HSV-1 infection suppresses TGF-beta1 and SMAD3 expression in human corneal epithelial cells

The present study was undertaken to investigate whether transforming growth factor-beta (TGF-beta) isoforms (TGF-beta1, TGF-beta2, and TGF-beta3) and SMADs (SMAD2 and SMAD3) are involved in herpes simplex virus type 1 (HSV-1) corneal infection.

Human corneal epithelial cells (HCE) were infected with HSV-1 at a multiplicity of infection of 5. Cell morphological changes were observed under phase-contrast microscopy. Levels of mRNA for TGF-beta isoforms 1, 2, and 3 as well as for SMAD2 and SMAD3 were measured by reverse transcription polymerase chain reaction (RT-PCR) at 0 h, 4 h, 8 h, 12 h, and 24 h after infection. Protein expression of TGF-beta1, TGF-beta2, SMAD3, and phospho-SMAD3 were analyzed by indirect immunofluorescence at 0 h, 12 h, and 24 h post-infection (p.i.) in HCE cells. Protein expression of TGF-beta1 was also evaluated by ELISA.

Following HSV-1 infection, a cytopathic effect in HCE cells was observed at 8 h p.i. and became significant at 24 h p.i. Compared with normal cells, the mRNA levels of TGF-beta1 in HSV-1 infected HCE cells decreased significantly at 8 h, 12 h, and 24 h p.i. (p<0.01), and the expression of SMAD3 was also dramatically decreased 12 h and 24 h p.i. (p<0.01). No noticeable changes were found as a result of infection with respect to levels of TGF-beta2, TGF-beta3, and SMAD2 in HCE cells. Protein expression of TGF-beta1, SMAD3, and phospho-SMAD3 decreased in infected cells at 12 h and 24 h p.i. compared with normal cells, but TGF-beta2 had no change.

TGF-beta1 and SMAD3 may be involved in the pathology of corneal diseases associated with HSV-1 infection.