Hypotensive activity of novokinin, a potent analogue of ovokinin(2-7), is mediated by angiotensin AT(2) receptor and prostaglandin IP receptor

Counter-regulatory renin-angiotensin system in hypertension: Review and update in the era of COVID-19 pandemic

Cardiovascular disease is the major cause of mortality and disability, with hypertension being the most prevalent risk factor. Excessive activation of the renin-angiotensin system (RAS) under pathological conditions, leading to vascular remodeling and inflammation, is closely related to cardiovascular dysfunction. The counter-regulatory axis of the RAS consists of angiotensin-converting enzyme 2 (ACE2), angiotensin (1-7), angiotensin (1-9), alamandine, proto-oncogene Mas receptor, angiotensin II type-2 receptor and Mas-related G protein-coupled receptor member D. Each of these components has been shown to counteract the effects of the overactivated RAS. In this review, we summarize the latest insights into the complexity and interplay of the counter-regulatory RAS axis in hypertension, highlight the pathophysiological functions of ACE2, a multifunctional molecule linking hypertension and COVID-19, and discuss the function and therapeutic potential of targeting this counter-regulatory RAS axis to prevent and treat hypertension in the context of the current COVID-19 pandemic.

The Angiotensin AT2 Receptor: From a Binding Site to a Novel Therapeutic Target

Discovered more than 30 years ago, the angiotensin AT2 receptor (AT2R) has evolved from a binding site with unknown function to a firmly established major effector within the protective arm of the renin-angiotensin system (RAS) and a target for new drugs in development. The AT2R represents an endogenous protective mechanism that can be manipulated in the majority of preclinical models to alleviate lung, renal, cardiovascular, metabolic, cutaneous, and neural diseases as well as cancer. This article is a comprehensive review summarizing our current knowledge of the AT2R, from its discovery to its position within the RAS and its overall functions. This is followed by an in-depth look at the characteristics of the AT2R, including its structure, intracellular signaling, homo- and heterodimerization, and expression. AT2R-selective ligands, from endogenous peptides to synthetic peptides and nonpeptide molecules that are used as research tools, are discussed. Finally, we summarize the known physiological roles of the AT2R and its abundant protective effects in multiple experimental disease models and expound on AT2R ligands that are undergoing development for clinical use. The present review highlights the controversial aspects and gaps in our knowledge of this receptor and illuminates future perspectives for AT2R research. SIGNIFICANCE STATEMENT: The angiotensin AT2 receptor (AT2R) is now regarded as a fully functional and important component of the renin-angiotensin system, with the potential of exerting protective actions in a variety of diseases. This review provides an in-depth view of the AT2R, which has progressed from being an enigma to becoming a therapeutic target.

Bone-Targeted Delivery of Novokinin as an Alternative Treatment Option for Rheumatoid Arthritis

Rheumatoid arthritis (RA) is an autoimmune inflammatory bone destructive disorder that is orchestrated by multiple systems in the body, including Renin-Angiotensin System (RAS) and arachidonic acid (ArA) pathway. Current therapeutic options are not highly effective and are associated with severe side effects, including cardiovascular complications. Therefore, new safe and effective disease modulators are seriously needed. In this study, we investigate the anti-inflammatory effects of a synthetic peptide, novokinin, through Angiotensin Type (II) receptor (AT2R). Peptide drugs like novokinin suffer from plasma instability and short half-life. Thus, we developed a novel bone targeting novokinin conjugate (Novo Conj). It uses the bone as a reservoir for sustained release and protection from systemic degradation, improving stability and enhancing pharmacological efficacy. We tested Novo Conj’s anti-inflammatory effects in adjuvant-induced arthritis (AIA) rat model to prove our hypothesis by measuring various RAS and ArA pathway components. We observed that inflammation causes a significant imbalance in cardioprotective RAS components like ACE2, AT2R, and Ang 1-7 and increases the ArA inflammatory metabolites like hydroxyeicosatetraenoic acids (HETEs). Treatment with novokinin or Novo Conj restores balance in the RAS and favors the production of different epoxyeicosatrienoic acids (EETs), which are anti-inflammatory mediators. This study demonstrated that the bone-targeted delivery improved the stability and enhanced the anti-inflammatory effects of the parent peptide novokinin in AIA. These observations offer an efficacious alternative therapy for managing RA.

Angiotensin-(1-9) in hypertension

Angiotensin-(1-9) [Ang-(1-9)] is a peptide of the non-canonical renin-angiotensin system (RAS) synthesized from angiotensin I by the monopeptidase angiotensin-converting enzyme type 2 (ACE2). Using osmotic minipumps, infusion of Ang-(1-9) consistently reduces blood pressure in several rat hypertension models. In these animals, hypertension-induced end-organ damage is also decreased. Several pieces of evidence suggest that Ang-(1-9) is the endogenous ligand that binds and activates the type-2 angiotensin II receptor (AT2R). Activation of AT2R triggers different tissue-specific signaling pathways. This phenomenon could be explained by the ability of AT2R to form different heterodimers with other G protein-coupled receptors. Because of the antihypertensive and protective effects of AT2R activation by Ang-(1-9), associated with a short half-life of RAS peptides, several synthetic AT2R agonists have been synthesized and assayed. Some of them, particularly CGP42112, C21 and novokinin, have demonstrated antihypertensive properties. Only two synthetic AT2R agonists, C21 and LP2-3, have been tested in clinical trials, but none of them like an antihypertensive. Therefore, Ang-(1-9) is a promising antihypertensive drug that reduces hypertension-induced end-organ damage. However, further research is required to translate this finding successfully to the clinic.

Functional rice with tandemly repeated Cbl-b ubiquitin ligase inhibitory pentapeptide prevents denervation-induced muscle atrophy in vivo

Ubiquitin ligase Casitas B-lineage lymphoma-b (Cbl-b) play a critical role in nonloading-mediated skeletal muscle atrophy: Cbl-b ubiquitinates insulin receptor substrate-1 (IRS-1), leading to its degradation and a resulting loss in muscle mass. We reported that intramuscular injection of a pentapeptide, DGpYMP, which acts as a mimic of the phosphorylation site in IRS-1, significantly inhibited denervation-induced skeletal muscle loss. In order to explore the possibility of the prevention of muscle atrophy by diet therapy, we examined the effects of oral administration of transgenic rice containing Cblin (Cbl-b inhibitor) peptide (DGYMP) on denervation-induced muscle mass loss in frogs. We generated transgenic rice seeds in which 15 repeats of Cblin peptides with a WQ spacer were inserted into the rice storage protein glutelin. A diet of the transgenic rice seeds had significant inhibitory effects on denervation-induced atrophy of the leg skeletal muscles in frogs, compared with those receiving a diet of wild-type rice.

Update on Angiotensin II Subtype 2 Receptor: Focus on Peptide and Nonpeptide Agonists

Angiotensin II (Ang II) is the most dominant effector component of the renin-angiotensin system (RAS) that generally acts through binding to two main classes of G protein-coupled receptors, namely Ang II subtype 1 receptor (AT1R) and angiotensin II subtype 2 receptor (AT2R). Despite some controversial reports, the activation of AT2R generally antagonizes the effects of Ang II binding on AT1R. Studying AT2R signaling, function, and its specific ligands in cell culture or animal studies has confirmed its beneficial effects throughout the body. These characteristics classify AT2R as part of the protective arm of the RAS that, along with functions of Ang (1-7) through Mas receptor signaling, modulates the harmful effects of Ang II on AT1R in the activated classic arm of the RAS. Although Ang II is the primary ligand for AT2R, we have summarized other natural or synthetic peptide and nonpeptide agonists with critical evaluation of their structure, mechanism of action, and biologic activity. SIGNIFICANCE STATEMENT: AT2R is one of the main components of the RAS and has a significant prospective for mediating the beneficial action of the RAS through its protective arm on the body's homeostasis. Targeting AT2R offers substantial clinical application possibilities for modulating various pathological conditions. This review provided concise information regarding the AT2R peptide and nonpeptide agonists and their potential clinical applications for various diseases.

Evidence that Nitric Oxide is Involved in the Blood Pressure Lowering Effect of the Peptide AVFQHNCQE in Spontaneously Hypertensive Rats

AVFQHNCQE is an antihypertensive nonapeptide obtained from a chicken foot protein hydrolysate. The present study aims to investigate the mechanisms involved in its blood pressure (BP)-lowering effect. Male (17–20 weeks old) spontaneously hypertensive rats (SHR) were used in this study. Rats were divided into two groups and orally administered water or 10 mg/kg body weight (bw) AVFQHNCQE. One hour post-administration, animals of both groups were intra-peritoneally treated with 1 mL of saline or with 1 mL of saline containing 30 mg/kg bw Nω-nitro-L-arginine methyl ester (L-NAME), an inhibitor of nitric oxide (NO) synthesis, or with 1 mL of saline containing 5 mg/kg bw indomethacin, which is an inhibitor of prostacyclin synthesis (n = 6 per group). Systolic BP was recorded before oral administration and six hours after oral administration. In an additional experiment, SHR were administered water or 10 mg/kg bw AVFQHNCQE (n = 6 per group) and sacrificed six hours post-administration to study the mechanisms underlying the peptide anti-hypertensive effect. Moreover, the relaxation caused by AVFQHNCQE in isolated aortic rings from Sprague-Dawley rats was evaluated. The BP-lowering effect of the peptide was not changed after indomethacin administration but was completely abolished by L-NAME, which demonstrates that its anti-hypertensive effect is mediated by changes in endothelium-derived NO availability. In addition, AVFQHNCQE administration downregulated aortic gene expression of the vasoconstrictor factor endothelin-1 and the endothelial major free radical producer NADPH. Moreover, while no changes in plasma ACE activity were observed after its administration, liver GSH levels were higher in the peptide-treated group than in the water group, which demonstrates that AVFQHNCQE presents antioxidant properties.

Intracerebroventricular infusion of angiotensin AT2 receptor agonist novokinin aggravates some diabetes-mellitus-induced alterations in Wistar rats

Cumulative data suggest the significant role of the renin–angiotensin system in the development of the pathological consequences of diabetes mellitus (DM). Newly synthesized AT2 receptor agonists gained importance as a target for creating new antihypertensives. The aim of the present work was to study the effects of peptide AT2 agonist novokinin, infused intracerebroventricularly, on the consequences of the streptozotocin-induced type 1 DM (T1DM) in Wistar rats. Food and water consumption, body mass, urine excretion (metabolic cages), motor activity (open-field test), anxiety (elevated plus maze), nociception (paw pressure analgesimeter test), spatial memory (T-maze alternation test), and plasma levels of glucose and corticosterone (ELISA) were assessed 2 weeks after the T1DM induction. Novokinin increased water and food consumption, as well as urine output, and reduced mass gain in the control rats. Diabetic rats demonstrated hyperalgesia, increased level of plasma corticosterone, decreased motor and exploratory activity, and impaired spatial memory. Novokinin infusion increased water intake, diuresis, and mortality rate, decreased food intake, exacerbated diabetes-induced hyperalgesia, and provoked anxiety-like behavior but improved spatial memory in diabetic rats. These initial data suggest that angiotensin AT2 receptors participate in the pathogenesis of T1DM-induced complications in the function of the nervous system.

Novokinin inhibits gastric acid secretion and protects against alcohol-induced gastric injury in rats

Novokinin (Arg-Pro-Leu-Lys-Pro-Trp), a potent vasorelaxing and hypotensive peptide modified from ovokinin, exhibits highly selective affinity for the AT₂ receptor. However, its role in gastrointestinal functions is still not fully understood. In this study, we found that novokinin inhibited basal gastric acid secretion and protected gastric mucosa from alcohol-induced injury in a dose-related manner in rats after intracerebroventricular (i.c.v.) administration. Novokinin significantly decreased basal gastric acid output at the dose of 50 and 100 nmol/rat. The effect of novokinin on gastric acid secretion was reversed by central injection of PD 123319 (10 nmol/rat), an AT₂ receptor antagonist, and peripheral injection of indomethacin (10 mg/kg), an inhibitor of prostaglandin synthesis. Meanwhile, pre-treatment with novokinin at doses of 10, 50, and 100 nmol/rat significantly reduced the alcohol-induced gastric mucosal injury compared to the ulcer-control group, which was inhibited by indomethacin (10 mg/kg). The result showed a remarkable increase in the level of prostaglandin E2 (PGE₂), glutathione (GSH), and a decrease in malondialdehyde (MDA) after i.c.v. administration of novokinin. These findings suggest that the inhibitory effect of novokinin on gastric acid secretion is probably mediated via an AT₂ receptor-prostaglandins (PGs) pathway. The gastroprotective effect of novokinin might be attributed to the inhibition of acid secretion, the cytoprotection of PGs, and the antioxidant property.

Bioactive peptides derived from natural proteins with respect to diversity of their receptors and physiological effects

We have found various bioactive peptides derived from animal and plant proteins, which interact with receptors for endogenous bioactive peptides such as opioids, neurotensin, complements C3a and C5a, oxytocin, and formyl peptides etc. Among them, rubiscolin, a δ opioid peptide derived from plant RuBisCO, showed memory-consolidating, anxiolytic-like, and food intake-modulating effects. Soymorphin, a μ opioid peptide derived from β-conglycinin showed anxiolytic-like, anorexigenic, hypoglycemic, and hypotriglyceridemic effects. β-Lactotensin derived from β-lactoglobulin, the first natural ligand for the NTS2 receptor, showed memory-consolidating, anxiolytic-like, and hypocholesterolemic effects. Weak agonist peptides for the complements C3a and C5a receptors were released from many proteins and exerted various central effects. Peptides showing anxiolytic-like antihypertensive and anti-alopecia effects via different types of receptors such as OT, FPR and AT2 were also obtained. Based on these study, new functions and post-receptor mechanisms of receptor commom to endogenous and exogenous bioactive peptides have been clarified.

Vascular effects of a tripeptide fragment of novokinine in hypertensive rats: Mechanism of the hypotensive action

BACKGROUND

Activation of angiotensin AT2 receptors (AT2R) counteracts vasoconstrictor effects of AT1R stimulation and contributes to blood pressure control. We examined effects on mean arterial pressure (MAP) and renal hemodynamics of LKP, a tripeptide fragment of novokinine, an established AT2R agonist.

METHODS

Effects of intravenous LKP infusion and then superimposed losartan (AT1R antagonist) on MAP, total renal (RBF, Transonic probe) and renal medullary blood flows (laser-Doppler), and on renal excretion, were examined in anesthetized (1) Wistar rats with acute norepinephrine-induced hypertension, untreated or pretreated with AT2R antagonist (PD 123319) and (2) spontaneously hypertensive rats (SHR) maintained on standard or high-sodium (HS) diet.

RESULTS

In Wistar rats LKP decreased MAP (-4%, p<0.01) and increased renal medullary perfusion, these effects were abolished in rats pretreated with PD 123319 in which a post-LKP increase in MAP (+6%, p<0.02) occurred. LKP did not alter MAP in SHR; in those on HS diet RBF decreased (-14%, p<0.02), the response that was reverted by losartan. Addition of losartan always decreased or tended to decrease MAP.

CONCLUSIONS

LKP lowered MAP in norepinephrine-induced hypertension, probably via activation of AT2R. At reduced availability of AT2R, as in SHR, LKP appeared to bind to different receptors, possibly AT1, and induced systemic or renal vasoconstriction. Compared to the parent novokinine, a smaller LKP molecule might be easier absorbed after oral application and more useful in therapy.

Food-derived bioactive peptides on inflammation and oxidative stress

Chronic diseases such as atherosclerosis and cancer are now the leading causes of morbidity and mortality worldwide. Inflammatory processes and oxidative stress underlie the pathogenesis of these pathological conditions. Bioactive peptides derived from food proteins have been evaluated for various beneficial effects, including anti-inflammatory and antioxidant properties. In this review, we summarize the roles of various food-derived bioactive peptides in inflammation and oxidative stress and discuss the potential benefits and limitations of using these compounds against the burden of chronic diseases.

Prostacyclin mediates neuropathic pain through interleukin 1β-expressing resident macrophages

Prostacyclin is an important mediator of peripheral pain sensation. Here, we investigated its potential participation in mediating neuropathic pain and found that prostacyclin receptor (IP) knockout mice exhibited markedly decreased pain behavior. Application of an IP antagonist to the injury site or selective IP deficiency in myeloid cells mimicked the antinociceptive effect observed in IP knockout mice. At the site of nerve injury, IP was expressed in interleukin (IL) 1β-containing resident macrophages, which were less common in IP knockout mice. Local administration of the IP agonist cicaprost inhibited macrophage migration in vitro and promoted accumulation of IP- and IL1β-expressing cells as well as an increase of IL1β concentrations at the application site in vivo. Fittingly, the IL1-receptor antagonist anakinra (IL-1ra) decreased neuropathic pain behavior in wild-type mice but not in IP knockout mice. Finally, continuous, but not single administration, of the cyclooxygenase inhibitor meloxicam early after nerve injury decreased pain behavior and the number of resident macrophages. Thus, early synthesis of prostacyclin at the site of injury causes accumulation of IL1β-expressing macrophages as a key step in neuropathic pain after traumatic injury.

Novel long-acting prostacyclin agonist (ONO-1301) with an angiogenic effect: promoting synthesis of hepatocyte growth factor and increasing cyclic AMP concentration via IP-receptor signaling

The purpose of this study was to evaluate the angiogenic potency of ONO-1301, a novel prostacyclin agonist, using a murine sponge model. Solutions of ONO-1301 or hepatocyte growth factor (HGF), as a positive control, were injected into sponges in the backs of mice, daily for 14 days. Hemoglobin and HGF levels in the sponge were increased for up to 14 days on daily treatment with ONO-1301 while on HGF treatment, they peaked on day 7 and had decreased again by day 14. ONO-1301 also upregulated c-Met expression for 14 days in a dose-dependent manner. When the mice were pretreated with an antibody to HGF or the prostaglandin I (IP)-receptor antagonist CAY10441, the angiogenic effect of ONO-1301 was dramatically reduced. Plasma concentrations of cyclic adenosine monophosphate (cAMP) were increased in a dose-dependent manner by once daily treatment with ONO-1301 for 14 days. This effect was reduced by pretreatment with the IP-receptor antagonist. In conclusion, hemoglobin level was increased by repeated treatment with ONO-1301 for 14 days. It is suggested that ONO-1301 induced angiogenesis by promoting the synthesis of HGF and upregulated c-Met expression, followed by an increase in cAMP concentrations mediated by IP-receptor signaling.

The Angiotensin II Type 2 Receptor in Brain Functions: An Update

Angiotensin II (Ang II) is the main active product of the renin-angiotensin system (RAS), mediating its action via two major receptors, namely, the Ang II type 1 (AT₁) receptor and the type 2 (AT₂) receptor. Recent results also implicate several other members of the renin-angiotensin system in various aspects of brain functions. The first aim of this paper is to summarize the current state of knowledge regarding the properties and signaling of the AT₂ receptor, its expression in the brain, and its well-established effects. Secondly, we will highlight the potential role of the AT₂ receptor in cognitive function, neurological disorders and in the regulation of appetite and the possible link with development of metabolic disorders. The potential utility of novel nonpeptide selective AT₂ receptor ligands in clarifying potential roles of this receptor in physiology will also be discussed. If confirmed, these new pharmacological tools should help to improve impaired cognitive performance, not only through its action on brain microcirculation and inflammation, but also through more specific effects on neurons. However, the overall physiological relevance of the AT₂ receptor in the brain must also consider the Ang IV/AT₄ receptor.

Rapakinin, an anti-hypertensive peptide derived from rapeseed protein, dilates mesenteric artery of spontaneously hypertensive rats via the prostaglandin IP receptor followed by CCK(1) receptor

The anti-hypertensive peptide Arg-Ile-Tyr, which was isolated based on its inhibitory activity (IC(50)=28microM) for angiotensin I-converting enzyme (ACE) from the subtilisin digest of rapeseed protein, exhibited vasorelaxing activity (EC(50)=5.1microM) in an endothelium-dependent manner in the mesenteric artery of spontaneously hypertensive rats (SHRs). We named the peptide rapakinin. ACE inhibitors are reported to induce nitric oxide (NO)-dependent vasorelaxation by elevating the endogenous bradykinin level; however, the vasorelaxation induced by 10microM of rapakinin was blocked only insignificantly by HOE140 or N(G)-nitro-l-arginine methyl ester (l-NAME), antagonists of bradykinin B(2) receptor and an inhibitor of NO synthase, respectively. On the other hand, the vasorelaxation induced by 10microM rapakinin was significantly blocked by indomethacin and CAY10441, a cyclooxygenase (COX) inhibitor and an antagonist of the IP receptor, respectively. The vasorelaxing activity of rapakinin was also blocked by lorglumide, an antagonist of the cholecystokinin (CCK) CCK(1) receptor, although rapakinin has no affinity for the IP and CCK(1) receptors. The vasorelaxation induced by 10microM iloprost, an IP receptor agonist, was also blocked by lorglumide, suggesting that CCK-CCK(1) receptor system is activated downstream of the PGI(2)-IP receptor system. The anti-hypertensive activity of rapakinin after oral administration in SHRs was also blocked by CAY10441 and lorglumide. These results suggest that the anti-hypertensive activity of rapakinin might be mediated mainly by the PGI(2)-IP receptor, followed by CCK-CCK(1) receptor-dependent vasorelaxation.

Orally administered novokinin, an angiotensin AT2 receptor agonist, suppresses food intake via prostaglandin E2-dependent mechanism in mice

Novokinin (Arg-Pro-Leu-Lys-Pro-Trp), having affinity for the AT(2) receptor, is a potent vasorelaxing and hypotensive peptide designed based on the structure of ovokinin(2-7), a bioactive peptide derived from ovalbumin. Here we show that intracerebroventricularly (i.c.v.) administered novokinin dose-dependently suppresses food intake at a dose of 30-100 nmol/mouse in fasted conscious mice. Orally administered novokinin (30-100mg/kg) also suppressed food intake. Novokinin suppressed food intake in wild-type and AT(1) receptor-knockout mice but not in AT(2) receptor-knockout mice after i.c.v. or oral administration. Novokinin-induced anorexigenic activity after i.c.v. administration was blocked by indomethacin, a cyclooxygenase inhibitor, or ONO-AE3-208, an antagonist for EP(4) receptor for PGE(2). Taken together, novokinin may suppress food intake via activation of PGE(2)-EP(4), downstream of the AT(2) receptor.

Angiotensin AT(2) receptor agonists act as anti-opioids via EP(3) receptor in mice

Novokinin (Arg-Pro-Leu-Lys-Pro-Trp) is a vasorelaxing and hypotensive peptide acting through the angiotensin AT(2) receptor. Centrally administrated novokinin (30nmol/mouse) inhibited the antinociceptive effect of micro agonist morphine in mice, as evaluated by the tail-pinch test. The anti-opioid effect of novokinin was blocked by PD123319, an antagonist of the AT(2) receptor. Angiotensin II (0.01nmol/mouse, i.c.v.) and [p-aminophenylalanine(6)]-angiotensin II [p-NH(2)Phe(6)]-Ang II (0.1nmol/mouse, i.c.v.), a highly selective AT(2) receptor agonist, also inhibited the antinociceptive effect of morphine, and the effects were also blocked by PD123319. Angiotensin II did not suppress the antinociceptive effect induced by kappa or delta agonists. Novokinin, angiotensin II and [p-NH(2)Phe(6)]-Ang did not have affinity for the micro receptor. The anti-opioid effects induced by these peptides were blocked by ONO-AE3-240, an antagonist of the EP(3) receptor. These results suggest that the anti-opioid effects of AT(2) agonists are mediated by the PGE(2)-EP(3) receptor system downstream of the AT(2) receptor.

Activation of the PGI(2)/IP system contributes to the development of circulatory failure in a rat model of endotoxic shock

Prostacyclin levels are increased in septic patients and several animal models of septic shock, and selective inhibition of cyclooxygenase-2 improved cardiovascular dysfunction in rats treated with lipopolysaccharide (LPS). Here, we examine the specific role of prostacyclin and of the receptor for prostacyclin (IP) in the development of LPS-induced circulatory failure. Intravenous injection of LPS (10 mg/kg) into male Sprague-Dawley rats caused a strong increase in plasma prostacyclin levels, which was paralleled by a decrease in blood pressure and an increase in heart rate. Moreover, LPS injection increased the mRNA expression of the IP receptor in the heart, aorta, lung, liver, adrenal glands, and kidneys. Cotreatment with the IP antagonist CAY-10441 (1, 10, 30, and 100 mg/kg) dose-dependently moderated the LPS-induced changes in mean arterial blood pressure, heart rate, cardiac output, and systemic vascular resistance. The development of cardiovascular failure was ameliorated by CAY-10441 in spite of the typical LPS-induced increases in plasma levels of cytokines and NO. In vitro, cytokines dose- and time-dependently induced IP expression in rat vascular smooth muscle cells. Incubation of cells with the stable IP agonist iloprost in the presence of the phosphodiesterase inhibitor 3-isobutyl-1-mehylxanthine resulted in higher cAMP levels in cytokine-treated cells compared with untreated cells. Taken together, our data demonstrate a prominent role of the prostacyclin/IP system in the development of LPS-induced cardiovascular failure.

Anti-hypertensive activity of genetically modified soybean seeds accumulating novokinin

Novokinin (Arg-Pro-Leu-Lys-Pro-Trp), which has been designed based on the structure of ovokinin (2-7), significantly reduces the systolic blood pressure at a dose of 100 microg/kg after oral administration in spontaneously hypertensive rats (SHRs). In this study, we generated a transgenic soybean which accumulates novokinin. A vector encoding a modified beta-conglycinin alpha' subunit (4novokinin-alpha') in which four novokinin sequences have been incorporated by site-directed mutagenesis was introduced into somatic embryos by whisker-mediated gene transformation to produce a transgenic soybean. The 4novokinin-alpha' occupied 0.5% of total soluble protein and 5% of the beta-conglycinin alpha' subunit in the transgenic soybean seeds. Protein extracted from the transgenic soybean reduced systolic blood pressure after single oral administration in SHRs at a dose of 0.15 g/kg. Defatted flour from the transgenic soybean also reduced the systolic blood pressure at a dose of 0.25 g/kg. Thus, the 4novokinin-alpha' produced in soybean exhibited an anti-hypertensive activity in SHRs after oral administration.