Synergistic Effect of Fluconazole and Calcium Channel Blockers against Resistant Candida albicans

Abstract

Candidiasis has increased significantly recently that threatens patients with low immunity. However, the number of antifungal drugs on the market is limited in comparison to the number of available antibacterial drugs. This fact, coupled with the increased frequency of fungal resistance, makes it necessary to develop new therapeutic strategies. Combination drug therapy is one of the most widely used and effective strategy to alleviate this problem. In this paper, we were aimed to evaluate the combined antifungal effects of four CCBs (calcium channel blockers), amlodipine (AML), nifedipine (NIF), benidipine (BEN) and flunarizine (FNZ) with fluconazole against C. albicans by checkerboard and time-killing method. In addition, we determined gene (CCH1, MID1, CNA1, CNB1, YVC1, CDR1, CDR2 and MDR1) expression by quantitative PCR and investigated the efflux pump activity of resistant candida albicans by rhodamine 6G assay to reveal the potential mechanisms. Finally, we concluded that there was a synergy when fluconazole combined with the four tested CCBs against resistant strains, with fractional inhibitory concentration index (FICI) <0.5, but no interaction against sensitive strains (FICI = 0.56 ~ 2). The mechanism studies revealed that fluconazole plus amlodipine caused down-regulating of CNA1, CNB1 (encoding calcineurin) and YVC1 (encoding calcium channel protein in vacuole membrane).

Antihypertensive, Amlodipine Besilate Inhibits Growth and Biofilm of Human Fungal PathogenCandida

“…C. glabrata is naturally resistant to azoles due to the presence of less affinity to lanosterol 14 a-demethylase (Erg11p), inherent mechanism for the upregulation of ERG11 (for ergosterol biosynthesis) and ABC transporters (for increased drug efflux). 47 Our results are in agreement with the findings of Liu et al, 40 where it has been shown that AB alone is not much effective against the planktonic cells of C. albicans. 40 Another study has shown that CCH1 mutant of C. glabrata is more susceptible to the azole drugs.…”

“…47 Our results are in agreement with the findings of Liu et al, 40 where it has been shown that AB alone is not much effective against the planktonic cells of C. albicans. 40 Another study has shown that CCH1 mutant of C. glabrata is more susceptible to the azole drugs. 35 AB is a known inhibitor of Ca 2+ channel and has shown good affinity with C. glabrata Cch1p, Fig.…”

“…[36][37][38][39] A recent study has shown the antifungal properties of amlodipine, against C. albicans, in combination with fluconazole. 40 An in silico study has also exhibited the docking potential of AB against CgCch1. 41 In this report, we have documented the anti-Candida properties of a Ca 2+ channel blocker against two most prevalent Candida species, C. glabrata and C. albicans.…”

Endosomal Trafficking Defects Can Induce Calcium-Dependent Azole Tolerance in Candida albicans

“…Nonetheless, it is clear from our experiments that chemical inhibition of calcineurin is sufficient to abrogate the growth of the vps21⌬/⌬ mutant in the presence of fluconazole. Interestingly, Liu et al (42) showed that dihydropyridine treatment suppresses the fluconazole-induced expression of the two calcineurin subunits, sensitizing azole-resistant C. albicans isolates to fluconazole. Thus, the resensitization of the vps21⌬/⌬ mutant by nisoldipine is also consistent with the mutant's azole tolerance depending upon enhanced calcineurin-dependent responses.…”

Calcineurin in fungal virulence and drug resistance: Prospects for harnessing targeted inhibition of calcineurin for an antifungal therapeutic approach

“…10,12 For example, combinations of calcium and calcineurin inhibitors with known antifungal compounds have been shown to inhibit the growth of drug resistant fungal strains. [13][14][15][16][17][18][19] Therefore, inhibition of calcineurin signaling is a novel antifungal strategy that both attenuates fungal virulence and increases the efficacy of the existing antifungals with concomitant suppression of antifungal resistance. 10,20,21 Calcineurin is a conserved Ca 2C -calmodulin (CaM) activated protein phosphatase 2B belonging to the phospho-protein phosphatase family of enzymes and is involved in calcium-dependent signaling and regulation of several important cellular processes in both yeasts and filamentous fungi (Fig.…”