Renin inhibitor aliskiren exerts beneficial effect on trabecular bone by regulating skeletal renin-angiotensin system and kallikrein-kinin system in ovariectomized mice.

SUMMARY: The skeletal renin-angiotensin system contributes to the development of osteoporosis. The renin inhibitor aliskiren exhibited beneficial effects on trabecular bone of osteoporotic mice, and this action might be mediated through angiotensin and bradykinin receptor pathways. This study implies the potential application of renin inhibitor in the management for postmenopausal osteoporosis. INTRODUCTION: The skeletal renin-angiotensin system plays key role in the pathological process of osteoporosis. The present study is designed to elucidate the effect of renin inhibitor aliskiren on trabecular bone and its potential action mechanism in ovariectomized (OVX) mice. METHODS: The OVX mice were treated with low dose (5 mg/kg) or high dose (25 mg/kg) of aliskiren or its vehicle for 8 weeks. The bone turnover markers were measured by ELISA. The structural parameters of trabecular bone at lumbar vertebra (LV) and distal femoral metaphysis were measured by micro-CT. The expression of messenger RNA (mRNA) and protein was studied by RT-PCR and immunoblotting, respectively. RESULTS: Aliskiren treatment reduced urinary excretion of calcium and serum level of tartrate-resistant acid phosphatase in OVX mice. The treatment with aliskiren significantly increased bone volume (BV/TV) and connectivity density (Conn.D) of trabecular bone at LV-2 and LV-5 as well as dramatically enhanced BV/TV, Conn.D, bone mineral density (BMD/BV) and decreased bone surface (BS/BV) at the distal femoral end. Aliskiren significantly down-regulated the expression of angiotensinogen, angiotensin II (Ang II), Ang II type 1 receptor, bradykinin receptor (BR)-1, and osteocytic-specific gene sclerostin as well as the osteoclast-specific genes, including carbonic anhydrase II, matrix metalloproteinase-9, and cathepsin K. CONCLUSIONS: This study revealed that renin inhibitor aliskiren exhibited the beneficial effects on trabecular bone of ovariectomy-induced osteoporotic mice, and the underlying mechanism for this action might be mediated through Ang II and BR signaling pathways in bone.

C1-esterase inhibitor treatment: preclinical safety aspects on the potential prothrombotic risk.

Human plasma-derived C1-esterase inhibitor (C1-INH) is an efficacious and safe treatment for hereditary angioedema. However, thrombotic events in subjects treated with C1-INH at recommended or off-label, high doses have been reported. In this study, we addressed the potential prothrombotic risk of C1-INH treatment in high doses using a non-clinical rabbit model. Following intravenous infusion of C1-INH to rabbits at doses up to 800 IU/kg, the exposure and the pharmacodynamic efficacy of C1-INH in rabbits were confirmed by activity measurements of C1-esterase, and coagulation factors XIa and XIIa, respectively. Potential prothrombotic effects were assessed following induction of venous and arterial thrombosis using in vivo models of venous and arterial stasis, complemented by various in vitro assays of coagulation markers. Administration of C1-INH at doses up to 800 IU/kg did not potentiate thrombus formation during venous stasis. In contrast, inhibition of arterial occlusion was observed upon C1-INH administration when compared with isotonic saline treatment, indicating antithrombotic rather than prothrombotic activity of high dose C1-INH treatment in vivo. This was further confirmed in vitro by decreased thrombin generation, increased activated partial thromboplastin time, clotting time and clot formation time, and inhibition of platelet aggregation. No relevant changes in fibrinolysis or in the levels of thrombin-antithrombin complexes, and prothrombin fragment 1+2 were observed upon high dose C1-INH treatment. The data suggest that treatment of healthy rabbits with high doses of C1-INH could potentially inhibit coagulation and thrombus formation rather than induce a prothrombotic risk.

[Changes in the proteinase-inhibitor system of rats with hyperlipoproteinemia during transcerebral exposures to a 100-Hz-frequency pulse current and to an ultrahigh-frequency field]. / Izmeneniia v sisteme proteinazy--ingibitory u krys s giperlipoproteidemiei pri transtserebral'nykh vozdeistviiakh impul'snym tokom s chastotoi 100 Gts i ul'travysokochastotnym polem.

Experiments on 36 male rats with experimental hyperlipoproteinemia demonstrated that transcerebral exposure to impulse current (100 Hz, 2mA) aggravates atherogenic alterations, provokes hyperactivation of kallikrein-kinin system and unbalance of elastase inhibitory activity in the serum and myocardium. The latter may contribute to better vascular permeability for low-density lipoproteins, to development of edema of vascular intima, lability of cellular and lysosomal membranes with hydrolysis of elastine and collagen fibers of myocardial vessels and other organs. Transcerebral exposure to electromagnetic UHF field (40.68 MHz) is not hypolipidemic but has no negative effect on experimental atherosclerosis, promotes normalization of kallikrein-kinin system in the serum, activation of this system in the myocardium and cerebral cortex, correction of destructive processes in the serum and cerebral cortex with a risk of their development in the myocardium.

[Changes in some of the kallikrein-kinin system indices in patients with acute pancreatitis]. / Promiana na niakoi ot pokazatelite na kalikrein-kininovata sistema pri bolni s ostur pankreatit.

Proceeding from the major role played by kinins in the pathophysiology of endogenic intoxication among acute pancreatitis patients (AP), and the conflicting and scarce literature data on the issue, the changes in the level of prekallikrein, high-molecular kininogen, alpha 2-macroglobulin, alpha 1-antitrypsin, plasminogen and carboxypeptidase N in the blood are studied in dynamics at 1, 3, 5, 7, 9 and 14 days after admission of 48 patients with mild, and 121 with severe form of acute pancreatitis. Forty-eight individuals are used for control purpose. PK, KG and plasminogen are assayed using the colorimetric method of the Boehringer Company--Mannheim, KG--by chronometric test of the Sigma Diagnostics Company, CPO N--after Folk's method, as modified by Erdös, alpha 2-MG--by radial immunodiffusion according to Mancini, and alpha 1-AJ--by immunoturbidometric method. As shown by the results, in acute pancreatitis KKS activation occurs, demonstrated by the reduced PK, KG and alpha 2-MG values, and by the statistically significant enhancement of alpha 1-DJ, COP N and plasminogen activity. In patients presenting mild forms the aforementioned changes are rather weakly manifested and transient, while in the serious forms they are markedly expressed and persisting. In either form the deviations are rather pronounced in the first three days of disease. Coinciding with a clinical course characterized by cardiovascular changes similarly strongly manifested.

Contribution of the renin-angiotensin and kallikrein-kinin systems to short-term variability of blood pressure in two-kidney, one-clip hypertensive rats.

Spectral analysis was recently chosen to characterize the fast oscillations, depending on the autonomic nervous system, in heart rate and blood pressure variabilities. Humoral stimuli could impinge on the low-frequency domain of blood pressure variability since the time lag to humoral system activation is greater. This study was designed to analyse low-frequency components of short-term variability of blood pressure of conscious rats in conditions where humoral systems were activated. We studied rats with two-kidney, one-clip Goldblatt hypertension in which the blood pressure level was dependent upon the renin-angiotensin and kallikrein-kinin systems. Spectral powers of the systolic and diastolic blood pressure and heart rate were computed in the high (respiratory)-, mid (0.2-0.6 Hz)- and low (0.02-0.2 Hz)-frequency bands, as detected by the fast Fourier transform technique in consecutive 102-s stationary periods. Hypertensive rats exhibited a marked low-frequency component of systolic (+261%) and diastolic (+169%) blood pressure variabilities when compared to sham-operated animals. First, losartan, a selective non-peptide angiotensin AT1 receptor antagonist, reduced this low-frequency component (-44% and -25% for systolic and diastolic blood pressure). In a second series of hypertensive rats, HOE 140, D-Arg-[Hyp3,Thi5,D-Tic7,Oic8]bradykinin, a bradykinin B2 receptor antagonist, decreased the low-frequency component of systolic (-28%) and diastolic (-40%) blood pressure. Losartan, added after HOE 140, induced a supplementary decrease of the low-frequency component (-60% and -42% for systolic and diastolic blood pressure). After the combined blockade, the low-frequency components of systolic and diastolic blood pressure variabilities of the hypertensive rats were equivalent to those of the control rats. Two-kidney, one-clip hypertension was also associated with an elevation of the mid-frequency component of the systolic blood pressure (+55%). The administration of HOE 140 did not change this component while losartan, alone or added after HOE 140, led to an increase (around +100%) in mid-frequency oscillations of systolic blood pressure. The high-frequency oscillations of systolic blood pressure were increased by losartan in the two series of hypertensive rats. Losartan increased the mid-frequency component of heart rate variability in sham-operated rats while the heart rate variability was not modified during any of the treatment periods in two-kidney, one-clip rats. In conclusion, an increase in the low-frequency component of blood pressure variability was observed in a model of hypertension where the blood pressure is dependent upon humoral activities. The reduction of the slow fluctuations following the combined blockade of the kallikrein-kinin and the renin-angiotensin systems suggested the contribution of these humoral systems to this low-frequency component of blood pressure variability.

Involvement of the kallikrein-kinin system in the salivary secretion elicited in rats by heat stress.

1. During heat exposure, rats secrete large amounts of saliva. Salivation started when body temperature exceeded 39 degrees C and was reduced by kininogen deficiency or by HOE 140, a bradykinin antagonist. This secretory response was associated with a partial depletion of glandular kallikrein from the submaxillary glands. The depletion was abolished by simultaneous treatment of the animals with an alpha- and a beta-adrenergic antagonist. During heat exposure, plasma levels of kininogens were reduced. 2. Pilocarpine and substance P induced a similar flow of saliva in normal and kininogen-deficient rats and released low amounts of kallikrein from salivary glands. Phenylephrine and isoproterenol induced a larger flow of saliva in normal rats than in kininogen-deficient rats. Both agents released large amounts of kallikrein in saliva but isoproterenol was only active at large doses. 3. During heat exposure, the blood content of submaxillary glands in normal as well as in kininogen-deficient rats increased as a function of the ambient temperature. This increase was suppressed by atropine and NG-nitro-L-arginine, a NO-synthase inhibitor, but was not modified by HOE 140. Simultaneously, a swelling of the glands and of the surrounding soft tissues occurred in normal but not in kininogen-deficient rats. Kallikrein was present in the edema fluid. 4. The kallikrein-kinin system would thus participate in heat-induced salivary secretion and kinins may be a factor responsible for electrolyte and water exchanges in the glands.

Hemodynamic, renal, and hormonal actions of aprotinin in an ovine model of septic shock.

BACKGROUND AND METHODS: Previous studies documented activation of protease enzymes such as the plasma kallikrein-kinin system in endotoxemia and sepsis, both in experimental animals and in patients. We investigated the actions of aprotinin (a protease inhibitor that binds to plasma kallikrein) on systemic hemodynamics and renal function, in an ovine model of septic shock. Aprotinin was infused intravenously in high dosage (1 x 10(6) kallikrein inhibitor units [KIU] loading, 200,000 KIU/hr), commencing 30 mins after surgical induction of sepsis (cecal ligation and puncture). RESULTS: In the control group (n = 6), there were significant decreases with time in BP and systemic vascular resistance, an increase in pulmonary artery pressure, reductions in creatinine clearance and sodium excretion, and an increase in plasma renin activity. In aprotinin-treated animals (n = 6), none of these changes occurred. There were significant between-group differences (controls vs. treatment) for mean arterial pressure, pulmonary artery pressure, and plasma renin activity. CONCLUSIONS: In this large animal model of septic shock, which reproduces the important features of clinical sepsis, treatment with aprotinin after the initiation of sepsis appears beneficial in relation to systemic hemodynamics, renal function, and hormonal stimulation, with no evidence of adverse effects.

The role of the kallikrein-kinin system in joint inflammatory disease.

Components of kallikrein-kininogen-kinin are activated in response to noxious stimuli (chemical, physical or bacterial), which may lead to excessive release of kinins in the synovial joints that may produce inflammatory joint disease. The inflammatory changes observed in synovial tissue may be due to activation of B2 receptors. Kinins also stimulate the synthesis of other pro-inflammatory agents (PGs, LTs, histamine, EDRF, PGI2 and PAF) in the inflamed joint. B2 receptor antagonists may provide valuable new analgesic drugs. The mode of excessive kinin release in inflamed synovial joints leads to stimulation of pro-inflammatory actions of B2 kinin receptors. These properties could be antagonized by novel B2 receptor antagonists (see Fig. 4). Further, it is suggested that substances directed to reduce the activation of KKS may provide a pharmacological basis for the synthesis of novel antirheumatic or anti-inflammatory drugs.