Allicin Induces Keratinocytes Apoptosis in vivo and vitro
The resistance of keratinocytes to apoptosis is well-established to contribute to psoriatic epidermal thickening. We examined the effect of allicin on inducing apoptosis in keratinocytes. An analysis of flow cytometry with Annexin V/PI staining was carried out to determine the percentage of apoptotic cells. As shown in Figures 4A and 4B, the proportion of apoptotic cells was 8.74%, 21.90%, and 29.40% after treatment with 6.4, 9.6, and 12.8μg/mL of allicin, respectively, which was significantly higher than the control group (5.39%). Overall, treatment with various concentrations of allicin dose-dependently induced keratinocyte apoptosis. The molecular mechanism of allicin-mediated apoptosis was explored using Western blot. Allicin induced the levels of pro-apoptotic proteins Bax and cleaved-caspase3 and inhibited the expression of the anti-apoptotic protein Bcl-2 in HaCaT cells (Figures 4C) and skin lesions (Figures 4D). In addition, TUNEL-DAPI staining was performed to examine keratinocyte apoptosis in skin lesions sections. Figure 4E showed that allicin treatment could induce keratinocyte apoptosis in psoriatic skin. These data corroborated the pro-apoptotic role of allicin in keratinocytes of psoriasis skin lesions.