Luke J. Janssen

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 PGF1α, 8‐iso PGF2α and 8‐iso PGF2β) on vasomotor tone in human and porcine bronchial arterial tissues. In the human bronchial arteries, 8‐iso PGE2 and 8‐iso PGF2α 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 6.5, respectively; 8‐iso PGE1 was less potent (EC50 not calculated, since a clear peak contraction was not obtained), while the other isoprostanes were largely ineffective. In the porcine arteries, on the other hand, all three F‐ring isoprostanes as well as 8‐iso PGE2 evoked constrictor responses, although the peak magnitudes were approximately 50% of the KCl‐evoked response; 8‐iso PGE2 and 8‐iso PGF2α were the most potent, with negative log EC50 values of 6.5. We next sought to characterize the signaling pathways underlying the vasoconstrictor responses to 8‐iso PGE2, since this was the most potent of the isoprostanes we tested. These responses were largely reversed by the thromboxane A2‐selective (TP) prostanoid receptor antagonist ICI 192605 (10−8 M; 4(Z)‐6‐[(2,4,5 cis)2‐(2‐chlorophenyl)‐4‐(2‐hydroxy phenyl)1,3‐dioxan‐5‐yl]hexenoic acid) as well as by the nonspecific tyrosine kinase inhibitor genistein (10−5 and 10−4 M), and were reversed approximately 50% by the Rho‐kinase inhibitor Y27632 (10−5 M; (+)‐(R)‐trans‐4‐(1‐aminoethyl)‐N‐(pyridyl) cyclohexanecarboxamide dihydrochloride). We conclude, therefore, that 8‐iso PGE2 constricts bronchial vasculature through the activation of TP receptors, which in turn trigger tyrosine kinase and Rho‐kinase activities, resulting in powerful vasoconstriction. These findings are highly relevant to lung transplantation and to exercise‐induced asthma.

The TRPV1 channel in rodents is a major target for antinociceptive effect of the probiotic Lactobacillus reuteri DSM 17938.

Certain probiotic bacteria have been shown to reduce distension‐dependent gut pain, but the mechanisms involved remain obscure. Live luminal Lactobacillus reuteri (DSM 17938) and its conditioned medium dose dependently reduced jejunal spinal nerve firing evoked by distension or capsaicin, and 80% of this response was blocked by a specific TRPV1 channel antagonist or in TRPV1 knockout mice. The specificity of DSM action on TRPV1 was further confirmed by its inhibition of capsaicin‐induced intracellular calcium increases in dorsal root ganglion neurons. Another lactobacillus with ability to reduce gut pain did not modify this response. Prior feeding of rats with DSM inhibited the bradycardia induced by painful gastric distension. These results offer a system for the screening of new and improved candidate bacteria that may be useful as novel therapeutic adjuncts in gut pain.

The NADPH oxidase inhibitor diphenyleneiodonium is also a potent inhibitor of cholinesterases and the internal Ca2+ pump

Background and purpose:u2002 Diphenyleneiodonium (DPI) is often used as an NADPH oxidase inhibitor, but is increasingly being found to have unrelated side effects. We investigated its effects on smooth muscle contractions and the related mechanisms.

Emerging airway smooth muscle targets to treat asthma.

Asthma is characterized in part by variable airflow obstruction and non-specific hyperresponsiveness to a variety of bronchoconstrictors, both of which are mediated by the airway smooth muscle (ASM). The ASM is also involved in the airway inflammation and airway wall remodeling observed in asthma. For all these reasons, the ASM provides an important target for the treatment of asthma. Several classes of drugs were developed decades ago which targeted the ASM - including β-agonists, anti-cholinergics, anti-histamines and anti-leukotrienes - but no substantially new class of drug has appeared recently. In this review, we summarize the on-going work of several laboratories aimed at producing novel targets and/or tools for the treatment of asthma. These range from receptors and ion channels on the ASM plasmalemma, to intracellular effectors (particularly those related to cyclic nucleotide signaling, calcium-homeostasis and phosphorylation cascades), to anti-IgE therapy and outright destruction of the ASM itself.

ATP stimulates Ca2+-waves and gene expression in cultured human pulmonary fibroblasts

Given that extracellular ATP is markedly elevated in inflammation and is known to modulate fibroblast function, we examined the effects of exogenously added ATP on Ca(2+)-handling and gene expression in human pulmonary fibroblasts. Cells were loaded with the Ca(2+)-indicator dye fluo-4 and studied using confocal fluorimetry. Standard RT-PCR was used to probe gene expression. ATP (10(-5)M) evoked recurring Ca(2+)-waves which were completely occluded by cyclopiazonic acid (depletes the internal Ca(2+)-store) or the phospholipase inhibitor U73122. Pretreatment with ryanodine (10(-5)M), however, had no effect on the ATP-evoked responses. Regarding the receptor through which ATP acted, we found the ATP-response to be mimicked by UTP or ADP but not by adenosine or alpha,beta-methylene-ATP, and to be blocked by the purinergic receptor blocker PPADS. The ATP-evoked response was greater and longer lasting within the nucleus than in the non-nuclear portion of the cytosol. RT-PCR showed that ATP also rapidly and dramatically increased gene expression of P2Y(4) receptors, the cytokine TGF-beta (an important modulator of wound repair) and two matrix proteins (collagen A1 and fibronectin) approximately 4-5 times above baseline: this increase was not significantly affected by ryanodine but was abolished by PPADS. We conclude that, in human pulmonary fibroblasts, ATP acts upon P2Y receptors to liberate internal Ca(2+) through ryanodine-insensitive channels, leading to a Ca(2+)-wave which courses throughout the cell and modulates gene expression.

Platelet derived growth factor-evoked Ca2+ wave and matrix gene expression through phospholipase C in human pulmonary fibroblast

The primary role of fibroblasts is production and degradation of extracellular matrix, and thus it helps in the structural framework of tissues. The close relation between fibroblast malfunction and many diseases such as chronic obstructive pulmonary disease, asthma, and fibrosis is widely accepted. Fibroblasts are known to respond to different growth factors and cytokines including platelet-derived growth factors (PDGF). However, the intracellular signaling mechanisms are not entirely clear. In addition to complex phosphorylation-driven signaling pathways, PDGF is also known to work through Ca(2+) signaling. We hypothesize that in human pulmonary fibroblasts, Ca(2+) waves play an important role in PDGF-mediated changes. To test this hypothesis, we treated human pulmonary fibroblasts, obtained from the lungs of ten donors, with PDGF acutely or overnight plus/minus a variety of blockers under various conditions. Ca(2+) waves were monitored by confocal [Ca(2+)]i fluorimetry, while gene expression of extracellular matrix genes was assessed via RT-PCR method. We found that both acute and overnight PDGF treatment evoked Ca(2+) waves. Removal of external Ca(2+) or depletion of internal Ca(2+) store using Cyclopiazonic acid (CPA) completely occluded PDGF-evoked Ca(2+) waves. Ryanodine, which blocks ryanodine receptor channels, had no effect on PDGF-evoked Ca(2+) wave, whereas the phospholipase C inhibitor U73122 and Xestospongin C, a potent IP3 receptor blocker, reduced the rapid PDGF-response to a relatively slowly-developing rise in [Ca(2+)]i. We also found that PDGF dramatically increased the expression of fibronectin1 and collagen A1 genes, which was reversed by the use of CPA or U73122. Our study indicates that, in human pulmonary fibroblasts, PDGF acts through IP3-induced Ca(2+)-release to trigger Ca(2+) waves, which in turn modulate gene expression of several matrix proteins.

Intestinal, Airway, and Cardiovascular Relaxant Activities of Thymoquinone

Thymoquinone (TQ) is a bioactive component found in many medicinal herbs. In this study, we report the smooth and cardiac muscle relaxant activities of this compound. TQ concentration dependently suppressed spontaneously contracting rabbit jejunum while also relaxed high K+-(80u2009mM) induced contractions in jejunum and guinea-pig ileum, indicating activity at voltage-operated Ca++ channels (VOCC). Further, TQ displaced Ca++ concentration-response curves, obtained in a Ca++-free environment, to the right, showing blockade of VOCC. Similar activity was observed with verapamil, a standard VOCC blocker. TQ also exhibited nonadrenergic relaxation of agonist-induced contractions in guinea-pig trachea. When tested in fluo-4-loaded mouse lung slices, TQ inhibited ACh-induced airway narrowing and Ca++ signalling in airway smooth muscle cells. In endothelium-intact and endothelium-denuded rat aorta, TQ inhibited high K+-induced contractions at significantly lower concentrations than phenylephrine-(PE-) (1u2009microM) induced contractions. Relaxation of PE-induced contractions was resistant to blockade by L-NAME and atropine. In guinea-pig atria, TQ showed noncholinergic relaxation of atrial force and rate of contractions. These data suggest smooth and cardiac muscle relaxant activity of TQ possibly mediated, in part, via blockade of VOCC. The results also justify the use of TQ containing plants in related health disorders like colic, diarrhoea, cough, and asthma.

A natural way to cardiovascular health

The article by Dauchet et al. (Fruits, vegetables and coronary heart disease. Nat. Rev. Cardiol.xa06, 599–608; 2009),1 which reviews the available evidence for the cardioprotective potential of fruits and vegetables, highlights the importance of healthy foods and a balanced diet. This topic interests many researchers around the world who have spent time and effort demonstrating the efficacy of fruits and vegetables in the prevention of cardiovascular diseases and many other chronic conditions.

Nephroprotective drugs from traditionally used Aboriginal medicinal plants

To the Editor: The recent article by Farese et al.1 sheds light on a very important source area of drug development, medicinal plants. People in different cultures, all over the world, have used medicinal plants for a number of diseases. One such traditional medicine system is that of the Canadian Aboriginals. This system has been practiced for centuries and encompasses treating the whole person through mind, body, and spirit. Medicinal plants make up the most important tool in curing a disease. Table 1 lists selected plants used by Aboriginal tribes all over Canada for kidney diseases. Mostly, these are used for diuresis, renal stones and cleansing the kidneys. Plants have also been a major source of new drugs since the inception of modern pharmacology.2 According to a survey, one-third of all the newly approved compounds are derived from plants.2 A brief review of the literature shows different plants being effective in preventing/treating renal diseases either in animal models or in clinical trials.3, 4 Some renal conditions reported to respond to plant therapy are glomerulonephritis, IgA nephropathy, membranous nephropathy, glomerulosclerosis, immune complex nephritis, nephrotic syndrome, lupus, tubulointerstitial nephritis, chronic allograft nephropathy, kidney stones, etc.3, 4 Some pharmacological characteristics seen in plants that may contribute in the above-mentioned conditions are antiinflammation; antioxidation; diuresis; immunomodulation; prevention of acute allograft rejection and drug-induced nephrotoxicity; reduction in proteinuria, renal interstitial fibrosis, renal ischemia/reperfusion injury, tubular and mesangial cell proliferation, blood lipid levels, blood pressure, lipid peroxidation, apoptosis, renal necrosis, and calcium oxalate crystal aggregation; and stimulation of renal repair mechanisms, RNA and protein synthesis.3, 4 Continued efforts are required to identify and develop traditionally used medicinal plants in renal diseases so that more effective treatments are available from plants that have been known for their efficacy for hundreds of years.

L-type Ca2+ channels, Ca2+-induced Ca2+ release, and BKCa channels in airway stretch-induced contraction

Resistance arteries constrict in response to mechanical stress. This response is myogenic in nature, and reliant on membrane depolarization, activation of L-type Ca(2+) channels, Ca(2+)-induced Ca(2+)-release and large conductance Ca(2+)-dependent K(+) channels (BK(Ca)). Airway smooth muscle is also affected by mechanical stress: a deep inspiration produces a bronchodilation in healthy individuals, but bronchoconstriction in moderate to severe asthmatics. In this study, our objective was to investigate the regulation of this airway stretch-activated contractile response (R(stretch)), and explore its similarities to the vascular myogenic response. Using a pharmacological approach in intact bovine bronchial segments cannulated horizontally in an organ bath, we showed the ability of carbachol (2-carbamoyloxyethyl-trimethyl-azanium), KCl, neurokinin-A, and U46619 (9,11-dideoxy-9α,11α-methanoepoxy-prosta-5Z, 13E-dien-1-oic acid) to generate R(stretch) in a concentration-dependent manner. R(stretch) was significantly reduced by nifedipine, ryanodine, and iberiotoxin, suggesting that it possesses characteristics similar to those of the vascular smooth muscle myogenic response, such as a role for membrane depolarization, L-type Ca(2+) channel, ryanodine receptors and BK(Ca) channel activation. This study demonstrates a novel role for the L-type Ca(2+) channel in airway smooth muscle and provides new insights into possible mechanisms regulating the deep inspiration-induced bronchoconstriction seen in asthmatics.