Interaction of peptide boronic acids with elastase: circular dichroism studies

Dietary boron supplementation enhances sperm quality and immunity through influencing the associated biochemical parameters and modulating the genes expression at testicular tissue

INTRODUCTION

Dietary boron improves immune and antioxidant status and calcium metabolism in mammals. However, till date the effects of dietary boron supplementation on male reproduction, especially on sperm production and sperm quality in farm animals are not documented.

OBJECTIVE

The present study was aimed to investigate the influence of dietary boron on semen production, semen quality, immunity and molecular changes in the testis, blood and seminal plasma and to assess the interrelationship with other minerals in male goats.

METHODOLOGY

The study was conducted in 21 adult male goats divided into 3 groups (control, boron and selenium supplemented groups, n = 7 each). In boron group, boron was supplemented at 40 ppm and in selenium group, selenium was supplemented at 1 ppm over and above the basal level. In control group, only the basal diet was fed without supplementary boron or selenium. The feeding trial was carried out for 60 days. Selenium was taken as a positive control for the dietary boron supplementation experiment. Following feeding trials, the sperm concentration, kinematics and functional attributes, immunity and molecular level changes in the testis, biomolecular changes in the blood and seminal plasma and also interrelationship with other minerals were studied.

RESULTS

The average sperm concentration (million/ml) and the total sperm production (million/ejaculate) were significantly (p < 0.05) increased in boron supplemented group when compared to selenium and control groups. The boron levels in blood plasma (r = 0.65) and seminal plasma (r = 0.54) showed a positive correlation with sperm progressive motility. Blood and seminal plasma metabolic biomarker namely, aspartate aminotransferase (AST) (p < 0.01) was significantly lower in the boron and selenium supplemented group than control, while alanine aminotransferase (ALT) (p < 0.05) was significantly lower in the boron supplemented group than selenium and control group. There was a significant increase in the mRNA expression of serine proteinase inhibitor (SERPIN) and interferon γ (IFNγ) in the testis of boron supplemented than the control group. Boron supplementation up-regulated the immune-regulatory gene, interleukin 2 (IL2) and antioxidant gene, catalase (CAT) in the peripheral blood mononuclear cells (PBMC). On contrary, toll-like receptor 2 (TLR2) mRNA expression was significantly (p < 0.05) down-regulated in boron and selenium supplemented groups.

CONCLUSION

The study revealed that dietary boron supplementation increased the sperm output, sperm motility and enhanced the immune and antioxidant defense capacity in male goats. The improved semen quality can be attributed to enhanced expression of testicular SERPIN, a crucial protein for the regulation of spermatogenesis process.

The vital roles of boron in animal health and production: A comprehensive review

Boron (B) has many beneficial functions in biological, metabolic and physiological processes for plants and animals. It plays a vital role in maintaining animal health and preventing nutritional disorders. Boron deficiency has been correlated with low immune function and high incidence of osteoporosis which increases mortality risk. Extraordinary boron level causes cell damage and toxicity in human and different animal species. In the past few years, attention has been paid to clear the pleiotropic effects of boron including activating of immune response, antioxidant detoxification activities, affecting bone metabolism, enhancing animal performance and modulating various body systems. Furthermore, the role of boron as anti-heat stress agent has been identified in plants and suggested in animals. Liver metabolism also shows significant alterations in dairy cows in response to the dietary supplementation of boron. Likewise, adding boron to animal feed enhances bone density, wound healing and embryonic development. Additionally, boron has a potential impact on the metabolism of numerous minerals and enzymes. In view of the information about boron benefits, high or low level boron merits the concern. As well, researches are required to do more in-depth investigations on boron influences, and to adjust its requirements in different animal species.

Boron Induces Early Matrix Mineralization via Calcium Deposition and Elevation of Alkaline Phosphatase Activity in Differentiated Rat Bone Marrow Mesenchymal Stem Cells

OBJECTIVE

Boron (B) is essential for plant development and might be an essential micronutrient for animals and humans. This study was conducted to characterize the impact of boric acid (BA) on the cellular and molecular nature of differentiated rat bone marrow mesenchymal stem cells (BMSCs).

MATERIALS AND METHODS

In this experimental study, BMSCs were extracted and expanded to the 3rdpassage, then cultured in Dulbecco's Modified Eagle's Medium (DMEM) complemented with osteogenic media as well as 6 ng/ml and 6 µg/ml of BA. After 5, 10, 15 and 21 days the viability and the level of mineralization was determined using MTT assay and alizarin red respectively. In addition, the morphology, nuclear diameter and cytoplasmic area of the cells were studied with the help of fluorescent dye. The concentration of calcium, activity of alanine transaminase (ALT), aspartate transaminase (AST), lactate dehydrogenase (LDH) and alkaline phosphatase (ALP) as well as sodium and potassium levels were also evaluated using commercial kits and a flame photometer respectively.

RESULTS

Although 6 µg/ml of BA was found to be toxic, a concentration of 6 ng/ml increased the osteogenic ability of the cell significantly throughout the treatment. In addition it was observed that B treatment caused the early induction of matrix mineralization compared to controls.

CONCLUSION

Although more investigation is required, we suggest the prescription of a very low concentration of B in the form of BA or foods containing BA, in groups at high risk of osteoporosis or in the case of bone fracture.

Inhibition of the enzymatic activity of prostate-specific antigen by boric acid and 3-nitrophenyl boronic acid

BACKGROUND

Prostate specific antigen (PSA) is a well-established marker of prostate cancer, but it can also degrade extracellular matrix proteins such as fibronectin and could be involved in tumor progression and metastasis. In this study, we have addressed the use of boric acid and 3-nitrophenyl boronic acid (NPBA) as PSA inhibitors in vitro.

METHODS

The inhibition of PSA by boric acid was studied by using specific fluorogenic substrates. Fibronectin, a biologically relevant substrate for PSA, was used as a substrate in a zymographic assay, and the degradation of fibronectin by PSA in the presence of boric acid and NPBA was followed by Western Blot.

RESULTS

Low concentrations of boric acid partially inhibited the proteolytic activity of PSA toward a synthetic fluorogenic substrate. Also, by Western blot, we have found significant inhibition in the proteolysis of fibronectin by PSA in the presence of boric acid as well as NPBA. Results indicate that the boronated compounds used in this study can be used for the modulation of PSA activity.

CONCLUSION

PSA activity is inhibited in vitro by boric acid and NPBA. If degradation of fibronectin by PSA were, in fact, an important step in the progression of prostate cancer, then borate-induced inhibition of PSA activity should help reduce the development and proliferation of prostate carcinomas.

Potent and selective inhibitors of the proteasome: dipeptidyl boronic acids

Potent and selective dipeptidyl boronic acid proteasome inhibitors are described. As compared to peptidyl aldehyde compounds, boronic acids in this series display dramatically enhanced potency. Compounds such as 15 are promising new therapeutics for treatment of cancer and inflammatory diseases.

Regulation of enzymatic activity: one possible role of dietary boron in higher animals and humans

It is well established that vascular plants, diatoms, and some species of marine algal flagellates have acquired an absolute requirement for boron (B), although the primary role remains unknown. Discovery of naturally occurring organoboron compounds, all ionophoric macrodiolide antibiotics with a single B atom critical for activity, established at least one biochemical role of B. The unusual nature of B chemistry suggests the possibility of a variety of biological roles for B. At physiological concentrations and pH, B may react with one N group or one to four hydroxyl groups on specific biological ligands with suitable configuration and charge to form dissociable organoboron compounds or complexes. Suitable ligands include pyridine (e.g., NAD+ or NADP) or flavin (e.g., FAD) nucleotides and serine proteases (SP). B reacts with the cis adjacent hydroxyls on the ribosyl moiety of the nucleotides or, in the serine proteases, the N on the imidazole group of histidine or the hydroxyl group on the serine moiety. Reversible inhibition by B of activity of SP or oxidoreductases that require pyridine or flavin nucleotides is well known. Therefore, a proposed essential role for B is as a regulator of relevant pathways, including respiratory burst, that utilize these enzymes.

Cysteine proteases such as papain are not inhibited by substrate analogue peptidyl boronic acids

Peptidyl boronic acids that are close structural analogues of good substrates have been prepared and evaluated as potential transition state analogue inhibitors of the representative cysteine protease, papain. However, no inhibition could be detected at concentrations up to 10 mM. The reasons for the lack of inhibition were sought from molecular modeling. Molecular mechanics and semi-empirical quantum mechanics calculations indicated that the absence of inhibition was due to boronic acid-cysteine protease tetrahedral complexes being 0.79 kcal mol-1 less stable than their preceding noncovalent EI-complexes. In contrast, an analogous boronic acid-serine protease tetrahedral complex was calculated to be 2.74 kcal mol-1 more stable than its precursor Michaelis EI-complex. It thus appears that boronic acids are ineffective inhibitors of cysteine proteases due to the thermodynamic favoring of a weak EI-complex preceding tetrahedral intermediate formation, and that any oxyanion hole stabilization of the subsequent tetrahedral intermediate cannot overcome this energy handicap.

Interaction of the peptide CF3-Leu-Ala-NH-C6H4-CF3 (TFLA) with porcine pancreatic elastase. X-ray studies at 1.8 A

The peptide trifluoroacetyl-Leu-Ala-(p-trifluoromethylanilide), is a reversible inhibitor of pancreatic porcine elastase and is characterized by a Km of 2.5 x 10(-8) M. Co-crystals of the 1:1 complex were obtained in an acetate buffer + dimethylformamide solution at pH 5.7. Diffraction data were recorded on films at the LURE synchrotron facility. The inhibitor was localized on difference Fourier maps, and the refinement of the structure was performed by simulated annealing (XPLOR). The current agreement factor is R = 19% (for 13224 observed structure factors and 1.8 A effective resolution). The RMS deviations from ideality of bond distances and angles are 0.02 A and 2 degrees, respectively. The inhibitor molecule was found in the active site, bent around the side chain of Phe-215 in a geometry that resembles the previously reported structure of the CF3-Lys-Ala complex at 2.5 A, in a parallel beta-sheet association with the loop 214-216. The analysis of the close contacts (less than 3.5 A) indicates that the trifluoromethylamide bond interacts with the active site and not the Leu-Ala or Ala-anilide bonds. The two fluorinated groups of the inhibitor exhibit different specificities: the trifluoroacetyl group (N terminus) is tightly stacked between the two chain loops 191-195 and 213-215, while the trifluoromethylanilide (C terminus) shows less specificity and only a single contact.

Crystallographic analysis of the inhibition of porcine pancreatic elastase by a peptidyl boronic acid: structure of a reaction intermediate

The crystal structure of porcine pancreatic elastase (PPE) complexed to carbobenzoxy-alanylisoleucine-boronic acid (ZAIB) is reported to 2.09-A resolution and refined to an R factor of 0.15. This is the first reported structural analysis of PPE with an isoleucine residu in the primary specificity pocket. The results include (1) marked displacement of the inhibitor out of the active site leading to (2) a close (2.2 A) direct contact between B (boron atom of the inhibitor) and N epsilon of His-57 and also (3) covalent bonding (1.5 A) to O gamma of Ser-195. A scheme for the mechanism of inhibition of PPE by ZAIB is proposed. A comparison with a peptidyl difluoromethyl ketone-PPE complex (Ki = 9.5 microns) is made to explain the strong inhibition of PPE by ZAIB (Ki = 0.3 micron). These results lead us to characterize this structure as a time- and space-averaged reaction intermediate, providing fresh insight into the cramped dimensions available in enzymatic catalyses.