Interleukin 1 Alpha (IL1A) Is a Novel Regulator of the Blood-Testis Barrier in the Rat1

Abstract

Throughout spermatogenesis, leptotene spermatocytes must traverse the blood-testis barrier (BTB) at stages VIII-XI to gain entry into the adluminal compartment for continued development. However, the mechanism underlying BTB restructuring remains somewhat elusive. In this study, interleukin 1 alpha (IL1A) was administered intratesticularly to adult rats in order to assess its effects on spermatogenesis. IL1A was shown to perturb Sertoli-germ cell adhesion, resulting in germ cell loss from approximately 50% of seminiferous tubules by 15 days posttreatment. Equally important, the functional integrity of the BTB was compromised when inulin-fluorescein isothiocyanate was detected in the adluminal compartment of the seminiferous epithelium following its administration via the jugular vein. Interestingly, IL1A did not affect the steady-state levels of proteins that confer BTB function, namely OCLN, CLDN1, F11R, TJP1, and CDH2. Instead, the localizations of OCLN, F11R, and TJP1 in the seminiferous epithelium were altered; these proteins appeared to move away from sites of cell-cell contact. Moreover, IL1A was shown to perturb the orderly arrangement of filamentous actin at the BTB and apical ectoplasmic specialization with distinct areas illustrating loss of actin filaments. Taken collectively, these results suggest that IL1A-induced BTB disruption is not mediated via the reduction of target protein levels. Instead, IL1A's primary cellular target appears to be the Sertoli cell actin cytoskeleton. It is possible that localized production of IL1A by Sertoli and/or germ cells in vivo results in BTB restructuring, and this may facilitate the movement of leptotene spermatocytes across the BTB.

Intercellular adhesion molecule-1 is a regulator of blood–testis barrier function

“…In control testes, F-actin localized to the BTB and apical ES (Fig. 7Da-c) as previously described (Kopera et al, 2009;Sarkar et al, 2008). Following sICAM-1 overexpression, a loss of F-actin was observed at the BTB (Fig.…”

“…Readings obtained from Matrigel TM -coated 'blank' Millicell inserts (ones that did not contain any Sertoli cells) were then subtracted from each averaged value and subsequently multiplied by the effective growth surface area (0.6 cm 2 ). F-actin was stained as previously described (Kopera et al, 2009;Mruk and Lau, 2009;Sarkar et al, 2008).…”

“…and xylazine-HCl (15 mg/kg b.w.) anesthesia/analgesia as previously described (Kopera et al, 2009;Sarkar et al, 2008). Approximately 30 min thereafter, rats were euthanized by CO 2 asphyxiation, and testes were removed and snap-frozen in liquid nitrogen.…”

Actin-binding protein drebrin E is involved in junction dynamics during spermatogenesis

“…Cytokines, such as TGFβ3, TNFα and IL-1α, are known to regulate cell adhesion at the BTB 48,[61][62][63] by facilitating endocytic vesicle-mediated protein trafficking events. 43,44,64 Even though drebrin E per se was not highly expressed at the BTB during restructuring of the immunological barrier at stage VIII of the epithelial cycle (but only at stages V and VI of the cycle as shown herein) when transit of preleptotene spermatocytes at the BTB occurs, 14,65,66 the steadystate level of drebrin E was shown to be regulated by cytokines.…”

Anchoring Junctions As Drug Targets: Role in Contraceptive Development

“…For example, TNF-␣ was shown to disrupt actin microfilaments and microtubules (Domnina et al, 2002(Domnina et al, , 2004, whereas TGF-␤1 affected microtubule dynamics in endothelial cells (Birukova et al, 2005). In this context, it is interesting to note that intratesticular administration of IL-1␣ was shown to perturb Sertoli cell actin dynamics without significantly affecting the steady-state levels of cadherin and catenin, resulting in the depletion of germ cells from the seminiferous epithelium (Sarkar et al, 2008). From these examples, it is clear that cytoskeletal integrity is required for anchoring junction function.…”