Hydrogen-enriched water restoration of impaired calcium propagation by arsenic in primary keratinocytes Wei-Tai Yu, Yi-Ching Chiu, Chih-Hung Lee ⇑ , Tohru Yoshioka, Hsin-Su Yu Department of Dermatology, Kaohsiung Medical University Hospital and Kaohsiung Medical University, Kaohsiung, Taiwan article info Article history: Available online 23 July 2013 Keywords: Arsenic Oxidative stress Hydrogen water Calcium abstract Endemic contamination of artesian water for drinking by arsenic is known to cause several human can- cers, including cancers of the skin, bladder, and lungs. In skin, multiple arsenic-induced Bowen’s disease (As-BD) can develop into invasive cancers after decades of arsenic exposure. The characteristic histolog- ical features of As-BD include full-layer epidermal dysplasia, apoptosis, and abnormal proliferation. Cal- cium propagation is an essential cellular event contributing to keratinocyte differentiation, proliferation, and apoptosis, all of which occur in As-BD. This study investigated how arsenic interferes calcium prop- agation of skin keratinocytes through ROS production and whether hydrogen-enriched water would restore arsenic-impaired calcium propagation. Arsenic was found to induce oxidative stress and inhibit ATP- and thapsigaragin-induced calcium propagation. Pretreatment of arsenic-treated keratinocytes by hydrogen-enriched water or beta-mercaptoethanol with potent anti-oxidative effects partially restored the propagation of calcium by ATP and by thapsigaragin. It was concluded that arsenic may impair cal- cium propagation, likely through oxidative stress and interactions with thiol groups in membrane proteins. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Arsenic is one of the most abundant metal elements in the Earth crust. People can be exposed to arsenic through inhalation or drinking. Arsenic is a well-documented carcinogen that can lead to several human cancers, including liver, bladder, lungs, and skin, the most common arsenic-induced cancer and one of earliest known carcinogenic responses to arsenic (Tseng et al., 1968). Ar- senic-induced Bowen’s disease (As-BD), which is the most common arsenical skin cancer, provides a good disease model for the study of the early phase of arsenic carcinogenesis. The pathognomonic features of As-BD include full-layer epidermal dysplasia, epidermal thickening, and individual cell apoptosis, all of which feature aber- ant keratinocyte differentiation (Yeh et al., 1968). Physiological epidermal differentiation involves sequential dif- ferentiation from the basal layer, granular layer, spinous layer, to outermost corneal layer in epidermis, where the kerationcytes of terminal differentiation become apoptotic and lose their nuclei. In pathological circumstances, abnormal keratinocyte differentia- tion can lead to abnormal cell proliferation and evasion of apopto- tic cells with damaged DNA, resulting in proliferative diseases, including inflammatory skin lesions and benign or malignant skin cancers (Watt, 1989). This epidermal differentiation process is delicately regulated by calcium homeostasis (Hennings et al., 1980; O’Keefe and Payne, 1983), in which the elevation of calcium initiates keratinocyte differentiation. Thus, calcium homeostasis, which tightly regulates keratinocyte differentiation and cell apop- tosis, may play a role in skin carcinogenesis, and more specifically, in arsenic skin carcinogenesis. However, how arsenic affects the calcium signaling in primary keratinocytes is seldom addressed. Perez et al. found arsenic decreased terminal differentiation more in control primary keratinocytes than in calcium-treated primary keratinocytes (Perez et al., 2003), suggesting arsenic may interfere with keratinocyte differentiation through calcium regulation. One of our recent studies found that arsenic interferes with ATP-medi- ated calcium signaling in primary keratinocytes and but not in can- cerous keratinocytes (Hsu et al., 2012), further strengthening the possibility that arsenic might contribute to carcinogenesis through calcium signaling and homeostasis. In addition to calcium, oxidative stress has been presumed to be involved in arsenic carcinogenesis because increased level of 8-hydroxydeoxyguanosine (8-OHdG), an indicator for oxidative stress, has been found in urine from adults and schoolchildren exposed to arsenic (Wong et al., 2005; Yamauchi et al., 2004). In arsenical skin cancers, there is also an increased 8-OHdG expres- sion (Matsui et al., 1999), suggesting that oxidative stress may con- tribute at least in part to arsenic carcinogenesis as well. In fact, calcium mobilization and signaling play an important role in keratinocyte apoptosis induced by oxidative stresses. Treatment of HaCaT immortalized keratinocytes with the calcium chelator 1367-9120/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jseaes.2013.07.007 ⇑ Corresponding author. Tel.: +886 7 3121101x6105; fax: +886 7 3118901. E-mail address: dermlee@gmail.com (C.-H. Lee). Journal of Asian Earth Sciences 77 (2013) 342–348 Contents lists available at SciVerse ScienceDirect Journal of Asian Earth Sciences journal homepage: www.elsevier.com/locate/jseaes