Paracetamol inhibits Ca2+ permeant ion channels and Ca2+ sensitization resulting in relaxation of precontracted airway smooth muscle

Distribution of TRPC5 in the human lung: A study in body donors

Transient receptor potential channel canonical 5 (TRPC5) is a non-selective ion channel; ion influx through TRPC5 causes activation of downstream signaling pathways. In addition, TRPC5 has been identified as having a potential role in pathological processes, particularly in diseases caused by cellular cation homeostasis dysregulation, such as bronchial asthma or pulmonary hypertension. However, the expression and distribution of TRPC5 in the human lung remain unclear. To date, TRPC5 has only been detected in a few cell types in the human lung, such as airway, pulmonary venous and arterial smooth muscle cells. The present study therefore aimed to investigate the protein expression of TRPC5 in the human lung and to evaluate its histological distribution. Human lung samples were obtained from six preserved body donors. After processing, both hematoxylin & eosin staining, as well as immunohistochemistry were performed. Microscopic analysis revealed medium to strong immunostaining signals in all lung structures examined, including the pleura, pulmonary arteries and veins, bronchioles, alveolar septa, type 1 and 2 pneumocytes, as well as alveolar macrophages. Current research suggests that TRPC5 may be involved in various pathological processes in the human lung and some pharmacological compounds have already been identified that affect the function of TRPC5. Therefore, TRPC5 may present a novel drug target for therapeutic intervention in various lung diseases. The results of the present study indicate that the TRPC5 protein is expressed in all examined histological structures of the human lung. These findings suggest that TRPC5 may be more important for physiological cell function and pathophysiological cell dysfunction in the lung than is currently known. Further research is needed to explore the role and therapeutic target potential of TRPC5 in the human lung.

Evaluation of the mechanism of action of paracetamol, drotaverine, and peppermint oil and their effects in combination with hyoscine butylbromide on colonic motility: human ex-vivo study

Introduction

Drotaverine, paracetamol, and peppermint oil are often prescribed for the treatment of gastrointestinal spasm and pain. This study aimed to evaluate the effect of these drugs alone and combined with the well-known antispasmodic hyoscine butylbromide on the human colon.

Methods

Colon samples were obtained from macroscopically normal regions of 68 patients undergoing surgery and studied in muscle bath. Drotaverine, paracetamol, and peppermint oil were tested alone and in combination with hyoscine butylbromide on (1) spontaneous contractility induced by isometric stretch (in the presence of 1 µM tetrodotoxin) and (2) contractility induced by 10-5 M carbachol and after (3) electrical field stimulation-induced selective stimulation of excitatory (in the presence of 1 mM Nω-nitro-L-arginine and 10 µM MRS2179) and (4) inhibitory (under non-adrenergic, non-cholinergic conditions) pathways. (5) Drotaverine alone was also tested on cAMP-dependent pathway activated by forskolin.

Results

Compared with the vehicle, drotaverine and paracetamol (10-9-10-5 M) did not modify spontaneous contractions, carbachol-induced contractions, and responses attributed to selective activation of excitatory pathways. The addition of hyoscine butylbromide (10-7-10-5 M), concentration-dependently reduced myogenic contractions and carbachol- and electrical field stimulation-induced contractile responses. The association of paracetamol (10-4 M) and hyoscine butylbromide (10-7-10-5 M) was not different from hyoscine butylbromide alone (10-7-10-5 M). At higher concentrations (10-3M-3*10-3 M), paracetamol decreased myogenic and carbachol-induced contractions. The adenylate cyclase activator, forskolin, concentration-dependently reduced contractility, leading to smooth muscle relaxation. The effect of forskolin 10-7 M was concentration-dependently enhanced by drotaverine (10-6M-10-5M).

Discussion

Peppermint oil reduced myogenic activity and carbachol- and electrical field stimulation-induced contractions. The association of hyoscine butylbromide and peppermint oil was synergistic since the interaction index measured with the isobologram was lower than 1. No effect was seen on the neural-mediated inhibitory responses with any of the drugs studied although peppermint oil reduced the subsequent off-contraction. Drotaverine and hyoscine butylbromide have a complementary effect on human colon motility as one stimulates the cAMP inhibitory pathway and the other inhibits the excitatory pathway. Peppermint oil is synergic with hyoscine butylbromide suggesting that a combination therapy may be more effective in treating patients. In contrast, at therapeutic concentrations, paracetamol does not modify colonic contractility, suggesting that the association of paracetamol and hyoscine butylbromide has independent analgesic and antispasmodic properties.

Hyoscine butylbromide mode of action on bowel motility: From pharmacology to clinical practice

BACKGROUND

Hyoscine butylbromide (HBB) has been available for use as an antispasmodic since 1951 and is indicated for the treatment of abdominal pain associated with cramps. A previous review in 2007 summarized the evidence on the mode of action of HBB in vitro and in vivo in both animal and human studies. However, since then, novel publications have appeared within the literature and also our knowledge of what represents normal motility in humans has evolved.

PURPOSE

This review is the result of the collaboration between a basic scientist and clinicians with the aim of providing an updated overview of the mechanisms of action of HBB and its clinical efficacy to guide not only use in clinical practice, but also future research.

Acetaminophen treatment evokes anticontractile effects in rat aorta by blocking L-type calcium channels

BACKGROUND

Acetaminophen (APAP) is the most widely used analgesic and antipyretic in the world. However, in high or continuous doses, it can cause serious side effects including blood pressure variability and cardiovascular injuries, which are barely explored. This study aimed to evaluate the acute effect of APAP treatment on vascular tone focused on the blocking of Ca²⁺ channels.

METHODS

Rats were treated with APAP orally by gavage (500 mg/kg/single dose). After 12 h, the aorta was isolated for vascular reactivity studies in an isolated organ bath. Vascular contraction and relaxation were measured after different stimuli. Moreover, molecular docking studies were performed to evaluate the action of NAPQI (APAP metabolite) on L-type calcium channels.

RESULTS

Phenylephrine-induced maximal vascular contraction was reduced in the APAP group (138.4 ± 9.2%) compared to the control group (172.2 ± 11.1%). APAP treatment significantly reduced contraction induced by Ca²⁺ influx stimulated with phenylephrine or KCl and reduced contraction mediated by Ca²⁺ released from the sarcoplasmic reticulum induced by caffeine. There was no difference in vascular relaxation induced by acetylcholine or sodium nitroprusside. Computational molecular docking demonstrated that NAPQI is capable of blocking L-type Ca²⁺ channels (Ca_v1.2), which would limit the influx of Ca²⁺.

CONCLUSION

These results suggest that APAP treatment causes an anticontractile effect in rat aorta, possibly by blocking the influx of Ca²⁺ through L-type channels (Ca_v1.2).

Relaxation Effect of Schisandra Chinensis Lignans on the Isolated Tracheal Smooth Muscle in Rats and Its Mechanism

Schisandra chinensis (S. chinensis) is one of the core drugs used for relieving cough and asthma in traditional Chinese medicine. However, there are few basic studies on the treatment of respiratory diseases with S. chinensis in modern pharmacology, and the material basis and mechanism of its antiasthmatic effect are still unclear. Lignans are the main active components of S. chinensis. The aim of this study was to observe the relaxation effect of S. chinensis lignans (SCL) on the tracheal smooth muscle of rats by in vitro tracheal perfusion experiments, and to explore the mechanism by preincubation with L-type calcium channel blocker verapamil, four potassium channel blockers glibenclamide, tetraethylamine, 4-aminopyridine and barium chloride (BaCl₂), β-adrenoceptor blocker propranolol, nitric oxide synthase inhibitor Nω-nitro-L-arginine methyl ester (L-NAME), and the cyclooxygenase inhibitor indomethacin, respectively. The results showed that SCL (0.25-1.75 mg/mL) reduced the contraction of isolated tracheal smooth muscle induced by acetylcholine, the preincubation with verapamil and glibenclamide could attenuate the relaxation effect, whereas propranolol, 4-aminopyridine, BaCl₂, tetraethylamine, L-NAME, and indomethacin had no such effect. These results suggest that SCL has a significant relaxation effect on the isolated tracheal smooth muscle of rats, and the mechanism may be related to the inhibition of extracellular calcium influx and intracellular calcium release from the sarcoplasmic reticulum, as well as the activation of ATP-sensitive potassium channels. These findings may provide a pharmacological basis for the traditional use of S. chinensis to treat asthma.