The I1-imidazoline agonist moxonidine decreases sympathetic tone under physical and mental stress

Moxonidine ameliorates cardiac injury in rats with metabolic syndrome by regulating autophagy

AIMS

Reduced cardiac autophagy, ischemic injury, sympathetic overactivity, and apoptosis all contribute to metabolic syndrome (MetS)-associated cardiovascular risks. NR4A2, an orphan nuclear receptor NR4A family member, induces autophagy while suppressing apoptosis in myocardial infarction. Moxonidine, a sympathoinhibitor imidazoline1 receptor (I1R) agonist, has beneficial metabolic and hemodynamic effects; however, whether autophagy and/or NR4A2 signaling are involved in moxonidine's cardiovascular effects via I1R activation, is unknown, and is the aim of this study.

MATERIALS AND METHODS

To induce MetS, rats were fed 3 % salt in their diet and 10 % fructose in their drinking water for 12 weeks. MetS-rats were given either moxonidine (6 mg/kg/day, gavage), efaroxan (I1R antagonist, 0.6 mg/kg/day, i.p), both treatments, or vehicles for the last two weeks. Blood pressure, lipid profile, and glycemic control were evaluated. Histopathological examination, circulating cardiac troponin I (c-TnI), proinflammatory interleukin-6 (IL-6), apoptosis (active caspase-3 and Fas-immunostaining), interstitial fibrosis [transforming growth factor-β1 (TGF-β1), Mallory's trichrome staining], and extracellular matrix remodeling [matrix metalloproteinase-9 (MMP-9)], were used to assess cardiac pathology. Cardiac NR4A2 and its downstream factor, p53, as well as autophagic flux markers, SQSTM1/p62, LC3, and Beclin-1 were also determined.

KEY FINDINGS

Moxonidine significantly ameliorated MetS-induced metabolic and hemodynamic derangements and the associated cardiac pathology. Moxonidine restored NR4A2 and p53 myocardial levels and enhanced autophagic flux via modulating SQSTM1/p62, LC3, and Beclin-1. Efaroxan reversed the majority of the moxonidine-induced improvements.

SIGNIFICANCE

The current study suggests that autophagy modulation via I1R activation is involved in moxonidine-mediated cardiac beneficial effects in MetS.

Effects of moxonidine on sympathetic nervous system activity: An update on metabolism, cardio, and other target-organ protection

Moxonidine is the newest, second-generation, centrally acting antihypertensive agent. It has selective agonist activity at imidazoline I1 receptors and less adverse effects than the other centrally acting drugs. This fact authorizes the frequent use of moxonidine in clinical practice, as monotherapy or in combination with other antihypertensive agents. Also, moxonidine has beneficial effects in obese and metabolic syndrome and in target-organs, such as heart and kidneys.

Effects of moxonidine on sympathetic nerve activity in patients with end-stage renal disease

OBJECTIVE

End-stage renal disease (ESRD) is characterized by markedly increased sympathetic outflow that contributes to increased cardiovascular mortality in these patients. The central sympatholytic drug moxonidine (MOX) has been shown to reduce muscle sympathetic nerve activity (MSNA) in initial stages of chronic kidney disease; however, the effects in ESRD are not known. The aim of this study was to test the hypothesis that low-dose MOX causes sustained decreases in sympathetic outflow in ESRD patients.

DESIGN AND METHODS

Twenty-three ESRD patients (mean age 46.4 +/- 16 years, 14 men, seven women, no diabetic patients) were randomized to a daily treatment of 0.3 mg MOX or placebo (PLA) in addition to pre-existing antihypertensive therapy. At baseline and after 1 and 6 months of treatment, heart rate (HR, ECG), blood pressure (mean arterial pressure, automatic sphygmanometer), calf blood flow (CBF, venous occlusion plethysmography), muscle sympathetic nerve activity (MSNA) (microneurography at the peroneal nerve) were measured. Data are mean +/- SEM.

RESULTS

MOX acutely decreased MSNA within 2 h after oral intake (from 45 +/- 3.7 to 35 +/- 3.9 bursts/min, P < 0.05). This decrease was sustained over 6 months (MSNA 45 +/- 3.7, 35 +/- 4.6, 33 +/- 4.5 bursts/min at 0, 1 and 6 months, P < 0.05). PLA had no effect. Neither MOX nor PLA resulted in any significant acute or long-term changes in HR, MAP or CBF.

CONCLUSIONS

In ESRD patients, low-dose MOX produced sustained and substantial reductions in sympathetic outflow without hemodynamically compromising them. We suggest that the inhibition of central sympathetic outflow may improve cardiovascular prognosis in ESRD.

Modulation of stress by imidazoline binding sites: implications for psychiatric disorders

In this review, we present evidence for the involvement of imidazoline binding sites (IBS) in modulating responses to stress, through central control of monoaminergic and hypothalamo-pituitary-adrenal (HPA) axis activity. Pharmacological and physiological evidence is presented for differential effects of different IBS subtypes on serotoninergic and catecholaminergic pathways involved in control of basal and stress-stimulated HPA axis activity. IBS ligands can modulate behavioural and neuroendocrine responses in animal models of stress, depression and anxiety, and a body of evidence exists for alterations in central IBS expression in psychiatric patients, which can be normalised partially or fully by treatment with antidepressants. Dysfunction in monoaminergic systems and the HPA axis under basal and stress-induced activation has been extensively reported in psychiatric illnesses. On the basis of the literature, we suggest a potential therapeutic role for selective IBS ligands in the treatment of depression and anxiety disorders.

Mental workload under time pressure can trigger frequent hot flashes in menopausal women

The aim of this study is to examine the relationship between mental workload and occurrence of hot flashes. Twelve women with moderate to severe menopausal hot flashes participated in the study. Subjects participated in both a mental arithmetic task (Task) and control (Non-task) experiments. We measured heart rate, heart rate variability, blood pressure, near infrared spectroscopy, skin temperature, and skin potential level. The incidence of hot flashes was greater in Task than in Non-task. No significant differences between before, during and after hot flashes emerged for the percentage of correct responses and reaction time. However, the percentage of correct responses for two subjects among the ten who experienced hot flashes in Task substantially declined during hot flashes. Chest skin temperatures increased in both Task and Non-task during hot flashes, and regional oxygen saturation was significantly higher in Non-task than in Task. The present study suggested that mental workload under time pressure might be a risk factor for menopausal hot flashes, and the performance of most people who experienced hot flashes was not affected by hot flashes, however, work-related difficulties due to cognitive disturbance during hot flashes might arise in some people.

Moxonidine: a review of its use in essential hypertension

Moxonidine (Physiotens, Moxon, Cynt) is an orally administered imidazoline compound with selective agonist activity at imidazoline I1 receptors and only minor activity at alpha2-adrenoceptors. Moxonidine acts centrally to reduce peripheral sympathetic activity, thus decreasing peripheral vascular resistance. In patients with mild to moderate hypertension, moxonidine reduces blood pressure (BP) as effectively as most first-line antihypertensives when used as monotherapy and is also an effective adjunctive therapy in combination with other antihypertensive agents. It improves the metabolic profile in patients with hypertension and diabetes mellitus or impaired glucose tolerance, is well tolerated, has a low potential for drug interactions and may be administered once daily in most patients. Thus, moxonidine is a good option in the treatment of patients with mild to moderate hypertension, particularly as adjunctive therapy in patients with the metabolic syndrome.