The Role of ZIP9 and Androgen Receptor in the Establishment of Tight Junctions between Adult Rat Sertoli Cells

The effects of fine particulate matter on the blood-testis barrier and its potential mechanisms

With the rapid expansion of industrial scale, an increasing number of fine particulate matter (PM2.5) has bringing health concerns. Although exposure to PM2.5 has been clearly associated with male reproductive toxicity, the exact mechanisms are still unclear. Recent studies demonstrated that exposure to PM2.5 can disturb spermatogenesis through destroying the blood-testis barrier (BTB), consisting of different junction types, containing tight junctions (TJs), gap junctions (GJs), ectoplasmic specialization (ES) and desmosomes. The BTB is one of the tightest blood-tissue barriers among mammals, which isolating germ cells from hazardous substances and immune cell infiltration during spermatogenesis. Therefore, once the BTB is destroyed, hazardous substances and immune cells will enter seminiferous tubule and cause adversely reproductive effects. In addition, PM2.5 also has shown to cause cells and tissues injury via inducing autophagy, inflammation, sex hormones disorder, and oxidative stress. However, the exact mechanisms of the disruption of the BTB, induced by PM2.5, are still unclear. It is suggested that more research is required to identify the potential mechanisms. In this review, we aim to understand the adverse effects on the BTB after exposure to PM2.5 and explore its potential mechanisms, which provides novel insight into accounting for PM2.5-induced BTB injury.

ZIP9 mediates the effects of DHT on learning, memory and hippocampal synaptic plasticity of male Tfm and APP/PS1 mice

Androgens are closely associated with functions of hippocampal learning, memory, and synaptic plasticity. The zinc transporter ZIP9 (SLC39A9) regulates androgen effects as a binding site distinct from the androgen receptor (AR). However, it is still unclear whether androgens regulate their functions in hippocampus of mice through ZIP9. Compared with wild-type (WT) male mice, we found that AR-deficient male testicular feminization mutation (Tfm) mice with low androgen levels had learning and memory impairment, decreased expression of hippocampal synaptic proteins PSD95, drebrin, SYP, and dendritic spine density. Dihydrotestosterone (DHT) supplementation significantly improved these conditions in Tfm male mice, although the beneficial effects disappeared after hippocampal ZIP9 knockdown. To explore the underlying mechanism, we first detected the phosphorylation of ERK1/2 and eIF4E in the hippocampus and found that it was lower in Tfm male mice than in WT male mice, it upregulated with DHT supplementation, and it downregulated after hippocampal ZIP9 knockdown. Next, we found that the expression of PSD95, p-ERK1/2, and p-eIF4E increased in DHT-treated mouse hippocampal neuron HT22 cells, and ZIP9 knockdown or overexpression inhibited or further enhanced these effects. Using the ERK1/2 specific inhibitor SCH772984 and eIF4E specific inhibitor eFT508, we found that DHT activated ERK1/2 through ZIP9, resulting in eIF4E phosphorylation, thus promoting PSD95 protein expression in HT22 cells. Finally, we found that ZIP9 mediated the effects of DHT on the expression of synaptic proteins PSD95, drebrin, SYP, and dendritic spine density in the hippocampus of APP/PS1 mice through the ERK1/2-eIF4E pathway and affected learning and memory. This study demonstrated that androgen affected learning and memory in mice through ZIP9, providing new experimental evidence for improvement in learning and memory in Alzheimer's disease with androgen supplementation.