Peroxisome Proliferator Activated Receptor β/δ Activation Prevents Extracellular Regulated Kinase 1/2 Phosphorylation and Protects the Testis From Ischemia and Reperfusion Injury

Purpose

Testicular torsion is a medical emergency that requires immediate diagnosis and treatment to avoid subsequent testicular injury and infertility. PPARs are a family of nuclear hormone receptors belonging to the steroid receptor superfamily. Three PPAR isotypes (α, β/δ and γ) encoded by separate genes and showing different tissue distribution patterns have been identified. PPARβ/δ is expressed in testis and its role is largely unknown. We tested whether pharmacological activation of PPARβ/δ might protect the testis from ischemia and reperfusion injury.

Materials and Methods

Adult male Sprague-Dawley rats were subjected to 1-hour testicular ischemia, followed by 24 hours of reperfusion. Sham testicular ischemia-reperfusion rats served as controls. The animals were randomized to receive immediately after detorsion 1) L-165,041 (4 mg/kg intraperitoneally), a potent agonist of PPARβ/δ, 2) GW9662 (Calbiochem®) (4 mg/kg intraperitoneally), an antagonist of PPAR, 3) L-165,041 (4 mg/kg intraperitoneally) plus GW9662 (4 mg/kg intraperitoneally) concomitantly or 4) vehicle (1 ml/kg 10% dimethyl sulfoxide/NaCl solution). We evaluated testicular extracellular signal regulated kinase, tumor necrosis factor-α and interleukin-6 by Western blot. We also investigated PPARβ/δ activation by Western blot, mRNA expression and organ damage.

Results

Testicular ischemia-reperfusion injury caused a significant increase in extracellular signal regulated kinase, tumor necrosis factor-α and interleukin-6 expression in each testis. Furthermore, histological examination revealed marked damage. L-165,041 administration increased the PPARβ/δ message and protein, inhibited extracellular signal regulated kinase, tumor necrosis factor-α and interleukin-6 expression, and decreased histological damage. Concomitant administration of GW9662 reversed the protection exerted by PPARβ/δ agonist.

Conclusions

These findings indicate that PPARβ/δ agonists might be an attractive therapeutic candidate for managing testicular torsion.

Key Words: testis, spermatic cord torsion, reperfusion injury, peroxisome proliferator-activated receptors, cytokines

Abbreviations and Acronyms: ERK 1/2, extracellular regulated kinase 1/2, IL, interleukin, MAPK, mitogen activated protein kinase, PCR, polymerase chain reaction, p-ERK 1/2, phosphorylated ERK 1/2, PPAR, peroxisome proliferator-activated receptor, SDS, sodium dodecyl sulfate, TBS, tris buffered saline, TI/R, testicular ischemia/reperfusion, TNF-α, tumor necrosis factor-α