The contribution of epinephrine to experimentally induced urethral inflammation in the rat

Epinephrine promotes hemostasis in rats with cyclophosphamide-induced hemorrhagic cystitis

OBJECTIVES

To evaluate the hypothesis that intravesical instillation of epinephrine would attenuate bladder hemorrhage in a rat model of cyclophosphamide (CYP)-induced hemorrhagic cystitis.

METHODS

Female Sprague-Dawley rats were divided into seven treatment groups: positive control (CYP, 150 mg/kg), negative control (epinephrine, 10 microg/mL), intravesical instillation of normal saline (vehicle) and epinephrine (2.5, 5, and 10 microg/mL), and intraperitoneal administration of mesna (50 mg/kg). Rats were killed on days 1, 2, and 3, and the urinary bladders were removed, weighed, and evaluated by gross and histologic analysis. Vesical vascular permeability was determined by wet bladder weight and Evan's blue dye absorbance.

RESULTS

Cyclophosphamide administration induced severe hemorrhagic cystitis with marked edema, hemorrhage, and inflammation. All three epinephrine-treated groups had marked attenuation of hemorrhagic cystitis compared with the positive and negative control and mesna-treated groups. Epinephrine was also associated with significant inhibition of tissue edema, indicating decreased vesical vascular permeability.

CONCLUSIONS

In this rat model of CYP-induced hemorrhagic cystitis, intravesical instillation of epinephrine inhibited edema, hemorrhage, and inflammation.

Sexual dimorphism in the effect of nonhabituating stress on neurogenic plasma extravasation

The sympathoadrenal axis contributes to the sexual dimorphism of the inflammatory response. As stress both activates the sympathoadrenal axis and profoundly affects inflammation and inflammatory disease, we evaluated whether stress exerts a sexually dimorphic effect on a major component of the inflammatory response, plasma extravasation. We evaluated the effect of a nonhabituating stress, repeated intermittent sound (30 min/day for 4 days), on neurogenic synovial plasma extravasation, induced by bradykinin in the rat knee joint. Sound stress profoundly inhibited bradykinin-induced plasma extravasation in male rats, but profoundly enhanced it in female rats. These effects took 24 h to fully develop after the last exposure to stress. In gonadectomized males, bradykinin-induced plasma extravasation was lower than intact males, and sound stress now enhanced it, i.e. gonadectomized males were phenotypically like intact females. In gonadectomized females, bradykinin-induced plasma extravasation was greater than in intact adult females, and sound stress still enhanced it. Adrenal enucleation significantly attenuated the effect of sound stress on bradykinin-induced plasma extravasation in both male and female rats. We tested the hypothesis that these effects of sound stress were due to sustained enhanced plasma levels of stress hormones. Corticosterone and epinephrine, only when administered in combination, over five days, produced a qualitatively similar effect as sound stress, i.e. bradykinin-induced plasma extravasation was significantly decreased in males and increased in females. These findings suggest that a combined effect of the hypothalamic-pituitary adrenal and sympathoadrenal stress axes are responsible for the marked sexual dimorphism in the effect of stress on the inflammatory response.

The anti-inflammatory effect of bee venom stimulation in a mouse air pouch model is mediated by adrenal medullary activity

Cutaneous electrical or chemical stimulation can produce an anti-inflammatory effect, which is dependent on adrenal medullary-sympathetic activation. We have previously shown that peripheral injection of bee venom (BV) also produces a significant anti-inflammatory effect that is neurally mediated. In the present study, we examined whether this anti-inflammatory effect is also dependent on the adrenal gland using the mouse inflammatory air pouch model. Subcutaneous (s.c.) BV injection produced a marked suppression of leucocyte migration and tumour necrosis factor (TNF)-alpha concentration induced by zymosan injection into the air pouch. The role of the adrenal gland in this suppression was evaluated in adrenalectomized mice. Adrenalectomy significantly reversed the suppression of leucocyte migration and TNF-alpha elevation caused by BV. Serum concentrations of corticosteroid were increased in mice with zymosan-induced air-pouch inflammation and this increase was reduced by BV administration, suggesting that adrenal corticosteroid release is not involved in mediating the anti-inflammatory effects of BV. To test this hypothesis, the corticosteroid receptor antagonist (RU486) was administered and found not to affect the BV-induced inhibition of leucocyte migration. By contrast, pretreatment with the beta-adrenergic antagonist propranolol reversed the BV-induced inhibitory effect on leucocyte migration. These results suggest that the anti-inflammatory effect of s.c. BV administration is mediated in part by the release of catecholamines from the adrenal medulla.

Arterial blood flow and microcirculatory changes in a rat groin flap after thrombosis induced by electrical stimulation of the artery

An experimental model of acute arterial thrombosis was developed in a rat groin flap model. Electrical stimulation was delivered to the flap artery while measuring blood flow in the artery and in the flap microcirculation using a laser Doppler system. Electrical stimulation produced an occlusive thrombosis in 10 rats within 68.1 +/- 19.26 (mean +/- SE) min. Thrombosis formation produced a rapid decrease of the LDF readings in the artery (90%) and in the flap (70%), the decrease being fairly parallel. Following the spontaneous thrombolysis, the artery perfusion recovered to baseline level but the flap blood flow only recovered by 10-20%. During electrical stimulation there was no change of the systemic blood pressure. The dynamic course of thrombus formation was documented on a videotape recorder through a microscope-mounted video camera and monitored on a television screen. Segments of the artery were obtained during and at the end of the experiments. The histological examination revealed arterial thrombosis composed of red blood cells, fibrin, and white blood cells, without any significant architectural and endothelial changes in the vessel walls. The study suggests that this model using electric vessel stimulation is effective for inducing arterial thrombosis and provides a simple method for recording the dynamic course of thrombus formation.

Arterial blood flow and microcirculatory changes in the rat groin flap after ischemia provocation by electrical stimulation of the artery

An island groin flap based on the inferior epigastric vessels was raised in 10 rats in order to monitor simultaneous ischemic changes in arterial blood flow and skin microcirculation induced by electrical stimulation of the feeding artery. A modified laser Doppler perfusion system recorded blood flow in the epigastric artery and in the skin microcirculation of the flap before and for 40 min after the experimentally induced ischemia. Sections of the stimulated segment of the vessel were obtained at the end of the experimental procedure for histological analysis to determine the extent of endothelial changes, if any. Artery blood flow and the flap microcirculation decreased significantly immediately after stimulation, both slowly increasing to prestimulation levels after 30 min. Artery perfusion was quicker than microcirculation to recover to the baseline value, indicating that reperfusion of larger vessels could involve mechanisms fundamentally different from those active in the resolution of ischemia at the capillary level. Histological artery examination revealed no significant endothelial damage at the stimulation site, thus demonstrating that electrical stimulation induces reproducible ischemia without visible endothelial damage. The differential effects on the feeding artery and on capillary perfusion indicate recruitment of several different mechanisms.

Corticotropin-releasing hormone deficiency unmasks the proinflammatory effect of epinephrine

Traditionally, the adrenal gland has been considered an important endocrine component of the pathway to inhibit acute inflammation via hypothalamic corticotropin-releasing hormone (CRH)-mediated secretion of glucocorticoid. Immunoreactive CRH found in inflamed tissues is a potent proinflammatory factor. Using genetic and pharmacological models of CRH deficiency, we now show that CRH deficiency unmasks a major proinflammatory effect of epinephrine secreted from the adrenal medulla. Together, epinephrine and peripheral CRH stimulate inflammation, and glucocorticoid acts as a counterbalancing force in this regard. Our findings suggest that stimulation of the acute inflammatory response should be included with the other "fight-or-flight" actions of epinephrine.

Epinephrine reduces the severity of catheter-induced urethral inflammation by action at the alpha 2-adrenoceptors

We have studied the contribution of epinephrine to experimentally induced urethral inflammation in the rat. Inflammation was induced by inserting latex strips into the urethra. The effects of various experimental procedures were assessed according to a 4-point scale based on histological findings. The results showed that 0.5 mg/kg epinephrine decreased the severity of catheter-induced urethral inflammation. This effect was blocked by the alpha 2-adrenergic agonist, yohimbine, but not by alpha 1 (prazosin), beta 1 (M32 MTC), or beta 2 (butoxamine) antagonists. The results suggest that the suppressive effect of epinephrine is mediated by action at the alpha 2 adrenergic receptor.