Expression And Significance Of Mitochondrial Progesterone Receptor (PR-M) And Porin In Human Uterine Leiomyoma

Uterine leiomyoma is one of the most common gynecological tumor. It is foundin about half of women during childbearing age and is the primary cause ofhysterectomy in this age group. It places a big burden on women’s reproductive health,family and the whole society. Its pathogenesis is not entirely clear. Clinical researchand epidemiological surveys show that progesterone plays an important role inleiomyoma occurrence and development. Progesterone takes part in follicle growth,ovulation, fertilization&implantation and maintenance of pregnancy. The mainpathway for genomic action is diffusion of progesterone, dimerization of heat shockproteins, binding to specific gene promoters and regulation of downstream gene. nPRthat involved in genomic effects contains progesterone receptor B and A. Genomicactions of progesterone are carried out quite slowly ranging from several minutes tofew hours because of the transcription and translation process. However, some quickreactions of progestin such as apoptosis of breast cancer cells, regulation of oocytematuration, protection of the nervous system and regulation of calcium level can beaccomplished in a few seconds and are called nongenomic actions of progesterone.Mitochondrial progesterone receptor (PR-M) is a kind of truncated progesteronereceptor which was cloned from human aortic cells and adipose tissue, cDNA librarycontaining314amino acids, and cDNA of approximately2230bp. PR-M is the onlyone of steroid receptors that is involved in nongenomic actions of progesterone directly and we have confirmed its positioning in the outer mitochondrial membraneusing immortalized and primary cultured uterine myometrium cells as models.Researchers also found that progesterone can induce a dose-dependent increase inmitochondrial membrane potential in uterine smooth muscle cells. This reaction isindependent of the process of protein biosynthesis. This demonstrates thatprogesterone may act through PR-M nongenomic action in the increase of energymetabolism, inhibition of programmed cell death pathways and promotion ofabnormal proliferation in uterine leiomyoma cells. Researchers have already testedPR-M expression in leiomyoma and myometrium tissues in5cases and the resultsshowed that PR-M expressed in leiomyoma is higher than uterus myometrium. Avariety of human normal tissues were detected and the result showed that expressionof PR-M is closely related to mitochondria and is highly expressed in heart andmyometrium.Porin is also known as voltage dependent anion channels and it takes a part inmitochondrial permeablity transition pore. ATP, ADP, pyruvate, purine nucleotidesand many other kinds of metabolites go in and out of mitochondrial membranethrough porin. The abnormality of porin may leads to dysfunction of mitochondria,decrease in total ATP and transmembrane potential, release of cytochrome C, and thebegining of mitochondrial cell death pathways. Both mitochondrial membranepermeability and potential play an important role in the mitochondrial cell deathpathways.ObjectiveReverse transcription polymerase chain reaction (RT-PCR) and Western blottingwere used to examine the mRNA and protein expression of PR-M, porin, PR-B andPR-A in22uterine tissues, and relationship between the expressions of porin and PRswere also analyzed. The study intends to further illuminate the mechanism thatprogestin may take part in the occurance and growth of uterine leiomyoma and toprovide a theoretical basis for leiomyoma etiology. Methods and Materials1Sample Group22cases of hysterectomy tissues in our hospital from December2012toFebruary2013were collected, age between38to50,(45.11±4.28) years old onaverage. Uterine leiomyoma （leiomyoma group， LG） and the correspondingmyometrium tissue（scontrol group，CG）were stored at-80*C once leaving the body.All of the cases met the following requirement:(1) without taking any steroidpreparations or Chinese medicine within six months before surgery;(2) follicularphase endometrium;(3) pathology experts confirmed both leiomyoma andmyometrium tissues;(4) without any other complications;(5) the obtain of sampleswas approved by patients and their families.2MethodsReverse transcription polymerase chain reaction and Western blotting analysiswere used to examine the mRNA and protein expression of PR-M, porin, PR-B andPR-A in22uterine tissues. Relationship between the expressions of porin and PRswere also analyzed.3Statistics analysisSPSS17.0was used for data establishment and analysis. The expression of PRsand porin in leiomyoma and myometrium tissues were expressed byx s. Paired ttest was applied for the comparison between two groups. Pearson correlation analysiswas used for the correlation between porin and PRs, inspection level α=0.05.Results1RT-PCR analysisThe expressions of PR-M, porin, PR-B and PR-A mRNA in uterine leiomyomatissues were (0.351±0.043),(0.748±0.129),(0.594±0.110) and (0.492±0.052)respectively and those of myometrium were (0.117±0.019),(0.378±0.054),(0.405 ±0.049) and (0.353±0.059). The levels of PR-M, porin, PR-B and PR-A mRNA inleiomyoma were higher than those in myometrium tissues (P＜0.05).2Western blotting analysisThe expressions of PR-M, porin, PR-B and PR-A protein in uterine leiomyomatissues were (0.130±0.014),(0.537±0.081),(0.470±0.049) and (0.438±0.052)respectively and those of myometrium were (0.087±0.008),(0.207±0.037),(0.272±0.029) and (0.233±0.032). The levels of PR-M, porin, PR-B and PR-A protein inleiomyoma were higher than those in myometrium tissues (P＜0.05).3Pearson analysisThere was positive correlation between porin and PR-M in leiomyoma tissues（P＜0.05）and no relationship could be established between nPR and porin (P＞0.05).There was also no relation between porin and PRs in myometrium tissues.Conclusions1.The expressions of PR-M, porin, PR-B and PR-A of uterine leiomyoma werehigher than those in the adjacent myometrium and leiomyoma genesis anddevelopment may have a close relationship with the high levels of PR-M, porin,PR-B and PR-A.2.The correlation of PR-M and porin indicates that progesterone may act throughPR-M nongenomic actions in the enhancement of mitochondrial activity, increase ofenergy metabolism, inhibition of mitochondrial cell death pathways and promotion ofabnormal proliferation in uterine leiomyoma.3.Progesterone may act through nongenomic and genomic actions in theoccurence and development of leiomyoma.