Calcium antagonists in the management of asthma: breakthrough or ballyhoo?

Comorbidities and Susceptibility to COVID-19: A Generalized Gene Set Data Mining Approach

The COVID-19 pandemic has led to over 2.26 million deaths for almost 104 million confirmed cases worldwide, as of 4 February 2021 (WHO). Risk factors include pre-existing conditions such as cancer, cardiovascular disease, diabetes, and obesity. Although several vaccines have been deployed, there are few alternative anti-viral treatments available in the case of reduced or non-existent vaccine protection. Adopting a long-term holistic approach to cope with the COVID-19 pandemic appears critical with the emergence of novel and more infectious SARS-CoV-2 variants. Our objective was to identify comorbidity-associated single nucleotide polymorphisms (SNPs), potentially conferring increased susceptibility to SARS-CoV-2 infection using a computational meta-analysis approach. SNP datasets were downloaded from a publicly available genome-wide association studies (GWAS) catalog for 141 of 258 candidate COVID-19 comorbidities. Gene-level SNP analysis was performed to identify significant pathways by using the program MAGMA. An SNP annotation program was used to analyze MAGMA-identified genes. Differential gene expression was determined for significant genes across 30 general tissue types using the Functional and Annotation Mapping of GWAS online tool GENE2FUNC. COVID-19 comorbidities (n = 22) from six disease categories were found to have significant associated pathways, validated by Q-Q plots (p < 0.05). Protein-protein interactions of significant (p < 0.05) differentially expressed genes were visualized with the STRING program. Gene interaction networks were found to be relevant to SARS and influenza pathogenesis. In conclusion, we were able to identify the pathways potentially affected by or affecting SARS-CoV-2 infection in underlying medical conditions likely to confer susceptibility and/or the severity of COVID-19. Our findings have implications in future COVID-19 experimental research and treatment development.

Inhibition of histamine-induced bronchospasm in guinea pigs treated with Cecropia glaziovi Sneth and correlation with the in vitro activity in tracheal muscles

A standardized aqueous extract (AE) and a purified fraction (BuF) of Cecropia glaziovi Sneth leaves were tested in unrestrained guinea pigs challenged with histamine. Changes of the respiratory pressure and rate were recorded in a whole body plethysmograph before and after treatment. The concentration of histamine necessary to produce bronchospasm was increased by five-fold following administration of AE (1.0 g/kg p.o.), and by two-fold after treatment with the semi-purified procyanidin/flavonoids enriched BuF (0.1 g/kg p.o.). Both effects were blocked by previous treatment with propranolol (10.0 mg/kg i.p.). In vitro incubation of BuF (0.1-1.0 mg/ml) decreased by 13-55% the maximal response of guinea pig tracheal muscle to histamine, without significant change of EC50. The results confirmed old reports on the useful pulmonary effects of Cecropia extracts. The bronchodilation observed in vivo seems to be related to beta-adrenergic activity observed in vitro only with high concentrations of the purified extract.

Ca2+-signaling in airway smooth muscle cells is altered in T-bet knock-out mice

BACKGROUND

Airway smooth muscle cells (ASMC) play a key role in bronchial hyperresponsiveness (BHR). A major component of the signaling cascade leading to ASMC contraction is calcium. So far, agonist-induced Ca2+-signaling in asthma has been studied by comparing innate properties of inbred rat or mouse strains, or by using selected mediators known to be involved in asthma. T-bet knock-out (KO) mice show key features of allergic asthma such as a shift towards TH2-lymphocytes and display a broad spectrum of asthma-like histological and functional characteristics. In this study, we aimed at investigating whether Ca2+-homeostasis of ASMC is altered in T-bet KO-mice as an experimental model of asthma.

METHODS

Lung slices of 100 to 200 microm thickness were obtained from T-bet KO- and wild-type mice. Airway contraction in response to acetylcholine (ACH) was measured by video-microscopy and Ca2+-signaling in single ASMC of lung slices was assessed using two-photon-microscopy.

RESULTS

Airways from T-bet KO-mice showed increased baseline airway tone (BAT) and BHR compared to wild-type mice. This could be mimicked by incubation of lung slices from wild-type mice with IL-13. The increased BAT was correlated with an increased incidence of spontaneous changes in intracellular Ca2+-concentrations, whereas BHR correlated with higher ACH-induced Ca2+-transients and an increased proportion of ASMC showing Ca2+-oscillations. Emptying intracellular Ca2+-stores using caffeine or cyclopiazonic acid induced higher Ca2+-elevations in ASMC from T-bet KO- compared to wild-type mice.

CONCLUSION

Altered Ca2+-homeostasis of ASMC contributes to increased BAT and BHR in lung slices from T-bet KO-mice as a murine asthma model. We propose that a higher Ca2+-content of the intracellular Ca2+-stores is involved in the pathophysiology of these changes.

Respiratory therapeutics

Treatment of small animal respiratory diseases tends to target bronchodilators. Although this is not inappropriate, recent advances in the understanding of respiratory diseases have underscored the importance of inflammatory mediators in the pathophysiology of respiratory diseases. Drug therapy of the respiratory tract in small animals is most successful when it is based on a knowledge of normal physiology and disease pathophysiology of respiratory tract diseases.

The effect of three different oral doses of verapamil on the disposition of theophylline

Results of previous studies suggest that the theophylline-verapamil drug interaction may be dependent on verapamil dose. Therefore, in a randomized four-way cross over study, 12 healthy males received theophylline, as a single intravenous dose of aminophylline, alone (phase I) and after a four day regimen of oral verapamil 40 mg (phase II), 80 mg (phase III), and 120 mg (phase IV) every 8 h. Serial blood samples were collected over a 24 hour period for determination of serum theophylline concentration and subsequent pharmacokinetic analysis. Mean theophylline AUC for phase I-IV was 93.6, 105.6, 110.8, 120.1 mg.h.l-1, respectively. Mean theophylline clearance for phase I-IV was 3.89, 3.59, 3.35, and 3.20 l.h-1, respectively. The changes in AUC, clearance, and lambda z were linearly correlated to verapamil dose. These results suggest that the inhibitory effect of verapamil on the pharmacokinetic disposition of theophylline is directly related to verapamil dose.

Verapamil in the prophylaxis of bronchial asthma. Is the bronchoprotective effect related to the plasma level?

A single oral dose of verapamil 80 mg was shown significantly to inhibit histamine-induced broncho-constriction in 8 out of 16 asthmatic subjects (maximum increase in PD20FEVHi 416%). There was still significant protection (delta PD20FEV1Hi greater than 100%) in the responders 5 h after the oral dose. The relationship of the bronchoprotective effect to the plasma level of verapamil was also examined. Responders and non-responders did not differ significantly in the peak plasma level or the time course of the plasma verapamil concentration. The protective effect was not correlated with the peak plasma level of verapamil or with the baseline bronchial hyperreactivity.

The effect of verapamil on the pharmacokinetic disposition of theophylline in cigarette smokers

In a randomized cross-over study the effect of verapamil on the pharmacokinetics of theophylline was evaluated in eight cigarette smoking male volunteers. Theophylline was administered as an intravenous infusion of aminophylline, 6 mg/kg based on ideal body weight, over 30 minutes in the control phase. In the treatment phase, aminophylline was administered after a four day regimen of oral verapamil 80 mg every 8 hours. Serial blood samples were collected over a 24 hour period following aminophylline administration. Theophylline serum concentrations were determined by a fluorescence polarization immunoassay, the Abbott TDxR. Theophylline clearance decreased by 11.5%, from a mean (+/-SD) of 1.39 +/- 0.38 mL/min/kg in the control phase to 1.23 +/- 0.21 mL/min/kg with the co-administration of verapamil (P = 0.104). Theophylline elimination rate constant decreased by approximately 9.4% from 0.171 +/- 0.032 to 0.155 + 0.023 hr-1 during the treatment phase (P = 0.085). The area under the curve (AUCo alpha) and volume of distribution at steady-state (Vss) for theophylline were also not statistically different between the two study phases. These results are inconsistent with those of other investigators and the relevance of a potential theophylline-verapamil drug interaction remains unclear.

Calcium antagonists in hypertension

The calcium antagonists are effective and safe agents for the treatment of arterial hypertension. They are well tolerated by the patients. In contrast to other types of antihypertensive agents, they cause few metabolic disturbances. They can be combined with diuretics, beta-blockers, and angiotensin-converting enzyme (ACE) inhibitors. They can be safely prescribed to patients with hypertension and concomitant diseases such as diabetes mellitus, chronic obstructive lung disease, congestive heart failure, gout, renal failure, peripheral atherosclerotic disease, or Raynaud's phenomenon. Dietary sodium restriction during antihypertensive therapy with calcium antagonists is not required for optimal antihypertensive efficacy. The second generation of calcium antagonists especially the dihydropyridine analogues that have greater potency and vascular selectivity, and a longer duration of action, will optimize the treatment of hypertension. Their antiatherosclerotic, antiplatelet, and "antitrophic" effects in experimental models for atherogenesis and hypertension hold great promise for the future since, so far, there has been no major success in reducing the incidence of coronary death by the treatment of hypertension.