The combined effects of irradiation and herpes simplex virus type 1 infection on an immortal gingival cell line

Abstract

BackgroundOral mucosa is frequently exposed to Herpes simplex virus type 1 (HSV-1) infection and irradiation due to dental radiography. During radiotherapy for oral cancer, the surrounding clinically normal tissues are also irradiated. This prompted us to study the effects of HSV-1 infection and irradiation on viability and apoptosis of oral epithelial cells.MethodsImmortal gingival keratinocyte (HMK) cells were infected with HSV-1 at a low multiplicity of infection (MOI) and irradiated with 2 Gy 24 hours post infection. The cells were then harvested at 24, 72 and 144 hours post irradiation for viability assays and qRT-PCR analyses for the apoptosis-related genes caspases 3, 8, and 9, bcl-2, NFκB1, and viral gene VP16. Mann–Whitney U-test was used for statistical calculations.ResultsIrradiation improved the cell viability at 144 hours post irradiation (P = 0.05), which was further improved by HSV-1 infection at MOI of 0.00001 (P = 0.05). Simultaneously, the combined effects of infection at MOI of 0.0001 and irradiation resulted in upregulation in NFκB1 (P = 0.05). The combined effects of irradiation and HSV infection also significantly downregulated the expression of caspases 3, 8, and 9 at 144 hours (P = 0.05) whereas caspase 3 and 8 significantly upregulated in non-irradiated, HSV-infected cells as compared to uninfected controls (P = 0.05). Infection with 0.0001 MOI downregulated bcl-2 in non-irradiated cells but was upregulated by 27% after irradiation when compared to non-irradiated infected cells (P = 0.05). Irradiation had no effect on HSV-1 shedding or HSV gene expression at 144 hours.ConclusionsHSV-1 infection may improve the viability of immortal cells after irradiation. The effect might be related to inhibition of apoptosis.

Construction and characterization of a multilayered gingival keratinocyte culture model: the TURK-U model

“…Both HMK and HaCaT keratinocytes are nontumorigenic, spontaneously immortalized cell lines and do not contain any human papilloma virus DNA (Boukamp et al 1988;Turunen et al 2014). Although the origin of HaCaT cells is skin, this cell line has been widely used in multilayered cell culture models of the oral cavity and infection-related responses of this cell line against periodontal pathogens were demonstrated (Gursoy et al 2010(Gursoy et al , 2016Zeidán-Chuliá et al 2014).…”

“…These differences may be attributed to their genetic origins; gingival kerationcytes have significantly higher proliferation and migration rates in comparison with skin keratinocytes (Rowat and Squier 1986). Moreover, HaCaT cells have hypotetraploid karyotypes, while HMK cells have total tetraploid karyotypes (Turunen et al 2014).…”

Carriage of herpes simplex virus and human papillomavirus in oral mucosa is rare in young women: A long-term prospective follow-up

“…This observation led us to design an in vitro study to assess the effects of irradiation on HPV16-and HSV-1 co-infected epithelial cells. The results showed that HSV-1 infection may modulate the radiation resistance of HPV16-positive HNSCC cells by increasing cell survival after irradiation, most likely through the escape of apoptosis [19]. Given that oral epithelium is often exposed to radiation during dental radiography, it is relevant to assess the frequency of oral HSV-1 and HPV co-carriage in asymptomatic persons.…”

“…One possible hypothesis to explain the lack of dual infections in our study population is that epithelial HSV infection is often lytic and leads to elimination of the infected cell [2]. On the contrary, HPV infection of epithelial cells can be less lytic and immunologically more silent, thereby persisting for longer intervals [19]. The rare dual infections may thus represent either a state of dual infection when HSV infection has not yet led to elimination of the cell, or a rare long-term quiescent HSV infection could take place.…”

“…In the present study, we analysed HSV-1 and HSV-2 DNA in oral mucosal scrapings of the mothers included in the Finnish Family HPV Study, with special emphasis on co-carriage of these two viruses in oral mucosa. This study was prompted by recent observations implicating that the patients with HPV16 and HSV-1 positive head and neck carcinomas (HNSCC) had the worst disease outcome [13,14,15], as well as by the recent in vitro data showing that HSV-1 infection may modulate the radiation resistance of HPV16-positive HNSCC cells by increasing cell survival after irradiation [19]. Because oral mucosa is frequently exposed to irradiation during dental treatment and possibly to other risk factors such as tobacco, it is important to assess the frequency of HSV and HPV co-carriage in oral mucosa of asymptomatic subjects.…”