Differential expression and activity of matrix metalloproteinases 2 and 9 in canine early placenta

The zonary and endotheliochorial dog placenta is the most invasive placenta of carnivores. The importance of matrix metalloproteinases (MMP) in placenta invasiveness has been determined in several mammals including species with haemochorial, epitheliochorial and endotheliochorial placentation. Regarding the latter, the expression of MMP enzymes has been studied in the cat and the mature canine placenta. The aim of this study was to analyse the expression and activity of MMP-2 and MMP-9 in the early dog placenta. Placentae from 18 to 30 days of pregnancy were collected from four bitches. Two placentae from each bitch were analysed. Placental tissue from one uterine horn was fixed in formaldehyde for immunohistochemistry, while marginal haematoma, labyrinth, non-implantative and implantative endometrium from the contralateral horn were immediately frozen in dry ice for the analysis of MMP expression (Western blot [WB]) and activity (zymography). MMP-2 and MMP-9 were evidenced in the labyrinth, maternal glands and marginal haematoma; this finding was directly correlated with levels of MMP expression by WB, and with the activity of MMP-2, mainly in the haematoma (the area of major remodelling of tissues). Thus, although MMP-9 is well expressed in the early canine placenta, it is not active. Given the important role of MMPs for invasiveness, maternal-foetal angiogenesis and the establishment of a correct foetal nutrition, the results are consistent with the findings in other species in which the MMP-2 activation precedes the MMP-9 one in early placentation.

Impaired expression and distribution of adherens and gap junction proteins in the seminiferous tubules of rats undergoing autoimmune orchitis

Experimental autoimmune orchitis (EAO) is characterized by an interstitial lymphomononuclear cell infiltration and a severe lesion of seminiferous tubules (ST) with germ cells that undergo apoptosis and sloughing. The aim of this study was to analyse the expression and localization of adherens junction (AJ) proteins: N-cadherin, α-, β- and p120 catenins and gap junction protein, connexin 43 (Cx43), to explore some aspects of germ-cell sloughing during the development of orchitis. EAO was induced in Sprague-Dawley adult rats by active immunization with testicular homogenate and adjuvants. Control rats (C) were injected with saline solution and adjuvants. Concomitant with early signs of germ-cell sloughing, we observed by immunofluorescence and Western blot, a delocalization and a significant increase in N-cadherin and α-catenin expression in the ST of EAO compared with C rats. In spite of this increased AJ protein expression, a severe germ-cell sloughing occurred. This is probably due to the impairment of the AJ complex function, as shown by the loss of N-cadherin/β-catenin colocalization (confocal microscopy) and increased pY654 β-catenin expression, suggesting lower affinity of these two proteins and increased pERK1/2 expression in the testis of EAO rats. The significant decrease in Cx43 expression detected in EAO rats suggests a gap junction function impairment also contributing to germ-cell sloughing.

Adenosine regulates Sertoli cell function by activating AMPK

This work evaluates adenosine effects on Sertoli cell functions, which are different to those resulting from occupancy of purinergic receptors. The effects of adenosine and N(6)-cyclohexyladenosine (CHA) - an A(1) receptor agonist resistant to cellular uptake - on Sertoli cell physiology were compared. Adenosine but not CHA increased lactate production, glucose uptake, GLUT1, LDHA and MCT4 mRNA levels, and stabilized ZO-1 protein at the cell membrane. These differential effects suggested a mechanism of action of adenosine that cannot be solely explained by occupancy of type A(1) purinergic receptors. Activation by adenosine but not by CHA of AMPK was observed. AMPK participation in lactate production and ZO-1 stabilization was confirmed by utilizing specific inhibitors. Altogether, these results suggest that activation of AMPK by adenosine promotes lactate offer to germ cells and cooperates in the maintenance of junctional complex integrity, thus contributing to the preservation of an optimum microenvironment for a successful spermatogenesis.

Parathion induces mouse germ cells apoptosis

Germ cell loss occurs in normal spermatogenesis at defined stages of the seminiferous epithelial cycle. The process has been known for over a century but only recently it was analyzed under the concept of apoptosis. This is a programmed cell death that occurs during development and also in the adult. It is believed to play a key role as quality control in sperm formation, avoiding the passage of genetic defects to future generations. Chemical toxicants may increase apoptosis, disturbing tissue homeostasis. The effect of the agropesticide parathion upon apoptosis in mouse seminiferous tubules was analyzed in young mice (onset of spermatogenesis) and in adult animals (full spermatogenesis). In both young and adult mice, the pesticide increases the rate of apoptosis, which takes place at stages where spermatogonial proliferation occurs, affects spermatocytes at the beginning of the meiotic process and spermatids at the elongating period. Basal apoptotic rates are greater in young mice. In adults, commercial parathion is more toxic than the pure organophosphoric compound. From these observations plus in vitro effects of parathion reported previously, it can be concluded that the pesticide affects DNA (and RNA and protein) synthesis. The effect is reversible with moderate doses of the chemical after acute intoxication.

Sperm quality in mice acutely treated with parathion

AIM

To investigate the toxic effect of a single injection of the organophosphorous agropesticide, parathion, on spermatogenesis in immature male mice.

METHODS

Seven-day old mice received a single injection of parathion intraperitoneally at a dose of 1/3 LD50. The epididymal sperm count, sperm morphology and chromatin thermal stability were analyzed 28 and 50 days after injection.

RESULTS

Sperm counts were decreased and teratozoospermia and thermal denaturation of DNA increased after parathion injection. Sperm parameters were changed to a greater extent in younger animals, denoting a higher lability of spermatogenic process at its beginning. The damages could recover a long time after parathion administration.

CONCLUSION

Organophosphorous agropesticides are testicular toxicants, eliciting reversible cytotoxic and cytogenetic alterations in germ cells.