Cyclooxygenase 2 expression and apoptosis in normal and psoriatic epidermis models exposed to salt water soaks and narrowband ultraviolet B radiation

Background: Combined treatment using salt water baths and artificial ultraviolet (UV) radiation (balneophototherapy, BPT) is a common therapeutic option for conditions such as psoriasis. However, it remains unknown whether pre-treatment with salt water soaks alter inflammatory and/or carcinogenic effects of UVB phototherapy.

Objectives: We aimed to investigate the impact of BPT on COX-2 gene expression and apoptosis in normal and psoriatic keratinocytes.

Methods: Normal epidermis models (NEM) and psoriatic epidermis models (PEM) were treated using different salt water soaks (3% NaCl, 30% NaCl, 30% Dead Sea salt; DSS) and subsequent narrowband ultraviolet B (NB-UVB) for three consecutive days. RT-PCR was performed for cyclooxygenase 2 (COX-2), survivin, and caspase-3.

Results: Compared with untreated controls COX-2 mRNA was significantly increased in NB-UVB irradiated NEM and PEM. NB-UVB-exposed and non-exposed 30% NaCl and 30% DSS-treated NEM and PEM (except for NB-UVB-exposed and non-irradiated 30% DSS) showed significantly higher COX-2 mRNA when compared with controls and 3% NaCl. In NB-UVB-exposed 30% NaCl and 30% DSS-treated NEM and PEM survivin mRNA was significantly decreased when compared with controls and 3% NaCl. Compared with NB-UVB-exposed controls mRNA of caspase-3 was significantly increased in NB-UVB-exposed 30% NaCl and 30% DSS-treated PEM.

Conclusion: Although BPT using high-concentrated salt water solutions is associated with increased epidermal COX-2 mRNA expression, apoptosis of keratinocytes is enhanced possibly due to the down-regulation of survivin mRNA expression. If confirmed in larger studies these observations have important implications for BPT efficacy as well as safety, particularly with regard to the risk of early carcinogenesis.