The intraspecies diversity of C. albicans triggers qualitatively and temporally distinct host responses that determine the balance between commensalism and pathogenicity.

The host immune status is critical for preventing opportunistic infections with Candida albicans. Whether the natural fungal diversity that exists between C. albicans isolates also influences disease development remains unclear. Here, we used an experimental model of oral infection to probe the host response to diverse C. albicans isolates in vivo and found dramatic differences in their ability to persist in the oral mucosa, which inversely correlated with the degree and kinetics of immune activation in the host. Strikingly, the requirement of interleukin (IL)-17 signaling for fungal control was conserved between isolates, including isolates with delayed induction of IL-17. This underscores the relevance of IL-17 immunity in mucosal defense against C. albicans. In contrast, the accumulation of neutrophils and induction of inflammation in the infected tissue was strictly strain dependent. The dichotomy of the inflammatory neutrophil response was linked to the capacity of fungal strains to cause cellular damage and release of alarmins from the epithelium. The epithelium thus translates differences in the fungus into qualitatively distinct host responses. Altogether, this study provides a comprehensive understanding of the antifungal response in the oral mucosa and demonstrates the relevance of evaluating intraspecies differences for the outcome of fungal-host interactions in vivo.

Modulating human proteinase activated receptor 2 with a novel antagonist (GB88) and agonist (GB110).

BACKGROUND AND PURPOSE: Many cells express proteinase activated receptor 2 (PAR2) on their plasma membrane. PAR2 is activated by proteolytic enzymes, such as trypsin and tryptase that cleave the receptor N-terminus, inititating signalling to intracellular G proteins. Studies on PAR2 have relied heavily upon activating effects of proteases and peptide agonists that lack stability and bioavailability in vivo. EXPERIMENTAL APPROACH: A novel small molecule agonist GB110 and an antagonist GB88 were characterized in vitro against trypsin, peptide agonists, PAR2 antibody, PAR1 agonists and flow cytometry,in seven cell lines using intracellular Ca(2+) mobilization and examined in vivo against PAR2- and PAR1-induced rat paw oedema. KEY RESULTS: GB110 is a potent non-peptidic agonist activating PAR2-mediated Ca(2+) release in HT29 cells (EC(50) ∼200 nM) and six other human cell lines, inducing PAR2 internalization. GB88 is a unique PAR2 antagonist, inhibiting PAR2 activated Ca(2+) release (IC(50) ∼2 µM) induced by native (trypsin) or synthetic peptide and non-peptide agonists. GB88 was a competitive and surmountable antagonist of agonist 2f-LIGRLO-NH(2), a competitive but insurmountable antagonist of agonist GB110, and a non-competitive insurmountable antagonist of trypsin. GB88 was orally active and anti-inflammatory in vivo, inhibiting acute rat paw oedema elicited by agonist GB110 and proteolytic or peptide agonists of PAR2 but not by corresponding agonists of PAR1 or PAR4. CONCLUSIONS AND IMPLICATIONS: The novel PAR2 agonist and antagonist modulate intracellular Ca(2+) and rat paw oedema, providing novel molecular tools for examining PAR2-mediated diseases.

Histone deacetylase inhibitors and periodontal bone loss.

BACKGROUND AND OBJECTIVE: Bone loss caused by enhanced osteoclast activity is a significant feature of periodontitis. Histone deacetylase inhibitors (HDACi) can suppress osteoclast-mediated bone loss in vitro and in vivo. This study investigated whether HDACi can suppress bone loss in experimental periodontitis. MATERIAL AND METHODS: Experimental periodontitis was induced in mice by oral inoculation with Porphyromonas gingivalis bacteria. Mice were treated orally with olive oil alone, with olive oil and a novel compound - 1179.4b - which targets both Class I and Class II histone deacetylases (HDACs) or with olive oil and MS-275, which targets Class I HDACs. Micro-computed tomography scans of live mice, stereo imaging and histological analyses were used to detect changes in bone. RESULTS: In the absence of treatment there was a 13.2% increase in bone volume in controls compared with a 7.4% decrease in P. gingivalis-inoculated mice. 1179.4b significantly reduced bone loss, with a 3.4% increase in bone volume (p < 0.01). MS-275 did not have a significant effect on P. gingivalis-induced bone loss. Histological analysis revealed that 1179.4b reduced bone loss despite having no effect on inflammation. CONCLUSION: HDACi were found to effectively suppress bone loss in the mouse model of periodontitis. 1179.4b - the inhibitor of Class I and Class II HDACs - was more effective at suppressing bone loss than MS-275, which targets Class I HDACs only. These compounds may therefore have the potential to be used for the management of periodontitis.

Inhibitors of histone deacetylases in class I and class II suppress human osteoclasts in vitro.

Histone deacetylase inhibitors (HDACi) suppress cancer cell growth, inflammation, and bone resorption. The aim of this study was to determine the effect of inhibitors of different HDAC classes on human osteoclast activity in vitro. Human osteoclasts generated from blood mononuclear cells stimulated with receptor activator of nuclear factor kappa B (RANK) ligand were treated with a novel compound targeting classes I and II HDACs (1179.4b), MS-275 (targets class I HDACs), 2664.12 (targets class II HDACs), or suberoylanilide hydroxamic acid (SAHA; targets classes I and II HDACs). Osteoclast differentiation was assessed by expression of tartrate resistant acid phosphatase and resorption of dentine. Expression of mRNA encoding for osteoclast genes including RANK, calcitonin receptor (CTR), c-Fos, tumur necrosis factor (TNF) receptor associated factor (TRAF)6, nuclear factor of activated T cells (NFATc1), interferon-ß, TNF-like weak inducer of apoptosis (TWEAK), and osteoclast-associated receptor (OSCAR) were assessed. Expression of HDACs 1-10 during osteoclast development was also assessed. 1179.4b significantly reduced osteoclast activity (IC(50) < 0.16 nM). MS-275 (IC(50) 54.4 nM) and 2664.12 (IC(50) > 100 nM) were markedly less effective. A combination of MS-275 and 2664.12 inhibited osteoclast activity similar to 1179.4b (IC(50) 0.35 nM). SAHA was shown to suppress osteoclast activity (IC(50) 12 nM). 1179.4b significantly (P < 0.05) reduced NFATc1, CTR, and OSCAR expression during the later stages of osteoclast development. Class I HDAC 8 and Class II HDAC5 were both elevated (P < 0.05) during osteoclast development. Results suggest that inhibition of both classes I and II HDACs may be required to suppress human osteoclastic bone resorption in vitro.

Potent antimalarial activity of histone deacetylase inhibitor analogues.

The malaria parasite Plasmodium falciparum has at least five putative histone deacetylase (HDAC) enzymes, which have been proposed as new antimalarial drug targets and may play roles in regulating gene transcription, like the better-known and more intensively studied human HDACs (hHDACs). Fourteen new compounds derived from l-cysteine or 2-aminosuberic acid were designed to inhibit P. falciparum HDAC-1 (PfHDAC-1) based on homology modeling with human class I and class II HDAC enzymes. The compounds displayed highly potent antiproliferative activity against drug-resistant (Dd2) or drug sensitive (3D7) strains of P. falciparum in vitro (50% inhibitory concentration of 13 to 334 nM). Unlike known hHDAC inhibitors, some of these new compounds were significantly more toxic to P. falciparum parasites than to mammalian cells. The compounds inhibited P. falciparum growth in erythrocytes at both the early and late stages of the parasite's life cycle and caused altered histone acetylation patterns (hyperacetylation), which is a marker of HDAC inhibition in mammalian cells. These results support PfHDAC enzymes as being promising targets for new antimalarial drugs.