Cellular localization of kallistatin and tissue kallikrein in human pancreas and salivary glands

The tissue kallikrein-kinin system contributes to the regulation of local blood flow, vascular permeability, inflammatory responses, and ion transport. Tissue kallikrein is a serine proteinase which produces vasoactive kinin peptides. Kallistatin specifically binds to tissue kallikrein and inhibits its proteolytic activity. To investigate their anatomical relationship in the human pancreas and salivary glands, the expression and localization of kallistatin and tissue kallikrein were identified by immunoassays, immunohistochemistry, and in situ hybridization histochemistry. Human kallistatin and tissue kallikrein levels were measured by ELISA and radioimmunoassay, respectively, in pancreatic and salivary tissue extracts, and in pancreatic fluid and saliva. Immunoreactive kallistatin and kallikrein were colocalized in acinar cells of the human pancreas by immunohistochemistry. In situ hybridization histochemistry confirmed the presence of both mRNAs in pancreatic acini. In salivary glands, kallistatin and kallikrein mRNAs were also colocalized in serous acinar cells, and the kallikrein transcript was further localized to striated and interlobular ducts. Immunoreactive kallistatin was localized in serous acinar and demilune cells of salivary glands and kallikrein was localized to the epithelium of striated and interlobular ducts. The colocalization and/or coexpression of human tissue kallikrein and kallistatin in the pancreas and salivary glands suggest a role for kallistatin in the regulation of tissue kallikrein in these organs.

Sex and the evolution of intrahost competition in RNA virus phi6

Sex allows beneficial mutations that occur in separate lineages to be fixed in the same genome. For this reason, the Fisher-Muller model predicts that adaptation to the environment is more rapid in a large sexual population than in an equally large asexual population. Sexual reproduction occurs in populations of the RNA virus phi6 when multiple bacteriophages coinfect the same host cell. Here, we tested the model's predictions by determining whether sex favors more rapid adaptation of phi6 to a bacterial host, Pseudomonas phaseolicola. Replicate populations of phi6 were allowed to evolve in either the presence or absence of sex for 250 generations. All experimental populations showed a significant increase in fitness relative to the ancestor, but sex did not increase the rate of adaptation. Rather, we found that the sexual and asexual treatments also differ because intense intrahost competition between viruses occurs during coinfection. Results showed that the derived sexual viruses were selectively favored only when coinfection is common, indicating that within-host competition detracts from the ability of viruses to exploit the host. Thus, sex was not advantageous because the cost created by intrahost competition was too strong. Our findings indicate that high levels of coinfection exceed an optimum where sex may be beneficial to populations of phi6, and suggest that genetic conflicts can evolve in RNA viruses.

Adenovirus-mediated kallikrein gene delivery reverses salt-induced renal injury in Dahl salt-sensitive rats

BACKGROUND

The tissue kallikrein-kinin system has been shown to play a role in cardiac and renal functions. In this study, we investigated the ability of kallikrein gene delivery to reverse salt-induced cardiac hypertrophy and renal injury in Dahl salt-sensitive rats.

METHODS

Adenovirus harboring the human tissue kallikrein gene, Ad.CMV-cHK, was delivered intravenously into Dahl salt-sensitive rats suffering from hypertension, cardiac hypertrophy and renal damage induced by a high salt diet (4% NaCl) for four weeks.

RESULTS

Expression of human kallikrein mRNA was detected in rat kidney, heart, aorta and liver, and immunoreactive human kallikrein levels were measured in the serum and urine of rats receiving gene delivery. A single injection of Ad.CMV-cHK caused a significant reduction of blood pressure for more than two weeks. Kallikrein gene transfer caused left ventricular mass reduction and elevated glomerular filtration rate, renal blood flow, urinary excretion, urinary kinin, nitrite/nitrate content, cGMP and cAMP levels. Morphological investigations showed that kallikrein gene transfer caused a significant reversal in salt-induced tissue and organ damage. In the heart, cardiac hypertrophy and fibrosis were reduced, and in the kidney, both glomerular sclerotic lesions and tubular damage were reversed.

CONCLUSIONS

Adenovirus-mediated kallikrein gene delivery is effective in reversing salt-induced cardiac hypertrophy and renal injury in Dahl-salt sensitive rats.

Atrial natriuretic peptide gene delivery attenuates hypertension, cardiac hypertrophy, and renal injury in salt-sensitive rats

To investigate potential therapeutic effects of atrial natriuretic peptide (ANP) gene delivery on renal and cardiac disorders, adenovirus harboring the human ANP gene (Ad.RSV-cANP) was delivered into Dahl salt-sensitive (DSS) rats on a high-salt diet. A single intravenous injection of the ANP gene caused a significant delay of blood pressure increase 3 days post-injection and the effect lasted for more than 5 weeks. A maximal blood pressure reduction of 32.8 mmHg was observed after ANP gene delivery, as compared with that of control rats injected with Ad.CMV-LacZ. Immunoreactive human ANP can be detected in the heart, lung, and kidney of rats after gene delivery. ANP gene delivery caused significant increases in renal blood flow, glomerular filtration rate, sodium output, urine excretion, and urinary cGMP levels. These beneficial effects were reflected morphologically by a reduction in cardiomyocyte size, attenuation of the glomerular-sclerotic lesions, tubular injury and arterial thickening. This study demonstrated the usefulness of somatic gene transfer as a new tool for ANP gene delivery in studying salt-related hypertension and renal and cardiovascular diseases. In addition, the findings also suggest that ANP gene delivery may have potential in therapeutic applications.

Human kallikrein gene delivery protects against gentamycin-induced nephrotoxicity in rats

The tissue kallikrein-kinin system has been shown to play important roles in cardiovascular and renal function. The aim of this study was to investigate potential protective effects of kallikrein gene delivery in gentamycin-induced nephrotoxicity. Rats were injected subcutaneously with gentamycin daily for 10 to 14 days. Adenovirus, Ad.CMV-cHK carrying the human tissue kallikrein gene or Ad.CMV-LacZ carrying the beta-galactosidase gene under the control of the cytomegalovirus promoter, were delivered intravenously on the first day of gentamycin administration. The expression of human tissue kallikrein mRNA was identified in the kidney, aorta, heart and liver and immunoreactive human kallikrein levels were measured in the serum and urine of rats receiving kallikrein gene delivery. Adenovirus-mediated kallikrein gene delivery significantly increased the renal blood flow, glomerular filtration rates, and urine flow while it attenuated renal tubular damage, cellular necrosis, lumenal protein casts and reduced ventricular weight and cardiomyocyte size. Kallikrein gene delivery caused a decrease in blood urea nitrogen levels and increases in urinary kinin and nitrite/nitrate levels. This study shows that kallikrein gene delivery exhibits protection against gentamycin-induced nephrotoxicity, and raises the potential for kallikrein gene therapy to treat drug-induced renal diseases.

Kallikrein gene delivery attenuates hypertension and cardiac hypertrophy and enhances renal function in Goldblatt hypertensive rats

To demonstrate potential therapeutic effects of kallikrein gene delivery, we delivered adenovirus (Ad.CMV-cHK) carrying the human tissue kallikrein gene into two-kidney, one-clip Goldblatt hypertensive rats. A single intravenous injection of the recombinant adenovirus caused a delay of blood pressure increase that began 1 day after injection and continued for 24 days. A maximal blood pressure reduction was observed in rats receiving kallikrein gene delivery compared with control rats receiving Ad.CMV-LacZ (160+/-5 versus 186+/-7 mm Hg, n=6, P<.01). The expression of human tissue kallikrein mRNA was identified in the kidney, heart, aorta, and liver of rats receiving kallikrein gene delivery. Immunoreactive human kallikrein levels were measured in rat serum and urine in a time-dependent manner. Adenovirus-mediated kallikrein gene delivery caused a significant reduction in the left ventricular mass and cardiomyocyte size, as well as an increase in renal blood flow, urine flow, glomerular filtration rates, electrolyte output, and urine excretion. Enhanced renal responses were accompanied by significant increases in urinary kinin, nitrite/nitrate, and cyclic GMP levels. These findings show that the expression of human tissue kallikrein via gene delivery has protective effects against renovascular hypertension and cardiovascular and renal dysfunction.

Central delivery of human tissue kallikrein gene reduces blood pressure in hypertensive rats

The human tissue kallikrein gene, in the form of naked DNA (CMV-cHK) or an adenoviral vector (Ad.CMV-cHK), was directly delivered by intracerebroventricular injection into spontaneously hypertensive rats. Control rats received the same amount of vector DNA (pcDNA3) or adenoviral vector (Ad.CMV-LacZ) carrying the lacZ gene. A single injection of the human tissue kallikrein gene caused a rapid and prolonged blood pressure-lowering effect that began 1 day post injection and the effect lasted for more than 7 days. The expression of human tissue kallikrein and its mRNA was identified in the cortex, cerebellum, brain stem, hippocampus and hypothalamus. Cellular localization of beta-galactosidase was detected by X-gal staining in the thalamus, hypothalamus and third ventricle in rats injected with Ad.CMV-LacZ. This suggests that the tissue kallikrein-kinin system may function in the central control of blood pressure homeostasis.

Transcription factor nuclear factor kappaB regulates the inducible expression of the human B1 receptor gene in inflammation

Expression of the bradykinin B1 receptor gene is up-regulated in vascular smooth muscle cells (VSMCs) in response to a variety of inflammatory stimuli. We isolated the 5'-flanking region of the human bradykinin B1 receptor gene and examined its promoter activity by transient transfection analysis. This region (-2582 to +34) showed promoter activity inducible by lipopolysaccharide (LPS), tumor necrosis factor alpha (TNF-alpha), and interleukin-1beta (IL-1beta) in VSMCs. Further deletion analysis revealed that constructs containing 111 base pairs of 5'-flanking sequence were sufficient for transcriptional induction. Mutagenesis of a nuclear factor kappaB (NF-kappaB)-like site at -64 to -55 abolished most of the LPS, TNF-alpha, and IL-1beta inducibility, whereas a mutation of a cyclic AMP response element at -50 to -43 markedly reduced the basal promoter activity, and a mutation of the activator protein 1 (AP-1) site at -78 to -72 had minimal effects. Nuclear extracts from LPS, TNF-alpha, and IL-1beta-treated VSMCs, IL-1beta-treated human hepatoma HepG2, and human lung fibroblast IMR-90 cells showed strong inducible binding activity to the NF-kappaB-like site by gel shift assays. These results demonstrated that NF-kappaB-like nuclear factor was involved in the inducible expression of the human bradykinin B1 receptor gene during inflammatory processes.

Human kallikrein gene delivery attenuates hypertension, cardiac hypertrophy, and renal injury in Dahl salt-sensitive rats

The tissue kallikrein-kinin system has been documented to be involved in the pathogenesis of hypertension and renal diseases. To investigate the protective effects of kallikrein gene delivery on salt-induced renal damage, cardiac dysfunction, and hypertension, adenovirus harboring the human tissue kallikrein gene under the control of the cytomegalovirus promoter Ad.CMV-cHK was delivered into Dahl salt-sensitive (Dahl-SS) rats fed to a high-salt (4% NaCl) diet. A single intravenous injection of Ad.CMV-cHK resulted in a significant reduction of blood pressure beginning 2 days post injection and the effect lasted for 4 weeks. The human kallikrein mRNA was detected in rat heart, kidney, lung, liver, and adrenal gland; immunoreactive human kallikrein can be measured in the liver, kidney, sera, and urine of rats receiving kallikrein gene delivery. Following Ad.CMV-cHK injection, a significant increase in urine excretion, urinary sodium output, kinin, and cGMP level was observed. Kallikrein gene delivery caused a significant reduction in the left ventricular mass and cardiomyocyte size as well as inhibition of glomerular sclerotic lesions and tubular dilatation. This study shows that adenovirus-mediated gene delivery in Dahl-SS rats fed a high-salt diet resulted in (i) prolonged reduction of blood pressure and increased urinary kinin and cGMP levels, consistent with blood pressure reductions mediated via kinin through a cGMP-dependent signal transduction pathway, (ii) inhibition of cardiac hypertrophy, and (iii) attenuation of renal injury. The ability of kallikrein gene transfer to produce a wide spectrum of beneficial effects makes it an excellent candidate in treating salt-related hypertension as well as cardiovascular and renal diseases.

Evolution of sex and the molecular clock in RNA viruses

Although there exist many hypotheses for the advantage of sexual reproduction, Muller's ratchet is one that has received recent attention as an explanation for the evolution of sex in RNA viruses. Muller's ratchet provides for an advantage of sex when the rate of deleterious mutations is high and population size is small. A small population size intensifies genetic drift, which can lead to the random loss of genomes that are free of deleterious mutations. Sex becomes advantageous because it can re-create, through genetic exchange, genomes with fewer or no mutations. RNA viruses may be subject to Muller's ratchet because they have very high mutation rates and they may experience genetic drift if their populations are forced through small bottlenecks during infection. This review discusses the results of laboratory studies examining the possibility of an advantage of sex through Muller's ratchet in RNA viruses. Data from studies of wild populations of RNA viruses are also considered, and a model is presented for how an observed pattern of molecular evolution (or the molecular clock) in wild populations may be explained by Muller's ratchet (or a similar process) and the addition of compensatory mutations to Ohta's model of evolution by slightly deleterious mutations.

Adrenomedullin gene delivery reduces blood pressure in spontaneously hypertensive rats

Adrenomedullin (ADM) is a potent vasoactive peptide. In this study, we explored the effects of a continuous supply of ADM by somatic gene delivery on spontaneously hypertensive rats (SHR). DNA constructs containing the human ADM cDNA fused to either the cytomegalovirus promoter (CMV-cADM) or Rous Sarcoma virus 3'-long terminal repeat (RSV-cADM) were intravenously injected into SHR through the tail vein. Expression of human ADM in SHR was identified in the kidney, adrenal gland, heart, and lung by radioimmunoassay and reverse transcription-polymerase chain reaction followed by Southern blot analysis. A single injection of ADM plasmid DNA in young adult SHR (7 wk old) caused a significant reduction in systolic blood pressure for up to 5 wk (p < 0.05). A second injection of CMV-cADM 5 wk after the first delivery resulted in a further reduction in blood pressure for another 3 wk (p < 0.001). A maximal blood pressure reduction of 22 mmHg in SHR was observed 7 wk after injection of CMV-cADM plasmid DNA (185 +/- 1.7 mmHg, n = 6, p < 0.001), and a reduction of 15 mmHg was observed after injection of RSV-cADM (192 +/- 2.7 mmHg, n = 6, p < 0.001), as compared with control rats given vector DNA (207 +/- 2.4 mmHg, n = 6). Similarly, injection of CMV-cADM plasmid DNA in adult SHR (10 wk old) resulted in a significant reduction in blood pressure for up to 6 wk. Antibodies to either human ADM or its plasmid DNA were not detected in rat sera after the second injection. These studies indicate that intravenous injection of the human ADM gene in hypertensive rats results in expression of the foreign gene and induces a long-lasting reduction in blood pressure.

Effect of cyclosporin A on the expression of tissue kallikrein, kininogen, and bradykinin receptor in rat

The tissue kallikrein-kinin system is involved in vasodilation and blood pressure regulation. In the present study, we investigated the effects of chronic cyclosporin A (CsA) administration on blood pressure and the expression of tissue kallikrein, kininogen, and bradykinin receptor in normotensive Wistar rats. Chronic administration of CsA significantly increased systolic blood pressure compared with control rats (n = 6, P < 0.01), although body weight was significantly lower than control rats (n = 6, P < 0.01). The development of hypertension was accompanied by the altered expression of kallikrein-kinin system components. Immunoreactive renal kallikrein and urinary excretion of tissue kallikrein levels were increased by chronic administration of CsA (n = 5 or 6, P < 0.05). Levels of N-tosyl-L-phenylalanine chloromethyl ketone-trypsin and kallikrein-releasable kininogens in sera increased in response to chronic CsA treatment (n = 5 or 6, P < 0.05). Chronic CsA treatment significantly increased renal kallikrein, bradykinin B2 receptor, and hepatic kininogen mRNA levels. The increased levels of tissue kallikrein-kinin system components were accompanied by significant increases in 24-h urine excretion and water intake after chronic CsA treatment (n = 5, P < 0.05). These results suggest that enhanced activity of the tissue kallikrein-kinin system may compensate for the CsA-induced vasoconstriction and hypertension.

The advantage of sex in the RNA virus phi6

When laboratory populations of the RNA bacteriophage phi6 are subjected to intensified genetic drift, they experience a decline in fitness. These experiments demonstrate that the average effect of mutations is deleterious, and they are used to suggest that Muller's ratchet can operate in these viruses. However, the operation of Muller's ratchet does not alone guarantee an advantage of sex. When phi6 populations were subjected to a series of bottlenecks of one individual and then crossed, the measured advantage of sex was not significant. To determine whether a small sample size, as opposed to allelism or another explanation, can account for the negative result, we repeated the phi6 experiments by crossing a larger set of populations. We found that bottlenecked populations of phi6 could recover fitness through mutations. However, hybrids produced by crossing the populations recovered an additional amount over the contribution of mutations. This additional amount, which represents an advantage of sex to phi6, was determined to be significantly greater than zero. These results provide indirect support for an advantage of sex through Muller's ratchet. However, we also use our experimental design and results to propose an alternative to Muller's ratchet as a model for the evolution of sex.

Gene therapy in hypertension: adenovirus-mediated kallikrein gene delivery in hypertensive rats

Tissue kallikrein has been shown to play a role in blood pressure regulation, and abnormalities in the kallikreinkinin system are considered to be a factor in the pathogenesis of hypertension. To elucidate the potential therapeutic effects of kallikrein gene delivery in hypertension, an adenoviral vector containing the human tissue kallikrein gene under the control of a cytomegalovirus promoter, Ad.CMV-cHK, was intravenously injected into spontaneously hypertensive rats (SHR). A single injection of Ad.CMV-cHK into SHR caused a sustained delay in the increase in blood pressure from day 2 to day 41 post injection, as compared to control rats receiving Ad.CMV-LacZ adenovirus. Adenovirus-mediated kallikrein gene delivery had no effect on the blood pressure of normotensive Wistar-Kyoto rats. Human tissue kallikrein mRNA was detected in the liver, kidney, spleen, adrenal gland, and aorta. Immunoreactive human tissue kallikrein can be detected in sera and urine of rats receiving kallikrein gene delivery. Human tissue kallikrein in rat serum was at the highest level 5 days post injection, and the level declined gradually. Urinary kinin and cGMP levels were significantly increased in rats receiving kallikrein gene delivery compared to Ad.CMV-LacZ control rats. These results show that adenovirus-mediated delivery of human tissue kallikrein results in high-efficiency expression and blood pressure reduction in SHR. Application of adenovirus-mediated systemic expression of the tissue kallikrein gene may provide a unique way of delivering the gene product into the vasculature and could have important therapeutic implications in treating hypertension.

Molecular cloning and expression of rat kallistatin gene

We have previously purified and cloned human kallistatin and rat kallikrein-binding protein (RKBP), which are tissue kallikrein inhibitors belonging to the serine proteinase inhibitor superfamily. In this study, we have cloned and sequenced the gene encoding rat kallistatin with Phe-Phe-Ser-Ala-Gln at positions P2-P3', which is identical to the reactive center of human kallistatin. Rat kallistatin is highly similar to human kallistatin, sharing 68% and 57% sequence identity at the cDNA and the amino acid levels. The rat kallistatin gene exists in a single copy and is located on chromosome 6. An SphI RFLP is found between SHR and WKY rats at or near the rat kallistatin gene locus. Two amino acid polymorphisms of the rat kallistatin gene between these two strains were found by sequence analysis. A candidate promoter in the 5'-flanking region (109 bp) of the rat kallistatin gene has been identified by reporter assays. The expression of rat kallistatin in the liver is growth-dependent and down-regulated during acute phase inflammation. Recombinant rat kallistatin produced in E. coli is able to bind to tissue kallikrein, and the interaction is inhibited by heparin. These characteristics define rat kallistatin as the counterpart of human kallistatin.

Prolonged reduction of high blood pressure with human nitric oxide synthase gene delivery

Endothelium-derived nitric oxide (NO) in peripheral vessels has been shown to modulate vascular resistance and blood pressure. We explored the effect of a continuous supply of human endothelial NO synthase (eNOS) on the blood pressure of spontaneously hypertensive rats (SHR) by somatic gene delivery. A DNA construct containing the human eNOS gene fused to the cytomegalovirus promoter/enhancer was injected into SHR through the tail vein. A single injection of the naked eNOS plasmid DNA caused a significant reduction of systemic blood pressure for 5 to 6 weeks in SHR, and the effect continued for up to 10 to 12 weeks after a second injection. The differences were significant from 2 to 12 weeks postinjections (n=6, P<.01). In a separate experiment, L-arginine, the substrate of eNOS, was supplied in drinking water at a concentration of 7.5 g/L for 11 weeks after eNOS gene delivery. A maximal blood pressure reduction of 21 mm Hg in SHR was observed with eNOS DNA compared with that of control SHR injected with vector DNA (181.9+/-1.46 versus 202.7+/-2.79 mm Hg, mean+/-SEM, n=6, P<.01). Human eNOS gene delivery induces significant increases in urinary and aortic cGMP levels and urinary and serum nitrite/nitrate content (P<.05), while no significant differences in body weight, heart rate, water intake, food consumption, or urine excretion were observed. These results indicate that somatic delivery of the human eNOS gene induces a prolonged reduction of high blood pressure and raises the potential of using eNOS gene therapy for hypertension and cardiovascular diseases.

Distribution of tissue kallikreins in lower vertebrates: potential physiological roles for fish kallikreins

Fish skeletal muscle prokallikrein was purified from black sea bass, Centropritis striata, and used for the production of polyclonal antiserum. Tissue proteins from primitive fish and teleosts, an alligator, and an insectivore were resolved by sodium dodecylsulfate-polyacrylamide gel electrophoresis, Western blotted, and probed with fish muscle prokallikrein antiserum. A recurring theme was the presence of approximately 36 and 72 kDa kallikrein-like proteins in skeletal muscle, heart, gill, kidney, and spleen of higher teleosts and in selected tissues of sturgeon, shark, alligator, and mole. The presence of immunoreactive kallikreins in osmoregulatory organs such as the gills of teleosts and the rectal gland of sharks signifies a potential role for these proteins in osmoregulation. Black sea bass, rock bass, and sturgeon contained many immunoreactive kallikreins in their swimbladders, which implicates a role for kallikreins in the regulation of blood flow and vascular permeability to facilitate gas exchange within the bladder. Kallikreins were consistently identified in skeletal muscle and heart of all the species evaluated and may regulate local blood flow, muscle contraction or relaxation, or participate in various transport processes. The antiserum to fish prokallikrein recognized immunoreactive kallikreins from pancreatic tissues from fish and lower vertebrates, but not from the pyloric caecum of sea bass. The wide distribution of tissue kallikrein in lower vertebrates suggests that it may participate in a variety of physiological functions.

Purification, characterization and activation of fish muscle prokallikrein

Fish prokallikrein was isolated and characterized from skeletal muscle of the black sea bass, Centropristis striata. The prokallikrein was purified to apparent homogeneity by anion exchange perfusion chromatography and reversed phase high performance liquid chromatography. Initial identification was by its weak immunoreactivity with human tissue kallikrein antiserum. Two-dimensional gel electrophoresis and immunoblotting identified the protein as 36 kDa with a pI of 4.95-5.15. The prokallikrein was trypsin-activated to produce an approximately 36 kDa active enzyme as identified on an SDS-polyacrylamide gel overlayed with a membrane impregnated with the fluorogenic tripeptidyl substrate D-Val-Leu-Arg-7-amino-4-trifluoromethyl-coumarin. A potential dimer at 72 kDa was also enzymatically active. Bass kallikrein cleaved low molecular weight dog kininogen to release kinin peptide as determined by radioimmunoassay. The enzyme's amidolytic activity, with a pH optimum at 9.0, was inhibited by aprotinin, benzamidine, and phenylmethanesulphonyl fluoride, but not by elastatinal, soybean trypsin inhibitor, or limabean trypsin inhibitor. Polyclonal antiserum raised against the purified bass muscle prokallikrein recognized 36 kDa and 72 kDa proteins in bass heart, skeletal muscle, spleen, swimbladder, gill, and kidney by Western blot analyses. The wide distribution of immunoreactive proteins in the tissues suggests a potential physiological role for fish kallikreins in muscle contraction and/or relaxation, the regulation of local blood flow, and in osmoregulation. The detection of fish prokallikrein and its activation leads the way for an evaluation of the impact of kallikreins in fish health and disease processes and for studying the evolution of kallikreins and related serine proteinases.

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.

Tissue-specific expression and promoter analyses of the human tissue kallikrein gene in transgenic mice

The expression of the tissue kallikrein gene is tissue-specific and exhibits a complex pattern of transcriptional and post-translational regulation. Information concerning the mechanism of its tissue-specific expression has been limited owing to the lack of suitable cell lines for the expression study. We approached this problem by introducing human tissue kallikrein gene constructs into mouse embryos, creating transgenic lines carrying its coding sequence with varying lengths of the promoter region. One construct (PHK) contained 801 bp in the 5'-flanking region and two deletion constructs contained either 302 bp (D300) or 202 bp (D200) of the promoter region. The expression of human tissue kallikrein in these transgenic mice was monitored by Northern blot, reverse transcriptase-PCR followed by Southern blot, and radioimmunoassay. In all three lines, human tissue kallikrein was expressed predominantly in the pancreas and at lower levels in other tissues, including salivary gland, kidney and spleen. This pattern was similar to that of tissue kallikrein expression in human tissues. The D300 line has higher levels of transgene expression than the D200 and PHK lines. The results indicate that the 202 bp segment immediately upstream of the translation starting site is sufficient to direct a tissue-specific expression pattern of the human tissue kallikrein gene, and that regulatory elements might exist between -801 and -202.

DNA polymorphisms in the 5'-flanking region of the human tissue kallikrein gene

Human tissue kallikrein gene polymorphisms were identified in the promoter region by polymerase chain reaction (PCR) and DNA sequencing. One polymorphic region was identified between nucleotides -121 and -133 with respect to the transcription initiation site of the tissue kallikrein gene. Ten alleles with length and nucleotide sequence variations were detected among 108 unrelated Caucasians, African-Americans, and Asians. The polymorphisms show Hardy-Weinberg equilibrium. Allele-specific amplification and PCR analyses were used to detect the various forms of polymorphism. The promoter activity was analyzed in human embryonic kidney 293 cells by transient transfection assays. Sequential 5'-deletion analysis of the tissue kallikrein gene promoter revealed that the region from -144 to -98 is crucial for its promotor activity, while alleles D and H had significantly lower promoter activities than the other alleles in the -940/+10 deletion constructs. The high variability and the proximity to the tissue kallikrein gene render it suitable for application as a new tool in genetic studies for evaluation of the tissue kallikrein gene in the pathogenesis of human essential hypertension.

Kallikrein gene therapy in newborn and adult hypertensive rats

The tissue kallikrein-kinin system has been postulated to play an important role in blood pressure regulation. Kallikreins are serine proteinases that release potent vasodilating kinin peptides from precursor kininogens by limited proteolysis. Our recent studies show that systemic delivery of the human tissue kallikrein gene into adult spontaneously hypertensive rats (SHR) results in a sustained reduction of blood pressure for several weeks. The goal of this study is to evaluate whether early delivery of the kallikrein gene into newborn SHR could exert a suppressive effect on blood pressure phenotype during rat growth and development. A human tissue kallikrein cDNA construct, under the control of cytomegalovirus promoter (CMV-cHK), or vector DNA was injected subcutaneously into the necks of 2-day-old SHR. Blood pressures were monitored biweekly from 3 to 19 weeks by the tail-cuff method. A single injection of the human kallikrein cDNA construct caused a significant reduction of blood pressure (n = 6, p < 0.001) from 11 to 17 weeks after injection compared with control rats receiving vector DNA. Intravenous delivery of the human tissue kallikrein gene into adult SHR produced blood pressure lowering effects (n = 6, p < 0.001) that lasted for 6 weeks in male but not in female rats. The expression of human tissue kallikrein in rats was identified by reverse transcription polymerase chain reaction followed by Southern blot analysis and an ELISA specific for human tissue kallikrein. Kallikrein gene delivery did not cause any changes in body weight, urine volume, or water intake in the experimental animals compared with the control group. No antibodies to either human tissue kallikrein or its DNA were detected in rat sera 19 weeks postinjection. These results show that delivery of the kallikrein gene at an early stage of life has a protective effect against development of hypertension in adult SHR and that gender differences could be a factor in kallikrein gene therapy for the treatment of hypertensive disorders.

Expression of human tissue kallikrein in rat salivary glands and its secretion into circulation following adenovirus-mediated gene transfer

Replication-deficient adenovirus Ad.CMV-cHK, expressing human tissue kallikrein under the control of the cytomegalovirus enhancer/promoter, was introduced into rat salivary glands via a direct intracapsular injection. A single injection of Ad.CMV-cHK at a dose of 4 x 10(9) pfu resulted in a sustained expression of human tissue kallikrein in rat salivary glands. The level of immunoreactive human tissue kallikrein in rat sera was the highest at 1 day post gene delivery when both salivary glands were injected and decreased in a time-dependent manner after gene delivery. Human tissue kallikrein levels in sera increased concomitantly with the amount of adenovirus used in direct salivary injection. The detection of human tissue kallikrein in sera after gene delivery into salivary glands provided direct evidence indicating that rat salivary glands secrete locally synthesized human tissue kallikrein to the systemic circulation. The direct injection of salivary glands with replication-deficient adenovirus could provide a systemic route for gene delivery for studying salivary gland function and development. Targeted gene delivery to the salivary gland may provide the means to express therapeutic proteins in saliva and the systemic circulation.

Kallikrein gene therapy: a new strategy for hypertensive diseases

The tissue kallikrein-kinin system has been postulated to play a role in blood pressure homeostasis and the pathogenesis of clinical hypertension. To demonstrate the potential therapeutic effects of somatic gene delivery in treating hypertension, we used spontaneously hypertensive rats (SHR) as a model. The gene encoding the human tissue kallikrein was used because of its powerful hypotensive action. The human kallikrein DNA constructs were placed under the control of the metallothionein metal response element, the cytomegalovirus promoter/enhancer or the Rous sarcoma virus 3'-LTR. The human tissue kallikrein DNA constructs were incorporated into adenoviral vectors via homologous recombination. The naked plasmid DNA constructs or adenovirus containing the kallikrein gene were first introduced into kidney 293 cells and the expression of human tissue kallikrein was identified by ELISA. The kallikrein gene was delivered into SHR via intramuscular, intravenous, portal vein, intraperitoneal, and intracerebroventricular routes. A single injection of naked human kallikrein DNA constructs caused a prolonged reduction of high blood pressure for up to 8 weeks. Adenoviral-mediated gene delivery results in high efficiency of human tissue kallikrein expression. Immunoreactive human kallikrein was detected in rat serum at the highest level at 1 day post gene delivery. Portal vein delivery of a reporter gene, AdCMV-LacZ, results in intense staining of beta-galactosidase in rat liver, suggesting that recombinant kallikrein is mainly produced in liver and secreted into the circulation. These results show that kallikrein gene delivery causes a sustained reduction of blood pressure in genetically hypertensive rats and provide important information for a potential gene therapy approach to human hypertension and related diseases.