Clonidine decreases rat urine kallikrein excretion by alpha-adrenergic receptor stimulation

The role of the alpha-1 adrenoceptor in modulating human mesangial cell matrix production

BACKGROUND

The sympathetic nervous system is frequently activated in hypertension and may modify various aspects of renal function. Whether modulation of the sympathetic nervous system directly influences the development of renal fibrosis is yet to be established. The current study investigates the role of the alpha-1 adrenoceptor on human mesangial cell scarring.

METHODS

Human mesangial cells were injured with macrophage-conditioned medium (MPCM) and treated with doxazosin for 1 or 3 days.

RESULTS

alpha-1 Adrenoceptor antagonist doxazosin of 2 micromol/l reduced fibronectin protein in MPCM-injured female mesangial cells by 31 +/- 1.03% (P < 0.001) and by 9.5 +/- 0.3% (P = 0.01) in male mesangial cells. The differential response between sexes was significant (P = 0.004). alpha-1B Adrenoceptors were detected in human mesangial cells by reverse transcription-polymerase chain reaction with expression in female cells being 87% higher than in males (P = 0.04). Injury with MPCM reduced alpha-1B adrenoceptor mRNA expression in both cell types. Doxazosin had no effect on the protein levels of transforming growth factor-beta (TGF-beta) or interleukin-1beta (IL-1beta), however, a small reduction in tumour necrosis factor-alpha (TNF-alpha) levels was observed. Doxazosin had no effect on the modulators of matrix turnover matrix metalloproteinases MMP3, MMP9 and tissue inhibitor of matrix metalloproteinases (TIMP-1), although a significant reduction in tissue plasminogen activator (tPA); (36.5 +/- 2.6%, P < 0.001) was observed. Doxazosin caused an up-regulation of kallikrein expression, both at mRNA and protein levels. Co-treatment with the bradykinin B2 receptor antagonist HOE140 was able to attenuate the effects of doxazosin treatment on fibronectin levels.

CONCLUSION

These data suggest that inhibition of alpha-1B adrenoceptors in mesangial cells exerts an anti-fibrotic effect in a sex-specific manner via modulation of the kallikrein-kinin/plasminogen activator system.

The role of chemical mediators in the pathogenesis of inflammation with emphasis on the kinin system

In recent years, numerous agents have been recognized as inflammatory mediators. In this review, however, we discuss only those having direct relevance to human inflammatory diseases These mediators are clinically important due to their proinflammatory properties such as vasodilatation, increased vascular permeability, pain and chemotaxis. They may lead to the fifth cardinal sign, loss of function in inflammatory diseases. Agonists and non-specific antagonists are used as pharmacological tools to investigate the inflammatory role of PGs, LTs, PAF, IL-1, histamine, complement, SP, PMN-leukocytes, and kallikrein-kininogen-kinin systems. Unfortunately, no compound is known which concurrently abolishes all actions and interactions of inflammatory mediators. Therefore it would be highly useful to promote efforts in developing selective and competitive antagonists against proinflammatory actions of these chemical mediators. This may help to a better understanding of the pathogenesis of inflammatory reactions, and it may also be useful for the therapy of inflammatory diseases.

Interrelationship between the kallikrein-kinin system and hypertension: a review

The evidence presented here suggests strongly that the kallikreins-kininogens-kinins-kininase II system has most significant role in regulation of systemic BP. This system is involved in mediation and modulation of renin-angiotensin-aldosterone, PGS and vasopressin in the regulation of sodium water balance, renal hemodynamic and BP. Therefore, reduction in the kinin-formation due to high production of kininase II, and lower formation of tissue kallikrein might result in an increased release of vasoconstrictor angiotensin II on one side, and on the other side much reduced production of PGE, vasodilator. These changes might lead to deranged vascular smooth muscle structures and cell membrane functions, retention of sodium and water, increased plasma volume, and renovascular constriction. These physiological defects might result in the development of essential hypertension (Fig. 4). Although, it is possible now to treat hypertensive conditions with tissue kallikrein and kininase II inhibitors. These discoveries have opened up new vistas to research on the pharmacological applications of kallikreins-kininogens-kinins-kininases in human diseases.

Sympathetic nervous system mediates urinary kallikrein excretion in conscious rats

1. The influence of the sympathetic nervous system on urinary kallikrein excretion (UKal) was investigated in conscious rats during stress produced by inserting a silastic catheter through the urethra into the bladder. The effect of this stress on blood glucose (BG), mean arterial pressure (MAP), urinary volume (Uv), urinary sodium (UVNa), and glomerular filtration rate (GFR) was also studied. 2. In intact animals stress of 120 min duration produced a non-significant increase of MAP, a significant increase of BG and a decrease of UNa (P less than 0.001 t-test, 9 d.f.), but it did not affect Uv and GFR. In stressed rats UKal was considerably lower (52 milli Amidasic Units [mAU] per 100 g bodyweight, s.e.m. = 5, n = 6) than in control rats (170 mAU per 100 g, s.e.m. = 21, n = 5). The inhibitory effect on UKal was also observed when kallikrein was measured by the kininogenase method. 3. Adrenal medullectomy, performed 1 week before the experiment, suppressed the stress hyperglycaemia but did not affect the reduction of urinary kallikrein or the anti-natriuresis. 4. Intracerebroventricular (i.c.v.) injection of saline also had no effect in the control or in the stressed rats, while i.c.v. d-l-propranolol decreased MAP, suppressed the stress hyperglycaemia and the anti-natriuresis and stimulated UKal, without changes in Uv and GFR. Non-stressed control rats i.c.v. injected with saline excreted considerably less kallikrein than rats i.c.v. injected with d-l-propranolol (control saline: 162, s.e.m. = 14, n = 6; vs control d-l-propranolol: 559, s.e.m. = 20, n = 6). Even in stressed rats this difference was registered (stressed saline: 56, s.e.m. = 8, n = 6; vs stressed d-l-propranolol: 554 mAU per 100 g, s.e.m. = 33, n = 6). 5. Peripheral sympathectomy with 6-hydroxydopamine (6-OHDA) did not suppress the hyperglycaemic response to stress, but it stimulated UKal. Kallikrein excretion was similar in 6-OHDA stressed (534 mAU per 100 g, s.e.m. = 30, n = 6) than in 6-OHDA control rats (491 mAU per 100 g, s.e.m. = 34, n = 6). No differences were observed on UNa and GFR between control 6-OHDA treated rats and stressed 6-OHDA treated rats. 6. The present results suggest strongly that urinary kallikrein excretion is modulated by sympathetic activity. Results after central beta-adrenergic blockade and peripheral sympathectomy led to the hypothesis that normal sympathetic tone in the kidney inhibits the release of kallikrein into the urine.

Effect of metoprolol on 24-hour urinary excretion of adrenal steroids and kallikrein in patients with essential hypertension

Treatment of fifteen patients with essential hypertension over four weeks using the beta 1-adrenoceptor blocking agent, metoprolol, resulted in a decrease in 24 h urinary excretion of kallikrein and aldosterone along with a decrease in plasma renin activity. There was no significant change in 24 h excretion rates of the free adrenal steroids deoxycorticosterone, 18-OH-deoxycorticosterone, corticosterone, cortisol or 18-OH-corticosterone during treatment, which were not significantly different from excretion rates of normal males, thus excluding inhibitory effects of adrenal steroids on urinary kallikrein activity. A positive correlation was found between plasma renin activity and urinary excretion of kallikrein during the control period and after 2 weeks on metoprolol, supporting the assumption of a preserved link between the renin-angiotensin-aldosterone system and the renal excretion of kallikrein in these patients. The decrease in kallikrein excretion during beta 1-adrenoceptor blockade in patients with essential hypertension may be explained by a reduction in sympathetic tone and by reduced activity of the renin-aldosterone system.