Expression Of P2X Receptor Subtypes Research Articles

Comparison of mRNA Expression of P2X Receptor Subtypes in Different Arterial Tissues of Rats.

This study aims to compare the expression of P2X receptor subtype mRNA in different arterial tissues of rats. After the rats were sacrificed, the internal carotid, pulmonary, thoracic aorta, mesenteric and caudal arteries were dissected out. Then, the P2X receptor mRNA expression in different blood vessels was detected by reverse transcription-polymerase chain reaction (RT-PCR) and real-time quantitative polymerase chain reaction. The P2X1, P2X4 and P2X7 receptor mRNA amplification products revealed specific bands of the same size as the amplified target fragment in their respective lanes, while the P2X2, P2X3, P2X5 and P2X6 receptor mRNA amplification products did not reveal significant specific bands in their respective lanes by RT-PCR. Based on the P2X1 receptor mRNA expression of the mesenteric artery, there were no significant differences in the internal carotid, pulmonary and thoracic aorta (0.64 ± 0.07, 0.17 ± 0.11 and 1.49 ± 0.65, respectively). However, the P2X1 receptor mRNA expression level in the caudal artery significantly increased (11.06 ± 1.99, P < 0.01). Furthermore, there was no difference in P2X4 receptor mRNA expression among these five blood vessels (P > 0.05). The P2X7 receptor mRNA expression level was significantly different: pulmonary artery < tail artery = thoracic aorta < internal carotid artery < mesenteric artery. The relative P2X1 receptor mRNA expression in the caudal artery was observed to be elevated when compared to that of the internal carotid, pulmonary and thoracic aorta as well as the mesenteric arteries. The P2X7 receptor mRNA expression level is pulmonary artery < caudal artery = thoracic aorta < internal carotid artery < mesenteric artery. P2X4 receptor mRNA expression was not significantly different among these five blood vessels.

Expression of purinergic P2X receptor subtypes 1, 2, 3 and 7 in equine laminitis

Tissue sensitisation and chronic pain have been described in chronic-active laminitis in the horse, making treatment of such cases difficult. Purinergic P2X receptors are linked to chronic pain and inflammation. The aim of this study was to examine the expression of purinergic P2X receptor subtypes 1, 2, 3 and 7 in the hoof, palmar digital vessels and nerve, dorsal root ganglia and spinal cord in horses with chronic-active laminitis (n=5) compared to non-laminitic horses (n=5). Immunohistochemical analysis was performed on tissue sections using antibodies against P2X receptor subtypes 1–3 and 7.In horses with laminitis, there was a reduction in the thickness of the tunica media layer of the palmar digital vein as a proportion of the whole vessel diameter (0.48±0.05) compared to the non-laminitic group (0.57±0.04; P=0.02). P2X receptor subtype 3 was expressed in the smooth muscle layer (tunica media) of the palmar digital artery of horses with laminitis, but was absent in horses without laminitis. There was strong expression of P2X receptor subtype 7 in the proliferating, partially keratinised, epidermal cells of the secondary epidermal lamellae in the hooves of horses with laminitis, but no immunopositivity in horses without laminitis.

Expression of P2X Receptor Subtypes on CD34+ Cells and c-kit+ Cells of Human Umbilical Blood

The presence of several subtypes of P2X receptors on early hemopoietic precursors (CD34+) from human umbilical blood was detected by flow cytometry. The expression of P2X receptors on umbilical blood lymphocytes was an order of magnitude higher than that on adult human blood cells. Our results attest to early involvement of P2X receptors in differentiation of human hemopoietic cells.

Nerve growth factor‐stimulated neuronal differentiation induces changes in P2 receptor expression and nucleotide‐stimulated catecholamine release

Extracellular nucleotides modulate synaptic transmission and neuronal communication by activating purinergic 2 (P2) (nucleotide) receptors. Here, we assessed changes in the regulation by nucleotides and their receptors of an important physiological response - release and uptake of catecholamines - that accompanies sympathoadrenal neuronal differentiation. Nerve growth factor (NGF)-promoted differentiation of pheochromocytoma 12 (PC12) cells enhanced the ability of the non-hydrolyzable ATP analog, ATPgammaS, to stimulate catecholamine (norepinephrine, NE) release and this enhancement occurred without a significant alteration in NE uptake. In addition to ATPgammaS, 2-MeSATP and alphabetaMeATP, P2X receptor-selective agonists, caused greater NE release from NGF-differentiated than from undifferentiated PC12 cells. NGF-differentiated PC12 cells had altered mRNA expression of several P2Y and P2X receptors but protein expression was only increased for P2X, in particular P2X(1-4,) receptors and P2X, but not P2Y, receptor inhibitors blunted the NGF-promoted enhancement in nucleotide-regulated catecholamine release. Surprisingly, siRNA directed against P2X(2), the receptor with the highest expression, failed to alter NE release by ATPgammaS. These findings indicate that sympathetic neuronal differentiation by NGF increases both the expression of P2X receptor sub-types and their regulation of catecholamine release. NGF-promoted increased expression of P2X receptors thus appears to be a physiologically important response that characterizes sympathetic neuronal differentiation.

Alterations in purinergic and cholinergic components of contractile responses of isolated detrusor contraction in a rat model of partial bladder outlet obstruction

To study the effect of 3 weeks of partial bladder outlet obstruction (BOO), compared to a sham operation, on the cholinergic and purinergic components of detrusor contractile responses to agonists and to electrical field stimulation (EFS); the expression of P2X receptor subtypes was also examined. Partial BOO was induced in female Sprague-Dawley rats by surgically applying a jeweller's silver 'jump' ring around the urethra, such that the urethra was constricted but not closed. Sham-operated female rats underwent an identical procedure without placement of a ring. After 3 weeks of partial BOO the rat bladders became significantly hypertrophied, doubling in weight. Spontaneous activity was markedly increased, but the contractile response to a single bolus of KCl (120 mM) was unaltered. The neurogenic-induced contractile responses of strips of detrusor from obstructed bladders were significantly greater than those from sham-operated bladders, and the responses of strips of detrusor from obstructed bladders to EFS showed a significantly greater atropine-sensitive component than sham-operated detrusor. However, the response of detrusor strips to EFS that was susceptible to desensitization by alpha,beta-methylene ATP was not significantly changed in obstructed bladders. The sensitivity of the strips from obstructed bladders to carbachol, ATP and beta,gamma-methylene ATP was less than in sham-operated detrusor. Immunohistochemical studies showed no difference in the P2X receptor subtypes expressed on detrusor smooth muscle from obstructed and sham-operated rats. In the rat, after moderate bladder hypertrophy, the atropine-sensitive component was significantly up-regulated, but the ATP-sensitive component was marginally reduced, although not significantly. These results suggest that up-regulation of the P2X component of bladder contraction seen in humans with bladder instability, and in other species models of BOO, is not mirrored in the rat, or occurs later in the pathological process of bladder hypertrophy.

Expression of P2X receptors on rat microglial cells during early development

We have used single- and double-labeling immunfluorescence and reverse transcription-polymerase chain reaction (RT-PCR) methods to examine expression of P2X receptor subtypes on microglial cells of brain in late embryonic and postnatal rat, in the N9 microglial cell line and primary cultured microglial cells. P2X1, P2X4, and P2X7 receptors were shown on microglial cells from late embryonic day 16. Almost all the microglial cells that were positive for the marker ED1, expressed P2X1 and P2X4 receptors, whereas only about 30% of the cells with ED1-immunoreactivity were found to express the P2X7 receptor. Positive cells were localized mainly in the white matter and around ventricles. From postnatal day 7, many microglial cells with P2X4 receptor-immunoreactivity were seen around the blood vessels. At postnatal day 30, microglial cells with P2X1 receptor-immunoreactivity disappeared and the cells with P2X4 receptor-immunoreactivity were mainly localized around blood vessels and lining the subarachnoid space. From postnatal day 30, the microglial cells with P2X7 receptor-immunoreactivity were found to be distributed widely in the forebrain. Cells with P2X7 receptor-immunoreactivity from P30 were not labeled by ED1, but some were labeled by isolectin B4. The expression of P2X1, P2X4, and P2X7 receptor mRNA and protein on primary cultures of rat microglial cells and on the N9 microglial cell line was demonstrated with immunocytochemistry and RT-PCR. This is the first report that the P2X1 receptor is expressed on microglial cells, at least in early development, before postnatal day 30.

Immunohistochemical identification of cells expressing ATP-gated cation channels (P2X receptors) in the adult rat thyroid.

We carried out immunohistochemistry and western blotting of fresh frozen sections and crude extracts from adult rat thyroids. The histochemical and immunoblotting studies were performed with P2X receptor antibodies from 2 different sources. P2X-immunopositive cells were identified by fluorescence double labelling and confocal microscopy. Results of the western blotting experiments showed double bands of approximately 70 kDa and 140 kDa for all 7 P2X receptor subtypes with both sets of antibodies. Histochemical stains with antibodies from both sources also gave essentially identical results. P2X1, P2X, and P2X6 receptors were detected exclusively in vascular smooth muscle; P2X5 and P2X7 receptors were also present on vascular smooth muscle. Endothelial cells stained for P2X3, P2X4 and P2X7 receptors. Thyroid follicular cells displayed immunoreactivity for P2X3, P2X4 and P2X5 receptors. No immunostaining for P2X receptors was observed on C-cells. Possible roles for the broad expression of P2X receptor subtypes in the rat thyroid are discussed.