Excess iodine impairs spermatogenesis by inducing oxidative stress and perturbing the blood testis barrier

• Published in: Reproductive toxicology (Elmsford, N.Y.) N.Y.), 2020-09, Vol.96, p.128-140
• Main Authors: Chakraborty, Arijit, Singh, Vertika, Singh, Kiran, Rajender, Singh
• Format: Article
• Language: English
• Subjects: Animals; Apoptosis; Apoptosis Regulatory Proteins - metabolism; Blood-Testis Barrier - drug effects; Cell Cycle Proteins - metabolism; Cellular progression; Excess iodine; Iodine - toxicity; Male; Oxidative stress; Oxidative Stress - drug effects; Rats, Sprague-Dawley; Sperm Count; Sperm Motility - drug effects; Spermatogenesis - drug effects; Testicular junction complexes; Testis - drug effects; Testis - metabolism; Testis - pathology; Tight Junction Proteins - genetics; Tight Junction Proteins - metabolism
• ISSN: 0890-6238; 1873-1708
• DOI: 10.1016/j.reprotox.2020.06.012

•Excess iodine (EI) causes substantial loss of sperm count and fine motility parameters.•EI induces oxidative stress (OS) with increased apoptosis and seminiferous tubules degeneration.•Reduced Nrf2, HO-1 & elevated SOD, NF-kB-Follistatin pathways observed after EI exposure.•OS leads to reduced expression of BTB, cytoskeleton coding genes & proteins impeding spermatogenesis. Approximately 2 billion people worldwide are susceptible to iodine deficiency. Iodine deficiency has largely been tackled by iodine fortification in salt; however indiscriminate use of iodine raises the risk of iodine toxicity. In this study, we aimed to investigate the molecular mechanisms underlying adverse effect of excess iodine on spermatogenesis. Sprague Dawley (SD) rats were orally administered with 0.7 mg potassium iodide (KI)/100 g Bw and 3.5 mg potassium iodide (KI)/100 g Bw for a period of 60 days. This resulted in significant loss of sperm count and motility. Molecular investigations provided evidence for the generation of oxidative stress with high SOD levels, reduced Nrf2, HO-1 and increased NF-kB and Follistatin. Further investigations showed increased apoptosis evidenced by reduced expression of anti-apoptotic (BCL-2, Survivin), increased expression of pro-apoptotic (Bid, Bax) markers, and increased expression of p53 and other modulators/effectors of apoptosis (cytochrome c, cleaved PARP, caspase3 and caspase9). Analysis of the blood testis barrier proteins showed reduced expression of tight junction (JAM-A, Tricellulin), ectoplasmic specialization (Integrin- β1), adherens junction (N-Cadherin, E-cadherin, β-catenin) proteins, and reduced expression of other junction protein coding genes (Claudin1, Claudin 5, Occludin, ZO-1, Testin, Fibronectin, CAR-F). Focal adhesion kinase (FAK) and key regulators of spermatogenesis (c-Kit receptor, androgen receptor) were also parallelly decreased. Further investigation showed reduced expression of germ cell proliferation and differentiation markers (PCNA, Cyclin D1, c-Kit, Cdk-4). These findings collectively explain the loss of spermatogenesis under excess iodine conditions. In conclusion, excess iodine causes loss of spermatogenesis by inducing oxidative stress and disrupting the blood testis barrier and cytoskeleton.