Caffeine relaxes smooth muscle through actin depolymerization.

Caffeine is sometimes used in cell physiological studies to release internally stored Ca(2+). We obtained evidence that caffeine may also act through a different mechanism that has not been previously described and sought to examine this in greater detail. We ruled out a role for phosphodiesterase (PDE) inhibition, since the effect was 1) not reversed by inhibiting PKA or adenylate cyclase; 2) not exacerbated by inhibiting PDE4; and 3) not mimicked by submillimolar caffeine nor theophylline, both of which are sufficient to inhibit PDE.

Reduction of arterial graft smooth muscle mass by moderate heat therapy.

Radial artery (RA) graft spasm is a major cause of early graft failure in coronary artery bypass grafting surgeries. We explored the feasibility of thermal reduction of smooth muscle mass to attenuate vasoconstriction. Rat and rabbit femoral arteries were treated thermally in situ (45°C to 65°C; 0 s to 120 s) and then excised at various time points for histological and physiological study (pressure-diameter relationships).

Acute response of airway muscle to extreme temperature includes disruption of actin-myosin interaction.

Despite the emerging use of bronchial thermoplasty in asthma therapy, the response of airway smooth muscle (ASM) to extreme temperatures is unknown. We investigated the immediate effects of exposing ASM to supraphysiologic temperatures. Isometric contractions were studied in bovine ASM before and after exposure to various thermal loads and/or pharmacologic interventions.

Isoprostanes constrict human radial artery by stimulation of thromboxane receptors, Ca2+ release, and RhoA activation.

Objectives: Radial artery vasospasm remains a potential cause of early graft failure after coronary bypass graft surgery, despite pretreatment with alpha-adrenergic or calcium channel blockers. We examined the roles of isoprostanes and prostanoid receptors selective for thromboxane A2 in the vasoconstriction of human radial arteries.

Methods: Human radial arterial segments were pretreated intraoperatively with verapamil/papaverine or nitroglycerine/phenoxybenzamine, or not treated.

Role of tyrosine phosphorylation in U46619-induced vasoconstriction of pulmonary vasculature and its modulation by genistein, daidzein, and equol.

We compared the effects of genistein with its structural derivatives daidzein and equol on excitation of pulmonary artery and vein. The concentration of genistein necessary to inhibit contractions evoked by U46619 (1nM-100 microM) ranged from 10 to 100 microM. Genistein (55 microM) reduced KCl-responses by approximately 50% and essentially abolished those evoked by U46619.

E-ring isoprostane augments cholinergic neurotransmission in bovine trachealis via FP prostanoid receptors.

Isoprostanes are prostaglandin-like molecules that accumulate in oxidative stress and also exert powerful biological effects on a wide variety of tissues. We investigated the effects of several different isoprostanes on contractions evoked by electrical field stimulation (EFS) in bovine trachealis, finding only 15-E2t-IsoP to augment those responses. Many others have shown that isoprostanes act on prostanoid receptors, usually those of the thromboxane-selective prostanoid receptor (TP) subtype, although some describe actions through prostaglandin E2-selective prostanoid receptor (EP) or less frequently through prostaglandin F2alpha-selective prostanoid receptors (FP).

Pharmacological actions of isoprostane metabolites and phytoprostanes in human and bovine pulmonary smooth muscles.

We examined the responses to various isoprostane derivatives in bovine/human airway and pulmonary arteries. All biological activity of 15-F(2t)-IsoP was lost in its two major metabolites (15-keto-15-F(2t)-IsoP and 13,14-dihydro-15-keto-15-F(2t)-IsoP). We also examined the effects of several metabolites of 15-F(2t)-IsoP synthesized within our own laboratory-both epimers of 2,3-dinor-15-F(2t)-IsoP and of 2,3-dinor-5,6-dihydro-15-F(2t)-IsoP, as well as 20-carboxy-2,3,4,5-tetranor-15 oxo-5,6,13,14-tetrahydro-15-F(2t)-isoP)-finding none of these to have any substantial excitatory effect.

Isoprostane-induced airway hyperresponsiveness is dependent on internal Ca2+ handling and Rho/ROCK signaling.

We previously reported the ability of isoprostanes to induce airway hyperresponsiveness (AHR). In this study, we examined the signaling mechanisms underlying that phenomenon with the standard muscle bath technique. Responses to a threshold concentration of carbachol (CCh, 3 x 10(-9) M) were significantly augmented by pretreatment for 20 min with 8-isoprostaglandin E(2) (15-E(2t)-IsoP, 10(-6) M): this AHR was obliterated in tissues pretreated with the selective Rho kinase (ROCK) inhibitor Y-27632 added 20 min before isoprostane, but not by cyclopiazonic acid (CPA).

Membrane potassium currents in human radial artery and their regulation by nitric oxide donor.

Objective: The human radial artery has demonstrated superior long-term results as a graft in coronary bypass surgery, but undesirable post-surgical spasm limits its clinical application. Few have examined its excitatory properties, especially the underlying ion channel mechanisms. In this study, we investigated the kinetic and pharmacological properties of the smooth muscle membrane potassium currents of this important artery.

KCl evokes contraction of airway smooth muscle via activation of RhoA and Rho-kinase.

Airway smooth muscle (ASM) cells express voltage-dependent Ca2+ channels, primarily of the L-subtype. These may play a role in excitation-contraction coupling of ASM, although other signaling pathways may also contribute: one of these includes Rho and its downstream effector molecule Rho-associated kinase (ROCK). Although voltage-dependent Ca2+ influx and Rho/ROCK signaling have traditionally been viewed as entirely separate pathways, recent evidence in vascular smooth muscle suggest differently.

Silk suture used in standard organ bath studies contracts upon exposure to Krebs buffer.

Introduction: Muscles of all types are routinely excised and studied under isometric conditions using force transducers in standard organ baths. In such studies, the muscle is stretched or "preloaded," as the magnitudes of the contractions evoked by various stimuli can vary markedly depending on this baseline parameter: many such studies refer to an optimal length and/or preload tension. While calibrating our equipment, we were surprised to find that the silk suture, which is commonly used in such studies, can generate considerable tension of its own, completely independent of any muscle tissue.

Vasoconstrictor responses, and underlying mechanisms, to isoprostanes in human and porcine bronchial arterial smooth muscle.

We investigated the effects of five different isoprostanes (8-iso PGE1, 8-iso PGE2, 8-iso PGF1alpha, 8-iso PGF2alpha and 8-iso PGF2beta) on vasomotor tone in human and porcine bronchial arterial tissues. In the human bronchial arteries, 8-iso PGE2 and 8-iso PGF2alpha evoked powerful constrictions (magnitudes several fold greater than the responses to high millimolar KCl) with negative log concentration causing 50% excitation (EC50) values of 6.8 and 6.

Enhanced myosin phosphatase and Ca(2+)-uptake mediate adrenergic relaxation of airway smooth muscle.

We examined the mechanisms underlying relaxations evoked by isoproterenol (Iso) in isolated porcine, bovine, or human tracheal and bronchial tissues (TSM and BSM, respectively). Iso had little effect against contractions evoked by high KCl, indicating that it does not directly suppress voltage-dependent Ca(2+)-influx nor directly inhibit myosin light chain kinase. Furthermore, Iso was equally potent against carbachol (CCh) contractions in the presence versus absence of nifedipine (10(-6) M), establishing that the primary action of Iso is not through membrane hyperpolarization.

Involvement of TP and EP3 receptors in vasoconstrictor responses to isoprostanes in pulmonary vasculature.

Although isoprostanes generally act on smooth muscle via TXA(2)-selective prostanoid receptors (TPs), some suggest other prostanoid receptors or possibly even a novel isoprostane-selective receptor might be involved. We studied contractions to several isoprostanes in porcine pulmonary vasculature using organ bath techniques. 8-iso-prostaglandin E(2) (PGE(2)) was the most potent and efficacious of the isoprostanes, with a log EC(50) of -7.