Simona Tafuri

Expression of orexin A and its receptor 1 in the bovine urethroprostatic complex.

Orexin A (oxA) and orexin B are recently discovered peptides derived from the proteolytic cleavage of the common precursor prepro‐orexin. They bind two G protein‐coupled receptors, defined orexin 1 (ox1R) and orexin 2 receptor. Both peptides are highly expressed in the lateral hypothalamic area of the brain and are involved in the regulation of many functions of the body, the best investigated of which is food intake. Recent data described the presence of orexins in peripheral organs such as the adrenal glands, stomach, bowel, pancreas, and testis. Here, we report the detection of oxA and ox1R in the exocrine and endocrine cytotypes of the cattle urethroprostatic complex by using immunohistochemistry. The expression of prepro‐orexin and ox1R mRNA transcripts in the prostatic tissue was assessed by reverse‐transcriptase polymerase chain reaction, while the presence of both the proteins in the tissue was confirmed by Western blotting analysis. Our findings provide the first evidence for the presence of oxA and ox1R in the urethroprostatic complex of the cattle and demonstrate that both proteins are locally synthesized, thus suggesting a role for oxA on both physiological and pathological functioning of the complex. Anat Rec, 291:169–174, 2008.

Novel localization of orexin A in the tubular cytotypes of the rat testis.

The hypothalamic peptides orexin A (OXA) and orexin B (OXB), deriving from the proteolytic cleavage of the precursor molecule prepro-orexin, have also been localized in multiple cerebral areas and peripheral organs. They regulate food intake, arterial blood pressure, heart rate, sleep/wake cycle, sexual behavior, arousal, and the hypothalamic/hypophyseal axes. Prepro-orexin mRNA expression and OXA-immunoreactivity were previously detected in the rat testis at different ages of postnatal development, with strong peptide signal in Leydig cells and spermatocytes. In this study, OXA-immunoreactivity was found in Sertoli cells and spermatids of rat testis. Hematoxylin-counterstained sections revealed OXA positive spermatids in the stages of the germinal epithelium cycle ranging from the VIIth to the XIVth. The expression of prepro-orexin mRNA and of the protein in the testis tissue was ascertained by reverse-transcription polymerase chain reaction and Western blotting analysis, respectively. Although the functional role of OXA in the male genital tract still remains to be elucidated, our findings provide the first evidence that Sertoli cells, belonging to the tubular compartment of testis, represent an important source of OXA, thus suggesting the potential involvement of the peptide in the control of seminiferous epithelium development.

H2O2 activity on platelet adhesion to fibrinogen and protein tyrosine phosphorylation

Platelets represent a target of reactive oxygen species produced under oxidative stress conditions. Controversial data on the effect of these species on platelet functions have been reported so far. In this study we evaluated the effect of a wide range of H(2)O(2) concentrations on platelet adhesion to immobilized fibrinogen and on pp72(syk) and pp125(FAK) tyrosine phosphorylation. Our results demonstrate that: (1) H(2)O(2) does not affect the adhesion of unstimulated or apyrase-treated platelets to immobilized fibrinogen; (2) H(2)O(2) does not affect pp72(syk) phosphorylation induced by platelet adhesion to fibrinogen-coated dishes; (3) H(2)O(2) reduces, in a dose-dependent fashion, pp125(FAK) phosphorylation of fibrinogen-adherent platelets; (4) concentrations of H(2)O(2) near to physiological values (10-12 microM) are able to strengthen the subthreshold activation of pp125(FAK) induced by epinephrine in apyrase-treated platelets; (5) H(2)O(2) doses higher than 0.1 mM inhibit ADP-induced platelet aggregation and dense granule secretion. The ability of H(2)O(2) to modulate pp125(FAK) phosphorylation suggests a role of this molecule in physiological hemostasis as well as in thrombus generation.

Expression of Orexin A and Its Receptor 1 in the Vestibular Glands of the Cattle Genital Tract

The hypothalamic peptide orexin A (oxA) binds specifically the G‐protein–coupled orexin receptor 1 (ox1R). It is involved in many physiological functions including the regulation of food intake, sleep–wake cycle, arterial blood pressure, heart rate, and sexual behavior. The localization of oxA in adrenal glands, stomach, bowel, pancreas, and testis has recently been assessed. Here, we provide the first evidence for the expression of oxA and ox1R in the vestibular glands of mammalian genital tract. Anat Rec, 2009. copy; 2008 Wiley‐Liss, Inc.

INTEGRIN RECEPTORS PLAY A ROLE IN THE INTERNALIN B- DEPENDENT ENTRY OF Listeria monocytogenes INTO HOST CELLS

Listeria monocytogenes enters non-phagocytic cells by binding its surface proteins inlA (internalin) and inlB to the host’s E-cadherin and Met, respectively. The two internalins play either separate or cooperative roles in the colonization of infected tissues. Here, we studied bacterial uptake into HeLa cells using an L. monocytogenes mutant strain (ΔinlA) carrying a deletion in the gene coding for inlA. The ΔinlA mutant strain showed the capability to invade HeLa cells. The monoclonal anti-β3- and anti-β1-integrin subunit antibodies prevented bacterial uptake into the cells, while the anti-β2- and anti-β4-integrin subunit antibodies failed to affect L. monocytogenes entry into HeLa cells. Three structurally distinct disintegrins (kistrin, echistatin and flavoridin) also inhibited bacterial uptake, showing different potencies correlated to their selective affinity for the β3- and β1-integrin subunits. In addition to inducing Met phosphorylation, infection of cells by the L. monocytogenes ΔinlA mutant strain promoted the tyrosine phosphorylation of the focal adhesion-associated proteins FAK and paxillin. Our findings provide the first evidence that β3- and β1-integrin receptors play a role in the inlB-dependent internalization of L. monocytogenes into host cells.

Expression of orexin A and its receptor 1 in the rat epididymis

The hypothalamic peptide orexin A (oxA) derives from the proteolytic cleavage of the precursor molecule prepro-orexin. It binds with the high affinity G-protein-coupled orexin receptor 1 (OX1R). Here, we report the detection of oxA and OX1R in the principal cells of the rat caudal epididymis by immunohistochemistry. Both oxA and OX1R immunolabelling showed cytoplasmic supranuclear localization, filling the apical portion of the cells. The expression of prepro-orexin and OX1R mRNA transcripts in the rat epididymis was assessed by reverse-transcriptase polymerase chain reaction, while the presence of both these proteins in the tissue was confirmed by Western blotting analysis. Our findings provide the evidence for the presence of oxA and OX1R in the rat epididymis, and demonstrate that both proteins are locally synthesised, thus suggesting a role for oxA in governing the fertilizing capability of the immature male gamete.

Role of connexin-43 hemichannels in the pathogenesis of Yersinia enterocolitica.

Connexin (Cx) channels are sites of cytoplasmic communication between contacting cells. Evidence indicates that the opening of hemichannels occurs under both physiological and pathological conditions. In this paper, the involvement of Cx-43 hemichannels is demonstrated in the pathogenesis of Yersinia. Parental HeLa cells and transfected HeLa cells stably expressing Cx-43 (HCx43) were infected with Yersiniaenterocolitica, and bacterial uptake was measured by the colony-forming unit method. Bacterial uptake was higher in HCx43 cells than in parental cells and was inhibited by the Cx channel blocker, 18-alpha-glycyrrhetinic acid (AGA). The inhibitory effect of AGA was more pronounced on the Y. enterocolitica uptake by HCx43 cells than by parental cells. The ability of HCx43 cells to incorporate the permeable fluorescent tracer Lucifer Yellow (LY) was assessed. Dye incorporation was inhibited by AGA, whereas Y. enterocolitica infection of HCx43 cells increased LY incorporation. Western blotting analysis demonstrated that Y. enterocolitica infection of HCx43 cells induced tyrosine phosphorylation of Cx-43, thus supporting a critical role for Cx-43 in the strategies exploited by bacterial pathogens to invade non-phagocytic cells.

THE MYCOTOXIN FUMONISIN B1 INHIBITS INTEGRIN-MEDIATED CELL-MATRIX ADHESION

Fumonisin B1 (FB1), a mycotoxin produced by the corn fungus Fusarium moniliforme, causes a variety of animal diseases and is a suspected human carcinogen. The FB1 molecule bears remarkable structural resemblance to the long-chain sphingoid base backbones of sphingolipids. The toxicity and carcinogenicity of FB1 has been ascribed to its ability to inhibit ceramide synthase, a key enzyme in the metabolism of complex sphingolipids. In this study we have investigated whether the exposure of B16-BL6 mouse melanoma cells to FB1 affects cell growth and integrin-mediated cell matrix adhesion. Cell treatment with the highest tested dose (75 microM) of FB1 for 72 h induced an about 20% inhibition of cell growth. FB1 strongly affected B16-BL6 cell adhesion to immobilized fibronectin, by causing a dose-dependent inhibition of cell attachment to this substrate. FB1 also inhibited in a dose-dependent manner the adhesion of B16-BL6 cells to the immobilized anti-fibronectin receptor antibody, whereas it affected only to a low extent cell attachment to concanavalin A. Our results demonstrate that FB1 treatment alters integrin adhesive activity, thus affecting all cellular integrin-dependent functions.

Expression of orexin B and its receptor 2 in rat testis.

The peptides orexin A (OxA) and orexin B (OxB) deriving from a common precursor molecule, prepro-orexin, by proteolytic cleavage, bind the two G-coupled OX1 and OX2 receptors. While OX1 selectively binds OxA, OX2 shows similar affinity for both orexins. Firstly discovered in the hypothalamus, orexins and their receptors have been found in other brain regions as well as in peripheral tissues of mammals, thus resulting involved in the regulation of a broad variety of physiological functions. While the functional localization of OxA and OX1 in the mammalian genital tract has been already described, the expression of OxB and OX2 and their potential role in the reproductive functions remain to be explored. Here, we investigated the presence of OxB and OX2 in the rat testis by immunohistochemical and biochemical analyses. The results definitely demonstrated the localization of OxB and OX2 in pachytene and second spermatocytes as well as in spermatids at all stages of the cycle of the seminiferous epithelium. The expression of both OX2 mRNA and protein in the rat testis was also established by RT-PCR and Western blotting, respectively. The analysis of the molecular mechanism of action of OxB in the rat testis showed that OxB, in contrast with OxA, is unable to promote steroidogenesis. These results translate into the regulation of diverse biological actions by OxA and OxB in the male gonad.

Ochratoxin A affects COS cell adhesion and signaling

Ochratoxin A (OTA), a metabolite produced by strains of Aspergillus and Penicillium, has nephritogenic, carcinogenic, and teratogenic activity in animals and humans. Nanomolar concentrations of OTA promote apoptosis in a cell-type specific fashion. In this study, we have analyzed the molecular mechanism by which OTA affects COS cell adhesion and signaling resulting in an apoptotic response. OTA, at noncytotoxic doses, was able to detach collagen- and fibronectin-adherent cells from immobilized substratum. However, prior to inducing detachment of adherent cells, OTA caused apoptosis as measured by caspase-3 activation. The treatment of adherent cells by OTA caused a reduction of tyrosine phosphorylation levels of FAK and of the adapter protein paxillin. The down-regulation of FAK preceded apoptosis and cell detachment induced by OTA. The mycotoxin was also able to cause a decrease of the phosphorylation levels of the two Shc isoforms, P66 and P52, in adherent cells. Since these Shc isoforms have been implicated in the activation of protein kinase c-Src, which is required for FAK tyrosine phosphorylation, the observed dephosphorylation of FAK and of the FAK substrate paxillin by OTA could be ascribed to the early down-regulation of Shc isoforms. However, whether FAK and Shc phosphorylation contribute both to the same pathway leading to the induction of apoptosis by OTA or are involved in two parallel signaling pathways remains to be investigated.