Molecular determinants for the activating/blocking actions of the 2H-1,4-benzoxazine derivatives, a class of potassium channel modulators targeting the skeletal muscle KATP channels

The 2H-1,4-benzoxazine derivatives are modulators of the skeletal muscle ATP-sensitive-K+ channels (KATP), activating it in the presence of ATP but inhibiting it in the absence of nucleotide. To investigate the molecular determinants for the activating/blocking actions of these compounds, novel molecules with different alkyl or aryl-alkyl substitutes at position 2 of the 1,4-benzoxazine ring were prepared. The effects of the lengthening of the alkyl chain and of branched substitutes, as well as of the introduction of aliphatic/aromatic rings on the activity of the molecules, were investigated on the skeletal muscle KATP channels of the rat, in excised-patch experiments, in the presence or absence of internal ATP (10 -4 M). In the presence of ATP, the 2-n-hexyl analog was the most potent activator (DE50 = 1.08 × 10-10 M), whereas the 2-phenylethyl was not effective. The rank order of efficacy of the openers was 2-n-hexyl ≥2-cyclohexylmethyl >2-isopropyl = 2-n-butyl = 2-phenyl ≥ 2-benzyl = 2-isobutyl analogs. In the absence of ATP, the 2-phenyl analog was the most potent inhibitor (IC50 = 2.5 × 10-11 M); the rank order of efficacy of the blockers was 2-phenyl ≥ 2-n-hexyl > 2-n-butyl > 2-cyclohexylmethyl, whereas the 2-phenylethyl, 2-benzyl, and 2-isobutyl 1,4-benzoxazine analogs were not effective; the 2-isopropyl analog activated the KATP channel even in the absence of nucleotide. Therefore, distinct molecular determinants for the activating or blocking actions for these compounds can be found. For example, the replacement of the linear with the branched alkyl substitutes at the position 2 of the 1,4-benzoxazine nucleus determines the molecular switch from blockers to openers. These compounds were 100-fold more potent and effective as openers than other KCO against the muscle KATP channels. Copyright © 2008 The American Society for Pharmacology and Experimental Therapeutics

Growth hormone secretagogues exert differential effects on skeletal muscle calcium homeostasis in male rats depending on the peptidyl/non-peptidyl structure

TheorexigenicandanaboliceffectsinducedbyghrelinandthesyntheticGHsecretagogues(GHSs) are thought to positively contribute to therapeutic approaches and the adjunct treatment of a number of diseases associated with muscle wasting such as cachexia and sarcopenia. However, manyquestionsaboutthepotentialutilityandsafetyofGHSsinboththerapyandskeletalmuscle functionremainunanswered.Byusingfura-2cytofluorimetrictechnique,wedeterminedtheacute effectsofghrelin,aswellasofpeptidylandnonpeptidylsyntheticGHSsoncalciumhomeostasis, a critical biomarker of muscle function, in isolated tendon-to-tendon male rat skeletal muscle fibers.ThesyntheticnonpeptidylGHSs,butnotpeptidylghrelinandhexarelin,wereabletosignificantlyincreaserestingcytosoliccalcium[Ca2]i.ThenonpeptidylGHS-induced[Ca2] iincrease was independent of GHS-receptor 1a but was antagonized by both thapsigargin/caffeine and cyclosporineA,indicatingtheinvolvementofthesarcoplasmicreticulumandmitochondria.EvaluationoftheeffectsofapseudopeptidylGHSandanonpeptidylantagonistoftheGHS-receptor 1a together with a drug-modeling study suggest the conclusion that the lipophilic nonpeptidyl structureofthetestedcompoundsisthekeychemicalfeaturecrucialfortheGHS-inducedcalcium alterationsintheskeletalmuscle.Thus,syntheticGHSscanhavedifferenteffectsonskeletalmuscle fibersdependingontheirmolecularstructures.Thecalciumhomeostasisdysregulationspecifically induced by the nonpeptidyl GHSs used in this study could potentially counteract the beneficial effects associated with these drugs in the treatment of muscle wasting of cachexia- or other age-related disorders

Convenient synthesis of some 3-phenyl-1-benzofuran-2-carboxylic acid derivatives as new potential inhibitors of CLC-Kb channels

Improved experimental conditions were carried out for the preparation in high yields of some 3-phenyl-1-benzofuran-2-carboxylic acids, potent inhibitors of C1C-K chloride channels. A one-pot condensation-cyclization was set up starting from different 2-hydroxybenzophenones whose reactivity was significantly affected from the electronic properties of their substituents

An efficient synthesis of the optically active isomers of 2H-1,4-benzoxazine derivatives, novel KATP channel modulators

2H-1,4-Benzoxazine amidine derivatives are drugs acting as modulators of the skeletal muscle and pancreatic beta cell ATP-sensitive-K+ (KATP) channels. With the aim of evaluating the influence of absolute configuration on the biological activity of these drugs, we herein report the optimization of a synthetic route to obtain both enantiomers of some of these compounds with improved chemical yield and high enantiomeric excess