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The enzymatic activities of purified horseradish peroxidase, selenium-dependent glutathione peroxidase, thyroid peroxidase and myeloperoxidase, but not that of lactoperoxidase, were markedly enhanced when added into a reaction mixture containing 5 lm native seminal vesicle protein 4, a major protein secreted from rat seminal vesicle epithelium. A further increase of horseradish peroxidase activity was obtained using Ser58-phosphorylated or acetylated seminal vesicle protein 4. The activating effect of native seminal vesicle protein 4 was highest (about 60-fold) on horseradish peroxidase when 4-chloro-1-naphtol was used as the electron donor substrate. The main kinetics parameters of the stimulatory effect on horseradish peroxidase were evaluated and the enzyme–electron donor substrate interaction was investigated by HPLC and electrospray-MS. A native seminal vesicle protein 4 ⁄ 4-chloro-1-naphtol noncovalent adduct was detected when the protein and 4-chloro-1-naphtol were present in the appropriate molar ratio in the horseradish peroxidase-catalyzed reaction. By contrast, no adducts were formed between native seminal vesicle protein 4 and horseradish peroxidase. This native seminal vesicle protein 4 ⁄ 4-chloro-1-naphtol interaction might underlie the native seminal vesicle protein 4-induced horseradish peroxidase stimulation. Furthermore, native seminal vesicle protein 4 was shown by spectrophotometric and electrospray-MS analysis to interact with NADPH, an electron donor substrate of the selenium-dependent glutathione peroxidase ⁄ glutathione reductase redox system, with formation of an adduct between them. Although further investigation is required to elucidate the mechanism of adduct formation, this interaction, probably by promoting the release of the NADPH electrons required for glutathione disulphide reduction, could explain the stimulatory effect of seminal vesicle protein 4 on mammalian peroxidases possibly involved in its physiological function on the selenium-dependent glutathione peroxidase ⁄ glutathione reductase system. The biological significance of these properties of native seminal vesicle protein 4 might be related to its ability to downregulate reactive oxygen species and oxidative stress-induced apoptosis.

BACKGROUND/AIMS: Calbindin D28k has been reported to be involved in transcellular calcium transport along the rat distal convoluted tubule (DCT). It has also been shown that administration of bumetanide is associated with hypercalciuria. The experiments reported here were designed to verify whether chronic infusion of this diuretic affects the gene expression and protein abundance of calbindin D28k along rat kidney DCT. METHODS: Bumetanide was subcutaneously infused by an osmotic minipump for 7 days at a rate of 1.5 mg x h(-1) x kg(-1). cDNA was synthesized from total RNA extracted from DCT microdissected from collagenase-treated kidneys. RESULTS: Calbindin D28k mRNA abundance, quantified by competitive PCR, was found to be 13.7 +/- 1.9 amol x ng(-1) total RNA in DCT of control rats (n = 4) as compared to 24.2 +/- 2.4 amol x ng(-1) total RNA in DCT of bumetanide- treated rats (n = 5) (p < 0.01). This effect was associated with a 52% increase (p < 0.005) in calbindin D28k protein abundance, as detected by Western blot performed on tissue slices from renal cortex (n = 4). CONCLUSION: These data not only demonstrate that bumetanide upregulates the mRNA and protein abundance of calbindin D28k in rat DCT, but also suggest that DCT calcium reabsorption is increased following the administration of this loop diuretic.

Aim. The alveolar epithelium of human lower respiratory tract is susceptive to the deleterious effects of reactive oxigen metabolites (ROM) derived from different sources, including inhaled pollutants and inflammatory cells. The high levels of ROM produce the peroxidation of cell membrane phospholipids with consequent alteration of the normal function of pulmonary cells. These cells defend themselves against ROM by using anti-oxidant systems, including the glutathione peroxidase/glutathione reductase (GPX/GR) enzymatic system. In this study we evaluated the amount of lipoperoxides and of the enzymatic activity of glutathione peroxidase (GPX) in the bronchoalveolar lavage (BAL) cells of normal subjects and of patients with lung disease treated or not with prednisone. Methods. The study population consisted of 5 healthy individuals with acute or chronic lung disease without pharmacological treatment and 8 patients with pharmacological treatment. All individuals participating in this study underwent a broncoscopy with BAL. After preparation of BAL cells lipoperoxides concentration and GPX activity was evaluated. Results. Our results show that the untreated patients possess high levels of lipoperoxides in their BAL cells, while the GPX activity is lower than the one found in normal subjects. In contrast, in the BAL cells of treated patients the level of lipoperoxides is lower than the one detected in untreated patients, while there is an increase in the GPX activity in comparison with both normal subjects and untreated patients. Conclusion. In conclusion, these data show that prednisone could determine an increase in anti-oxidative defences in pulmonary cells.

In this study we show that SV-IV, a major immunomodulatory, anti-inflammatory, and sperm immunoprotective protein secreted from the rat seminal vesicle epithelium, acts in vitro as a substrate of protein kinase C (PKC) competing efficiently with H1 histone, a very well known PKC substrate. Electrospray mass spectrometry (ES-MS) analysis demonstrated that approximately 10% of the native SV-IV molecules were phosphorylated by PKC and that such a modification involved only a single serine residue (Ser58) out of the 22 occurring in the protein. Interestingly, this modification produced a substantial enhancement (approximately 50%) of the native SV-IV's ability to stimulate the activity of both horseradish peroxidase (POD) and selenium-dependent glutathione peroxidase (GPX), an enzyme that is known to protect the mammalian spermatozoa from oxidative stress and loss of motility in the female genital tract following ejaculation. In contrast, the phosphorylation of SV-IV on Ser58 did not produce any effect on the anti-inflammatory properties of SV-IV, as measured by its ability to inhibit the phospholipase A2.

Increase of VPAC receptor s binding to the (16)gamma-glutamyl diaminopropane vasoactive intestinal peptide (VIP-DAP) agonist, a vasoactive intestinal polypeptide (VIP) structural analogue containing a positive charge at position 16, has confirmed the importance of a positive charge at this site. By investigating the effect of distance from the peptide backbone Calpha of a positive charge in position 16, data are reported here concerning: (i) a novel chemical method used for the synthesis of a new family of (16)gamma-glutamyl diamine VIP derivatives differing among them for single carbon atoms and including diaminoethane (VIP-DAE2), diaminopropane (VIP-DAP3), diaminobutane (VIP-DAB4), diaminopentane (VIP-DAP5), and diaminohexane (VIP-DAH6); (ii) functional characterization of these compounds on human VPAC1 and VPAC2 receptors. In more detail, the EC50 and IC50 values, when measured as a function of the alkylic chain length, show in more detail, that the use of VIP-DAB4 derivative changes the IC50 but not the EC50, thus indicating on hVPAC2 receptor an unexpected relationship between binding and activity that differs from that obtained on hVPAC1.

Seminal vesicle protein IV (SV-IV) is a secretory anti-inflammatory, procoagulant, and immunomodulatory protein produced in large amounts by the seminal vesicle epithelium of the rat under the strict transcriptional control of androgen. In particular, this protein was shown to possess the ability to markedly inhibit in vivo the humoral and cell-mediated immune responses of mice to nonbacterial cellular antigens (sheep erythrocytes and spermatozoa). We report data that demonstrate that in mice treated with SV-IV and infected with Salmonella enterica serovar Typhimurium, SV-IV is able to downregulate some important immunological and biochemical parameters that serovar Typhimurium normally upregulates in these animals. This event did not correlate with a lower bacterial burden but was associated with a markedly increased one (300%). Furthermore, the treatment of mice with SV-IV alone also produced a significant increase in the rate of mortality among serovar Typhimurium-infected animals. The mechanism underlying these phenomena was investigated, and the strong immunosuppression produced by SV-IV in serovar Typhimurium-infected mice was suggested to be the basis for the increased rate of mortality. The SV-IV-mediated immunosuppression was characterized by a decrease in the humoral and cell-mediated immune responses, altered lymphocyte-macrophage interaction, downregulation of cytokine and inducible nitric oxide synthase gene expression, inhibition of macrophage phagocytosis and intracellular killing activities, and absence of apoptosis in the splenocyte population of SV-IV- and serovar Typhimurium-treated mice. The immunosuppressive activity of SV-IV was specific and was not due to aspecific cytotoxic effects. SV-IV-specific receptors (K(d) = 10(-8) M) occurring on the macrophage and lymphocyte plasma membranes may be involved in the molecular mechanism underlying the SV-IV-mediated immunosuppression. Some results obtained by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay also revealed a functional impairment of mitochondria (a decrease in mitochondrial dehydrogenase activity), thus indicating the possible implication of these organelles in the immunosuppressive process.

Previous data showing an increase of receptor binding activity of [R16]VIP, a vasoactive intestinal peptide (VIP) structural analogue containing arginine at the position 16 of its amino acid sequence, have pointed out the importance of a positive charge at this site. Here, the functional characterization of three VIP polyaminated adducts (VIPDap, VIPSpd, and VIPSpm), obtained by a transglutaminase-catalysed reaction between the VIP Gln16 residue and 1,3-diaminopropane (Dap), spermidine (Spd), or spermine (Spm), is reported. Appropriate binding assays and adenylate cyclase enzymatic determinations have shown that these VIP adducts act as structural VIP agonists, both in vitro and in vivo. In particular, their IC50 and EC50 values of human and rat VIP/pituitary adenylate cyclase activating peptide (PACAP)1 and VIP/PACAP2 receptors indicate that VIPDap is a VIP agonist, with an affinity and a potency higher than that of VIP, while VIPSpd and VIPSpm are also agonists but with affinities lower than that of VIP. These findings suggest that the difference in adduct agonist activity reflects the differences in the positive charge and carbon chain length of the polyamine covalently linked with the VIP Gln16 residue. In addition, the data obtained strongly suggest that the length of polyamine carbon chain could be critical for the interaction of the agonist with its receptor, even though possible hydrophobic interaction cannot be ruled out. In vivo experiments on murine J774 macrophage cell cultures have shown the ability of these compounds to stimulate the inducible nitric oxide synthase activity at the transcriptional level.