High-dose epinephrine acts at alpha 2-adrenoceptors to suppress experimental arthritis

A History of Psycho-Neuro-Endocrine Immune Interactions in Rheumatic Diseases

BACKGROUND

All active scientists stand on the shoulders of giants and many other more anonymous scientists, and this is not different in our field of psycho-neuro-endocrine immunology in rheumatic diseases. Too often, the modern world of publishing forgets about the collective enterprise of scientists. Some journals advise the authors to present only literature from the last decade, and it has become a natural attitude of many scientists to present only the latest publications. In order to work against this general unempirical behavior, neuroimmunomodulation devotes the 30th anniversary issue to the history of medical science in psycho-neuro-endocrine immunology.

SUMMARY

Keywords were derived from the psycho-neuro-endocrine immunology research field very well known to the authors (R.H.S. has collected a list of keywords since 1994). We screened PubMed, the Cochran Library of Medicine, Embase, Scopus database, and the ORCID database to find relevant historical literature. The Snowballing procedure helped find related work. According to the historical appearance of discoveries in the field, the order of presentation follows the subsequent scheme: (1) the sensory nervous system, (2) the sympathetic nervous system, (3) the vagus nerve, (4) steroid hormones (glucocorticoids, androgens, progesterone, estrogens, and the vitamin D hormone), (5) afferent pathways involved in fatigue, anxiety, insomnia, and depression (includes pathophysiology), and (6) evolutionary medicine and energy regulation - an umbrella theory.

KEY MESSAGES

A brief history on psycho-neuro-endocrine immunology cannot address all relevant aspects of the field. The authors are aware of this shortcoming. The reader must see this review as a viewpoint through the biased eyes of the authors. Nevertheless, the text gives an overview of the history in psycho-neuro-endocrine immunology of rheumatic diseases.

Modulation of peripheral inflammation by the spinal cord

The central nervous system, and the spinal cord in particular, is involved in multiple mechanisms that influence peripheral inflammation. Both pro- and anti-inflammatory feedback loops can involve just the peripheral nerves and spinal cord or can also include more complex, supraspinal structures such as the vagal nuclei and the hypothalamic-pituitary axis. Analysis is complicated by the fact that inflammation encompasses a constellation of end points from simple edema to changes in immune cell infiltration and pathology. Whether or not any of these individual elements is altered by any potential mechanism is determined by a complex algorithm including, but not limited to, chronicity of the inflammation, tissue type, instigating stimulus, and state/tone of the immune system. Accordingly, the pharmacology and anatomical substrate of spinal cord modulation of peripheral inflammation are discussed with regard to peripheral tissue type, inflammatory insult (initiating stimulus), and duration of the inflammation.

Function of the sympathetic supply in acute and chronic experimental joint inflammation

Joints are densely innervated by postganglionic sympathetic nerve fibers. These fibers control the blood flow in the joint and vascular permeability, either directly or indirectly, in cooperation with leukocytes. Chemical sympathectomy or suppression of adrenergic signaling significantly reduces inflammatory processes in the initial acute state of inflammation whereas the same procedures may increase inflammation at later stages. These findings indicate that the sympathetic nervous system supports the development of inflammation but may reduce inflammation at more chronic stages. During chronic inflammation the density of sympathetic nerve fibers in synovial tissue is reduced but other tyrosine hydroxylase-positive cells secreting noradrenaline appear in the inflamed joint. In addition to local vascular effects in the joint, the sympathetic nervous system influences numerous immune processes in the joint and in lymphoid organs. Hence the net effect of the sympathetic nervous system on inflamed tissue results from local sympathetic effects in the joint as well as from sympathetic influences on major systemic immune processes.

The role of regulatory T cells in neurodegenerative diseases

A sustained neuroinflammatory response is the hallmark of many neurodegenerative diseases, including Parkinson's disease, Alzheimer's disease, amyotrophic lateral sclerosis, multiple sclerosis, and HIV-associated neurodegeneration. A specific subset of T cells, currently recognized as FOXP3(+) CD25(+) CD4(+) regulatory T cells (Tregs), are pivotal in suppressing autoimmunity and maintaining immune homeostasis by mediating self-tolerance at the periphery as shown in autoimmune diseases and cancers. A growing body of evidence shows that Tregs are not only important for maintaining immune balance at the periphery but also contribute to self-tolerance and immune privilege in the central nervous system. In this article, we first review the current status of knowledge concerning the development and the suppressive function of Tregs. We then discuss the evidence supporting a dysfunction of Tregs in several neurodegenerative diseases. Interestingly, a dysfunction of Tregs is mainly observed in the early stages of several neurodegenerative diseases, but not in their chronic stages, pointing to a causative role of inflammation in the pathogenesis of neurodegenerative diseases. Furthermore, we provide an overview of a number of molecules, such as hormones, neuropeptides, neurotransmitters, or ion channels, that affect the dysfunction of Tregs in neurodegenerative diseases. We also emphasize the effects of the intestinal microbiome on the induction and function of Tregs and the need to study the crosstalk between the enteric nervous system and Tregs in neurodegenerative diseases. Finally, we point out the need for a systems biology approach in the analysis of the enormous complexity regulating the function of Tregs and their potential role in neurodegenerative diseases.

Restoring the balance of the autonomic nervous system as an innovative approach to the treatment of rheumatoid arthritis

The immunomodulatory effect of the autonomic nervous system has raised considerable interest over the last decades. Studying the influence on the immune system and the role in inflammation of the sympathetic as well as the parasympathetic nervous system not only will increase our understanding of the mechanism of disease, but also could lead to the identification of potential new therapeutic targets for chronic immune-mediated inflammatory diseases, such as rheumatoid arthritis (RA). An imbalanced autonomic nervous system, with a reduced parasympathetic and increased sympathetic tone, has been a consistent finding in RA patients. Studies in animal models of arthritis have shown that influencing the sympathetic (via α- and β-adrenergic receptors) and the parasympathetic (via the nicotinic acetylcholine receptor α7nAChR or by electrically stimulating the vagus nerve) nervous system can have a beneficial effect on inflammation markers and arthritis. The immunosuppressive effect of the parasympathetic nervous system appears less ambiguous than the immunomodulatory effect of the sympathetic nervous system, where activation can lead to increased or decreased inflammation depending on timing, doses and kind of adrenergic agent used. In this review we will discuss the current knowledge of the role of both the sympathetic (SNS) and parasympathetic nervous system (PNS) in inflammation with a special focus on the role in RA. In addition, potential antirheumatic strategies that could be developed by targeting these autonomic pathways are discussed.

Sympathetic modulation of immunity: relevance to disease

Optimal host defense against pathogens requires cross-talk between the nervous and immune systems. This paper reviews sympathetic-immune interaction, one major communication pathway, and its importance for health and disease. Sympathetic innervation of primary and secondary immune organs is described, as well as evidence for neurotransmission with cells of the immune system as targets. Most research thus far has focused on neural-immune modulation in secondary lymphoid organs, has revealed complex sympathetic modulation resulting in both potentiation and inhibition of immune functions. SNS-immune interaction may enhance immune readiness during disease- or injury-induced 'fight' responses. Research also indicate that dysregulation of the SNS can significantly affect the progression of immune-mediated diseases. However, a better understanding of neural-immune interactions is needed to develop strategies for treatment of immune-mediated diseases that are designed to return homeostasis and restore normal functioning neural-immune networks.

Peripheral Suppression of Arthritic Pain by Intraarticular Fadolmidine, an α2-Adrenoceptor Agonist, in the Rat

BACKGROUND

Earlier results suggest that peripheral alpha(2)-adrenoceptors and opioid receptors may reduce arthritic pain. Fadolmidine is a highly selective alpha(2)-adrenoceptor agonist that has only limited central access after peripheral administration. We assessed the peripheral antinociceptive properties of fadolmidine and the potential contribution of peripheral opioid receptors to its antinociceptive effect in experimental monoarthritis.

METHODS

After induction of monoarthritis in the knee joints of rats, we determined the frequency of vocalization induced by repetitive movement of the knee joint. Fadolmidine and clonidine were administered intraarticularly ipsi- or contralateral to the inflamed joint. Reversal of the fadolmidine-induced effect was attempted with subcutaneous (s.c.) administration of atipamezole, an alpha(2)-adrenoceptor antagonist, and intraarticular administration of naloxone methiodide, an opioid receptor antagonist that does not penetrate the blood-brain barrier.

RESULTS

Fadolmidine produced a dose-dependent attenuation of the vocalization response to movement of the inflamed knee joint, and this effect was significantly stronger after ipsi- than contralateral drug administration. Clonidine also produced a dose-dependent attenuation of the vocalization response, but this effect was not significantly different after ipsi- versus contralateral drug administration. Fadolmidine-induced antinociception was reversed by s.c. administration of atipamezole. Furthermore, intraarticular administration of naloxone methiodide into the inflamed, but not the contralateral, joint reversed the antinociceptive effect of fadolmidine independent of whether fadolmidine was administered into the inflamed or contralateral joint.

CONCLUSIONS

In rats, intraarticular administration of fadolmidine provides a marked suppression of pain-related behavior in arthritis, due to a selective action on peripheral alpha(2)-adrenoceptors and opioid receptors.

Periphere analgetische Wirkung durch intraartikulär verabreichtes Clonidin

BACKGROUND AND AIM

Clonidine applied intra-articularly into the knee joint has a peripheral analgesic effect. We examined intra-articularly injected clonidine to determine whether resorption with a measurable systemic concentration could be detected.

METHODS

A randomised, placebo-controlled double-blind study was carried out on patients undergoing knee arthroscopies. The 69 patients were randomised into three groups: group 1 received 150 ug clonidine intra-articularly, group two 150 ug clonidine intravenously and group three a placebo. Postoperative pain therapy was carried out with i.v. morphine hydrochloride. Pain scores and side-effects were documented for 24 h.

RESULTS

There were no significant differences between the three groups in demographics, duration of operation, duration of anaesthesia, diagnoses or type of operation. The pain score at rest was significantly lower in group 1. In the first 20 min, the systemic concentration of clonidine was significantly higher in the intravenous group than in the intra-articular group.

CONCLUSION

Intra-articular clonidine has a postoperative analgesic effect after knee arthroscopies due to a peripheral action.

The importance of timing of adrenergic drug delivery in relation to the induction and onset of adjuvant-induced arthritis

Stressful events often precede onset and exacerbate established rheumatic diseases. There are numerous reports of abnormal autonomic function in rheumatoid arthritis (RA) patients. Targeting the sympathetic nervous system (SNS) with adrenergic receptor (AR) drugs in RA patients and animal models of the disease have revealed mixed results, with treatments inhibiting and exacerbating disease pathology. We tested the hypothesis that variability in disease outcome following adrenergic drug treatment is due to different roles played by the SNS at different disease stages. The contribution of beta2- and alpha-AR subtypes to disease pathology was studied at different disease stages in adjuvant-induced arthritis (AA), an animal model of RA. Lewis rats were given twice-daily intraperitoneal (i.p.) injections of an alpha-AR antagonist (phentolamine: 500 microg/kg) or a beta2-AR agonist (terbutaline: 1200 microg/day), initiated at adjuvant challenge or disease onset, and continued through severe disease. Both adrenergic therapies, when initiated at adjuvant challenge exacerbated disease pathology. In contrast, SH1293, an adrenergic drug that targets both alpha- and beta-AR (300 microg/day; twice-daily), initiated at adjuvant challenge did not exacerbate disease severity. Additionally, the same treatment regimen of phentolamine, terbutaline or SH1293 initiated at disease onset attenuated joint-inflammation and dramatically reduced bone destruction in the arthritic hind limbs. These data support the SNS playing different roles in disease pathology preclinically and after disease onset. Given current drug therapies are not effective in preventing bone destruction, these data support using adrenergic drugs as bone sparing treatments in RA.

Double-Blind Parallel Comparison of Multiple Doses of Apraclonidine, Clonidine, and Placebo Administered Intra-Articularly to Patients Undergoing Arthroscopic Knee Surgery

OBJECTIVE

This clinical study assessed and compared the potential analgesic and adverse effect of IA apraclonidine with IA clonidine.

METHODS

Eighty patients scheduled for arthroscopic knee surgery under general anesthesia were randomized to receive, in a double-blind manner, either IA normal saline (group 1), 50 microg IA apraclonidine (group 2), 150 microg IA apraclonidine (group 3), or 150 microg IA clonidine (group 4), all in a volume of 20 mL subsequent to surgery. Visual analog pain scores (VAS), the duration of analgesia as defined by the time to first demand for supplemental analgesics, the subsequent 24-hour consumption of postoperative supplementary analgesics, and patient adverse effects were evaluated.

RESULTS

The patients from groups 3 and 4 demonstrated a longer duration of analgesia and used fewer analgesics in the first postoperative 24 hour period compared with group 1 and 2 patients (P < 0.05). The VAS scores corresponding to the periods 1, 2, and 4 hours postoperatively were significantly lower for group 3 than for group 1 patients. The VAS scores at 1 and 4 hours postoperatively were also lower for group 3 than for group 2 patients (P < 0.05). There was no significant difference in the incidence of side effects among the 4 groups.

DISCUSSION

The IA application of 150 microg apraclonidine and 150 microg clonidine provide similar degree of postoperative analgesia following knee arthroscopic surgery without any difference in adverse events.

Molecular mechanisms for alpha2-adrenoceptor-mediated regulation of synoviocyte populations

The sympathetic nervous system has been indicated to influence the severity of inflammatory disease including rheumatoid arthritis. In this study, we elucidated the effects of catecholamine on the synovial cell populations. Stimulation with epinephrine or norepinephrine for 1-2 weeks dose- and time-dependently increased the number of synovial A (macrophage-like) cells but decreased that of B (fibroblast-like) cells. These responses in A and B cells were inhibited by the alpha2-antagonist yohimbine, the G-protein inactivator pertussis toxin and the phospholipase C (PLC) inhibitor U-73122. Furthermore, the protein kinase C (PKC) inhibitor calphostin C and mitogen-activated protein (MAP) kinase inhibitors PD98059 and wortmannin also abolished the norepinephrine effects on A and B cell numbers. In A cells cloned from an A and B cell mixture, norepinephrine also increased the cell number. In immunoblotting and immunocytostaining analyses, among the PKC isozymes, only PKC betaII immunoreactivity was observed in the cytoplasm of unstimulated A and B cells. After alpha2-adrenoceptor stimulation, PKC betaII immunoreactivity increased in the plasma membranes of both A and B cells with decreases in the cytoplasm. These findings indicated that alpha2-adrenoceptor stimulation of type A and B synoviocytes produced an increase and a decrease in the respective cell number, probably through Gi-coupled PLC activation and the resulting stimulation of the PKC betaII/MAP kinase.

Regulation of cytokine and chemokine production by transmitters and co-transmitters of the autonomic nervous system

The sympathetic nervous system innervates immune organs and, when activated, releases its signaling molecules in the vicinity of immune cells. The released molecules include the "classical" transmitters norepinephrine and epinephrine and the co-transmitters ATP and adenosine. Immune cells express various adrenergic and purinergic receptors that are sensitive to these molecules, and the production of immune/inflammatory mediators (cytokines, chemokines, and free radicals) is modulated by activation of these receptors. Notably, the production of tumor necrosis factor-alpha, interleukin-6, -10, and -12, and the chemokine macrophage inflammatory protein 1alpha and the production of the free radical nitric oxide, produced by the inducible nitric oxide synthase, have been shown to be altered by activation of these receptors. Alterations in the production of the immune mediators may contribute to the development of various diseases. On the other hand, novel experimental therapies based on the modulation of adrenergic or purinergic receptors on immune cells are emerging. Such approaches may have beneficial effects in limiting tissue injury and suppressing symptoms in certain pathophysiological states.

Adrenergic regulation of macrophage-derived tumor necrosis factor-alpha generation during a chronic polyarthritis pain model

Increases in the levels of proinflammatory cytokines, such as TNF alpha, have been intricately linked with arthritis and the pathogenesis of several models of neuropathic pain. In addition, arthritis (as well as other types of persistent pain) is associated with increased sympathetic activity and alterations of other responses in autonomic nervous activity. Adrenergic regulation of LPS-stimulated TNF production by M phi isolated from rats with streptococcal-cell-wall (SCW)-induced arthritis has been examined. Serum TNF levels and the cellular composition of peritoneal exudates have also been assessed. M phi were obtained from: (1) normal control rats, (2) animals injected with complete Freund's adjuvant (CFA), 3 rats injected with SCW and arthritic, and (4) those injected with SCW, which failed to develop arthritis. Serum levels of TNF alpha in rats that develop arthritis are significantly greater (2.4 fold) than levels from the other groups. The proportion of OX19-positive T cell subpopulations are the same in peritoneal exudates from all groups. Immunocytochemical staining also reveals differences between M phi subgroups in the degree of activation. Peritoneal exudates from rats that develop arthritis contain a greater proportion of the high TNF producing subclass of M phi, as identified by positive ED3 staining (p < 0.001). In contrast, Ia antigen presenting M phi (OX6-positive) in the peritoneal exudate cells are only elevated in rats administered CFA. The selective blockade of adrenergic receptors by idazoxan or propranolol demonstrates that the constitutive involvement of either alpha 2 or beta-adrenergic regulation of M phi-derived TNF production is pronounced in rats with arthritis (p < 0.001). These investigations demonstrate a distinctive pattern of peripheral M phi populations in rats that develop chronic polyarthritic pain. We believe that identification of interactions between the adrenergic responses and proinflammatory cytokines will lead to the development of improved strategies to treat patients with chronic pain.

Beta-adrenergic receptor regulation of macrophage-derived tumor necrosis factor-alpha production from rats with experimental arthritis

Prostaglandin E2 (PGE2) and beta-adrenergic agonists can suppress lipopolysaccharide-induced tumor necrosis factor-alpha (TNF) production from elicited macrophages. We assessed the responsiveness of rat peritoneal macrophages to PGE2 and the beta-adrenergic agonist isoproterenol during immunologically-mediated arthritis. We assessed macrophage sensitivity to these mediators from resident macrophages and macrophages elicited with either streptococcal cell wall or complete Freund's adjuvant. Peritoneal macrophages were obtained from female Lewis rats that were (1) injected with complete Freund's adjuvant and non-arthritic (CFA); (2) injected with streptococcal cell wall and arthritic (ART); (3) injected with streptococcal cell wall and non-reactive (NON) and (4) non-elicited resident macrophages (RES). When challenged with graded concentrations of lipopolysaccharide (0.1 to 10,000 ng/ml), macrophages obtained from each group of rats released TNF in a concentration-dependent manner, with macrophages from arthritic rats (ART) producing the greatest amount of TNF (p < 0.001). While PGE2 suppressed lipopolysaccharide (100 ng/ml) stimulated TNF production in a concentration-dependent manner in all groups, the greatest sensitivity to PGE2 was observed with macrophages obtained from rats which received streptococcal cell wall when compared to both complete Freund's adjuvant-elicited and resident macrophages (p < 0.05). The beta-adrenergic agonist isoproterenol also inhibited lipopolysaccharide-stimulated TNF production from macrophages in all groups. In addition, the specific beta 2-adrenergic antagonist, ICI 118.551, shifted isoproterenol concentration-effect curves to the right (p < 0.01). Minimal responsiveness to isoproterenol was observed with resident peritoneal macrophages. Maximum isoproterenol-induced inhibition of TNF production was observed with complete Freund's adjuvant-elicited macrophages, and significantly less in macrophages of streptococcal cell wall-injected rats. Of particular interest, macrophages obtained from streptococcal cell wall-injected rats, which became arthritic, were significantly less sensitive to isoproterenol than those which did not develop arthritis (p < 0.02). In addition, these changes in sensitivity were not reflected by changes in the sensitivity of both CFA and ART groups to dibutyryl cAMP. The present study demonstrates a shift in the balance between inhibitory mediator responses in rats inoculated with one of two different adjuvants. These investigations support the role of PGE2 and a neurotransmitter as immunomodulating compounds which may effectively maintain an inflammatory lesion such as arthritis.

Peripheral analgesic effect of intra-articular clonidine

Sympathetic nervous system stimulation, which releases noradrenaline, influences the nociceptor activity which develops after tissue injury. The alpha 2-adrenergic agonist, clonidine, produces analgesia through a central mechanism but also inhibits noradrenaline release at terminal nerve fibre endings. Clonidine may induce analgesia when administered at peripheral sites. This study assesses the potential analgesic effect of clonidine after intra-articular administration. Forty ASA I-III patients, scheduled for arthroscopic knee surgery under general anaesthesia were allocated randomly in 4 groups of 10 patients each, at the end of the surgical procedure. In the control group (group 1), the patients received 20 ml of intra-articular isotonic saline. In group 2, the patients received 150 micrograms of clonidine diluted in 20 ml of isotonic saline injected into the knee joint. In group 3, the patients were given 20 ml of intra-articular isotonic saline and clonidine 150 micrograms was injected subcutaneously. In group 4, morphine 1 mg, diluted in 20 ml of isotonic saline, was injected into the knee joint. Postoperative pain was assessed in a double-blind fashion using a visual analogue scale (VAS) at 1, 2, 3, 6 and 24 h after the end of surgery. VAS scores were significantly lower in groups 2 and 4, compared to groups 1 and 3, at 1 and 2 h after surgery. The delay between intra-articular injection and further postoperative analgesic administration was significantly longer (P < 0.05) in group 2 (533 +/- 488 min) compared to groups 1 and 3 (70 +/- 30 min and 132 +/- 90 min, respectively). The difference was not significant between group 4 (300 +/- 419 min) and the other groups. We conclude that a low dose of intra-articular clonidine produces analgesia unrelated to vascular uptake of the drug. This study further supports a peripheral analgesic effect of clonidine.

Adrenergic suppression of peripheral blood T cell reactivity in the rat is due to activation of peripheral alpha 2-receptors

A 20-h treatment of rats with catecholamines using s.c.implantable retard tablets markedly suppresses the in vitro reactivity of peripheral blood (PBL) T lymphocytes, provided that beta-receptors are blocked with propranolol (Felsner et al., 1992). The results can be summarized as follows: (i) the suppressive effect of noradrenaline+propranolol to the concanavalin A (ConA) response of PBL was abolished by the simultaneous application of the alpha-blocker phentolamine. Using selective agonists, the relevant receptor was identified to belong to the alpha 2-subtype. (ii) The alpha-adrenergic suppression of the PBL T cell response was likewise observed in adrenalectomized animals, which rules out the participation of secondarily induced glucocorticoids. Furthermore, the combination of noradrenaline with the watersoluble beta-blocker nadolol was equally effective to suppress the ConA response of PBL. (iii) An analogous alpha-mediated suppression of T cell function of PBL, but not spleen cells, was observed 1 h after i.p. treatment with tyramine, which leads to the release of endogenous noradrenaline. From these results it is concluded that the adrenergic suppression of PBL T cell functions is primarily due to the activation of peripheral alpha 2-receptors and that it is likewise observed under acute indirect sympathomimetic treatment.

Acute joint inflammation--mechanisms and mediators

1. This review discusses factors contributing to acute joint inflammation, particularly sensory neuropeptides. 2. Mediators known to contribute importantly to the inflammatory process include cytokines, eicosanoids, complement and the kinin systems, histamine and 5-hydroxytryptamine and sensory neuropeptides substance P (SP) and calcitonin gene-related peptide (CGRP). 3. The pro-inflammatory neurokinins, SP and CGRP, are present in nerves innervating joints and could significantly contribute to the increased vascular permeability and hyperaemia occurring in acute arthritis. 4. Although perhaps contributing to the pathogenesis of chronic inflammatory joint disease, there is little evidence for involvement of the sympathetic nervous system in acute models of inflammation.

The role of brain-immune interactions in immunotoxicology

Certain xenobiotics (or the metabolites) can damage immunocompetence by directly interacting with one or more of the cells of the immune system and adversely affecting its function. It has also been proposed that xenobiotics may indirectly affect immune function by affecting other organ systems that will in turn affect immunocompetence. This review surveys evidence that supports the existence of a functional link between the brain and the immune system. In addition, we review data that support the concept that a xenobiotic-induced dysfunction in the neuroendocrine system may be associated with an immune dysfunction as well. Such chemicals do not necessarily interact directly with immunocompetent cells but would instead act to disrupt regulatory brain-immune interactions. This class of indirectly acting immunotoxic xenobiotics would not be detected in the typical in vitro screening assays.

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

We have studied the effect of the adrenal medulla and epinephrine on experimentally induced urethral inflammation in the rat. Urethral inflammation was induced by inserting latex strips into the urethra. The effects of different experimental procedures were assessed by using a 4-graded inflammation scale based on histological findings. Adrenal medullectomy significantly reduced experimentally induced urethral inflammation. This effect was reversed if the rats were treated repeatedly with epinephrine or salbutamol. On the other hand high doses of epinephrine reduced the experimentally induced urethral inflammation.