Mycopathologia 153: 125–128, 2001. © 2002 Kluwer Academic Publishers. Printed in the Netherlands.

125

Cell-associated collagenolytic activity by Candida albicans Masahiro Nishimura1,2, Hiroki Nikawa1 , Hirofumi Yamashiro1, Haruki Nishimura1, Taizo Hamada1 & Graham Embery2 1 Department

of Prosthetic Dentistry, Hiroshima University Faculty of Dentistry, 1-2-3 Kasumi Minami-ku, Hiroshima 734-8553, Japan; 2 Department of Basic Dental Science, Dental School, University of Wales College of Medicine, Heath Park, Cardiff, CF14 4XY, UK

Received 26 October 2000; accepted 5 October 2001

Abstract Cell associated collagenolytic activity of Candida albicans was quantified by measuring the degradation of synthetic peptide 2-furanacryloyl-Leu-Gly-Pro-Ala (FALGPA), which is a specific substrate for collagenase, by the freeze-thaw procedure method. This collagenolytic activity was enhanced by cells cultured in the presence of bovine serum albumin (BSA) in culture medium. However, this activity was inhibited in the presence of ethylenediaminetetraacetic acid disodium salt (EDTA-2Na), but not by the serine proteinase inhibitor p-amidinophenyl methanesulfonyl fluoride (APMSF), nor the aspartyl proteinase inhibitor pepstatin A. These results suggested the presence of a metalloenzyme on pericellular C. albicans. Key words: Candida albicans, collagenolytic activity, root caries

Introduction Candida species are frequently recovered from oral cavities, and these species of yeast, particularly C. albicans, are widely known to cause a range of oral infections, such as oral thrush and denture stomatitis [1, 2]. Several reports have also indicated a possible relationship between C. albicans and /or denture plaque, root caries, or periodontitis [3]. In this regard, Beighton et al. (1995) have reported the relatively high prevalence of Candida spp. (58.5%) from 82 root caries lesions (C. albicans; 54.9%) [4], and others have shown that the wearing of an over denture or partial denture is associated with a high risk of caries and progression of periodontal disease adjacent to the abutment teeth [5–9]. The aetiological role of C. albicans in relation to these conditions is, however, less well documented. It has been reported that the Candida spp. produce secreted aspartyl proteinases (SAPs), and these proteinases are routinely expressed in vitro in candidal cultures containing high molecular weight nitrogen * Published in 2002.

sources, such as bovine serum albumin (BSA) [10]. These proteinases have been proposed as one of the important virulence factors in oral infections [11, 12]. Kaminishi et al. (1986) previously reported a secreted proteinase produced by C. albicans that is capable of degrading dentinal collagen, and have suggested that this proteinase might be related to the progression of dentinal caries [13, 14]. However, little has been reported to investigate the collagenolytic activity of C. albicans. Although collagenolytic enzymes have usually been detected in culture supernatant fluids [13, 15, 16], detection of collagenase activity from culture supernatant fluid is difficult for strains producing low levels of collagenase. So we used the new method as reported by Jackson et al. [17]. Using this method, we investigated the enzyme on the surface of C. albicans.

126 Material and methods Materials The synthetic peptide FALGPA (F-5135), Clostridium histolyticum collagenase (C-6885) and pepstatin A (P-5318) were purchased from Sigma Chemical Co. (St. Louis, MO) p-amidinophenyl methanesulfonyl fluoride (APMSF) was purchased from Wako Pure Chemical Co. (Osaka, Japan). Candida albicans and culture conditions C. albicans ATCC MYA-273 (GDH16), IFO1385 and ATCC 90028 were used throughout the study. The GDH 16 was an oral isolate obtained from the routine microbiology services of the Glasgow Dental Hospital and School, and the IFO 1385 was purchased from the Institute for Fermentation, Osaka, Japan. The ATCC 90028 was a gift from Prof. L.P. Samaranayake, Oral Biology Unit, Hong Kong University School. All C. albicans strains were identified by a sugar assimilation test using the API 20C system (API Products, Biomerieux, Lyon, France), and the “germ-tube’ test. A loopful of each strain was inoculated in a yeast nitrogen base medium (Difco, Detroit, Mich., USA) containing 250 mM glucose and cultured aerobically at 37 ◦ C for 24 h. The C. albicans strains were harvested in their late exponential growth phase, washed twice with a yeast carbon base (YCB; Difco), and resuspended to a final concentration of 105 cells/ml in YCB (with 1mg/ml BSA or without BSA) using a haemocytometer. All cells observed were in the blastospore phase. The prepared inoculums were cultured in 5 ml YCB (±BSA) at 37 ◦ C and 5% CO2 for 48 h. Collagenolytic activity assay The FALGPA assay was performed as described by Jackson et al. [17]. Briefly, 5.0 ml of cultured medium of each isolate was centrifuged at 1,000 × g for 10 min at 25 ◦ C. The supernatant was removed, and the cells were washed three times in assay buffer (50 mM Tricine, 400 mM NaCl, 10 mM CaCl2 , 0.02% NaN3 , pH. 7.5, except for those with EDTA, in which the CaCl2 was omitted). The washed organisms were subjected to a freeze-thaw procedure by storage at −20 ◦ C for 24 h, and then thawed to 25 ◦ C before addition of the substrate solution (FALGPA, 500 µg/ml). FALGPA substrate was added to each sample, mixed with a vortex mixer, and incubated at 25 ◦ C for 24 h. After incubation, each sample was

centrifuged for 10 min at 10,000 × g, and supernatant fluid was transferred to a semi micro-cuvette. The absorbance of each sample was measured at OD345 using a spectrophotometer (V-530, JASCO Co. Tokyo). We defined, (the decrease of 1 OD345/109 cultured cells in 24 h) = 1 unit in this paper. Substrate solutions containing the inhibitors EDTA, APMSF and Pepstatin A without microorganisms were included as controls. Statistics Each experiment was carried out in triplicate. All data were subjected to the analysis of variance (ANOVA).

Results FALGPA hydrolysis by C. albicans Table 1 shows the results of FALGPA hydrolysis/ 109 cells at 24 h by the 3 species of C. albicans tested. The C. histolyticum collagenase used as a positive control showed a decrease in absorbance (OD345) of approximately 0.53, similar to the findings reported by Jackson et al. (1994) [18] (data not shown). Results show that ATCC MYA-273 and IFO-1385 grew in YCB (without BSA) hydrolyzed FALGPA for 4.47 and 5.81 units, respectively. However, ATCC 90028 hydrolyzed FALGPA grew at quite a low level (0.31 units). The addition of BSA (1 mg/ml) to the culture medium increased cell numbers for all species of C. albicans (data not shown). In spite of increased cell numbers, the addition of BSA in the culture medium further increased the collagenolytic activity per cell by IFO 1385 and ATCC 90028 (P < 0.01) to a significant degree. Inhibition of FALGPA hydrolysis by C. albicans Table 2 shows the results of inhibition assay of collagenolytic activity by ATCC MYA-273 cultured with BSA. No activity was detected following the addition of EDTA (final 10 mM), or after the cells were boiled. The addition of APMSF, a serine proteinase inhibitor (100 µM final concentration), or pepstatin A, an aspartyl proteinase inhibitor (10 µM final concentration), was not found to affect the extent of hydrolysis (P > 0.05).

127 Table 1. Cell associated collagenolytic activity of various spices of Candida albicans Candida species

BSA

Unitsa

ATCC MYA-273

− + − + − +

4.47 ± 0.49 3.48 ± 0.08 5.81 ± 3.04 13.98 ± 0.59∗ 0.31 ± 0.15 7.34 ± 0.56∗

IFO 1385 ATCC 90028

a 1 unit = collagenolytic activity of decreased

absorbance of FALGPA at OD345 for 24 h by 109 cultured cells. ∗ Significantly different from non BSA system (P < 0.01) by ANOVA. Table 2. Effect of boiling or inhibitors on the activity of cell associated collagenolytic activity of Candida albicans ATCC MYA-273 Protease inhibitor or boiling

Conc. Tested

% Residual activity

Control (no inhibitor) Boiling EDTA-2Na Pepstatin A APMSF

– – 10 mM 10 µM 100 µM

100 0 0 98.3∗ 83.2∗

∗ Not significantly different to control (P > 0.05) by ANOVA.

results revealed that C. albicans could produce a collagenolytic enzyme at the same levels as those from S. mutans. No hydrolytic activity was detected following the addition of EDTA or after boiling of the C. albicans cells. These results imply that the cell-associated collagenolytic enzyme of C. albicans is a kind of metalloenzyme, and is heat sensitive. The finding that pepstatin A did not inhibit the C. albicans FALGPA hydrolytic activity suggests that the cell-associated collagenolytic enzyme might be different from previously described SAPs [12, 20]. From the point of view of active pH, the optimum pH of SAPs is 2.2– 3.3 [20]; however, this hydrolytic activity was detected at pH 7.5, which also provides evidence that this collagenolytic enzyme is different from SAPs. The finding that APMSF did not inhibit hydrolytic activity suggests that this enzyme is not a serine proteinase. Further investigation of the influence of proteinase inhibitors might be needed to clarify these observations. It is tempting to speculate on the role of the C. albicans collagenolytic activity on the pathogenesis of oral disease such as oral thrush and denture stomatitis or dentin caries [3]. The detection of the cell-associated collagenolytic activity of C. albicans offers a further factor for describing the pathogenic potential.

Discussion

Acknowledgments

The findings of this study indicate that C. albicans possesses collagenolytic activity as defined by its ability to hydrolyze the specific synthetic peptide FALGPA. This peptide is a specific substrate for collagenase, and is not hydrolyzed with trypsin, thermolysin, elastase, papain, or carboxypeptidase A [19]. C. albicans has been shown to produce a specific group of enzymes termed secreted aspartyl proteinases (SAPs) [12, 20]. Although it was not intended to further study SAPs, the growth conditions established for these enzymes were used to study collagenolytic activity by C. albicans. The results confirm and extend some previous reports on this topic by Kaminishi et al. [13, 14]. In addition, the findings draw parallel results on the ability of a well-known oral microorganism, Streptococcus mutans, to degrade the FALGPA substrate [17, 18, 21], or Streptococcus mitis, Peptostreptocuccus productus, and Lactobacillus casei etc. to degrade gelatin (denatured collagen) [22]. Our

The authors would like to thank Dr. David Williams, Department of Oral Surgery, Medicine & Pathology, Dental School, Cardiff, for his helpful advice. This study was supported in part by grant-in-aid for scientific research 11671934 from the Ministry of Science, Education and Culture of Japan.

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15. Welton RL, Woods DR. Collagenase production by Achromobacter iophagus. Biochem Acta 1975; 384: 228–234. 16. Mäkinen KK, Mäkinen PL. Purification and properties of an extracellular collagenolytic protease produced by the human oral bacterium Bacillus cereus (Strain Soc 67). J Biol Chem 1987; 262: 12488–12495. 17. Jackson RJ, Dao ML, Lim DV. Modified FALGPA assay for cell-associated collagenolytic activity. J Microbiol Meth 1995; 21: 209–215. 18. Jackson RJ, Dao ML, Lim DV. Cell-associated collagenolytic activity by group B streptococci. Infect Immun 1994; 62: 5647–5651. 19. Van Wart HE, Steinbrink DR. A continuous spectrophotometric assay for Clostridium histolyticum collagenase. Anal Biochem 1981; 113: 356–365. 20. Hoegl L, Ollert M, Korting HC. The role of Candida albicans secreted aspartic proteinase in the development of candidoses. J Mol Med 1996; 74: 135–142. 21. Jackson RJ, Lim DV, Dao ML. Identification and analysis of a collagenolytic activity in Streptococcus mutans. Curr Microbiol 1997; 34: 49–54. 22. van Strijp AJ, van Steenbergen TJ, de Graaff J, ten Cate JM. Bacterial colonization and degradation of demineralized dentin matrix in situ. Caries Res 1994; 28: 21–27. Address for correspondence: Dr. Masahiro Nishimura, Department of Prosthetic Dentistry, Hiroshima University Faculty of Dentistry, 1-2-3 Kasumi Minami-Ku, Hiroshima, 734-8553, Japan Tel: +81 (0)82 257 5681; Fax: +81 (0)82 257 5684; E-mail: [email protected]