The effects of lipid extraction on the immunomodulatory activity of Malassezia species in vitro

Abstract

Malassezia spp. are believed to be the causative agents of pityriasis versicolor and are strongly implicated in seborrhoeic dermatitis. The yeast also forms part of the normal human cutaneous microflora. We have previously shown that when Malassezia yeast cells are incubated with human peripheral blood mononuclear cells (PBMCs), they are capable of reducing the levels of pro-inflammatory cytokines produced. In order to test the hypothesis that this immunoevasive phenomenon may be related to the unusually high level of lipid in the Malassezia yeast cell wall, we have compared the immunomodulatory capacity of normal and lipid-depleted yeast cells. Stationary phase yeast cells of Malassezia sympodialis, M. globosa and M. restricta were treated with chloroform/methanol to extract the surface lipids. The lipid-depleted and non-depleted yeast cells were then co-cultured with human PBMCs from three different human donors at a ratio of 20 yeasts per leukocyte for 24 h. The levels of interleukin (IL)-1beta, IL-6 and tumour necrosis factor (TNF)-alpha were then determined by enzyme-linked immunosorbent assay (ELISA). The results demonstrated that extraction of lipid reversed the yeast cell capacity to reduce the levels of pro-inflammatory cytokines. The levels of IL-1beta, IL-6 and TNF-alpha produced in response to lipid-extracted Malassezia of all three species were either no different from or significantly greater (P < 0.05; ANOVA) than the constitutive control levels. These results suggest that the lipid microfibrillar layer of Malassezia may prevent the yeast cells from inducing inflammation and provide an explanation for the normal commensal status of the organism on human skin. The hypothesis that the lipid layer is absent or altered in seborrhoeic dermatitis may provide an explanation for the inflammatory nature of this dermatosis.

The Effect of Detergents on the Morphology and Immunomodulatory Activity ofMalassezia furfur

“…Kesavan et al 6 have examined the effect of the Malassezia species with and without the capsular layer on the cytokine production by monocytes. As a result, the levels of IL-1α, IL-6 and TNF-α production were lower in the Malassezia with the capsular layer, suggesting that the capsule suppresses the release of proinflammatory cytokine and it prevents an inflammatory response 7 . Moreover, Oh et al 9 revealed that when M. furfur lipids were removed from the cell wall, the capacity to activate primary human monocytes was restored, and this was correlated with the induction of proinflammatory cytokine production via a TLR2-dependent mechanism.…”

“…Malassezia is also capable of downregulating the immune system 7,19 . When various preparations of Malassezia were co-incubated with monocytes, the levels of IL-1β released by the monocytes were significantly lower than those of the negative control 17 .…”

“…This apparent contradictory behavior may be related to the lipid-rich capsule-like layer that surrounds the yeast cells. Removal of the capsule-like layer reverses the suppression of cytokine production by monocytes 7 . Kesavan et al 6 have examined the effect of the Malassezia species with and without the capsular layer on the cytokine production by monocytes.…”

“…It has been reported that Malassezia is capable of suppressing cytokine release and downregulating the phagocytic function of monocytes. Moreover, lipid-extracted M. furfur was shown to produce high levels of TNF-α, IL-6 and IL-1β in monocytes 7,8 , and it induced proinflammatory cytokine production via a TLR2-dependent mechanism 9 . It could be inferred that the detergents in shampoo and soap alter the composition of the lipid in the cell wall of M. furfur, and this may have some role in Malassezia-associated inflammatory dermatoses.…”

Secreted lipases from Malassezia globosa: recombinant expression and determination of their substrate specificities

“…However, other studies showed reduced free fatty acid levels in dandruff sufferers (Harding et al, 2002;Rogers et al, 2003), contradicting this hypothesis. While, the role of lipid cycling in the aetiology of dandruff is still obscure, the lipid microfillar layer of Malassezia cells has been shown to down-regulate the inflammatory immune response, implying once more that the lipid dependency of the fungus might have a role in its virulence (Kesavan et al, 2000).…”