Expression and regulation of the prointerleukin-1alpha processing enzymes calpain I and II in the rat testis

Membrane-Permeable Calpain Inhibitors Promote Rat Oral Mucosal Epithelial Cell Proliferation by Inhibiting IL-1α Signaling

To standardise regenerative medicine using cultured cells, the use of serum-free, chemically defined media will be necessary. We have reported that IL-1α inhibits the growth of epithelial cells in culture and that recombinant IL-1 receptor antagonist (IL-1RA) significantly promotes epithelial cell growth in no feeder layer condition. In this study, we examined inhibitors of calpain, a cysteine proteinase that plays crucial roles in various cellular functions, including IL-1α maturation and secretion. The culturing of epithelial cells in serum-free media supplemented with a membrane-permeable calpain inhibitor significantly promoted growth while suppressing IL-1α maturation and secretion. By contrast, non-membrane-permeable calpain inhibitor treatment did not have these effects. Interestingly, immunoblotting analysis revealed that immature, untruncated, IL-1α expression was also downregulated by cell-permeable calpain inhibitor treatment, and the difference in IL-1α gene expression increased from day 2 to day 6. Although IL-1RA has been reported to promote epithelial cell growth, we detected no synergistic promotion of epithelial cell growth using a calpain inhibitor and IL-1RA. These findings indicate that calpain inhibitors promote epithelial cell proliferation by inhibiting IL-1α maturation at an early phase of epithelial cell culture and by suppressing the positive feedback-mediated amplification of IL-1α signalling.

The efficacy of an IL-1alpha vaccine depends on IL-1RI availability and concomitant myeloid-derived suppressor cell reduction

We recently reported that tumor-derived interleukin (IL)-1beta strongly promotes tumor growth by inducing myeloid-derived suppressor cell (MDSC) and regulatory T-cell (T(reg)) expansion. To see whether redirection of an immune response can be achieved through immune response-supporting IL-1alpha application, IL-1RI competent (IL-1RI(comp)) and IL-1RI-deficient (IL-1RI(-/-)) mice received IL-1alpha cDNA-transformed attenuated Salmonella typhimurium (SL-IL-1alpha) and/or lysates from methycholanthrene-induced IL-1(comp) or IL-1(-/-) fibrosarcoma cells. Vaccination with SL-IL-1alpha and/or tumor lysate exerted only a minor effect on the survival of IL-1alpha/beta(-/-) and none on IL-1alpha(comp) tumor-bearing mice despite induction of a potent antitumor response, that was overridden by intratumoral and systemic expansion of MDSC. Application of all-trans-retinoic acid together with anti-CD25 efficiently coped with MDSC and T(reg) expansion. Vaccination concomitantly with application of all-trans-retinoic acid and anti-CD25 treatment significantly increased the survival time and rate of IL-1alpha/beta(comp), but even of IL-1alpha(-/-)beta(comp) IL-1RI(comp) tumor-bearing mice. Instead, in IL-1RI(-/-) mice, though MDSC expansion was weaker, SL-IL-1alpha application hardly displayed any therapeutic efficacy, which implies signal transduction through IL-1alpha binding to the IL-1RI as an essential component for immune response induction. Taken together, IL-1alpha can efficiently support tumor vaccination, as far as expansion of MDSC and T(reg) is controlled. However, care should be taken to interfere with MDSC expansion/activation not through a blockade of the IL-1RI, which is the preferential target of IL-1alpha.

Regulation of interleukin 1alpha, activin and inhibin by lipopolysaccharide in Sertoli cells from prepubertal rats

Bacterial lipopolysaccharide increased the production of interleukin 1alpha and activin A, and reduced production of inhibin B, in Sertoli cells from immature male rats measured by enzyme-linked immunosorbent assay (ELISA). The majority of immunoreactive interleukin 1alpha remained within the Sertoli cell, while both activin A and inhibin B were secreted. Lipopolysaccharide-stimulated expression of two interleukin 1alpha mRNA transcripts, measured by quantitative RT-PCR, but the levels of bioactive interleukin 1alpha in Sertoli cell extracts and medium, measured by in vitro bioassay, were comparatively low to undetectable. A specific antagonist of interleukin 1alpha had no effect on lipopolysaccharide-stimulated activin A or inhibin B responses. These data indicate that, in contrast to Sertoli cells from adult rats, lipopolysaccharide-induced regulation of activin A and inhibin B by prepubertal Sertoli cells does not involve secreted interleukin 1alpha. The data highlight the possibility of a role for intracellular interleukin 1alpha in the Sertoli cell response to inflammation, particularly in the immature testis.

Tumorigenicity of IL-1alpha- and IL-1beta-deficient fibrosarcoma cells

Analyzing the growth of fibrosarcoma lines derived from IL-1alpha-, IL-1beta- , or IL-1alphabeta-knockout (-/-) mice in the immunocompetent host revealed that tumor-derived IL-1alpha and IL-1beta exert strong and opposing effects on immune response induction, which prohibited the evaluation of a potential impact on tumorigenicity. Therefore, in vivo growth of IL-1-deficient tumor lines was evaluated in nu/nu mice and was compared with in vitro growth characteristics. All IL-1-deficient fibrosarcoma lines grow in immunocompromised mice. However, IL-1alpha(-/-)beta-competent (comp) lines grow more aggressively, efficiently induce angiogenesis, and recruit inflammatory cells. Despite stronger tumorigenicity of IL-1beta(comp) lines, IL-1alpha strengthens anchorage-independent growth, but both IL-1alpha and IL-1beta support drug resistance. Corresponding to the aggressive growth, IL-1beta(comp) cells display increased matrix adhesion, motility, and cable formation on matrigel, likely supported by elevated alpha(v)/beta3 and matrix metalloroteinase expression. Recruitment of myeloid cells requires IL-1beta but is regulated by IL-1alpha, because inflammatory chemokine and cytokine expression is stronger in IL-1alpha(-/-)beta(comp) than in IL-1(wt) lines. This regulatory effect of tumor-derived IL-1alpha is restricted to the tumor environment and does not affect systemic inflammatory response induction by tumor-derived IL-1beta. Both sarcoma cell-derived IL-1alpha and IL-1beta promote tumor growth. However, IL-1alpha exerts regulatory activity on the tumor cell-matrix cross-talk, and only IL-1beta initiates systemic inflammation.

The expression of calpain 1 and calpain 2 in spermatogenic cells and spermatozoa of the mouse

There is some evidence suggesting that Ca2+is involved in processes that occur during the development and function of spermatozoa. Calcium-dependent proteins, such as calmodulin, are expressed during mammalian spermatogenesis further suggesting that Ca2+takes part in its regulation. However, the precise roles of Ca2+in spermatogenesis remain to be elucidated. Calpains are a family of Ca2+-dependent cysteine proteases whose members are expressed ubiquitously or in a tissue-specific manner. Calpain has been demonstrated to mediate specific Ca2+-dependent processes including cell fusion, mitosis and meiosis. We herein followed the expression pattern of calpain’s ubiquitous isoforms, 1 and 2, throughout spermatogenesis at the RNA and protein levels by RT-PCR and Western blotting analysis. Both RNA and protein studies revealed that these isoforms are expressed in all spermatogenic cells. The expression of calpain 1 levels is slightly higher in spermatocytes entering the meiotic phase. Both calpain isoforms are also expressed in mouse spermatozoa and are localized to the acrosomal cap. Inducing capacitated spermatozoa to undergo the acrosome reaction in the presence of a selective calpain inhibitor significantly reduced the acrosome reaction rate in a dose-dependent manner. Thus, calpain, a pluripotential protease with numerous substrates, may serve as an effector in more than one pathway in the complex process of spermatogenesis and in the events preceding fertilization, such as the acrosome reaction.

The Blood‐Testis Barrier: Its Biology, Regulation, and Physiological Role in Spermatogenesis

The blood-testis barrier (BTB) in mammals, such as rats, is composed of the tight junction (TJ), the basal ectoplasmic specialization (basal ES), the basal tubulobulbar complex (basal TBC) (both are testis-specific actin-based adherens junction [AJ] types), and the desmosome-like junction that are present side-by-side in the seminiferous epithelium. The BTB physically divides the seminiferous epithelium into basal and apical (or adluminal) compartments, and is pivotal to spermatogenesis. Besides its function as an immunological barrier to segregate the postmeiotic germ-cell antigens from the systemic circulation, it creates a unique microenvironment for germ-cell development and confers cell polarity. During spermatogenesis, the BTB in rodents must physically disassemble to permit the passage of preleptotene and leptotene spermatocytes. This occurs at late stage VII through early stage VIII of the epithelial cycle. Studies have shown that this dynamic BTB restructuring to facilitate germ-cell migration is regulated by two cytokines, namely transforming growth factor-beta3 (TGF-beta3) and tumor necrosis factor-alpha (TNFalpha), via downstream mitogen-activated protein kinases. These cytokines determine the homeostasis of TJ- and basal ES-structural proteins, proteases, protease inhibitors, and other extracellular matrix (ECM) proteins (e.g., collagen) in the seminiferous epithelium. Some of these molecules are known regulators of focal contacts between the ECM and other actively migrating cells, such as macrophages, fibroblasts, or malignant cells. These findings also illustrate that cell-cell junction restructuring at the BTB is regulated by mechanisms involved in the junction turnover at the cell-matrix interface. This review critically discusses these latest findings in the field in light of their significance in the biology and regulation of the BTB pertinent to spermatogenesis.