Regional Difference of Inflammatory Acne Lesions According to |[beta]|-Defensin-2 Expression

TO THE EDITOR The pathogenesis of acne is complex, involving increased sebum production and perifollicular inflammation. The inflammation of acne is initiated by disruption of the follicular epithelium, triggering granulomatous reactions. These inflammatory reactions usually developed from cross talk of sebaceous lipid fractions, hormones, and immune-active molecules (Zouboulis, 2001; Jeremy et al., 2003; Zouboulis, 2005). The sebaceous gland was traditionally thought to only provide physical protection to the external skin surface, but its numerous functions are gradually being discerned. Lipids produced by the sebocyte exhibit antibacterial activity (Georgel et al., 2005), and antimicrobial peptides (AMPs) have been found in human pilosebaceous units (Chronnell et al., 2001). A recent study showed that sebum-free fatty acids (FFAs) may provide direct antibacterial activities against Propionibacterium acnes (enhance the innate antibacterial defense of the skin by inducing the expression of human β-defensin (hBD)-2 in sebocytes (Nakatsuji et al., 2010). These findings indicate a direct induction of innate immunity by FFAs in human sebocytes, whereas recruitment of hBD-2 to the site can potentiate the inflammatory events of acne. Facial areas can be categorized as T-zone (high-sebum-secreting area; forehead, nose, chin area) and U-zone (low-sebum-secreting areas; both the cheek areas) on the basis of sebum secretion levels (Park et al., 1999). One previous study showed that noninflammatory comedones in the T-zone (especially chin) and inflammatory lesions in the U-zone were significantly associated with local sebum secretion (Youn et al., 2005). However, evidence supporting the rationale behind these findings is lacking, which implies that several factors contribute to the topographical distinction of acne lesions. In this study, we examined the regional differences in inflammatory acne lesions according to facial topography and investigated the relationship between hBD-2 expression and inflammatory acne lesion development. Two hundred acne patients were enrolled to evaluate the regional differences in acne lesions. We divided the surface of the face into T-zone and U-zone (Figure 1a). The numbers of inflammatory and noninflammatory acne lesions per square centimeter on the face were counted through standard photographic examination. Results indicated significantly more noninflammatory lesions in the T-zone. However, to our surprise, there was a significantly lower number of inflammatory lesions in the T-zone, which is a high-sebum-secreting area, compared with that in the U-zone (Figure 1b). This result prompted us to explore regional differences in factors that affect formation of inflammatory acne lesions. To investigate the hypothesis that these findings result from topographic differences of antibacterial activities against P. acnes produced by AMP, we examined hBD-2 and LL-37 expression in the U-zone and T-zone from 10 fresh cadavers. Histological analysis revealed that more intense cytoplasmic staining of hBD-2 was observed in sebaceous glands of the T-zone (Figure 2a). However, there was no difference in LL-37 expression in each area (data not shown). These results are consistent with previous findings in human sebocytes that sebum FFAs dramatically enhanced hBD-2 expression, but only slightly increased LL-37 expression (Nakatsuji et al., 2010). To explore regional differences in hBD-2 expression in vitro, we used primary human sebocytes obtained from the same cadaver donors. hBD-2-specific immunoreactivity was more highly expressed in sebocytes from the T-zone versus the U-zone (Figure 2b). We next identified differences in protein and mRNA levels of hBD-2 using western blotting and reverse transcriptase–PCR. The mean hBD-2 protein level was higher in sebocytes from the T-zone (Figure 2c). These site-specific differences in hBD-2 expression were consistent in RT-PCR (Figure 2d). In addition, the productions of hBD-2 from sebocyte extracts in each area were measured by ELISA. Under the similar cell number (2 × 106 cells), sebocytes from T-zone showed a relatively high concentration of hBD-2 compared with U-zone (Figure 2e). To test the antimicrobial activity of sebocytes from each area against P. acnes, we performed antimicrobial assay. As shown in figure 2f, sebocyte extracts from T-zone significantly inhibited the growth of P. acnes as compared with U-zone. We further analyzed the difference of P. acnes-induced cytokine expression in sebocytes from each area. ELISA analysis showed that sebocytes from U-zone significantly increased IL-8 and tumor necrosis factor-α secretion after P. acnes stimulation, whereas those from T-zone did not (Figure 2g). These data suggest that higher amount of hBD-2 in the sebocytes from T-zone enhanced antimicrobial activity against P. acnes and inhibited the expression of proinflammatory cytokines, such as IL-8 and tumor necrosis factor-α. Our data showed that the T-zone had a low incidence of inflammatory acne lesions compare with U-zone. These data support the previous findings that hBD-2 levels indicate the presence of antiinflammatory lipids, which inhibit inflammation, therefore, only a few clinically inflammatory lesions occur (Georgel et al., 2005; Zouboulis et al., 2010). Previous studies demonstrated that FFAs enhance the innate antibacterial defenses of the skin by inducing the expression of AMP (Lee et al., 2008; Nakatsuji et al., 2010). Our findings also showed that considerable FFAs in the high-sebum-secreting area (T-zone) induce more abundant hBD-2 expression, and enhanced antimicrobial activity against P. acnes and inhibited the expression of proinflammatory cytokines. However, it needs to further evaluation for the expression of other AMP in each area, because other AMP may also have a role in regional difference of inflammatory acne lesions (Lee et al., 2008, 2009). There was a previous study that hBD-2 strikingly killed P. acnes at concentrations higher than 10 mM (Nakatsuji et al., 2010). Although we showed which amount of hBD-2 in sebocytes from T-zones able to influence the growth of P. acnes in vitro, it needs further in vivo study especially in acne lesions. In conclusion, we suggest that increased hBD-2 in the T-zone prevents the progress of comedones to papulopustular lesions via either an upregulation of antiinflammatory sebaceous lipid synthesis and/or an inhibitory activity of P. acnes proliferation. These data suggest a functional link between topographical variation of inflammatory acne lesions and innate immunity in acne pathogenesis. Further studies of the relationship between hBD-2 expression and P. acnes in acne lesion are warranted to gain the confirmation of the effects of hBD-2 on regional difference of inflammatory acne lesions. The authors state no conflict of interest. This study was supported by a grant of the Traditional Korean Medicine R&D Project, Ministry of Health & Welfare, Republic of Korea (HI13C0615). SUPPLEMENTARY MATERIAL Supplementary material is linked to the online version of the paper