Altered expression profile of mycobacterial surface glycopeptidolipids following treatment with the antifungal azole inhibitors econazole and clotrimazole

Abstract

The azole antifungal drugs econazole and clotrimazole are known cytochrome P450 enzyme inhibitors. This study shows that these drugs are potent inhibitors of mycobacterial growth and are more effective against Mycobacterium smegmatis than isoniazid and ethionamide, two established anti-mycobacterial drugs. Several non-tuberculous mycobacteria, including the pathogenic members of the Mycobacterium avium-intracellulare complex (MAC) and the fast-growing saprophytic organism M. smegmatis, produce an array of serovar-specific (ss) and non-serovar-specific (ns) glycopeptidolipids (GPLs). GPL biosynthesis has been investigated for several years but has still not been fully elucidated. The authors demonstrate here that econazole and clotrimazole inhibit GPL biosynthesis in M. smegmatis. In particular, clotrimazole inhibits all four types of nsGPLs found in M. smegmatis, suggesting an early and common target within their biosynthetic pathway. Altogether, the data suggest that an azole-specific target, most likely a cytochrome P450, may be involved in the hydroxylation of the N-acyl chain in GPL biosynthesis. Azole antifungal drugs and potential derivatives could represent an interesting new range of anti-mycobacterial drugs, especially against opportunistic human pathogens including MAC, M. scrofulaceum, M. peregrinum, M. chelonae and M. abscessus. INTRODUCTIONThe genus Mycobacterium includes the important human pathogens Mycobacterium tuberculosis and Mycobacterium leprae, which are responsible for tuberculosis and leprosy respectively. Pathogenic mycobacteria produce an array of unusual lipophilic compounds that are required for growth and survival of the organism in the human host (Karakousis et al., 2004). The use of refined analytical techniques coupled with structural characterization has continued to provide detailed structural knowledge on the species-and serotypespecific glycolipids of the genus Mycobacterium (Khoo et al., 1996a;Mederos et al., 1998;Nishiuchi et al., 2004). These highly diverse glycosylated surface antigens have been broadly classified into three major families: the phenolic glycolipids (PGLs), the trehalose-containing lipooligosaccharides (LOSs) and the glycopeptidolipids (GPLs) (Brennan & Nikaido, 1995;Vergne & Daffé, 1998).PGLs were discovered some years ago in pathogenic mycobacteria, such as Mycobacterium bovis (Chatterjee et al., 1989;Daffé et al., 1987), Mycobacterium kansasii Riviere et al., 1987) and Mycobacterium marinum (Navalkar et al., 1965; Sarda & GastambideOdier, 1967). PGLs all possess similar aglycon structures, mainly formed from polymethyl-branched fatty (mycocersoic) acids esterified to a diol (phenolphthiocerol A) unit. However, their oligosaccharide units, and hence their inherent antigenicity, are species-specific (Brennan, 1988;Daffé, 1989;Dobson et al., 1990;Minnikin, 1982). The identification of a PGL as a species-specific antigen of the leprosy bacillus renewed interest in this molecule as a potential antigen for serodiagnosis (Hunter et al., 1982). LOSs were first d...

Characterization of Active Site Structure in CYP121: A Cytochrome P450 Essential for Viability of Mycobacterium Tuberculosis H37Rv*

“…In M. smegmatis, econazole and clotrimazole inhibited synthesis of glycopeptidolipids, a major component of the bacterial outer layer (40). Although CYP121 is refractory to optical change upon interaction with a variety of lipids and steroids, we have been able to demonstrate binding interactions between CYP121 and crudely fractionated lipids from Mtb (ongoing studies).…”

Modifying Culture Conditions in Chemical Library Screening Identifies Alternative Inhibitors of Mycobacteria

“…A number of these compounds, e.g., calcimycin, demeclocycline, doxycycline, lomefloxacin, minocycline, ofloxacin, and vancomycin, are known antibacterials, and therefore, activity against mycobacteria was not unexpected. In (6,22). From our review of the literature, antimycobacterial activity has not been previously reported for the remaining compounds, calmidazolium, diphenyleneiodonium, idarubicin, and methoctramine.…”

Cloning and Characterization of CYP51 from Mycobacterium avium

“…Econazole was found to be bactericidal for M. smegmatis grown in culture. Additionally, a recent study showed that the biosynthesis of M. smegmatis glycopeptidolipids is inhibited with econazole and clotrimazole treatment, and that both azoles inhibited M. smegmatis growth with MIC values of 2 and 0.5 g/ml, respectively; the authors speculate that inhibition of the CYP51 from M. smegmatis is involved in the biosynthesis of glycopeptidolipids (42).…”