Theophylline and cAMP inhibit lysophosphatidic acid‐induced hyperresponsiveness of bovine tracheal smooth muscle cells

Abstract

We have established an in vitro model of airway hyperresponsiveness, using a bovine tracheal smooth muscle cell (BTSMC)‐embedded collagen gel lattice. When the gel was pretreated with lysophosphatidic acid (LPA), which activates the small G protein RhoA, ATP‐ and high K+ solution‐induced gel contraction was significantly augmented. This was not due to the modulation of Ca2+ mobilizing properties, since ATP‐ and high K+‐induced Ca2+ transients were not significantly different between control and LPA‐treated BTSMC. Y‐27632, an inhibitor of Rho‐kinase, suppressed the LPA‐induced augmentation of gel contraction, whereas it did not inhibit the contraction of control gels. Theophylline (> 1 μm) reversed the LPA‐induced augmentation of gel contraction, whereas it inhibited control gel contraction only with a very high concentration (100 μm). We confirmed that theophylline increased the intracellular concentration of cAMP ([cAMP]i) in BTSMC. Elevation of [cAMP]i with dibutyryl cAMP or forskolin also reversed the LPA‐induced augmentation of gel contraction. Furthermore, theophylline, as well as dibutyryl cAMP and forskolin, suppressed the LPA‐induced membrane translocation of RhoA, indicating that they prevented airway hyperresponsiveness by inhibiting RhoA. We conclude from these results that theophylline inhibits LPA‐induced, RhoA/Rho‐kinase‐mediated hyperresponsiveness of tracheal smooth muscle cells due to the accumulation of cAMP.

Dual Modulation of Airway Smooth Muscle Contraction by Th2 Cytokines via Matrix Metalloproteinase-1 Production

“…These histological characteristics of airway SM are conserved in BTSMC-embedded collagen gels, i.e., randomly oriented and not connected to each other, as demonstrated previously (16). Recently, a role of the interrelationship between airway SM cells and extracellular matrix in airway diseases has been discussed (40).…”

“…3B). Furthermore, activation of the RhoA/Rho-kinase pathway, which increases the Ca 2ϩ sensitivity of the contractile proteins in airway SM cells (16), is unlikely because neither IL-13 nor IL-4 affected the membrane translocation of RhoA, which is considered as a hallmark of RhoA activation (23) (Fig. 3C).…”

“…We have previously shown that contractility of cultured bovine tracheal SM cells (BTSMCs) can be restored by embedding them into a collagen gel lattice (16). Because drugs can easily access the cells that are embedded into the collagen gel lattice, we used this technique in the present study to examine the effects of Th1 and Th2 cytokines on the contractility of BTSMCs.…”

Phosphodiesterase-5 inhibition synergizes rho-kinase antagonism and enhances erectile response in male hypertensive rats

“…33,34 Crossregulation of intracellular cGMP and cAMP signaling pathways has been demonstrated in cultured human corpus cavernosum smooth muscle cells. 33 Sakai et al 35 reported that accumulation of cAMP in cells inhibited the RhoA activation in tracheal smooth muscle. Using vascular smooth muscle cells, Sauzeau et al 36 demonstrated that cGMP inhibited RhoA-dependent calcium sensitization.…”

Airway Smooth Muscle in Asthma Symptoms: Culprit but Maybe Innocent

“…Most studies were performed using freshly dissected ASM strips or bronchial rings from which isometric force was measured ex vivo (12,32,38,48,71,87,98,122,135,156,173,174,184,185,195,203,204,215,230). In vitro preparations (i.e., cell culture) have also been used on occasions (205). These reported synergisms are also enumerated inTable 1.…”