MEHP-induced rat testicular inflammation does not exacerbate germ cell apoptosis

Abstract

The testis is an organ that maintains an immune suppressive environment. We previously revealed that exposure of pre-pubertal rats to an acute dose of a well-described Sertoli cell toxicant, mono-(2-ethylhexyl) phthalate (MEHP), leads to an accumulation of CD11b+ immune cells in the testicular interstitial space that closely correlates with a robust incidence of germ cell (GC) apoptosis. Here, we test the hypothesis that the infiltrating immune cells contribute to GC apoptosis. Postnatal day 28 Fischer rats that received an oral dose of 700 mg/kg MEHP showed a significant infiltration of both CD11bc+/CD68+/CD163- macrophages and neutrophils. The infiltration peaked at 12 h, but had reduced by 48 h. Testicular macrophages from MEHP-treated rats showed significantly upregulated expression of and, and the ratio was reduced compared to controls. However, small increases in anti-inflammatory genes and were also observed. Depletion of circulating monocytes with clodronate liposomes prior to MEHP treatment reduced the macrophage influx into the testis, but did not lower GC apoptosis. Additionally, depletion of neutrophils using an anti-polymorphonuclear cell antibody prevented both macrophage and neutrophil infiltration into the testis, and also did not affect GC apoptosis. Together, these results show that exposure to MEHP leads to a rapid and temporary influx of pro-inflammatory monocytes and neutrophils in the interstitium of the testis. However, with this acute dosing paradigm, these infiltrating leukocytes do not appear to contribute to MEHP-induced testicular GC apoptosis leaving the functional significance of these infiltrating cells in the pathogenesis of MEHP-induced testicular injury unresolved.

Responses of peritubular macrophages and the testis transcriptome profiles of peripubertal and adult rodents exposed to an acute dose of MEHP

“…Additionally, the expression pattern of tight-junction genes ( Ctnnb1 , Itgb1 , Sorbs1 ) suggested the potential involvement of the blood-testis barrier (BTB) in PTMφ response, consistent with previous observations of BTB disruption by MEHP exposure in peripubertal Fischer CDF344 rats ( Tiwary and Richburg, 2023 ). In prior studies, we also demonstrated that exposure to MEHP in peripubertal Fischer CDF344 rats resulted in a significant influx of immune cells when compared with adult rats ( Murphy et al , 2014 ; Voss et al , 2018 ). In line with those findings, the current study observed downregulation of several normal macrophage marker genes ( C1qa , C1qb , CX3CR1 ) and upregulation of the monocyte lineage gene marker CD68 , as well as upregulation of M2 macrophage-associated genes ( Arg1 , Mmp9 , Mafb ).…”

“…Finally, sections were counterstained with DAPI and cover-slipped for microscopic observation. For Caspase 3 staining, the apoptotic index (AI) was calculated as the percentage of essentially round seminiferous tubules containing more than 3 Caspase 3-positive GCs in each cross section, as described in previous study ( Voss et al , 2018 ). An isotype-matched rabbit IgG antibody was used to evaluate the nonspecific binding of the primary antibody.…”

“…Specifically, young rodents are more sensitive to phthalate’s toxic effects on the testis than adult rodents. We have previously shown that MEHP exposure in peripubertal rats elicits a robust infiltration of macrophages and neutrophils compared with adult rats ( Murphy et al , 2014 ; Voss et al , 2018 ), this increased sensitivity might be attributed to the fact that the immature developing physiological systems of the young animals ( Blacher et al , 2022 ; Gardner, 1980 ), makes them more vulnerable to the toxicity of MEHP but capable of repair and regeneration. In addition to age, we have also observed species differences in susceptibility to MEHP, with rats being more sensitive than mice.…”

IL-17A deficiency alleviate fluoride-induced injury by inhibiting immune response and apoptosis in testis

“…The changes of testicular environment caused by abnormal expression of cytokines can induce excessive apoptosis [42,43]. Hence, we detected the expression of two key apoptosis proteins in testis, caspase-3 and caspase-9 acted an irreplaceable role in apoptosis [44].…”

Predictive value of hematological parameters in testicular salvage: A 12-year retrospective review

“…After tissue injury, monocytes proliferate rapidly in the bone marrow and enter the circulation under the action of monocyte chemokine CCL2, which can reach the site of tissue injury within 1 h ( 23 ). Monocytes can also differentiate into dendritic cells or macrophages involved in the inflammatory response caused by testicular injury ( 22 , 24 ). Nemeth et al ( 25 ) examined the hematological parameters of rats after testicular ischemia-reperfusion, and observed that the white blood cell count and monocyte-granulocyte ratio increased significantly, and the monocyte-granulocyte ratio doubled on the first postoperative day.…”