Contents lists available at ScienceDirect Experimental Gerontology journal homepage: www.elsevier.com/locate/expgero Aging in the Syrian hamster testis: Inflammatory-oxidative status and the impact of photoperiod M.E. Matzkin a,b , P. Valchi a , E. Riviere a,c , S.P. Rossi a,b , Y.E. Tavalieri d , M.M. Muñoz de Toro d , A. Mayerhofer e , A. Bartke f , R.S. Calandra a , M.B. Frungieri a,c, ⁎ a Instituto de Biología y Medicina Experimental, CONICET, Ciudad de Buenos Aires, 1428, Argentina b Cátedra de Bioquímica Humana, Facultad de Medicina, Universidad de Buenos Aires, Ciudad de Buenos Aires, 1121, Argentina c Cátedra de Química, Ciclo Básico Común, Universidad de Buenos Aires, Ciudad de Buenos Aires, 1405, Argentina d Instituto de Salud y Ambiente del Litoral, Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Santa Fe, 3000, Argentina e Biomedical Center Munich (BMC), Cell Biology, Anatomy III, Ludwig-Maximilians-University (LMU), D-82152 Planegg, Germany f Geriatrics Research, Department of Internal Medicine, School of Medicine, Southern Illinois University, Springfield, IL 62794, USA ARTICLE INFO Section Editor: Dr Michal Masternak Keywords: Aging Testis Inflammation Oxidative stress Melatonin Photoperiod ABSTRACT Testicular aging is linked to histological, morphological and functional alterations. In the present study, we investigated whether aging affects the inflammatory and oxidative status in the testis by comparing young adult, middle-aged adult and aged hamsters. The Syrian hamster, a thoroughly studied seasonal breeder, was chosen as the experimental model since it allows further investigations on the role of photoperiod and melatonin in tes- ticular aging with a minimal impact of the experimental intervention on the animal well-being and the sub- sequent results achieved. In testes of aged hamsters, we found a decrease in melatonin concentration, a thickening of the wall of the seminiferous tubules as well as a significant increase in IL-1β, NLRP3 and cyclooxygenase 2 expression, PGD2 production, macrophages numbers, lipid peroxidation and anti-oxidant enzyme catalase levels. Interestingly, when aged hamsters were transferred from a long day (LD) to a short day (SD) photoperiod for 16 weeks, testicular melatonin concentration increased while local inflammatory processes and oxidative stress were clearly reduced. Overall, these results indicate that melatonin might display anti-inflammatory and anti-oxidant capacities in the aged testes. 1. Introduction Although the definition of aging is constantly changing and evolving (Rose et al., 2012; Flatt, 2012), most evolutionary biologists agree that the aging process involves an age-dependent or age-progressive decline in intrinsic physiological function, leading to an increase in age-specific mortality rate and a decrease in age-specific reproductive rate (Medawar, 1955; Tatar, 2001; Promislow and Bronikowski, 2006; Bronikowski and Flatt, 2010; Fabian and Flatt, 2011). Aging of the male reproductive system includes, among others, changes in the testicular tissue, androgen levels, sperm production, and erectile function. Literature about the alterations taking place in the aged testes has been, so far, limited and controversial. It is known that during aging the testis undergoes severe histological and morphological alterations (Jiang et al., 2014; Sibert et al., 2014) as well as a significant decrease of the steroidogenic and spermatogenic capacities (Gravance et al., 1997; Zirkin and Chen, 2000). Although the decreased androgen production and spermatogenesis during aging lead to a decline in fer- tility, they do not necessarily result in infertility (Bray et al., 2006). Because ethical and legal considerations exclude the possibility of performing functional studies in testicular samples from elderly men, different rodent experimental models have been used to investigate the physiological mechanisms involved in testicular aging. In this context, Brown-Norway rats presenting a pathological decline of the re- productive function (Wang et al., 1993; Zirkin et al., 1993; Syntin and Robaire, 2001), mice with mutations within the GH/IGF1 pathway showing extended or reduced longevity (Matzkin et al., 2016) as well as other rodent models have been utilized for the study of the age-related molecular changes in the testis. In this context, results previously ob- tained by our group and by others in rodent experimental models led to https://doi.org/10.1016/j.exger.2019.110649 Received 27 March 2019; Received in revised form 30 May 2019; Accepted 30 June 2019 ⁎ Corresponding author at: Instituto de Biología y Medicina Experimental, CONICET, Ciudad de Buenos Aires 1428, Argentina. E-mail address: mfrungieri@dna.uba.ar (M.B. Frungieri). Experimental Gerontology 124 (2019) 110649 Available online 02 July 2019 0531-5565/ © 2019 Elsevier Inc. All rights reserved. T