Calcium sensitization of smooth muscle mediated by a Rho-associated protein kinase in hypertension

Abnormal smooth-muscle contractility may be a major cause of disease states such as hypertension, and a smooth-muscle relaxant that modulates this process would be useful therapeutically. Smooth-muscle contraction is regulated by the cytosolic Ca2+ concentration and by the Ca2+ sensitivity of myofilaments: the former activates myosin light-chain kinase and the latter is achieved partly by inhibition of myosin phosphatase. The small GTPase Rho and its target, Rho-associated kinase, participate in this latter mechanism in vitro, but their participation has not been demonstrated in intact muscles. Here we show that a pyridine derivative, Y-27632, selectively inhibits smooth-muscle contraction by inhibiting Ca2+ sensitization. We identified the Y-27632 target as a Rho-associated protein kinase, p160ROCK. Y-27632 consistently suppresses Rho-induced, p160ROCK-mediated formation of stress fibres in cultured cells and dramatically corrects hypertension in several hypertensive rat models. Our findings indicate that p160ROCK-mediated Ca2+ sensitization is involved in the pathophysiology of hypertension and suggest that compounds that inhibit this process might be useful therapeutically.

Cloning of cDNAs for the precursor protein of a low-molecular-weight subunit of the inner layer of the egg envelope (chorion) of the fish Oryzias latipes

cDNA clones for L-SF, the precursor of a low-molecular-weight subunit (ZI-3) of the inner layer of the Oryzias latipes egg envelope were isolated from Lambda ZAP cDNA libraries constructed from the poly(A)+ RNA of the liver of spawning female fish and estrogen-treated male fish. Among them, a clone, L-SF41, is 1473 bp long and contains an open reading frame encoding a signal peptide of 19 amino acids and L-SF protein of 420 amino acids. L-SF protein seems to be glycosylated, judging from the result of the glycanase digestion. L-SF protein contains a domain similar to ZP-domains in ZP3 of some mammalian species. Northern blot analysis employing XhoI-SmaI fragments of the cloned cDNA as probes revealed that expression of the L-SF gene occurred exclusively in the livers of spawning female fish and estrogen-treated male fish and that there was no mRNA encoding L-SF in the ovary of the spawning female fish.

Isolation of cDNAs for LCE and HCE, two constituent proteases of the hatching enzyme of Oryzias latipes, and concurrent expression of their mRNAs during development

The hatching enzyme of medaka consists of two types of proteases (HCE, LCE). cDNA clones for LCE and HCE were isolated from a lambda gt11 cDNA library constructed with poly(A)+ RNA of Day 3 embryos. LCE cDNA is 936 bp long and contains an 813-bp open reading frame encoding a preproenzyme with a 20-amino-acid signal sequence, a 51-amino-acid propeptide, and a 200-amino-acid mature enzyme. For HCE, two distinct cDNAs (HCE21, HCE23) having nucleotide sequences with 92.8% similarity were obtained. These cDNAs contain open reading frames encoding preproenzymes of 279 and 270 amino acids, respectively. The mature enzyme forms of both consist of 200 amino acids, the similarity between them being 95.5%. On Northern blotting analysis, the transcripts of LCE and HCE genes were first detected coincidentally in Day 2 embryos shortly before the production of LCE and HCE, accumulated thereafter in parallel, and dramatically decreased after hatching. The amino acid sequence, the HExxH motif, which is known to constitute an active site in some Zn proteases, is also found in LCE and HCE. However, the sequence analyses strongly suggest that both the enzymes belong to the astacin (protease) family, being distinct from sea urchin hatching enzyme, which is reportedly similar to collagenase.

Purification and partial characterization of high choriolytic enzyme (HCE), a component of the hatching enzyme of the teleost, Oryzias latipes

The hatching enzyme is an embryo-secreted enzyme(s) which digests the egg envelope, allowing the embryo to emerge at the time of hatching. The hatching enzyme of the fish, Oryzias latipes, has recently been found to consist of two kinds of proteases which may digest the inner layer of chorion (egg envelope) cooperatively [Yasumasu, S. et al. (1988) Zool. Sci. 5, 191-195]. In the present study, one of them, high choriolytic (egg envelope digesting) enzyme (HCE) was purified and some biochemical and enzymological properties were examined. The enzyme was a basic protein with a molecular weight of about 24 kDa, and exhibited choriolytic activity as well as proteolytic (caseinolytic) activity. The results of inhibitor studies and metal analyses strongly suggested that it was a zinc-protease. The purified HCE consisted of two probable isomers, HCE-1 and HCE-2. Both of them were markedly similar in amino acid composition, specific activities of choriolysis and proteolysis, and substrate specificity as determined using MCA-peptides. Moreover, they were not separable on SDS-PAGE, electrofocusing PAGE, or ultracentrifugal analysis, but were discriminated only on HPLC with a CM-300 column. Thus, the mixture of HCE-1 and HCE-2 could be regarded as almost a single enzyme, HCE. When it acted on an intact chorion, the purified HCE caused a remarkable swelling of its inner layer with concomitant release of peptides from it. Once the inner layer of chorion was swollen, the enzyme hardly digested it.

Cloning of cDNA and estrogen-induced hepatic gene expression for choriogenin H, a precursor protein of the fish egg envelope (chorion)

A cDNA for choriogenin H (Chg H; formerly high-molecular weight spawning female-specific substances, or H-SF), a precursor protein of the inner layer subunits of egg envelope (chorion) of the teleost fish, Oryzias latipes, was cloned and analyzed. The clone consisted of 1913 bp and contained an open reading frame encoding a signal peptide of 22 aa and Chg H protein of 569 aa. The Chg protein possessed three potential N-glycosylation sites and Pro-X-Y repeat sequences in the first two-fifths of the N terminus. There were amino acid sequence similarities between Chg H and a gene product expressed in the liver of female winter flounder during vitellogenesis. Moreover, the amino acid sequence of Chg H is similar to that of ZP2 rather than ZP3 of zona pellucida of some mammals. Northern blot analysis indicated that gene expression for Chg H occurred only in the livers of spawning female fish and 17beta-estradiol-treated male fish, but not in the ovary of the spawning female fish. Gene expression for Chg H and Chg L (formerly low-molecular weight spawning female-specific substance, or L-SF) was induced and increased in parallel in the male fish liver after 17beta-estradiol treatment.

A glycoprotein from the liver constitutes the inner layer of the egg envelope (zona pellucida interna) of the fish, Oryzias latipes

A glycoprotein from the liver, which shares epitopes with chorion (egg envelope or zona pellucida) glycoproteins, is present only in the spawning female fish, Oryzias latipes, under natural conditions. This spawning female-specific (SF) substance is distinct from vitellogenin but closely resembles a major glycoprotein component, ZI-3, of the inner layer (zona radiata interna) of the ovarian egg envelope with respect to some biochemical and immunochemical characteristics. Here we report that the [125I]SF substance, injected into the abdominal cavity of the spawning female fish, was rapidly transported by the blood circulation into the ovary and incorporated into the inner layer of egg envelope of the growing oocytes. The result strongly suggests that the SF substance from the liver is a precursor substance of the major component, ZI-3, of the inner layer of egg envelope in the fish.

Species-dependent migration of fish hatching gland cells that express astacin-like proteases in common [corrected]

Two constituent proteases of the hatching enzyme of the medaka (Oryzias latipes), choriolysin H (HCE) and choriolysin L (LCE), belong to the astacin protease family. Astacin family proteases have a consensus amino acid sequence of HExxHxxGFxHExxRxDR motif in their active site region. In addition, HCE and LCE have a consensus sequence, SIMHYGR, in the downstream of the active site. Oligonucleotide primers were constructed that corresponded to the above-mentioned amino acid sequences and polymerase chain reactions were performed in zebrafish (Brachydanio rerio) and masu salmon (Oncorynchus masou) embryos. Using the amplified fragments as probes, two full-length cDNA were isolated from each cDNA library of the zebrafish and the masu salmon. The predicted amino acid sequences of the cDNA were similar to that of the medaka enzymes, more similar to HCE than to LCE, and it was conjectured that hatching enzymes of zebrafish and masu salmon also belonged to the astacin protease family. The final location of hatching gland cells in the three fish species: medaka, zebrafish and masu salmon, is different. The hatching gland cells of medaka are finally located in the epithelium of the pharyngeal cavity, those of zebrafish are in the epidermis of the yolk sac, and those of masu salmon are both in the epithelium of the pharyngeal cavity and the lateral epidermis of the head. However, in the present study, it was found that the hatching gland cells of zebrafish and masu salmon originated from the anterior end of the hypoblast, the Polster, as did those of medaka by in situ hybridization. It was clarified, therefore, that such difference in the final location of hatching gland cells among these species resulted from the difference in the migratory route of the hatching gland cells after the Polster region.

Isolation and some properties of low choriolytic enzyme (LCE), a component of the hatching enzyme of the teleost, Oryzias latipes

One of the two component proteases of the hatching enzyme of the fish, Oryzias latipes, low choriolytic enzyme (LCE), was isolated from the hatching liquid and partly characterized. The enzyme was a basic protein with molecular weight of about 25.5 kDa. Like high choriolytic enzyme (HCE), the other component of the O. latipes hatching enzyme [Yasumasu, S. et al. (1989) J. Biochem. 105, 204-211], LCE was considered to be a zinc-protease from the results of inhibitor studies and metal analyses. However, LCE was found to be distinct from HCE not only in some biochemical characteristics such as molecular weight, amino acid composition, and isoelectric point, but also in some enzymological properties such as substrate specificity, heat stability, and mode of action toward their natural substrate, chorion (egg envelope). Although LCE was almost incapable of digesting the inner layer of intact chorion, it very efficiently digested the inner layer of chorion that had been swollen previously by the action of HCE. Taking account of the fact that HCE swells the inner layer of intact chorion by partial proteolysis but does not efficiently digest the swollen chorion any more [Yasumasu, S. et al. (1989) J. Biochem. 105, 204-211], the present results demonstrated an essential role of LCE in choriolysis, in cooperation with HCE.

Serum uric acid and the renin-angiotensin system in hypertension

To study whether the renin-angiotensin system is related to hyperuricemia in hypertension, the serum concentration of uric acid was determined in 96 patients with various types of hypertension and various degrees of plasma renin activity (PRA). In malignant hypertension, both PRA and the serum uric acid level were higher than in essential hypertension; but in primary aldosteronism or desoxycorticosterone-excess hypertension, they were lower than in the essential type. In renovascular hypertension, PRA was higher than in essential hypertension, but the serum uric acid levels were similar. There were no differences in PRA and serum uric acid concentration between Cushing's syndrome and essential hypertension. The serum uric acid level in high-renin essential hypertension was higher than in either the normal-renin or the low-renin type. There was a significant correlation between serum uric acid concentration and PRA in the basal state, and between the change in PRA and the change in serum uric acid induced by administration of furosemide. Apparently the close correlation between the renin-angiotensin system and the concentration of serum uric acid is related to changes in extracellular fluid volume, although an intrarenal effect of angiotensin II cannot be excluded.

Temporal and spatial patterns of gene expression for the hatching enzyme in the teleost embryo, Oryzias latipes

The hatching enzyme of the medaka, Oryzias latipes, consists of two proteases, high choriolytic enzyme (HCE) and low choriolytic enzyme (LCE). They are synthesized and accumulated in the same unicellular hatching glands and are secreted from them at the end of embryonic development to digest the egg envelope. Recently, these enzymes were purified, and their cDNA clones were isolated. In the present study, we examined temporal and spatial patterns of expression of the hatching enzyme genes during embryogenesis using cDNAs for HCE and LCE as probes. According to Northern blotting analysis, the expression of both genes started at the same time (stage 21-22 embryos: brain differentiation and lens formation) and the patterns of expression changed in parallel during development. In situ hybridization to whole embryo and the sections revealed that the expression of the HCE genes was detected first in the anterior end of the hypoblast layer in stage 16-17 (late gastrula) embryos. Distinct signals of the HCE gene expression were then detected in a group of cells located at the front of the head rudiment of embryos at stage 18-19 (1 somite). Treatment of the embryos with retinoic acid, which is known to affect the anterior differentiation of embryos, suppressed the hatching gland cell differentiation in accordance with the result of in situ hybridization. In stage 22 embryos, the HCE-positive cells dispersed in an ectodermal layer under the forebrain and optic vesicles. Thereafter, the hatching gland cells expressing the HCE mRNA were aligned along the branchial arches and finally rearranged to the inner wall of the pharyngeal cavity, following a marked elongation of the lower jaw. The results of in situ hybridization to whole embryos at consecutive developmental stages demonstrated that the hatching gland cells located at the most anterior portion of the hypoblast migrated posteriorward to endoderm (pharyngeal endoderm) by way of ectoderm, while they were expressing mRNA for the hatching enzyme. Retinoic acid treatment of embryos gave rise to aberrations in the final location of the hatching gland cells probably by disturbing their migration. Moreover, the number of hatching gland cells increased markedly during their migration. This fact strongly suggested a concurrence of gene expression and mitosis of a gland cell and/or a successive initiation of gene expression in maturing gland cells during migration.

Studies on the hatching enzyme (choriolysin) and its substrate, egg envelope, constructed of the precursors (choriogenins) in Oryzias latipes: a sequel to the information in 1991/1992

Enzymatic hatching of fish embryos is caused by a sequential occurrence of many elementary processes from the commitment of the hatching gland cells to the emergence of the embryos. Molecular biological approaches to the formation, properties and function of the hatching enzyme should be required for elucidation of the enzymatic hatching, since this enzyme is a key molecule to analyze these processes. Besides them, there are some other processes indirectly related to hatching, e.g., formation and hardening of the egg envelope. The present article describes the results of our studies on some of the above-mentioned problems in the fish, Oryzias latipes, which have been obtained mostly in the early 1990s.

Effects of geranyl-geranyl-acetone administration before heat shock preconditioning for conferring tolerance against ischemia-reperfusion injury in rat livers

The effect of geranyl-geranyl-acetone (GGA) administration before heat shock preconditioning on heat shock protein (HSP) 72 induction and on the acquisition of tolerance against ischemia-reperfusion Injury was studied in rat livers. Male Wistar rats were divided into four groups: a control group (group C); a GGA group (group G); a simple heat shock group (group VH); and a heat shock with GGA premedication group (group GH). Five-, 10-, and 15-minute periods of heat shock preconditioning at 42 degrees C were performed in groups VH and GH. Subgroups were determined according to the period of heat shock exposure. After a 48-hour recovery, rats in groups C, VH5, VH15, and GH5 received a 30-minute period of hepatic ischemia. Induction of HSP72, survival rates, and changes in biochemical and histologic parameters were compared among the groups. Five-minute heat shock preconditioning was not enough to Induce HSP72. However, livers in group GH5 expressed approximately the same amount of HSP72 as those in group VH15. The expression of HSP72 in group GH15 was stronger than that found in group VH15. The degree and location of HSP72 expression were not different between groups GH5 and VH15. Seven-day survival was significantly better in groups GH5 (16/16) and VH15 (15/16) than in group C (8/16) or VH5 (9/16). The recovery of adenosine triphosphate in liver tissue was faster, and the release of liver-related enzymes during reperfusion was lower in groups GH5 and VH15 than in group C or VH5. Administration of GGA before heat shock preconditioning augmented the induction of HSP72 by decreasing the threshold for triggering the stress response.

Heat shock preconditioning ameliorates liver injury following normothermic ischemia-reperfusion in steatotic rat livers

The decreased tolerance of steatotic livers to warm ischemia complicates liver surgery. The efficacy of heat shock preconditioning in steatotic livers to lessen ischemia-reperfusion injury was studied in rats. Steatotic liver was produced in Lewis rats with a choline-deficient diet. Rats with steatotic livers were divided into a heat shock preconditioned group (group HS) and a control group (group C). All rats received 45 min of hepatic warm ischemia. Survival rates and changes in biochemical and histological parameters were compared in both groups. Heat shock protein 72 (HSP72) was produced only in group HS. The 7-day survival of the rats after warm ischemic intervention was significantly better in group HS (13/15) than in group C (5/15) (P < 0.01). The concentration of ATP in liver tissue (n = 10, P < 0.01) and serum levels of aspartate aminotransferase (n = 10, P < 0.05), alanine aminotransferase (n = 10, P < 0.01), and lactic dehydrogenase (n = 10, P < 0.01) at 40 min reperfusion were also significantly better in group HS than in group C. Histological examination at 40 min reperfusion showed severe sinusoidal congestion, hepatocyte necrosis, and increased positivity to 4-hydroxy-2-nonenal-modified proteins in group C livers; these signs were markedly suppressed in group HS livers. The data indicate that heat shock preconditioning provides the steatotic rat liver with significant tolerance to warm ischemia-reperfusion injury.

Pharmacologic stimulation of adenosine A2 receptor supplants ischemic preconditioning in providing ischemic tolerance in rat livers

BACKGROUND

Ischemic preconditioning (IPC) is a promising strategy for conferring ischemic tolerance. We confirmed the acquisition of ischemic tolerance in the liver immediately after IPC and the role of adenosine kinetics in this process.

METHODS

Male Lewis rats were used. IPC was administered with a 10-minute ischemia followed by a 10-minute reperfusion. Ischemic tolerance was tested with a 45-minute ischemia. Changes in the adenosine concentrations in liver tissue were evaluated, and the effects of adenosine A1 or A2 receptor agonists or antagonists were examined either in place of or against IPC.

RESULTS

The 7-day animal survival was significantly better in the IPC group than in the control group (87% vs 53%; n = 15, P < .05). The release of liver-related enzymes during reperfusion was suppressed better in the IPC group (P < .01). Recovery of adenosine triphosphate levels was faster in the IPC group (P < .01). After IPC, adenosine concentrations in liver tissue immediately increased to 1555 +/- 299 pmol/g wet tissue and were maintained at that level during a subsequent 45-minute ischemia. The ischemic tolerance generated by IPC was mimicked by the administration of adenosine A2 receptor agonist and opposed by adenosine A2 receptor antagonist.

CONCLUSIONS

The ischemic tolerance of the liver immediately after IPC can be supplanted by selective pharmacologic stimulation of adenosine A2 receptors.

Formation of mature egg envelope subunit proteins from their precursors (choriogenins) in the fish, Oryzias latipes: loss of partial C-terminal sequences of the choriogenins

The inner layer of egg envelope of the medaka, Oryzias latipes, comprises two major groups of glycoprotein subunits, ZI-1,2 and ZI-3. Their precursor proteins, choriogenin H (Chg H) and choriogenin L (Chg L), respectively, are synthesized in spawning female liver. In the present study, the primary structures of the precursors and the corresponding mature subunits were compared by peptide mapping and amino acid sequencing to find what difference in their molecular structures is relevant to the assembly of the soluble precursors into the insoluble inner layer. The primary structures of the solubilized subunits were mostly identical to those of the respective precursors, but they lacked C-terminal partial sequences that their precursors possessed, namely, ZI-1,2 subunit was shorter than Chg H by 34 amino acid residues and ZI-3 was shorter than Chg L by 27 residues. In addition, a consensus amino acid sequence, Arg-Lys-X-Arg, was found at the putative cleavage sites in the C-terminal region of the precursors. It is conjectured that the truncation of the precursor proteins is prerequisite for formation of mature chorion subunit proteins and their assembly into chorion.

Decrement of muscarinic receptor-stimulated low-KM GTPase in striatum and hippocampus from the aged rat

Previous studies have shown that there is an age-related loss of responsiveness in several different receptor systems (e.g. beta-adrenergic, dopaminergic and muscarinic). Our research, using perifused striatal slices and examining muscarinic agonist enhancement of K(+)-evoked dopamine release, has determined that at least part of the loss of sensitivity in muscarinic receptors (mAChR) may occur early in the post-receptor signal transduction process. The present study was carried out to further characterize and localize this deficit by examining carbachol- and oxotremorine-stimulated low-KM guanosine triphosphatase (GTPase) activity in striatal as well as hippocampal tissue obtained from adult (6 months) and old (24 months) Wistar rats. Receptor stimulated low-KM GTPase catalyzes the conversion of GTP to GDP to end the signal transduction cycle and is an indicator of receptor-G-protein coupling/uncoupling. The results showed that stimulated GTPase activity was significantly reduced in hippocampal and striatal tissue from the old animals. These findings suggest that there may be an age-related coupling/uncoupling deficit between muscarinic receptor and G-proteins, and that this deficit may contribute to the reduced mAChR responsiveness in senescence.

Two constituent proteases of a teleostean hatching enzyme: concurrent syntheses and packaging in the same secretory granules in discrete arrangement

Formation, accumulation, and storage of two components of the Oryzias latipes hatching enzyme, high and low choriolytic enzymes (HCE and LCE), were examined by immunocytochemical and immunoblotting methods. Both of the enzymes were found to be formed specifically in the hatching gland cells at the stages of lens formation to eye pigmentation and their accumulation proceeded markedly and concurrently up to Day 5.5 embryos (the stage just before hatching). The amount of HCE formed was more abundant than that of LCE. In the hatching gland cells, HCE and LCE were found to be packaged in the same secretory granules but in distinct arrangement; HCE is localized to the inside of granules whereas LCE is situated at the periphery of the same granules. Their segregated arrangement is compatible with their relative quantities formed per embryo. The results provide not only the cellular and developmental basis for a view that this hatching enzyme is an enzyme system composed of HCE and LCE but also a clue to the regulatory mechanism of concurrent syntheses of two different specific proteins in the same embryonic cell.

Analysis of the origin and development of hatching gland cells by transplantation of the embryonic shield in the fish, Oryzias latipes

Hatching gland cells of the medaka, Oryzias latipes, have been observed to differentiate from the anterior end of the hypoblast, which seems to first involute at the onset of gastrulation. These results suggest that the hatching gland cells of medaka originate from the embryonic shield, the putative organizer of this fish. The present study investigated whether hatching gland cells really originate from the embryonic shield in the medaka. Transplantation experiments with embryonic shield and in situ hybridization detection of hatching enzyme gene expression as a sign of terminal differentiation of the gland cells were carried out. The analysis was performed according to the following processes. First, identification and functional characterization of the embryonic shield region were made by determining the expression of medaka goosecoid gene and its organizer activity. Second, it was confirmed that the embryonic shield had an organizer activity, inducing a secondary embryo, and that the developmental patterns of hatching gland cells in primary and secondary embryos were identical. Finally, the hatching gland cells as identified by hatching enzyme gene expression were found to coincide with the dye-labeled progeny cells of the transplanted embryonic shield. In conclusion, it was determined that hatching gland cells were derived from the embryonic shield that functioned as the organizer in medaka.