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Characterization of EDG receptor expression and proliferative response in cultured human BPH smooth muscle cells
Linköping University, Department of Medicine and Care, Pharmacology. Linköping University, Faculty of Health Sciences.
Linköping University, Department of Biomedicine and Surgery, Urology. Linköping University, Faculty of Health Sciences.
Linköping University, Department of Biomedicine and Surgery, Urology. Linköping University, Faculty of Health Sciences.
Linköping University, Department of Medicine and Care, Pharmacology. Linköping University, Faculty of Health Sciences.
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

The endogenous phospholipids, lysophosphatidic acid (LPA) and sphingosine 1-phosphate (S1P) are both known to generate a Vvide variety of effects in various cell systems by the endothelial differentiation gene (Edg) receptor family, including 7 different G-protein coupled Edg receptors.

In this study, expression of LPA- and SlP Edg receptors was examined, and so was the effect with respect to proliferation on cultured BPH smooth muscle cells smc. Mmeover, theresponse on cAMP levels was examined. Finally, a potential link between activation of the MAP kinase cascade and the LPA stimulated proliferation was investigated.

First, the RT-PCR analysis of the Edg receptors in BPH smc, demonstrated a heterogeneous expression including all receptors except the Edg6 subtype. Further, in contrast to LPA, the mitogen effect of SIP, demonstrated a concentration-dependent biphasic response, including stimulation below 1μM, whereas inhibition was obtained at higher concentrations. Forskolin induced a rapid and transient cAMP response in LPA stimulated cells, with a peak-value after 3 minutes. After 15 minutes the cAMP level had retmned to base-line level. However a gradual increase to 15% of maximum value was obtained after additional 30 minutes, and thereafter a gradual reduction was observed. The mentioned antiproliferative response generated by SIP could not be conelated to an intracellular cAMP increase. Finally, when the LPA treated smc was co-incubated with the MAPK kinase inhibitor PD98059 (10 μM) the mitogen response was eliminated.

The cAIVIP increase, which was induced by forskolin, corresponds with mentioned antiproliferative effect whereas a similar con-elation was not obtained regarding SIP. The intracellular signal mechanisms triggered by LPA and S1P in BPH smc remain to be further investigated.

National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-80084OAI: oai:DiVA.org:liu-80084DiVA: diva2:545471
Available from: 2012-08-20 Created: 2012-08-20 Last updated: 2012-08-20Bibliographically approved
In thesis
1. Regulatory importance of cyclic nucleotides in smooth muscle growth of the urogenital tract
Open this publication in new window or tab >>Regulatory importance of cyclic nucleotides in smooth muscle growth of the urogenital tract
2001 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Smooth muscle hyperplasia/hypertrophy is, if not responsible for, so at least involved in those diseases, which impair life quality for most people in today's society.

This thesis, presents a pharmacological investigation, related to the regulatory role of cyclic nucleotides, of smooth muscle hyperplasia/hypeitrophy in human uterine leiomyoma and benign prostate hyperplasia (BPH).

Four main aspects, with cAMP as a connecting thought, have been analyzed, namely expression and characterization of the adrenergic receptors (AR), determination of adenylyl cyclase (AC)- and phosphodiesterase (PDE)-activity, and finally the connection between mentioned issues and proliferation of cultured smooth muscle cells (smc).

In the frrst paper, characterization of the a 2-adrenergic receptor (az-AR) subtypes in human myometrium at term pregnancy was examined by combining radioligand binding-studies with reverse transcriptase-polymerase chain reaction (RT-PCR). Results demonstrated a significant eo-expression of α2A and α2B, and a weak indication of the α2C-AR, which however was identified at the mRNA level by the RT-PCR analysis.

In the next investigatio~ smooth muscle tissue of human uterine leiomyoma (benign smooth muscle tumor) was compared with surrounding myometrial tissue (control). The expression of AR, AC- and PDE-activity was analyzed, as well as the effect of cAMP with respect to growth regulation of cultured leiomyoma smc. Primarily, a significantly reduced ß2-AR expression and AC-activity was detected in leiomyoma compared to control tissue, whereas the PDE-activity was approximately 100% higher. In addition, the α2-AR population in leiomyoma was slightly increased. When cultured leiomyoma smc was treated with cAMP increasing agents as forskolin, an AC stimulating agent, or papaverin, a general PDE inhibitor, a considerable inhibition of DNA replication and protein synthesis was obtained.

In the thh·d paper, a proliferation study was made on cultured benign prostate hyperplasia smc, were the mitogen effect of lysophosphatidic acid (LPA) and cAMP/cGMP increasing agents was investigated. LPA generated a dose-dependent mitogen response, which was efficiently inhibited, both by forskolin, and by papaverin. In addition, sildenafil (Viagra®), which serve as a potent and selective PDE5 inhibitor, also decreased the LPA mediated growth promotion in a dose dependent manner.

The last study, demonstrate primarily the expression pattem of LPA receptors (Edg) in BPH smc. Further, the intracellular cAMP changes in LPA stimulated BPH smc and the proliferative effect of the LPA analogue sphingosine 1-phosphate (SIP) was considered. First, all Edg was identified with exception of Edg6. Moreover, the cAMP level was unchanged by LPA per se, whereas co-incubation with forskolin generated a rapid and transient response. Further, SIP generated a divergent response including a LPA equivalent mitogen effect at low concentrations whereas inhibition of DNA replication was obtained at higher concentrations.

In summary, this project demonstrates that cyclic nucleotides inhibit smooth muscle hyperplasia/hypertrophy in the luogenital tract. These results also suggest that manipulation of cyclic nucleotide level using tissue specific PDE inhibitors might constitute a new therapeutic approach for hyperplasia/hypertrophy related diseases in the urogenital tract.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2001. 45 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 694
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-27452 (URN)12105 (Local ID)91-7373-136-6 (ISBN)12105 (Archive number)12105 (OAI)
Public defence
2001-11-02, Berzeliussalen, Universitetssjukhuset, Linköping, 13:00 (Swedish)
Opponent
Available from: 2009-10-08 Created: 2009-10-08 Last updated: 2012-10-22Bibliographically approved

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