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Candida albicans ?-Glucan-Containing Particles Increase HO-1 Expression in Oral Keratinocytes via a Reactive Oxygen Species/p38 Mitogen-Activated Protein Kinase/Nrf2 Pathway.

ABSTRACT: Oral keratinocytes provide the first line of host defense against oral candidiasis. We speculated that interactions of fungal cell wall components with oral keratinocytes regulate the stress response against Candida infection and examined the expression of genes induced by heat-killed Candida albicans in oral immortalized keratinocytes using a cDNA microarray technique. Of 24,000 genes revealed by that analysis, we focused on HO-1, a stress-inducible gene, as its expression was increased by both heat-killed and live C. albicans In histological findings, HO-1 expression in the superficial layers of the oral epithelium following Candida infection was elevated compared to that in healthy epithelium. We then investigated fungal cell wall components involved in induction of HO-1 expression and found that ?-glucan-containing particles (?-GPs) increased its expression. Furthermore, ?-glucan was observed on the surface of both heat-killed C. albicans and Candida cells that had invaded the oral epithelium. Fungal ?-GPs also promoted induction of intracellular reactive oxygen species (ROS), NADPH oxidase activation, and p38 mitogen-activated protein kinase (MAPK) phosphorylation, while those specific inhibitors inhibited the HO-1 expression induced by fungal ?-GPs. Moreover, fungal ?-GPs induced Nrf2 translocation into nuclei via p38 MAPK signaling, while the HO-1 expression induced by fungal ?-GPs was inhibited by Nrf2-specific small interfering RNA (siRNA). Finally, knockdown of cells by HO-1- and Nrf2-specific siRNAs resulted in increased ?-GP-mediated ROS production compared to that in the control cells. Our results show that the HO-1 induced by fungal ?-GPs via ROS/p38 MAPK/Nrf2 from oral keratinocytes may have important roles in host defense against the stress caused by Candida infection in the oral epithelium.

SUBMITTER: Ishida Y

PROVIDER: S-EPMC5865035 | biostudies-literature | 2018 Apr

REPOSITORIES: biostudies-literature

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Candida albicans β-Glucan-Containing Particles Increase HO-1 Expression in Oral Keratinocytes via a Reactive Oxygen Species/p38 Mitogen-Activated Protein Kinase/Nrf2 Pathway.

Ishida Yoko Y Ohta Kouji K Naruse Takako T Kato Hiroki H Fukui Akiko A Shigeishi Hideo H Nishi Hiromi H Tobiume Kei K Takechi Masaaki M

Infection and immunity 20180322 4

Oral keratinocytes provide the first line of host defense against oral candidiasis. We speculated that interactions of fungal cell wall components with oral keratinocytes regulate the stress response against <i>Candida</i> infection and examined the expression of genes induced by heat-killed <i>Candida albicans</i> in oral immortalized keratinocytes using a cDNA microarray technique. Of 24,000 genes revealed by that analysis, we focused on HO-1, a stress-inducible gene, as its expression was inc ...[more]

PMID: 29311246

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Project description:Candida albicans is among the most prevalent opportunistic human fungal pathogens. The ability to mask the immunogenic polysaccharide ? (1,3)-glucan from immune detection via a layer of mannosylated proteins is a key virulence factor of C. albicans We previously reported that hyperactivation of the Cek1 mitogen-activated protein (MAP) kinase pathway promotes ? (1,3)-glucan exposure. In this communication, we report a novel upstream regulator of Cek1 activation and characterize the impact of Cek1 activity on fungal virulence. Lrg1 encodes a GTPase-activating protein (GAP) that has been suggested to inhibit the GTPase Rho1. We found that disruption of LRG1 causes Cek1 hyperactivation and ? (1,3)-glucan unmasking. However, when GTPase activation was measured for a panel of GTPases, the lrg1?? mutant exhibited increased activation of Cdc42 and Ras1 but not Rho1 or Rac1. Unmasking and Cek1 activation in the lrg1?? mutant can be blocked by inhibition of the Ste11 MAP kinase kinase kinase (MAPKKK), indicating that the lrg1?? mutant acts through the canonical Cek1 MAP kinase cascade. In order to determine how Cek1 hyperactivation specifically impacts virulence, a doxycycline-repressible hyperactive STE11?N467 allele was expressed in C. albicans In the absence of doxycycline, this allele overexpressed STE11?N467 , which induced production of proinflammatory tumor necrosis factor alpha (TNF-?) from murine macrophages. This in vitro phenotype correlates with decreased colonization and virulence in a mouse model of systemic infection. The mechanism by which Ste11?N467 causes unmasking was explored with RNA sequencing (RNA-Seq) analysis. Overexpression of Ste11?N467 caused upregulation of the Cph1 transcription factor and of a group of cell wall-modifying proteins which are predicted to impact cell wall architecture.IMPORTANCE Candida albicans is an important source of systemic infections in humans. The ability to mask the immunogenic cell wall polymer ? (1,3)-glucan from host immune surveillance contributes to fungal virulence. We previously reported that the hyperactivation of the Cek1 MAP kinase cascade promotes cell wall unmasking, thus increasing strain immunogenicity. In this study, we identified a novel regulator of the Cek1 pathway called Lrg1. Lrg1 is a predicted GTPase-activating protein (GAP) that represses Cek1 activity by downregulating the GTPase Cdc42 and its downstream MAPKKK, Ste11. Upregulation of Cek1 activity diminished fungal virulence in the mouse model of infection, and this correlates with increased cytokine responses from macrophages. We also analyzed the transcriptional profile determined during ? (1,3)-glucan exposure driven by Cek1 hyperactivation. Our report provides a model where Cek1 hyperactivation causes ? (1,3)-glucan exposure by upregulation of cell wall proteins and leads to more robust immune detection in vivo, promoting more effective clearance.

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Dataset Information

Candida albicans ?-Glucan-Containing Particles Increase HO-1 Expression in Oral Keratinocytes via a Reactive Oxygen Species/p38 Mitogen-Activated Protein Kinase/Nrf2 Pathway.

Publications

Candida albicans β-Glucan-Containing Particles Increase HO-1 Expression in Oral Keratinocytes via a Reactive Oxygen Species/p38 Mitogen-Activated Protein Kinase/Nrf2 Pathway.

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