Manuscript in preparation

A review of anti-infective and anti-inflammatory chalcones.

To date, studies suggest that biological signaling by nitric oxide (NO) is primarily mediated by cGMP, which is synthesized by NO-activated guanylyl cyclases and broken down by cyclic nucleotide phosphodiesterases (PDEs). Effects of cGMP occur through three main groups of cellular targets: cGMP-dependent protein kinases (PKGs), cGMP-gated cation channels, and PDEs. cGMP binding activates PKG, which phosphorylates serines and threonines on many cellular proteins, frequently resulting in changes in activity or function, subcellular localization, or regulatory features. The proteins that are so modified by PKG commonly regulate calcium homeostasis, calcium sensitivity of cellular proteins, platelet activation and adhesion, smooth muscle contraction, cardiac function, gene expression, feedback of the NO-signaling pathway, and other processes. Current therapies that have successfully targeted the NO-signaling pathway include nitrovasodilators (nitroglycerin), PDE5 inhibitors [sildenafil (Viagra and Revatio), vardenafil (Levitra), and tadalafil (Cialis and Adcirca)] for treatment of a number of vascular diseases including angina pectoris, erectile dysfunction, and pulmonary hypertension; the PDE3 inhibitors [cilostazol (Pletal) and milrinone (Primacor)] are used for treatment of intermittent claudication and acute heart failure, respectively. Potential for use of these medications in the treatment of other maladies continues to emerge.

cGMP-Dependent Protein Kinases and cGMP Phosphodiesterases in Nitric Oxide and cGMP Action

Voltage-gated calcium channels are required for many key functions in the body. In this review, the different subtypes of voltage-gated calcium channels are described and their physiologic roles and pharmacology are outlined. We describe the current uses of drugs interacting with the different calcium channel subtypes and subunits, as well as specific areas in which there is strong potential for future drug development. Current therapeutic agents include drugs targeting L-type Ca(V)1.2 calcium channels, particularly 1,4-dihydropyridines, which are widely used in the treatment of hypertension. T-type (Ca(V)3) channels are a target of ethosuximide, widely used in absence epilepsy. The auxiliary subunit α2δ-1 is the therapeutic target of the gabapentinoid drugs, which are of value in certain epilepsies and chronic neuropathic pain. The limited use of intrathecal ziconotide, a peptide blocker of N-type (Ca(V)2.2) calcium channels, as a treatment of intractable pain, gives an indication that these channels represent excellent drug targets for various pain conditions. We describe how selectivity for different subtypes of calcium channels (e.g., Ca(V)1.2 and Ca(V)1.3 L-type channels) may be achieved in the future by exploiting differences between channel isoforms in terms of sequence and biophysical properties, variation in splicing in different target tissues, and differences in the properties of the target tissues themselves in terms of membrane potential or firing frequency. Thus, use-dependent blockers of the different isoforms could selectively block calcium channels in particular pathologies, such as nociceptive neurons in pain states or in epileptic brain circuits. Of important future potential are selective Ca(V)1.3 blockers for neuropsychiatric diseases, neuroprotection in Parkinson's disease, and resistant hypertension. In addition, selective or nonselective T-type channel blockers are considered potential therapeutic targets in epilepsy, pain, obesity, sleep, and anxiety. Use-dependent N-type calcium channel blockers are likely to be of therapeutic use in chronic pain conditions. Thus, more selective calcium channel blockers hold promise for therapeutic intervention.

The Physiology, Pathology, and Pharmacology of Voltage-Gated Calcium Channels and Their Future Therapeutic Potential

What is a drug target? And how many such targets are there? Here, we consider the nature of drug targets, and by classifying known drug substances on the basis of the discussed principles we provide an estimation of the total number of current drug targets.

Drugs, their targets and the nature and number of drug targets

Blood pressure is regulated by a number of key molecules involving G-protein-coupled receptors, ion channels and monomeric small G-proteins. The relative contribution of these different signaling pathways to blood pressure regulation remains to be determined. Tamoxifen-induced, smooth muscle-specific inactivation of the L-type Cav1.2 Ca2+ channel gene in mice (SMAKO) reduced mean arterial blood pressure (MAP) in awake, freely moving animals from 120 +/- 4.5 to 87 +/- 8 mmHg. Phenylephrine (PE)- and angiotensin 2 (AT2)-induced MAP increases were blunted in SMAKO mice, whereas the Rho-kinase inhibitor Y-27632 reduced MAP to the same extent in control and SMAKO mice. Depolarization-induced contraction was abolished in tibialis arteries of SMAKO mice, and development of myogenic tone in response to intravascular pressure (Bayliss effect) was absent. Hind limb perfusion experiments suggested that 50% of the PE-induced resistance is due to calcium influx through the Cav1.2 channel. These results show that Cav1.2 calcium channels are key players in the hormonal regulation of blood pressure and development of myogenic tone.

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Dominant role of smooth muscle L-type calcium channel Cav1.2 for blood pressure regulation.

The L-type Cav1.2 calcium channel is present throughout the animal kingdom and is essential for some aspects of CNS function, cardiac and smooth muscle contractility, neuroendocrine regulation, and...

L-Type CaV1.2 Calcium Channels: From In Vitro Findings to In Vivo Function

To study the role of cGMP-dependent protein kinase I (cGKI) for cardiac contractility, force of contraction (Fc) was studied in electrically driven heart muscle from wild-type (WT) mice and from conventional and conditional cGKI knockout mice. Both 8-Br-cGMP and 8-pCPT-cGMP reduced Fc in cardiac muscle from juvenile WT but not from juvenile cGKI-null mutants. Similarly, the cGMP analogues reduced Fc in forskolin-stimulated ventricular muscle from WT mice but not from cGKI-null mutants. In contrast, carbachol reduced Fc in both groups of animals. 8-Br-cGMP reduced Fc also in heart muscle from adult WT mice but not from adult cardiomyocyte-specific cGKI-knockout mice. These results demonstrate that cGKI mediates the negative inotropic effect of cGMP in the myocardium of juvenile and adult mice.

cGMP-Dependent Protein Kinase I Mediates the Negative Inotropic Effect of cGMP in the Murine Myocardium

Signalling by cGMP-dependent protein kinase type I (cGKI) relaxes various smooth muscles modulating thereby vascular tone and gastrointestinal motility. cGKI-dependent relaxation is possibly mediated by phosphorylation of the inositol 1,4,5-trisphosphate receptor I (IP3RI)-associated protein (IRAG), which decreases hormone-induced IP3-dependent Ca2+ release. We show now that the targeted deletion of exon 12 of IRAG coding for the N-terminus of the coiled-coil domain disrupted in vivo the IRAG–IP3RI interaction and resulted in hypomorphic IRAGΔ12/Δ12 mice. These mice had a dilated gastrointestinal tract and a disturbed gastrointestinal motility. Carbachol- and phenylephrine-contracted smooth muscle strips from colon and aorta, respectively, of IRAGΔ12/Δ12 mice were not relaxed by cGMP, while cAMP-mediated relaxation was unperturbed. Norepinephrine-induced increases in [Ca2+]i were not decreased by cGMP in aortic smooth muscle cells from IRAGΔ12/Δ12 mice. In contrast, cGMP-induced relaxation of potassium-induced smooth muscle contraction was not abolished in IRAGΔ12/Δ12 mice. We conclude that cGMP-dependent relaxation of hormone receptor-triggered smooth muscle contraction essentially depends on the interaction of cGKI–IRAG with IP3RI.

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IRAG is essential for relaxation of receptor‐triggered smooth muscle contraction by cGMP kinase

Mice deficient in the smooth muscle Cav1.2 calcium channel (SMACKO, smooth muscle alpha1c-subunit calcium channel knockout) have a severely reduced micturition and an increased bladder mass. L-type calcium current, protein, and spontaneous contractile activity were absent in the bladder of SMACKO mice. K+ and carbachol (CCh)-induced contractions were reduced to 10-fold in detrusor muscles from SMACKO mice. The dihydropyridine isradipine inhibited K+- and CCh-induced contractions of muscles from CTR but had no effect in muscles from SMACKO mice. CCh-induced contraction was blocked by removing extracellular Ca2+ but was unaffected by the PLC inhibitor U73122 or depletion of intracellular Ca2+ stores by thapsigargin. In muscles from CTR and SMACKO mice, CCh-induced contraction was partially inhibited by the Rho-kinase inhibitor Y27632. These results show that the Cav1.2 Ca2+ channel is essential for normal bladder function. The Rho-kinase and Ca2+-release pathways cannot compensate the lack of the L-type Ca2+ channel.

/pdf/an-essential-role-of-cav1-2-l-type-calcium-channel-for-16tjg9uli1.pdf

Jörg W. Wegener

Papers

Dominant role of smooth muscle L-type calcium channel Cav1.2 for blood pressure regulation.

L-Type CaV1.2 Calcium Channels: From In Vitro Findings to In Vivo Function

cGMP-Dependent Protein Kinase I Mediates the Negative Inotropic Effect of cGMP in the Murine Myocardium

IRAG is essential for relaxation of receptor‐triggered smooth muscle contraction by cGMP kinase

An essential role of Cav1.2 L-type calcium channel for urinary bladder function