Synthetic arylquinuclidine derivatives exhibit antifungal activity against Candida albicans, Candida tropicalis and Candida parapsilopsis.
BACKGROUND
Sterol biosynthesis is an essential pathway for fungal survival, and is the biochemical target of many antifungal agents. The antifungal drugs most widely used to treated fungal infections are compounds that inhibit cytochrome P450-dependent C14α-demethylase (CYP51), but other enzymes of this pathway, such as squalene synthase (SQS) which catalyses the first committed step in sterol biosynthesis, could be viable targets. The aim of this study was to evaluate the antifungal activity of SQS inhibitors on Candida albicans, Candida tropicalis and Candida parapsilopsis strains.


METHODS
Ten arylquinuclidines that act as SQS inhibitors were tested as antiproliferative agents against three ATCC strains and 54 clinical isolates of Candida albicans, Candida tropicalis and Candida parapsilopsis. Also, the morphological alterations induced in the yeasts by the experimental compounds were evaluated by fluorescence and transmission electron microscopy.


RESULTS
The most potent arylquinuclidine derivative (3-[1'-{4'-(benzyloxy)-phenyl}]-quinuclidine-2-ene) (WSP1267) had a MIC50 of 2 μg/ml for all species tested and MIC90 varying from 4 μg/ml to 8 μg/ml. Ultrathin sections of C. albicans treated with 1 μg/ml of WSP1267 showed several ultrastructural alterations, including (a) loss of cell wall integrity, (b) detachment of the plasma membrane from the fungal cell wall, (c) accumulation of small vesicles in the periplasmic region, (d) presence of large electron-dense vacuoles and (e) significantly increased cell size and cell wall thickness. In addition, fluorescence microscopy of cells labelled with Nile Red showed an accumulation of lipid droplets in the cytoplasm of treated yeasts. Nuclear staining with DAPI revealed the appearance of uncommon yeast buds without a nucleus or with two nuclei.


CONCLUSIONS
Taken together, our data demonstrate that arylquinuclidine derivatives could be useful as lead compounds for the rational synthesis of new antifungal drugs.
Laboratório de Biologia Celular de Fungos, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Avenida Carlos Chagas Filho 373, Bloco C, Sala C0-026, Cidade Universitária, 21,941-902, Rio de Janeiro/RJ, Brazil.
Kelly
K
Ishida
Juliany Cola
JC
Fernandes Rodrigues
Simon
S
Cammerer
Julio A
JA
Urbina
Ian
I
Gilbert
Wanderley
W
de Souza
Sonia
S
Rozental
D000935:Antifungal Agents / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D002175:Candida / Q000187:drug effects* / Q000201:enzymology; D002176:Candida albicans / Q000187:drug effects / Q000201:enzymology; D041022:Candida tropicalis / Q000187:drug effects / Q000201:enzymology; D002177:Candidiasis / Q000188:drug therapy* / Q000382:microbiology; D004791:Enzyme Inhibitors / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D013186:Farnesyl-Diphosphate Farnesyltransferase / Q000037:antagonists & inhibitors; D005656:Fungal Proteins / Q000037:antagonists & inhibitors; D006801:Humans; D008826:Microbial Sensitivity Tests; D011812:Quinuclidines / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*
D000935:Antifungal Agents; D004791:Enzyme Inhibitors; D005656:Fungal Proteins; D011812:Quinuclidines; D013186:Farnesyl-Diphosphate Farnesyltransferase
Microbiol Res. 2008;163(5):579-85
16962755
Proc Natl Acad Sci U S A. 1993 Jan 1;90(1):80-4
8419946
Biochem Pharmacol. 1996 Jun 14;51(11):1477-87
8630089
Antimicrob Agents Chemother. 1997 Apr;41(4):850-2
9087504
Proc Am Thorac Soc. 2006;3(1):35-40
16493149
FEMS Microbiol Lett. 2006 Feb;255(1):33-42
16436059
Antimicrob Agents Chemother. 2004 Jul;48(7):2379-87
15215084
Proc Natl Acad Sci U S A. 1991 Jul 15;88(14):6038-42
2068081
J Clin Microbiol. 2005 Apr;43(4):1829-35
15815004
J Ethnopharmacol. 1999 Aug;66(2):141-50
10433470
Proc Natl Acad Sci U S A. 1987 Jun;84(12):4012-6
2438691
Trends Microbiol. 2003 Jun;11(6):272-9
12823944
Exp Parasitol. 2005 Dec;111(4):230-8
16198340
Antimicrob Agents Chemother. 2007 Nov;51(11):4049-61
17709461
BMC Microbiol. 2009 Apr 20;9:74
19379501
Rev Infect Dis. 1987 Jan-Feb;9 Suppl 1:S33-42
3027844
Protist. 2007 Oct;158(4):447-56
17719843
Bioorg Med Chem. 2005 May 16;13(10):3519-29
15848765
Mycoses. 2006 May;49(3):220-5
16681814
J Biol Chem. 1988 Jan 25;263(3):1301-6
3335546
Antimicrob Agents Chemother. 2003 Oct;47(10):3149-54
14506023
Antimicrob Agents Chemother. 1997 Aug;41(8):1840-2
9257776
J Antimicrob Chemother. 1999 Jul;44(1):109-12
10459817
Clin Microbiol Rev. 2004 Apr;17(2):268-80
15084501
Antimicrob Agents Chemother. 2008 Nov;52(11):4098-114
18765694
Mol Biochem Parasitol. 2002 Nov-Dec;125(1-2):35-45
12467972
Mini Rev Med Chem. 2007 Sep;7(9):900-11
17897080
Interdiscip Perspect Infect Dis. 2009;2009:642502
19680554
Lancet Infect Dis. 2002 Sep;2(9):550-63
12206971
J Med Chem. 1996 Jul 19;39(15):2971-9
8709131
J Lipid Res. 2003 Jan;44(1):128-35
12518031
Curr Pharm Des. 2009;15(27):3167-78
19754389
FEMS Microbiol Lett. 2000 Feb 1;183(1):89-94
10650207
J Antimicrob Chemother. 2006 Jul;58(1):59-65
16702175
J Clin Microbiol. 2006 Aug;44(8):2816-23
16891497