ACE2 expression and spike S1 protein-mediated immune responses in oral mucosal cells.

OBJECTIVES: ACE2, known as a host receptor involved with SARS-CoV-2 infection, binds to viral spike proteins for host cell entry. However, details regarding its induction and function in oral mucosal cells remain unknown. MATERIALS AND METHODS: We examined ACE2 expression and its induction by transfected mimic nucleotides and pro-inflammatory cytokines in oral keratinocytes (RT7) and fibroblasts (GT1). Subsequently, the effects of viral spike S1 protein via ACE2 on CXCL10 expression induced by pro-inflammatory cytokines in both cells were examined. RESULTS: ACE2 was constitutively expressed in RT7 and GT1. Transfected Poly(I:C) and Poly(dA:dT) increased ACE2 expression in those cells, while knockdown of RIG-I decreased ACE2 expression induced by those transfected ds nucleotides. IFN-γ and TNF-α enhanced transfected ds nucleotides-induced ACE2 expression in RT7 but not GT1. S1 protein alone did not affect CXCL10 expression in either cell type, whereas it enhanced IFN-ß-induced CXCL10 in both, while immune responses of IFN-γ- and TNF-α-induced CXCL10 enhanced by S1 protein were different between RT7 and GT1. Finally, knockdown of ACE2 decreased cytokines and S1 protein mediated-CXCL10 levels in both cells. CONCLUSIONS: ACE2 in oral mucosal cells may contribute to development of infection and inflammation in cooperation with pro-inflammatory cytokines following SARS-CoV-2 invasion.

LL-37-dsRNA Complexes Modulate Immune Response via RIG-I in Oral Keratinocytes.

Recognition of nucleic acids as pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs) promotes an inflammatory response. On the other hand, LL-37, an antimicrobial peptide, is a multifunctional modulator of immune response, though whether it modulates inflammatory responses induced by nucleic acids in oral keratinocytes is unknown. In this study, we firstly investigated the effect of LL-37 on CXCL10 induced by DAMPs and PAMPs in immortalized oral keratinocytes, RT7. Furthermore, the effects of LL-37 on translocation of exogenous nucleic acids into cytoplasm as well as cytosolic receptor, RIG-I on immune responses mediated by LL-37-nucleic acid complexes were examined. From these results, LL-37 enhanced necrotic cell supernatant (NCS)-induced CXCL10 expression in RT7, while the response was decreased by RNase. Complexes of LL-37 and double-stranded (ds) RNA, Poly(I:C) enhanced CXCL10 expression in comparison with each alone, which were associated with NF-κB activation. Furthermore, LL-37 was shown to bind with ds nucleotides and translocate into cytoplasm. Knockdown of RIG-I decreased expression of CXCL10 induced by LL-37-Poly(I:C) complexes, and RIG-I were co-localized with Poly(I:C) entered by LL-37 in cytoplasm. LL-37 modulates dsRNA-mediated inflammatory response via RIG-I in oral keratinocytes, which may play an important role in the pathogenesis of oral inflammatory diseases.

Effects of CEACAM1 in oral keratinocytes on HO-1 expression induced by Candida ß-glucan particles.

OBJECTIVE: Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) is a member of the carcinoembryonic antigen family. Although its expression has been found in chronic oral inflammatory epithelium, this study aimed to know whether CEACAM1 in oral keratinocytes participates in host immune response against Candida albicans . METHODOLOGY: We investigated CEACAM1 expression in oral keratinocytes induced by C. albicans as well as by Candida cell wall component ß-glucan particles (ß-GPs). Furthermore, the effects of CEACAM1 on ß-GPs-induced heme oxygenase-1 (HO-1) expression and its related signals were examined. RESULTS: Fluorescence staining showed CEACAM1 expression in oral keratinocytes (RT7) cells, whereas quantitative reverse transcription (RT)-PCR indicated that both live and heat-killed C. albicans increased CEACAM1 mRNA expression in RT7 cells. Examinations using quantitative RT-PCR and western blotting indicated that CEACAM1 expression was also increased by ß-GPs derived from C. albicans . Specific siRNA for CEACAM1 decreased HO-1 expression induced by ß-GPs from C. albicans as well as the budding yeast microorganism Saccharomyces cerevisiae . Moreover, knockdown of CEACAM1 decreased ß-GPs-induced ROS activity in the early phase and translocation of Nrf2 into the nucleus. CONCLUSION: CEACAM1 in oral keratinocytes may have a critical role in regulation of HO-1 for host immune defense during Candida infection.

Sunitinib promotes apoptosis via p38 MAPK activation and STAT3 downregulation in oral keratinocytes.

OBJECTIVE: Sunitinib, a targeted cancer drug, inhibits tyrosine kinases receptors and is widely used as first-line treatment for metastatic renal cell carcinoma. Patients undergoing chemotherapy with sunitinib frequently have oral mucosal complications, such as oral stomatitis, though cytotoxic effects of the drug on oral keratinocytes remain unknown. METHODS: The effects of sunitinib on immortalized oral keratinocytes, RT7 cells, in regard to cell injury and apoptosis, as well as apoptosis-mediated signaling pathways were investigated. RESULTS: Sunitinib treatment caused a significant increase in lactate dehydrogenase (LDH) in RT7 cells and primary oral keratinocytes. Additionally, the drug induced apoptosis-related events, such as DNA fragmentation, decreased anti-apoptotic Bcl-2 protein expression, and induction of cleaved PARP and caspase 3/9 in RT7 cells. Furthermore, phosphorylation of p38 MAPK, but not of ERK or JNK, was increased. On the contrary, constitutive phosphorylated STAT3 was decreased by sunitinib treatment, which was recovered by exposure to SB203580, a p38 MAPK inhibitor. Finally, SB203580 was found to reduce sunitinib-induced cell injury and apoptosis. CONCLUSION: The present results indicate that sunitinib promotes cell injury and apoptosis in oral keratinocytes via p38 activation and STAT3 downregulation. Sunitinib-mediated oral complications may be associated with cytotoxic effects of the drug on oral keratinocytes.

Inhibition of angiogenesis and tumor progression of MK-0429, an integrin αvß3 antagonist, on oral squamous cell carcinoma.

PURPOSE: Integrin αvß3 is an essential molecule for tumor angiogenesis. This study aimed to investigate the anti-tumor effect of MK-0429, an integrin αvß3 antagonist, on oral squamous cell carcinoma (OSCC) through its inhibitory effect on angiogenesis. METHODS: In this study, we investigated the effect of MK-0429 on cellular function and angiogenesis in vitro with the use of an immortalized human umbilical vein endothelial cell, HUEhT-1, which is immortalized by the electroporatic transfection of hTERT. The effect of MK-0429 on the integrin αvß3 signaling pathway was examined by FAK, MEK1/2 and ERK 1/2 phosphorylation. The anti-angiogenic effect of MK-0429 was evaluated by in vitro tube formation assay. The anti-tumor effect on OSCC was assessed by administrating MK-0429 to mouse oral cancer xenografts. RESULTS: MK-0429 inhibited cell proliferation, migration, and adhesion of HUEhT-1 in a dose-dependent manner. FAK, MEK and ERK phosphorylation were significantly blocked by MK-0429 treatment. Tube formation was suppressed by MK-0429 in dose-dependent manner. Tumor progression was significantly suppressed by MK-0429 administration in mouse oral cancer xenografts. Histological study revealed that MK-0429 decreased tumor vascularization. CONCLUSION: These results indicated integrin αvß3 as a therapeutic target for OSCC and suggested that MK-0429 might be clinically applicable as an anti-tumor agent with potent anti-angiogenic activity.

Effects of CEACAM1 in oral keratinocytes on HO-1 expression induced by Candida β-glucan particles

Abstract Objective Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) is a member of the carcinoembryonic antigen family. Although its expression has been found in chronic oral inflammatory epithelium, this study aimed to know whether CEACAM1 in oral keratinocytes participates in host immune response against Candida albicans . Methodology We investigated CEACAM1 expression in oral keratinocytes induced by C. albicans as well as by Candida cell wall component β-glucan particles (β-GPs). Furthermore, the effects of CEACAM1 on β-GPs-induced heme oxygenase-1 (HO-1) expression and its related signals were examined. Results Fluorescence staining showed CEACAM1 expression in oral keratinocytes (RT7) cells, whereas quantitative reverse transcription (RT)-PCR indicated that both live and heat-killed C. albicans increased CEACAM1 mRNA expression in RT7 cells. Examinations using quantitative RT-PCR and western blotting indicated that CEACAM1 expression was also increased by β-GPs derived from C. albicans . Specific siRNA for CEACAM1 decreased HO-1 expression induced by β-GPs from C. albicans as well as the budding yeast microorganism Saccharomyces cerevisiae . Moreover, knockdown of CEACAM1 decreased β-GPs-induced ROS activity in the early phase and translocation of Nrf2 into the nucleus. Conclusion CEACAM1 in oral keratinocytes may have a critical role in regulation of HO-1 for host immune defense during Candida infection.