Biochemical characterization and substrate specificity of rat prostate kallikrein (S3): comparison with tissue kallikrein, tonin and T-kininogenase

Short-term aromatase inhibition induces prostatic alterations in adult wistar rat: A biochemical, histopathological and immunohistochemical study

PURPOSE

This study aimed to evaluate the effects of estrogen reduction on amyloid deposition, some lipid metabolism and oxidative stress markers, PSA-like production and p63 expression in the prostate of the adult rat.

METHODS

Aromatase inhibitor: Formestane (4-OHA), was administrated to male rats, at a dose of 0.1 mg/kg b.w./day, for 10 days. The control group (CONT) received the same volume of placebo injection (NaCl 0.9%).

RESULTS

4-OHA treatment induced a significant accumulation of intraprostatic cholesterol (138.90 ± 17.64 vs 85.12 ± 2.87, p = 0.01); against an insignificant diminution of malondialdehyde (412.6 ± 54.35 vs 842.70 ± 336.50, p > 0.05) and glutathione (2.40 ± 0.23 vs 3.65 ± 0.88, p > 0.05). This was associated with a significant decrease of nitric oxide (31.76 ± 7.07 vs 179.40 ± 58.35, p = 0.024). Additionally, 4-OHA significantly increased the intraprostatic production of PSA-like (11.12 ± 2.78 vs 3.91 ± 0.43, p = 0.043). The prostatic histology revealed an amyloid deposition, in all prostatic lobes and a smooth muscle layer growth (p < 0.05); especially significant in the dorsal and lateral lobes. Theses lobes manifested a basal cells proliferation, with a 3-fold increase of p63 expression (p < 0.001). The ventral lobe presented epithelial atrophy (37.80 ± 16.20 vs 167.60 ± 5.16, p < 0.05); with occasional and significant proliferative foci (247.00 ± 9.573 vs 167.60 ± 5.16 p < 0.05).

DISCUSSION AND CONCLUSION

Aromatase inhibition, in the adult male rat, alters the prostatic function by reducing nitric oxide availability and inducing amyloid deposition along with limiting the differentiation of basal cells, through a lobe-specific p63-overexpression.

Altered expression of extracellular matrix and proteinases in Noble rat prostate gland after long-term treatment with sex steroids

BACKGROUND

Interactions between the epithelial cells and stromal tissues, which include the epithelial basement membrane, extracellular matrix, inducible factors, and various cell types, are believed to play a significant role in prostate gland carcinogenesis. Remodeling of extracellular matrix and degradation of basement membrane are the prerequisites for tumor cell invasion, and these changes are correlated with the expression of various proteinases.

METHODS

The present study examined the alterations of epithelial basement membrane, extracellular matrix, and proteinase activities in the Noble rat prostate gland after long-term treatments with androgen and estrogen (T+DES or T+E(2) for 4-12 months) by histochemistry, immunohistochemistry, electron microscopy, and gelatin-gel zymography.

RESULTS

After hormonal treatments, defects of epithelial basement membranes, such as focal disruption, diffuse staining and multilayering, were observed by histochemistry and immunohistochemistry in the dysplastic and neoplastic lesions induced in the lateral (LP) and ventral prostates (VP) but not in dorsal prostate (DP). An increase in the amount of extracellular matrix components, including hyaluronan (HA), chondroitin sulfate proteoglycan (CSPG) and tenascin, in the stroma of hormone-treated LP and VP was revealed by histochemistry and immunohistochemistry. Positive immunolabeling of matrix metalloproteinases 2 (MMP-2) and 9 (MMP-9) was detected in the fibromuscular layer surrounding the adenoma and adenocarcinoma induced in LP and VP after treatments with steroids for over 9-12 months. Zymography also detected an increase in activities of proteinases of apparent MW 120, 90, 86 and 68 kDa in the hormone-treated LP and VP, and these proteinases were characterized as metalloproteinases. In addition, two serine proteinases of MW 100 and 30 kDa were identified as being overexpressed in the hormone-treated LP and VP. Compared to LP and VP, there was no significant change in the proteinase activities in the hormone-treated DP.

CONCLUSIONS

The present study demonstrated that the epithelial basement membrane and stromal extracellular matrix were altered in dysplastic and neoplastic Noble rat prostates. Since HA and CSPG (or their complexes) are highly anionic molecules, their increased accumulation in the altered prostatic stroma would tend to hydrate this tissue. This would create an environment more favorable for tumor growth and invasion. These morphological changes were also correlated with the concurrent increase in gelatinolytic proteinase activities induced in these prostates. The results suggest that the remodeling of the stromal tissue might play a role in the early stage of prostate carcinogenesis as shown in the Noble rat model.

Detection and cloning of a protein recognized by anti-human prostate-specific antigen (PSA) antibody in the rat ventral prostate

Prostate-specific antigen (PSA), a 33 kDa glycoprotein produced in the epithelium of the human prostate, has become established as a useful tumor marker for prostate cancer in man. Since reports of homologous proteins in animals other than primates have been lacking, the present investigation was carried out to identify any PSA-like protein in rats. Immunoblot analysis using a specific monoclonal anti-human PSA antibody detected a 32 kDa immunoreactive protein in the ventral lobe of the rat prostate, but not in other lobes or in other tissues. Positive immunostaining was observed only for the luminal surface of the glandular epithelium and the intraductal fluid in the ventral prostate. Sequence analysis of a cDNA for the rat PSA-like protein, cloned by immunoscreening of an expression cDNA library prepared from the ventral lobe, revealed identity to the rat submaxillary gland S3 kallikrein. Human PSA also belongs to the kallikrein family. Thus, this protein produced in the rat ventral prostate was suggested to be a possible counterpart of human PSA.

Kallistatin is a potent new vasodilator

Kallistatin is a serine proteinase inhibitor which binds to tissue kallikrein and inhibits its activity. The aim of this study is to evaluate if kallistatin has a direct effect on the vasculature and on blood pressure homeostasis. We found that an intravenous bolus injection of human kallistatin caused a rapid, potent, and transient reduction of mean arterial blood pressure in anesthetized rats. Infusion of purified kallistatin (0.07-1.42 nmol/kg) into cannulated rat jugular vein produced a 20-85 mmHg reduction of blood pressure in a dose-dependent manner. Hoe 140, a bradykinin B2-receptor antagonist, had no effect on the hypotensive effect of kallistatin yet it abolished the blood pressure-lowering effect of kinin and kallikrein. Relaxation of isolated aortic rings by kallistatin was observed in the presence (ED50 of 3.4 x 10(-9) M) and in the absence of endothelium (ED50 of 10(-9) M). Rat kallikrein-binding protein, but not kinin or kallikrein, induced vascular relaxation of aortic rings. Neither Hoe 140 nor Nomega-nitro--arginine methyl ester, a nitric oxide synthase inhibitor, affected vasorelaxation induced by kallistatin. Kallistatin also caused dose-dependent vasodilation of the renal vasculature in the isolated, perfused rat kidney. Specific kallistatin-binding sites were identified in rat aorta by Scatchard plot analysis with a Kd of 0.25+/-0.07 nM and maximal binding capacity of 47.9+/-10.4 fmol/mg protein (mean+/-SEM, n = 3). These results indicate that kallistatin is a potent vasodilator which may function directly through a vascular smooth muscle mechanism independent of an endothelial bradykinin receptor. This study introduces the potential significance of kallistatin in directly regulating blood pressure to reduce hypertension.

Activation of angiotensin-generating systems in the developing rat kidney

The present study was designed to determine the developmental changes in intrarenal angiotensin (Ang) peptides in the rat. Kidney Ang I and II levels were threefold and sixfold higher in newborn than adult kidneys, respectively (Ang I, 678 +/- 180 versus 243 +/- 38 fmol/g, P < .01; Ang II, 667 +/- 75 versus 103 +/- 6 fmol/g, P < .001). Intrarenal Ang II levels correlated positively with the temporal changes in renin gene expression (r = .93, P < .001). However, no correlation was found between renal Ang II content and angiotensin-converting enzyme (ACE) expression during development, which prompted us to evaluate whether renal enzymes, other than renin and ACE, contribute to Ang II formation in the developing kidney. Angiotensin peptide levels were measured in newborn and adult kidney homogenates incubated with human angiotensinogen (a poor rat renin substrate) for 30 minutes at 37 degrees C. Inhibitors of aspartyl proteases and metalloproteases were ineffective in preventing the formation of Ang II in either newborn or adult kidneys. However, addition of the serine protease inhibitors soybean trypsin inhibitor and phenylmethylsulfonyl fluoride inhibited Ang II generation in the newborn kidneys only. In contrast, Ang I generation was not affected by inhibition of serine proteases in either newborn or adult kidneys. We conclude that Ang I and II synthesis is activated in the developing rat kidney. In addition to renin and ACE, the newborn rat kidney expresses serine protease activity that is capable of generating Ang II directly from angiotensinogen. This putative enzyme is induced in the newborn kidney and may cooperate with renin in the activation of Ang II synthesis during early development.

Pro-rat atrial natriuretic peptide-mimicking peptides as substrates for rat kallikreins rK2 (tonin) and rK9

Investigation of the substrate specificity of rat tissue kallikreins has shown the importance of an extended site of interaction, and that the proform of rat natriuretic peptides, pro-ANP, could be a substrate for two members of the family, rK2 (tonin) and rK9 (Moreau et al. (1992) J. Biol. Chem. 267, 10045-10051). Synthetic peptide substrates that reproduce the sequence of rat pro-ANP in the region of the activation sites were used to further assess the specificity of these two proteinases. Peptides 95-107 (AGPRSLRRSSCFG) and 91-107 (RALLAGPRSLRRSSCFG) of the rat pro-ANP sequence, which include all the cleavage sites for generating natriuretic peptides (R98, R101, R102), were synthesized and assayed as kallikrein substrates. Despite their homology, the two peptides had different susceptibilities to cleavage by rK2 and rK9. Peptide 91-107 was rapidly and specifically cleaved by both kallikreins, with a single cleavage site at the R98-S99 bond, which is the primary cleavage site in pro-ANP for generating ANP[1-28]. The kcat/Km values were 289,000 M-1 s-1 for rK2 and 39,000 M-1 s-1 for rK9. The N-terminally truncated peptide (95-107) was also cleaved at that bond by both proteinases, but far less rapidly than peptide 91-107, and additional cleavages appeared at secondary sites i.e those generating atriopeptin III (R101) and auriculin (R102) in rat pro-ANP. A commercial fluorogenic tetrapeptide substrate reproducing the sequence of rat pro-ANP was slowly hydrolysed under the same conditions. The kinin-releasing kallikrein rK1 did not cleave synthetic peptides at the R98-S99 bond, further demonstrating the different specificities of tissue kallikreins. The results indicate that residues in positions P5 to P8 with respect to the cleavage site in the substrate, are essential for the substrate binding and specificity of kallikreins rK2 and rK9. They also show that long peptide substrates should be used to identify biological substrates of kallikreins from the investigation of their kinetic properties. The biological significance of pro-ANP processing by these proteinases, remains, however, to be proven.

Expression and characterization of rat kallikrein-binding protein in Escherichia coli

Rat kallikrein-binding protein is a novel serine-proteinase inhibitor that forms a covalent complex with tissue kallikrein. We have purified rat kallikrein-binding protein and cloned the cDNA and the gene encoding rat kallikrein-binding protein [Chao, Chai, Chen, Xiong, Chao, Woodley-Miller, Wang, Lu and Chao (1990) J. Biol. Chem. 265, 16394-16401; Chai, Ma, Murray, Chao and Chao (1991) J. Biol. Chem. 266, 16029-16036]. In the present study, we have expressed rat kallikrein-binding protein in Escherichia coli with a T7-polymerase/promoter expression system. A high level of expression was detected by an e.l.i.s.a. with an average of 24.2 mg of recombinant rat kallikrein-binding protein per 1 of culture. The recombinant protein appeared as a major protein in a crude extract of Escherichia coli on SDS/PAGE. It showed a molecular mass of 43 kDa and was recognized by polyclonal antibody to the native rat kallikrein-binding protein in Western-blot analysis. The recombinant rat kallikrein-binding protein has been purified to apparent homogeneity by DEAE-Sepharose CL-6B, hydroxyapatite Bio-Gel HPHT and Mono P 5/5 column chromatography. The purified recombinant rat kallikrein-binding protein showed immunological identity with the native rat kallikrein-binding protein purified from rat serum, in a specific e.l.i.s.a. To confirm the fidelity of the expression, the N-terminal ten amino acids of the recombinant rat kallikrein-binding protein were sequenced and were shown to match perfectly with those of the native rat kallikrein-binding protein. The purified recombinant rat kallikrein-binding protein formed SDS- and heat-stable complexes with rat tissue kallikrein (rK1) and T-kininogenase (rK10) in vitro, but not with other enzymes in the rat kallikrein gene family, such as tonin (rK2) and S3 protein (rK9), which indicates enzyme-specific binding. The properties of the recombinant rat kallikrein-binding protein including its size, charge, complex formation with target enzymes and immunological characteristics were compared with those of the native protein. This expression system provides a simple way to obtain a large amount of the biologically active recombinant protein, to study structure-function relationships of the rat kallikrein-binding protein and its interaction with its target enzymes.