtropical zones and is closely related to tuberculosis and leprosy (38,47). It is widely distributed in more than 30 countries, and the rate of morbidity may surpass tuberculosis and leprosy in some endemic regions of Africa (2,49). Each year, between 5,000 and 6,000 new cases of BU are reported, and more than 50% of whom are children under 15 years of age (10, 50). Recent animal studies have shown that the BU spreads well beyond the skin and significantly affects the underlying tissues, including skeletal muscles. (25-28).Mycolactone, a macrolide toxin with highly destructive capacities, is the deleterious agent of MU. It can cause skin necrosis, cell cycle arrest, immunosuppression, cell death by apoptosis, and necrosis (19,23,36,48). Mycolactone-negative MU mutants are reportedly nonvirulent and noncytotoxic for subcutaneous tissues and leukocytes (1,8,36). Mycolactone diffuses passively through infected tissues and can rapidly penetrate cells. It enters ...

Muscle RANK is a key regulator of Ca2+ storage, SERCA activity, and function of fast-twitch skeletal muscles

“…Protein bands were revealed using the ECL-Plus chemiluminescent detection system (Perkin-Elmer). Films (Denville Scientific) were used to detect a chemiluminescent signal, scanned, and analyzed using Quantity One software (version 4.6.6; Bio-Rad) (10).…”

Contaminated open fracture and crush injury: a murine model

“…38 Despite these studies examining the effects of sepsis on systemic muscle wasting, little has been published on the local effects of infection on muscle. 39 …”

Buruli Ulcer in Animals and Experimental Infection Models

“…Again, preferences appear to be present in different laboratories, probably mostly dependent on which strains were available to the laboratory at some point in time and which strains could be maintained without loss of virulence. As repeated passage by in vitro culture prompts some of the M. ulcerans strains to lose their virulence plasmid [47,48], some laboratories opted to passage their strains trough mouse foot pads in order to preserve their virulence [49][50][51]. Alternatively, low passage primary isolates have been used for productive infection of mice [52].…”

“…It was originally obtained from a Malaysian BU patient in the 1960s and produces mycolactone A/B like the African isolates [55,56]. A spontaneous mycolactone negative mutant derived from this strain [47] has been used as avirulent M. ulcerans strain in the mouse model. S1013 was originally isolated in 2010 from a swab taken from the undermined edges of the ulcerative lesion of a Cameroonian BU patient [57].…”