title: Regulation of blood-testis barrier dynamics: an in vivo study.
abstract: An in vivo model was used to investigate the regulation of tight junction (TJ) dynamics in the testis when adult rats were treated with CdCl(2). It was shown that the CdCl(2)-induced disruption of the blood-testis barrier (BTB) associated with a transient induction in testicular TGF-beta2 and TGF-beta3 (but not TGF-beta1) and the phosphorylated p38 mitogen activated protein (MAP) kinase, concomitant with a loss of occludin and zonula occludens-1 (ZO-1) from the BTB site in the seminiferous epithelium. These results suggest that BTB dynamics in vivo are regulated by TGF-beta2/-beta3 via the p38 MAP kinase pathway. Indeed, SB202190, a specific p38 MAP kinase inhibitor, blocked the CdCl(2)-induced occludin and ZO-1 loss from the BTB. This result clearly illustrates that CdCl(2) mediates its BTB disruptive effects via the TGF-beta3/p38 MAP kinase signaling pathway. Besides, this CdCl(2)-induced occludin and ZO-1 loss from the BTB also associated with a significant loss of the cadherin/catenin and the nectin/afadin protein complexes at the site of cell-cell actin-based adherens junctions (AJs). An induction of alpha(2)-macroglobulin (a non-specific protease inhibitor) was also observed during BTB damage and when the seminiferous epithelium was being depleted of germ cells. These data illustrate that a primary disruption of the BTB can lead to a secondary loss of cell adhesion function at the site of AJs, concomitant with an induction in protease inhibitor, which apparently is used to protect the epithelium from unwanted proteolysis. alpha(2)-Macroglobulin was also shown to associate physically with TGF-beta3, afadin and nectin 3, but not occludin, E-cadherin or N-cadherin, indicating its possible role in junction restructuring in vivo. Additionally, the use of SB202190 to block the TGF-beta3/p-38 MAP kinase pathway also prevented the CdCl(2)-induced loss of cadherin/catenin and nectin/afadin protein complexes from the AJ sites, yet it had no apparent effect on alpha(2)-macroglobulin. These results demonstrate for the first time that the TGF-beta3/p38 MAP kinase signaling pathway is being used to regulate both TJ and AJ dynamics in the testis, mediated by the effects of TGF-beta3 on TJ- and AJ-integral membrane proteins and adaptors, but not protease inhibitors.
authors.affiliation: Population Council, Center for Biomedical Research, 1230 York Avenue, New York, NY 10021, USA.
authors.forename: Ching-Hang
authors.initials: CH
authors.lastname: Wong
authors.forename: Dolores D
authors.initials: DD
authors.lastname: Mruk
authors.forename: Wing-Yee
authors.initials: WY
authors.lastname: Lui
authors.forename: C Yan
authors.initials: CY
authors.lastname: Cheng
mesh_terms: D022005:Adherens Junctions / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D001814:Blood-Testis Barrier / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D019256:Cadmium Chloride / Q000494:pharmacology; D003598:Cytoskeletal Proteins / Q000378:metabolism; D007093:Imidazoles / Q000494:pharmacology; D020935:MAP Kinase Signaling System / Q000187:drug effects; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D062793:Occludin; D010447:Peptide Hydrolases / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D011480:Protease Inhibitors / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012670:Seminiferous Epithelium / Q000187:drug effects / Q000378:metabolism; D013737:Testis / Q000187:drug effects / Q000378:metabolism*; D019108:Tight Junctions / Q000378:metabolism / Q000648:ultrastructure; D016212:Transforming Growth Factor beta / Q000378:metabolism; D062826:Zonula Occludens-1 Protein; D000511:alpha-Macroglobulins / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D003598:Cytoskeletal Proteins; D007093:Imidazoles; D008565:Membrane Proteins; D062793:Occludin; C568987:Ocln protein, rat; D010750:Phosphoproteins; D011480:Protease Inhibitors; D011725:Pyridines; C569044:Tjp1 protein, rat; D016212:Transforming Growth Factor beta; D062826:Zonula Occludens-1 Protein; D000511:alpha-Macroglobulins; D048051:p38 Mitogen-Activated Protein Kinases; D010447:Peptide Hydrolases; D019256:Cadmium Chloride; C090942:4-(4-fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)imidazole