7) and cyclin A (data not shown) could indicate the activation of the wound-healing pathway against drug-induced damage. However, it is more likely that the changed expression Cetuximab in vivo patterns of PCNA and cyclin A indicate that exposure to ZDV induces a loss of cell cycle control, which could play a role in the development of oral complications in HIV-infected patients under treatment with this drug. Decreased cytokeratin 6 expression supports this possibility. Effects of ZDV were seen on established tissue as early as 48 h after exposure to the drug. Therefore, we performed an experiment in which 0.5,

1 and 2 μg/mL ZDV was added to the day 8 raft cultures for 6, 12 or 24 h in order to examine the effects of short-term treatment on gingival tissue (Fig. 1). Immunohistochemical staining was then performed as in the previous experiments. Effects similar to those seen in previous experiments were seen at all concentrations and at all time-points. Even as early as 6 h and at the lowest concentration of ZDV, haematoxylin and eosin Cabozantinib cell line staining and immunohistochemistry revealed that the drug changed both the morphology and the differentiation and proliferation status of tissues. Haematoxylin and eosin staining at the Cmax of ZDV showed that keratin pearls became more visible in treated tissue. Nuclei became more evident in the upper layers of the tissue and vaculation was reduced in tissues treated for 6, 12 and 24 h (Fig. 8, panels A–D). Similar

to tissue treated with ZDV for longer periods of time, tissue treated with the drug for 6, 12 and 24 h showed a decrease in cytokeratin 5 and involucrin expression at all drug concentrations (Fig. 8, panels E–L and data not shown). When ZDV was added to tissues at the 6-, 12- and 24-h time-points, a marked increase in cytokeratin 10 was seen in tissues at all drug concentrations (Fig. 8, panels M–P and data not shown). This was different from observations when ZDV was added for longer periods of time. Tissues treated at day 8 and harvested 2 and 4 days post treatment did

not sustain this increase in cytokeratin expression. Expression of cytokeratin 6, which is involved in wound healing, was decreased in tissues treated with ZDV for 6, 12 and 24 h at all drug concentrations tested (Fig. 8, panels before Q–T). Like tissues treated for longer periods of time, an increase in PCNA was seen in tissues after 6, 12 and 24 h of ZDV exposure. PCNA expression also became evident in upper layers of tissue (Fig. 8, panels U–X and data not shown). Effects similar to those seen in previous experiments were seen at all concentrations and at all time-points. The effects were strongest at the 2 μg/mL concentration (Cmax) (Fig. 6). These results suggest that ZDV is able to mediate its effects through fast-acting pathways. HIV-positive patients taking HAART have reported many oral complications, which have a major impact on their overall health and quality of life.