Abstract
The aim is to explore the mechanism of the apoptosis signal-regulating kinase-1 (ASK-1) signaling pathway and the involvement of the thioredoxin (Trx) system during testicular ischemia reperfusion injury (tIRI) by using ASK-1 specific inhibitor, NQDI-1. Male Sprague-Dawley rats (n = 36, 250–300 g) were equally divided into 3 groups: sham, tIRI, and tIRI + NQDI-1 (10 mg/kg, i.p, pre-reperfusion). For tIRI induction, the testicular cord and artery were occluded for 1 h followed by 4 h of reperfusion. Histological analyses, protein immunoexpression, biochemical assays, and real-time PCR were used to evaluate spermatogenesis, ASK-1/Trx axis expression, enzyme activities, and relative mRNA expression, respectively. During tIRI, ipsilateral testes underwent oxidative stress indicated by low levels of superoxide dismutase (SOD) and Glutathione (GSH), increased oxidative damage to lipids and DNA, and spermatogenic damage. This was associated with induced mRNA expression of pro-apoptosis genes, downregulation of antiapoptosis genes, increased caspase 3 activity and activation of the ASK-1/JNK/p38/survivin apoptosis pathway. In parallel, the expression of Trx, Trx reductase were significantly reduced, while the expression of Trx interacting protein (TXNIP) and the NADP+/ nicotinamide Adenine Dinucleotide phosphate (NADPH) ratio were increased. These modulations were attenuated by NQDI-1 treatment. In conclusion, the Trx system is regulated by the ASK-1/Trx/TXNIP axis to maintain cellular redox homeostasis and is linked to tIRI-induced germ cell apoptosis via the ASK-1/JNK/p38/survivin apoptosis pathway.
Highlights
Germ cell apoptosis (GCA) is one of the consequences of testicular ischemia reperfusion injury that underlies the etiology of testicular torsion and detorsion (TTD), a urologic emergency that affects young males [1,2]
The testis is characterized by a low oxygen tension microenvironment, a sudden influx of oxygenated blood will create a state of testicular oxidative stress (TOS) due to the generation of massive quantities of reactive oxygen species (ROS)
To evaluate damage to spermatogenesis, hematoxylin and eosin (H&E) staining was performed, slides were analyzed under light microscopy (10× and 40× magnifications), and the Johnsen score was used to assess spermatogenesis in each testis in each experimental group (Figure 1)
Summary
Germ cell apoptosis (GCA) is one of the consequences of testicular ischemia reperfusion injury (tIRI) that underlies the etiology of testicular torsion and detorsion (TTD), a urologic emergency that affects young males [1,2]. The gold standard treatment for TT is to surgically detorse the ischemic testis to allow for blood and oxygen reperfusion. The testis is characterized by a low oxygen tension microenvironment, a sudden influx of oxygenated blood will create a state of testicular oxidative stress (TOS) due to the generation of massive quantities of reactive oxygen species (ROS). Reactive Oxygen Species (ROS) will start to accumulate due to the incapacity of the intracellular antioxidant system to neutralize them. ROS by an aerobic metabolism that is required for normal sperm function, to facilitate capacitation, and to promote fertilization [3]. Overproduction and accumulation of ROS will have adverse effects on sperm motility, fertilization competence, and viability due to oxidative damage to proteins, Molecules 2019, 24, 3333; doi:10.3390/molecules24183333 www.mdpi.com/journal/molecules
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