The beta 2-adrenergic agonist terbutaline suppresses acute passive transfer experimental autoimmune myasthenia gravis (EAMG)

Current Treatment of Myasthenia Gravis

Myasthenia gravis (MG) is the most extensively studied antibody-mediated disease in humans. Substantial progress has been made in the treatment of MG in the last century, resulting in a change of its natural course from a disease with poor prognosis with a high mortality rate in the early 20th century to a treatable condition with a large proportion of patients attaining very good disease control. This review summarizes the current treatment options for MG, including non-immunosuppressive and immunosuppressive treatments, as well as thymectomy and targeted immunomodulatory drugs.

Noradrenergic regulation of glial activation: molecular mechanisms and therapeutic implications

It has been known for many years that the endogenous neurotransmitter noradrenaline (NA) exerts anti-inflammatory and neuroprotective effects both in vitro and in vivo. In many cases the site of action of NA are beta-adrenergic receptors (βARs), causing an increase in intracellular levels of cAMP which initiates a broad cascade of events including suppression of inflammatory transcription factor activities, alterations in nuclear localization of proteins, and induction of patterns of gene expression mediated through activity of the CREB transcription factor. These changes lead not only to reduced inflammatory events, but also contribute to neuroprotective actions of NA by increasing expression of neurotrophic substances including BDNF, GDNF, and NGF. These properties have prompted studies to determine if treatments with drugs to raise CNS NA levels could provide benefit in various neurological conditions and diseases having an inflammatory component. Moreover, increasing evidence shows that disruptions in endogenous NA levels occurs in several diseases and conditions including Alzheimer's disease (AD), Parkinson's disease (PD), Down's syndrome, posttraumatic stress disorder (PTSD), and multiple sclerosis (MS), suggesting that damage to NA producing neurons is a common factor that contributes to the initiation or progression of neuropathology. Methods to increase NA levels, or to reduce damage to noradrenergic neurons, therefore represent potential preventative as well as therapeutic approaches to disease.

Increasing CNS noradrenaline reduces EAE severity

The endogenous neurotransmitter noradrenaline (NA) is known to exert potent anti-inflammatory effects in glial cells, as well as provide neuroprotection against excitatory and inflammatory stimuli. These properties raise the possibility that increasing levels of NA in the central nervous system (CNS) could provide benefit in neurological diseases and conditions containing an inflammatory component. In the current study, we tested this possibility by examining the consequences of selectively modulating CNS NA levels on the development of clinical signs in experimental autoimmune encephalomyelitis (EAE). In mice immunized with myelin oligodendrocyte glycoprotein peptide to develop a chronic disease, pretreatment to selectively deplete CNS NA levels exacerbated clinical scores. Elevation of NA levels using the selective NA reuptake inhibitor atomoxetine did not affect clinical scores, while treatment of immunized mice with the synthetic NA precursor L-threo-3,4-dihydroxyphenylserine (L-DOPS) prevented further worsening. In contrast, treatment of mice with a combination of atomoxetine and L-DOPS led to significant improvement in clinical scores as compared to the control group. The combined treatment reduced astrocyte activation in the molecular layer of the cerebellum as assessed by staining for glial fibrillary protein but did not affect Th1 or Th17 type cytokine production from splenic T cells. These data suggest that selective elevation of CNS NA levels could provide benefit in EAE and multiple sclerosis without influencing peripheral immune responses.

Chemical sympathectomy has no effect on the severity of murine AIDS: murine AIDS alone depletes norepinephrine levels in infected spleen

Numerous studies have shown that alterations in sympathetic nervous system (SNS) function produced by beta-adrenergic receptor blockade or chemical sympathectomy can produce changes in T and B lymphocyte function and both innate and acquired immune responses. However, fewer studies have investigated changes in immune response following SNS alterations in animal models of disease. We tested whether blocking SNS activity using 6-OHDA or the beta-receptor antagonist nadolol alters the typical pattern in production of T helper 1 (Th1) and Th2 cytokines seen in cultures of spleen cells from C57BL/6 mice infected with murine AIDS (MAIDS). We found that neither method of sympathetic blockade affected cytokine response to MAIDS. We also found that the norepinephrine concentration and content of the spleen were reduced dramatically by the MAIDS infection itself at 3 and 6 weeks after LP-BM5 inoculation. This finding has not been previously reported in mice with MAIDS and suggests that the viral infection itself produces a functional sympathectomy in the spleen, a target of that infection.

Receptor-mediated interaction between the sympathetic nervous system and immune system in inflammation

The sympathetic nervous system plays a central role in establishing communication between the central nervous system and the immune system during inflammation. Inflammation activates the sympathetic nervous system, which causes release of the transmitters of the sympathetic nervous system in the periphery. The transmitters of the sympathetic nervous system are the catecholamines noradrenaline and adrenaline and the purines ATP, adenosine, and inosine. Once these transmitters are released, they stimulate both presynaptic receptors on nerve terminals and post-synaptic receptors on immune cells. The receptors that are sensitive to catecholamines are termed adrenoceptors, whereas the receptors that bind purines are called purinoceptors. Stimulation of the presynaptic receptors exerts an autoregulatory effect on the release of transmitters. Ligation of the postsynaptic receptors on inflammatory cells modulates the inflammatory activities of these cells. The present review summarizes some of the most important aspects of the current state of knowledge about the interactions between the sympathetic nervous system and the immune system during inflammation with a special emphasis on the role of adreno and purinoceptors.

The importance of beta-adrenergic receptors in immune regulation: a link between neuroendocrine and immune system

Our knowledge of autoimmunity and autoimmune diseases has been advanced in the past decades. Receptors present on the immune cells may potentially regulate the immune system, among them, beta-adrenergic receptors are of special interest. As neurotransmitter receptors which are also present on lymphocytes, beta-adrenergic receptors play an important role as the linkage of two important systems, neuroendocrine and immune systems. Here I summarize several lines of evidence of the importance of the beta-adrenergic receptors in immune regulation.

Dual role for noradrenergic innervation of lymphoid tissue and arthritic joints in adjuvant-induced arthritis

The role of noradrenergic innervation in the disease outcome of adjuvant-induced arthritis (AA) has been examined following (1) systemic administration of guanethidine and (2) local application of 6-hydroxydopamine (6-OHDA) into the lymph nodes that drain the hind limbs (DLN). Sympathetic denervation by these different neurotoxins produced directionally opposite effects on disease outcome. These conflicting findings could be explained from differential denervation of sympathetic nerves in key target tissues that result from different routes of neurotoxin administration. Alternatively, these conflicting data could be due to differences in the mechanisms by which guanethidine and 6-OHDA destroy sympathetic nerve terminals. In this study, we compared disease outcome in AA following systemic and local DLN application of 6-OHDA to determine whether the route of administration is important to the development and progression of AA. Bilateral local DLN application of 6-OHDA or vehicle was performed 1 day before injection of Freund's complete adjuvant (CFA) to induce arthritis. For systemic denervation, 6-OHDA or vehicle was given by ip injections on days 1, 3, and 5 prior to CFA challenge and then once a week. Local DLN application of 6-OHDA resulted in significant increases in dorsoplantar width in arthritic rats by 27 days following CFA treatment compared to those of non-denervated arthritic rats. In contrast, systemic denervation in arthritic rats significantly decreased dorsoplantar widths 27 days after CFA treatment compared to those in sympathetically intact arthritic animals. X-ray analysis confirmed these findings. Further, local DLN application of 6-OHDA exacerbated the disease regardless of whether the neurotoxin was administered prior to immunization with CFA or closer to the time of disease onset. Our findings indicate that the route of 6-OHDA administration for denervation of sympathetic innervation is an important parameter in determining disease outcome, presumably due to differential sympathetic denervation of target tissues that are involved in disease development and progression. 6-OHDA administration into local DLN denervated these lymph nodes, but spared sympathetic innervation of the hind limbs, a pattern of sympathetic denervation that resulted in disease exacerbation. In contrast, systemic 6-OHDA administration which denervated both the arthritic joints and the secondary lymphoid organs attenuated the severity of AA. This study supports a dual role for NA innervation in modulating the severity of AA by innervation of the arthritic joints and lymphoid organs.

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.

Acute effects of intravenous injection of beta-adrenoreceptor- and calcium channel at antagonists and agonists in myasthenia gravis

The effect of intravenous injection of propranolol, verapamil, terbutaline, calcium, and edrophonium on neuromuscular transmission has been studied with repetitive nerve stimulation and clinical tests in 10 patients with myasthenia gravis (MG). The drugs were given intravenously in doses commonly used in clinical practice. Only minor clinical effects were noted except for edrophonium. The mean decrement of the deltoid muscle was not significantly changed after injection of propranolol (before 31%, 15 min after injection 27%) and verapamil (before 29%, 15 min after injection 26%). Terbutaline applied after propranolol and calcium applied after verapamil improved the decrement substantially. Edrophonium applied after propranolol or verapamil also greatly improved the decrement. We conclude that there is no rapid deterioration of neuromuscular transmission in patients with moderately severe MG after injections with therapeutic doses of propranolol and verapamil. However, we do not know if the most severely disabled MG patient could have reacted otherwise. We consider that, in cardiovascular emergencies, propranolol and verapamil may be used even in severe MG but with resuscitation equipment as well as specific antidotes available.

Experimental allergic encephalomyelitis, beta-adrenergic receptors and interferon gamma-secreting cells in beta-adrenergic agonist-treated rats

Treatment with the beta 2-adrenergic agonist terbutaline or the beta-adrenergic agonist isoproterenol suppresses experimental allergic encephalomyelitis, decreases the number of IFN gamma-producing splenic cells, and decreases the number of beta-adrenergic receptors on splenic lymphocytes in Lewis rats. The effects of terbutaline are greater when the drug is given from the day of immunization through the acute phase of the illness or from day 15 postimmunization until recovery, than when given for the first 12 days after immunization.

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.

The beta 2-adrenergic agonist terbutaline suppresses experimental allergic neuritis in Lewis rats

Treatment of rats with experimental allergic neuritis with the beta 2-adrenergic agonist terbutaline suppresses clinical symptoms, decreases demyelination and Wallerian degeneration in peripheral nerves and improves electrophysiological parameters. Treatment is highly effective when given from the time of immunization through the acute phase of illness, when given for the first 12 days after immunization and also when given after the onset of the disease.