Transmembrane protease serine 2 (TMPRSS2) has been identified as a critical key for the entry of coronaviruses into human cells by cleaving and activating the spike protein of SARS-CoV-2. To block the TMPRSS2 function, 18 approved drugs, containing the guanidine group were tested against TMPRSS2's ectodomain (7MEQ). Among these drugs, Famotidine, Argatroban, Guanadrel and Guanethidine strongly binds with TMPRSS2 S1 pocket with estimated Fullfitness energies of -1847.12, -1630.87, -1605.81 and -1600.52 kcal/mol, respectively. A significant number of non-covalent interactions such as hydrogen bonding, hydrophobic and electrostatic interactions were detected in protein-ligand complexes. In addition, the ADMET analysis revealed a perfect concurrence with the aptitude of these drugs to be developed as an anti-SARS-CoV-2 therapeutics. Further, MD simulation and binding free energy calculations were performed to evaluate the dynamic behavior and stability of protein-ligand complexes. The results obtained herein highlight the enhanced stability and good binding affinities of the Argatroban and Famotidine towards the target protein, hence might act as new scaffolds for TMPRSS2 inhibition.Communicated by Ramaswamy H. Sarma.

Recent research suggests that NO may play a role in the physiological effects of some guanidine-containing drugs. In this report, three guanidine-containing drugs (guanadrel, guanoxan, and guanethidine) together with their N-hydroxyl derivatives were synthesized and their NO-releasing abilities catalyzed by nitric oxide synthases (NOSs) and horseradish peroxidase were evaluated. The guanidine containing compounds could not release NO in the presence of NOS or peroxidase. The corresponding N-hydroxyl compounds exhibited weak NO-releasing ability under the catalyzed of NOS and good NO-releasing ability under the oxidation by horseradish peroxidase in the presence of H(2)O(2). These compounds also displayed vasodilatory activity.

We tested the hypotheses that 1) there is an age-associated decrease in arterial alpha-adrenergic responsiveness and 2) there is upregulation of this response during suppression of sympathetic nervous system (SNS) activity. We measured forearm blood flow (FABF) by plethysmography during brachial artery infusions of the alpha-adrenergic agonist norepinephrine (NE) and the nonadrenergic agonist angiotensin II (ANG II) in 15 young and 14 older healthy human subjects. Among the old (O) relative to the young (Y) we identified greater plasma NE levels (Y: 1.29 +/- 0.07 nM vs. O: 2.14 +/- 0.17 nM; P = 0.0001); a decrease in NE-mediated reduction in FABF [analysis of variance (ANOVA) P = 0.04]; and, in contrast, no difference in ANG II-mediated reduction in FABF (ANOVA P = 0.43). In the nine older subjects studied during guanadrel (G) to suppress SNS activity, we identified decreased plasma NE levels [placebo (P): 2.11 +/- 0.24 nM vs. G: 1.09 +/- 0.09 nM; P = 0.002], increased NE-mediated FABF response (ANOVA P = 0.01), and no difference in FABF response to ANG II (ANOVA: P = 0.69) compared with P. We conclude that there is appropriate desensitization of arterial alpha-adrenergic responsiveness among the older relative to the young subjects that is specific for the alpha-adrenergic system. Among the older subjects there is homologous upregulation of this response when SNS activity is suppressed.

Low density lipoprotein (LDL) and intermediate density lipoprotein (IDL) classes have been shown to be composed of discrete metabolic entities or subclasses. Present ultracentrifugal methods are unable to precisely determine these subclasses. A new analytical micro-ultracentrifugal method was developed that facilitates the determination of IDL and LDL subclasses and their F1.21 flotation coefficient from ultracentrifugal scans. The method is based on the modification of a published equation (Fujita, H. 1956. J. Chem. Phys. 24: 1084-1090) adapted to calculate concentration gradient boundary curves for IDL and LDL that are approximately Gaussian in form. Using an extension of this modified equation, theoretical distributions of the gradient curves were calculated. By applying the theoretical distributions, IDL and LDL subclasses were resolved from absorbance scans as Gaussian concentration gradient boundary curves. Both theoretically calculated and experimentally determined boundary curves for IDL and LDL lipoproteins were plotted and found to be in excellent agreement. Three subclasses of LDL and four subclasses of IDL were determined. The mean flotation rates of the LDL subclasses were: LDL1 = 37.2 +/- 0.6, LDL2 = 31.1 +/- 0.9, and LDL3 = 26.7 +/- 0.7. The mean flotation rates of the IDL subclasses were: IDL1 = 61.6 +/- 0.9, IDL2 = 53.9 +/- 1.0, IDL3 = 50.1 +/- 0.6, and IDL4 = 45.6 +/- 1.1.

The purpose of this study was to test the hypothesis that there is homologous upregulation of arterial alpha-adrenergic responsiveness during suppression of sympathetic nervous system (SNS) activity in humans. 10 subjects (19-28 yr) were studied during placebo and when SNS activity was suppressed by guanadrel. Changes in forearm blood flow (FABF) mediated by the intraarterial infusion of norepinephrine (NE), angiotensin II (AII), and phentolamine were measured by plethysmography. During guanadrel compared with placebo, plasma NE levels (1.28 +/- 0.09-0.85 +/- 0.06 nM; P = 0.0001) and the extra vascular NE release rate derived from [3H]NE kinetics were lower (7.1 +/- 0.7-4.0 +/- 0.2 nmol/min per m2; P = 0.0004), suggesting suppression of SNS activity. During guanadrel, there was increased sensitivity in the FABF response to NE (analysis of variance P = 0.03). In contrast, there was no difference in the FABF response to AII (analysis of variance P = 0.81), suggesting that the upregulation observed to NE was homologous. The increase in FABF during phentolamine was similar during guanadrel compared with placebo (guanadrel: 141 +/- 37 vs. placebo; 187 +/- 27% increase; P = 0.33), suggesting that there was at least partial compensation to maintain constant endogenous arterial alpha-adrenergic tone. We conclude that there is homologous upregulation of arterial alpha-adrenergic responsiveness in humans when SNS activity is suppressed by guanadrel.

The purpose of this study was to test the hypothesis that heightened sympathetic nervous system (SNS) activity contributes to the mechanism by which hypertension is associated with insulin resistance in humans. We performed frequently sampled intravenous glucose tolerance tests to determine tissue sensitivity to metabolic effects of insulin (SI) and measured plasma norepinephrine (NE) levels in 21 normotensive and 14 hypertensive Caucasian subjects. Compared with the normotensive subjects, hypertensive subjects had decreased SI (5.4 +/- 0.5 vs. 4.0 +/- 0.7 x 10(-5) x min-1 x pM-1; P = 0.03) but similar plasma NE levels (normotensive: 1.82 +/- 0.12 vs. hypertensive: 1.73 +/- 0.16 nM; P = 0.23). In a multiple regression model, only body mass index (BMI) and mean arterial blood pressure (MABP) were significant independent predictors of SI [SI = (-0.513)(BMI) + (-0.058)(MABP) + 23.6; r = 0.748; P = 0.0001]; age, plasma glucose, epinephrine, and NE level did not enter this model. As an additional test of this hypothesis, seven hypertensive subjects were restudied after 10 days of guanadrel therapy to determine whether SI would increase during suppression of SNS activity by guanadrel. Despite a significant reduction in plasma NE levels with guanadrel (baseline: 1.63 +/- 0.18 vs. guanadrel: 0.99 +/- 0.14 nM; P = 0.01), there was no significant change in SI (baseline: 2.97 +/- 0.78 vs. guanadrel: 2.41 +/- 0.54 x 10(-5).min-1 x pM-1; analysis of variance P = 0.57). We conclude that, in the Caucasian population we studied, heightened SNS activity is not essential for the insulin resistance observed in hypertensive humans.

The incidence of both systolic and diastolic hypertension is increased in elderly patients, therefore antihypertensive drugs are commonly used in this population. In addition to changes in blood pressure, the aging process also causes numerous changes in other physiological parameters, resulting in altered pharmacokinetic and pharmacodynamic responses to the drugs. The dosage regimens for thiazide diuretics and amiloride must be individually titrated in the elderly patient, since the elimination of these agents decreases concurrently with decreased renal function, as indicated by compromised creatinine clearance. The initial doses of the calcium antagonists should be decreased in elderly patients, since representative compounds from all 3 chemically heterogeneous classes have been shown to have decreased clearance in these patients which appears to be primarily due to the status of hepatic function in the patient. However, with verapamil, the dosage should be further decreased in association with compromised renal function. The dosage of the angiotensin converting enzyme (ACE) inhibitors should be adjusted according to renal function rather than age. Lisinopril, which is primarily eliminated unchanged, is usually given in lower doses in the elderly, and doses of both captopril and enalapril may need to be reduced, depending on renal function. While there is no need to adjust the dosage regimen for the alpha-adrenoceptor blocking drugs (prazosin, terazosin), caution should be used with the beta-adrenergic blockers, particularly the hydrophilic agents, since they are renally eliminated. Labetalol may be a suitable alternative beta-blocker for the elderly patient, since its pharmacodynamic properties of decreased systemic vascular resistance without changes in heart rate or stroke volume are preferential for the elderly patient, and its pharmacokinetics are relatively unchanged in this population. Drugs that act primarily through the central nervous system, such as clonidine, methyldopa and guanfacine, require smaller doses in the presence of renal dysfunction. In contrast, guanabenz is metabolised primarily by the liver, so it would appear to be useful in elderly patients with renal dysfunction despite the lack of studies in this population. Guanadrel, an adrenergic neuron blocking drug, also requires a dosage reduction in patients with impaired renal function. In addition to the pharmacokinetic changes that occur in the elderly patient, pharmacodynamic changes may also be anticipated due to receptor modifications. Older patients have a decrease in beta-receptor sensitivity, while alpha-receptor sensitivity does not change. When designing the dosage regimen for a senior patient with hypertension, the combination of all these variables must be considered.

Decreased adrenergic responsiveness in human aging could be a result of downregulation mediated by the age-related increase in sympathetic nervous system (SNS) tone. If so, suppression of SNS tone in elderly subjects should upregulate adrenergic responsiveness into the range observed for younger subjects. To test this hypothesis, we examined alpha 1 (phenylephrine)- and alpha 2 (clonidine)-adrenergic agonist-mediated venoconstriction in a group of 15 older healthy subjects (age 59-73 yr) during placebo and when SNS tone was suppressed by guanadrel (15 mg twice daily for 3 wk). During guanadrel compared with placebo 1) there were decreases in plasma norepinephrine (NE) levels (1.47 +/- 0.07 to 0.80 +/- 0.06 nM; P less than 0.001) and in the extravascular NE release rate derived from [3H]NE kinetics (11.8 +/- 1.4 to 6.1 +/- 1.0 nmol.min-1.m-2; P = 0.01), suggesting suppression of SNS tone; 2) there was an augmented clonidine-mediated venoconstriction response [analysis of variance (ANOVA) P = 0.01]; and 3) there was no detectable change in phenylephrine-mediated venoconstriction (ANOVA P = 0.60). When compared with previous results from young subjects, maximal alpha 2-adrenergic venoconstriction during guanadrel was decreased in the elderly compared with the young, although their response appeared to be appropriately upregulated by the decrease in SNS tone. The lack of an age-related decrease in alpha 1-adrenergic venoconstriction, together with the lack of upregulation of this response during guanadrel, suggests that regulation of this alpha 1-adrenergic response is impaired in the older group.

In a controlled, double-blind, crossover study, the effects of guanadrel sulfate and propranolol on blood pressure (BP) and selected cardiopulmonary and metabolic variables were compared in 15 physically active and moderately hypertensive subjects. Guanadrel sulfate reduced systolic and diastolic BP at rest by -16 and -15 mm Hg, and at maximal exercise by -33 and -13 mm Hg, respectively (p less than 0.005), without affecting submaximal oxygen consumption (VO2), maximal VO2, ventilatory threshold, forced vital capacity, forced expiratory volume in 1 second, or fatigue, as assessed by perceived exertion. In contrast, propranolol significantly decreased diastolic BP at rest (-16 mm Hg) and systolic BP at maximal exercise (-44 mm Hg); however, it significantly decreased submaximal VO2 (-3.9 ml.kg-1.min-1), maximal VO2 (-3.9 ml.kg-1.min-1), ventilatory threshold (-0.3 liters.min-1), minute ventilation at submaximal exercise (-7.3 liters.min-1), forced expiratory volume in 1 second (-0.27 liters), and concomitantly increased the rating of perceived exertion at maximal exercise (1.9 U). Guanadrel sulfate was also associated with significant decreases in mean fasting plasma glucose and total serum cholesterol, whereas propranolol resulted in an increase in serum triglycerides (p less than 0.05). In contrast to propranolol, guanadrel sulfate appears to decrease BP without evoking negative metabolic consequences or impairing exercise tolerance.

The alpha 1- and alpha 2-adrenergic venoconstriction in dorsal hand veins of normal subjects was determined by infusion of phenylephrine or clonidine. Oral administration of prazosin reduced the constriction response to phenylephrine but not to clonidine. Subjects were treated for 3 weeks in a randomized crossover design with placebo or guanadrel sulfate. Guanadrel reduced sympathetic tone (i.e., plasma norepinephrine and norepinephrine release rate), whereas venous responses to phenylephrine and clonidine were both augmented during guanadrel treatment. The effect on phenylephrine responses was primarily attributable to a decrease in the median effective concentration with a small increase in maximum response. Clonidine showed a markedly increased maximum response with a small increase in the median effective concentration. Platelet alpha 2-adrenergic receptors increased slightly but there was no change in the amount of platelet pertussis toxin substrate during guanadrel treatment. Thus reduction in sympathetic tone in normal young men results in increased venous responses to both alpha 1- and alpha 2-agonists.

The disposition of a single 25 mg oral dose of guanadrel was evaluated in 22 subjects with various degrees of renal function. The terminal elimination half-life was significantly prolonged in subjects with a creatinine clearance (ClCr) less than 30 mL/min/1.73 m2 (19.2 +/- 16.8 h) compared to 3.7 +/- 1.9 h in subjects with a ClCr greater than 80 mL/min/1.73 m2. Apparent total body clearance (Clp/F) was also progressively lower in the patients with decreased renal function and the decline was significantly correlated with ClCr (Clp/F = 0.0294 + 0.0236 Clcr, r = 0.74, P = 0.002). Renal clearance and apparent nonrenal clearance also declined as creatinine clearance decreased, and both were significantly correlated with the observed ClCr. Apparent volume of distribution averaged 11.5 +/- 8.9 L/kg and did not differ in patients with decreased renal function compared to those with normal renal function. Thus, the disposition of guanadrel is significantly altered in the presence of renal insufficiency and dosage adjustments may be necessary, especially in patients with ClCr less than 50 ml/min.

To evaluate the pharmacokinetics and drug availability from various dosage formulations, a method for the determination of guanadrel, (1,4-dioxaspiro[4,5]dec-2-ylmethyl)guanidine, in plasma and urine was required. A gas chromatographic procedure, based on formation of a hexafluoroacetylacetone derivative in a two-phase system of water and toluene, was developed. The limit of determination of the method is 5 ng/ml guanadrel in plasma and 15 ng/ml guanadrel in urine. Statistical analyses indicate average recoveries of 98.1 +/- 18.0 and 104.4 +/- 15.6% from plasma and urine, respectively. Mass spectrometric analyses, in conjunction with gas chromatography, confirmed the specificity of the method for intact drug. The procedure was applied successfully to drug absorption studies in humans.

Hypertension is common in the elderly and is associated with higher morbidity and mortality, which may be decreased by effective blood pressure control. Many antihypertensive drugs, however, are not well tolerated by the aged. We treated 21 patients (ten men and 11 women) between ages 65 and 84 years (mean, 73.6 years) with guanadrel sulfate. All patients had received prior antihypertensive therapy, which either was ineffective or caused undesirable side effects. Average follow-up time was 17 months. Mean systolic pressure on enrollment was 188 +/- 17 mm Hg and mean diastolic pressure was 100 +/- 10 mm Hg. After treatment, the mean systolic pressure was 139 +/- 15 mm Hg and mean diastolic pressure was 82 +/- 8 mm Hg. Dosage varied from 5 to 30 mg/d with a mean of 16 mg/d. The only significant side effects were fatigue, dizziness, and dyspnea reported in four patients. Eleven patients took the medication as monotherapy and ten received diuretics or diuretics and beta-blockers as additional therapy. Our conclusion is that guanadrel is an effective, well-tolerated medication for treatment of hypertension in the elderly.

Several lines of evidence implicate sympathetic nervous system involvement in the pathophysiology of essential hypertension in man. Extrapolations are frequently made from in vitro measurements of plasma catecholamine levels to the physiologic role of the sympathetic system in hypertension. We assessed the utility and validity of such extrapolation from in vitro to in vivo measures of adrenergic function. Addition of guanadrel to diuretic therapy in 11 patients with essential hypertension reduced supine intra-arterial blood pressure from 135 +/- 14/76 +/- 9 to 127 +/- 13/67 +/- 5 mm Hg (P less than 0.02). Supine heart rate was also reduced, from 77 +/- 14 to 63 +/- 13 bpm (P less than 0.001). Plasma norepinephrine levels fell from 303 +/- 107 to 170 +/- 46 pg/ml (P less than 0.01). Platelet alpha 2-receptor number ([3H]yohimbine maximal binding) increased from 204 +/- 77 to 301 +/- 150 fmol/mg (P less than 0.02). The pupillary mydriatic response to phenylephrine and the forearm arterial vasoconstrictor response to intra-arterial norepinephrine did not change. Thus guanadrel reduced blood pressure by decreasing sympathetic tone. In this milieu of low sympathetic activity the platelet alpha 2-receptor number increased, but physiologic responses to exogenous alpha-agonists did not change. Caution is therefore advised when extrapolating from in vitro measurement of plasma catecholamine levels and platelet alpha 2-receptor number to the in vivo physiologic significance.