Cold stress-induced bladder overactivity in type 2 diabetic mellitus rats is mitigated by the combination of a M3 -muscarinic antagonist and a β3 -adrenergic agonist

OBJECTIVES

Goto-Kakizaki (GK) rats with type 2 diabetes mellitus respond to low temperature (LT) environments with bladder overactivity, including increased voiding frequency and decreased voiding interval and micturition volume. We determined if bladder overactivity could be inhibited by treatment with the combination of a M₃ -muscarinic receptor antagonist and a β₃ -adrenergic receptor agonist.

METHODS

Ten-week-old female GK rats were fed a high-fat diet for 4 weeks. Cystometric investigations were conducted at room temperature (RT, 27 ± 2°C). The rats were then intraperitoneally administered the vehicle, the M₃ -muscarinic receptor antagonist solifenacin, the β₃ -adrenergic agonist mirabegron, or a combination of solifenacin and mirabegron. Ten minutes after the administrations, the rats were transferred to the LT environment (4 ± 2°C), where the cystometric measurements were continued. The expressions of both M₃ -muscarinic and β₃ -adrenergic receptors were investigated.

RESULTS

After transfer from RT to LT, both voiding interval and bladder capacity of the vehicle-, solifenacin-, or mirabegron-treated rats were significantly decreased. However, the combination of solifenacin and mirabegron significantly mitigated the bladder overactivity. While both M₃ -muscarinic and β₃ -adrenergic receptors were detected, the expression of M₃ -muscarinic receptor mRNA was significantly higher than that of β₃ -adrenergic receptor mRNA.

CONCLUSIONS

The cold stress-induced bladder overactivity was not improved by either the M₃ -muscarinic receptor antagonist or the β₃ -adrenergic receptor agonist alone. However, the combined treatment mitigated the cold stress responses. Combined therapy with M₃ -muscarinic antagonists and β₃ -adrenergic agonists could reduce side effects and improve the quality of life for diabetic patients with bladder overactivity.

The Impact of Muscarinic Receptor Antagonists on Airway Inflammation: A Systematic Review

Long-acting muscarinic receptor antagonists (LAMAs) are the cornerstone for the treatment of chronic obstructive pulmonary disease (COPD); furthermore, tiotropium is approved as add-on therapy in severe asthmatic patients. Accumulating evidence suggests that LAMAs may modulate airway contractility and airway hyperresponsiveness not only by blocking muscarinic acetylcholine receptors (mAchRs) expressed on airway smooth muscle but also via anti-inflammatory mechanisms by blocking mAchRs expressed on inflammatory cells, submucosal glands, and epithelial cells. The aim of this systematic review, performed according to the PRISMA-P guidelines, was to provide a synthesis of the literature on the anti-inflammatory impact of muscarinic receptor antagonists in the airways. Most of the current evidence originates from studies on tiotropium, that demonstrated a reduction in synthesis and release of cytokines and chemokines, as well as the number of total and differential inflammatory cells, induced by different pro-inflammatory stimuli. Conversely, few data are currently available for aclidinium and glycopyrronium, whereas no studies on the potential anti-inflammatory effect of umeclidinium have been reported. Overall, a large body of evidence supports the beneficial impact of tiotropium against airway inflammation. Further well-designed randomized controlled trials are needed to better elucidate the anti-inflammatory mechanisms leading to the protective effect of LAMAs against exacerbations via identifying suitable biomarkers.

Structure-Activity Relationship Study of Psychostimulant Synthetic Cathinones Reveals Nanomolar Antagonist Potency of α-Pyrrolidinohexiophenone at Human Muscarinic M2 Receptors

Synthetic cathinones (SCs) are designer, psychostimulant drugs of abuse that primarily act on monoamine transporters; little is known about their off-target liability. Abuse of pyrrolidine-containing SCs, such as α-PHP, has been linked to clinical features, including tachycardia and hypertension, and psychiatric events, including delusions and memory impairments-effects mimicking deliriant hallucinogens that are acetylcholine muscarinic receptor (MR) antagonists. α-PHP and nine analogs with modifications in the α-carbon side chain length and/or containing a methylenedioxy moiety were screened for activity at each of the five human MRs. Increasing the length of the α-carbon side chain of 1-phenyl-2-(pyrrolidin-1-yl)ethan-1-one analogs from a methyl (α-PPP) to a propyl (α-PVP) group caused a steep increase in affinity at all MR subtypes, and one extra carbon (α-PHP) further enhanced MR affinity; the presence of a methylenedioxy moiety generally hindered this effect. Highest MR affinity was observed with α-PHP at M₂Rs-its M₂R affinity (K_i = 251 nM) was 302-fold higher than α-PPP's. M₂R-cAMP inhibition and β-arrestin recruitment assays showed that α-PHP is an M₂R antagonist (K_b = 120 and 502 nM, respectively). Additional experiments showed α-PHP is also an antagonist of M₁R-inositol phosphate production (K_b = 1.4 μM). Human toxicology studies report blood concentrations of pyrrolidine-containing SCs, including α-PHP, that reach micromolar levels during intoxication, indicating α-PHP's MR activity might have physiological relevance. As M₂Rs and M₁Rs are widely expressed in the autonomic and central nervous systems, α-PHP's anticholinergic activity might be relevant to adverse events associated with α-PHP intoxication.

Effects of the inhalation of the m3 receptor antagonist bencycloquidium bromide in a mouse cigarette smoke-induced airway inflammation model

Bencycloquidium bromide (BCQB), a novel M3 receptor antagonist, alleviates airway hyperresponsiveness, inflammation, and airway remodeling in a murine model of asthma. The aim of this study was to investigate the anti-inflammatory activity of inhaled BCQB in a cigarette smoke (CS)-induced model of acute lung inflammation. Mice exposed to CS developed chronic obstructive pulmonary disease (COPD). Inhalation of BCQB suppressed the accumulation of neutrophils and macrophages in airways and lung and also inhibited the CS-induced increases in mRNA levels of keratinocyte-derived chemokine, monocyte chemotactic protein-1, tumor necrosis factor-alpha, and interleukin-1β in lung and protein expression levels in bronchoalveolar lavage fluid. Moreover, BCQB (300 μg/ml) inhibited the CS-induced changes in superoxide dismutase and myeloperoxidase activities in the lungs. Our study suggests that BCQB might be a potential therapy for inflammation in CS-induced pulmonary diseases, including COPD.

Therapeutic modulation of urinary bladder function: multiple targets at multiple levels

Storage dysfunction of the urinary bladder, specifically overactive bladder syndrome, is a condition that occurs frequently in the general population. Historically, pathophysiological and treatment concepts related to overactive bladder have focused on smooth muscle cells. Although these are the central effector, numerous anatomic structures are involved in their regulation, including the urothelium, afferent and efferent nerves, and the central nervous system. Each of these structures involves receptors for—and the urothelium itself also releases—many mediators. Moreover, hypoperfusion, hypertrophy, and fibrosis can affect bladder function. Established treatments such as muscarinic antagonists, β-adrenoceptor agonists, and onabotulinumtoxinA each work in part through their effects on the urothelium and afferent nerves, as do α1-adrenoceptor antagonists in the treatment of voiding dysfunction associated with benign prostatic hyperplasia; however, none of these treatments are specifically targeted to the urothelium and afferent nerves. It remains to be explored whether future treatments that specifically act at one of these structures will provide a therapeutic advantage.