Cyclooxygenase enzyme expression and E series prostaglandin receptor signalling are enhanced in heavy menstruation

BACKGROUND

Although the mechanisms underlying the causes of heavy menstrual blood loss (MBL) remain to be elucidated, prostaglandins have been previously implicated. This study was initiated to elucidate a pattern of expression of the various components of the cyclooxygenase (COX)-prostaglandin signalling pathways present in the endometrium of women with normal and heavy MBLs.

METHODS

Endometrial biopsies were collected at different stages of the menstrual cycle from women who underwent measurement of MBL. Tissue was divided for either examination of gene expression by quantitative RT-PCR analysis or in vitro culture experimentation.

RESULTS

Analysis of gene expression demonstrated a significant elevation in expression of COX-1 and COX-2 mRNA in endometrium obtained from women with heavy MBL when compared with endometrium obtained from women with normal MBL. Tissue culture with PGE(2) stimulation caused a significantly elevated production of cyclic AMP (cAMP) by endometrium of women with heavy MBL when compared with normal MBL. Expression of phosphodiesterase 4B, an enzyme involved in cAMP breakdown, was reduced in these same endometrial samples obtained from women with heavy MBL.

CONCLUSIONS

These data identify the E series prostaglandin receptors and their signalling pathways as potential therapeutic targets in the treatment of heavy menstruation.

COX-2 inhibitors and their role in gynecology

This review summarizes current knowledge about the roles of cyclooxygenases and prostaglandins in reproductive medicine. With the development of COX-2 specific inhibitors, new therapeutic options are available to obstetricians and gynecologists, offering better-tolerated alternatives to conventional NSAIDs. The analgesic effectiveness of COX-2 specific inhibitors is well established, and they are already in use in a range of painful conditions. Both celecoxib and valdecoxib are indicated for the treatment of primary dysmenorrhea, and may be effective in postoperative pain, including hysterectomy, and pain associated with endometriosis. There is also speculation that COX-2 specific inhibitors may be effective tocolytic agents without the risks to the fetus seen with conventional NSAIDs. The role of COX-2 in oncogenesis is also under investigation, and COX-2 specific inhibitors may eventually be used in the prevention and treatment of gynecologic malignancies.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians Learning Objectives: After completion of this article, the reader will be able to describe the two types of cylooxygenase enzymes (COX), to list the effects and side effects of NSAIDs and COX-2 medications, and to outline the various changes in COX expression during pregnancy.

Endometrial lysosomal enzyme activity in ovulatory dysfunctional uterine bleeding, IUCD users and post-partum women

The aim of this study was to evaluate the role of lysosomal enzymes in excessively heavy menstruation by comparing women with menorrhagia due to dysfunctional bleeding or intrauterine contraceptive device (IUCD) use with those with normal menstrual periods or with amenorrhoea associated with breastfeeding. This was a prospective cohort investigation of the activity of four endometrial lysosomal enzymes in three contrasting groups: (i) women with ovulatory dysfunctional uterine bleeding and users of intrauterine contraceptive devices; (ii) breastfeeding post-partum women in whom there are long periods of amenorrhoea, particularly in the early months post-partum; and (iii) normal cycling women. It was found that the total activity of lysosomal enzymes, particularly acid phosphatase and N-acetyl-beta-D-glucosaminidase, was markedly elevated (P < 0.001) in IUCD-exposed endometrium, and endometrium from women with dysfunctional uterine bleeding when compared with endometrium from women with a history of entirely normal menstrual periods or that in post-partum breastfeeding women. The activity of alpha-L-fucosidase was moderately elevated in IUCD users (P < 0.05) and ovulatory dysfunctional uterine bleeding (P < 0.05), whereas alphaD-mannosidase activity was elevated in ovulatory dysfunctional uterine bleeding (P < 0.05), but decreased in IUCD users (P < 0.01). No significant differences were observed in the lysosomal enzyme activities of breastfeeding post-partum women and normal cycling women. These results show that total endometrial tissue activity of four lysosomal enzymes was substantially increased throughout the cycle in most circumstances in women with two different causes for increased menstrual bleeding. This suggests a contributory role to the increased bleeding.

Nitric oxide synthase expression and steroid regulation in the uterus of women with menorrhagia

Menorrhagia (excessive menstrual bleeding) is a common clinical problem of unknown aetiology. The free-radical and vasodilator nitric oxide (NO) relaxes the myometrial smooth muscle and is a strong candidate for the cause of excessive blood loss in menorrhagic patients. The aim of this study was to measure NO production in women with and without menorrhagia to detect nitric oxide synthase (NOS) isoforms in uterine cells and to investigate any steroid effects on myometrial NOS expression. We showed for the first time that menorrhagic endometrium produces significantly higher amounts of NOx (the sum of NO(2-) and NO(3-)) than control endometrium (P < 0.01). Inducible NOS (iNOS) protein was detected by immunoblotting in endometrial and myometrial tissue extracts. Quantitative reverse transcription-polymerase chain reaction (RT-PCR) experiments revealed an induction of myometrial smooth muscle endothelial NOS (eNOS) expression by progesterone and 17beta-oestradiol, while myometrial iNOS expression was unaffected by steroid hormones. These results are consistent with the hypothesis that NO plays a role in excessive menstrual bleeding and provide the first evidence on steroid regulation of eNOS in the human non-pregnant uterus.

Theta class glutathione S-transferase GSTT1 genotypes and susceptibility to cervical neoplasia: interactions with GSTM1, CYP2D6 and smoking

The factors that determine progression of cervical intra-epithelial neoplasia (CIN) to squamous cell carcinoma (SCC) are unknown. Cigarette smoking is a risk factor, suggesting polymorphism at loci that encode carcinogen-metabolizing enzymes such as glutathione S-transferase (GSTT1, GSTM1) and cytochrome P450 (CYP2D6) may determine susceptibility to these cancers. We have studied the frequency of the null genotype at the theta class GSTT1 locus in women with low-grade CIN, high-grade CIN and SCC. The control group comprised women with normal cervical pathology suffering menorrhagia. We found the frequency of GSTT1 null in the control and case groups was not significantly different, though frequency distributions of combinations of the genotype with smoking in mutually exclusive groups in the high-grade CIN group and the other case groups were significantly different. Interactive effects of GSTT1 null with the GSTM1 null and CYP2D6 EM genotypes, and cigarette smoking were also studied by comparing the multinomial frequency distributions of these factors over mutually exclusive categories. These showed no significant differences between the controls and SCC or low-grade CIN. Frequency distributions in high-grade CIN, however, were significantly different to the controls, and both SCC and low-grade CIN; frequency distributions of GSTT1 null with smoking and CYP2D6 EM, individually and in combination, were significantly different. However, inspection of our data does not indicate that GSTT1 null is a major factor mediating risk. Thus, comparison of chi 2 values for the differences between frequency distributions in high-grade CIN and other groups shows that values for combinations of GSTT1 null with other factors are lower than those for equivalent combinations with smoking and CYP2D6 EM. Interestingly, the combination GSTT1 null/GSTM1 null did not appear to influence susceptibility to CIN or SCC.

Endometrial fibrinolytic enzymes in women with normal menstruation and dysfunctional uterine bleeding

OBJECTIVE

To study fibrinolysis in the endometrium in women with normal menstruation and dysfunctional uterine bleeding (DUB).

DESIGN

Tissue plasminogen activator activity (t-PA) and antigen (t-PAAg) and plasminogen activator inhibitor Type 1 antigen (PAI-1) were measured in homogenates of endometrium sampled between 24 and 36 h after the onset of menstruation.

SUBJECTS

Women complaining of menorrhagia who had negative findings at clinical examination and curettage had their menstrual blood loss (MBL) measured from the third cycle after D&C. Those with MBL greater than 80 ml per cycle formed the DUB group.

MEASUREMENTS

Fibrinolytic enzyme antigen levels were measured with ELISAs. Tissue plasminogen activator activity was assayed by measuring the rate of conversion of Glu-plasminogen to plasmin, using a chromogenic plasmin substrate.

CONCLUSIONS

There is a strong positive correlation between endometrial t-PA activity on the second day of menstruation and measured menstrual loss (P < 0.05). Concentrations of endometrial t-PAAg and PAI-1 antigen are higher in women with DUB compared with normal women during menstruation.

Phospholipase activity in the endometrium of women with normal menstrual blood loss and women with proven ovulatory menorrhagia

The activity of phospholipase A2 types 1 and 2 and phospholipase C was measured in the endometrium of women with ovulatory menorrhagia and in those with normal menstrual blood loss. In both groups of subjects phospholipase A2 type 1 activity was significantly higher in the secretory phase than in the proliferative phase (P less than 0.001). The median activity (pmol/mg protein/min) for the proliferative phase was 27.6 in normal subjects and 40.4 in women with ovulatory menorrhagia and for the secretory phase the median activity was 144.5 in normal women and 138.1 in women with ovulatory menorrhagia. There was no difference between the two groups of women at either stage of the cycle. Phospholipase A2 type 2 activity was also higher in the secretory phase than in the proliferative phase (P less than 0.05 for normal subjects and P less than 0.001 for women with menorrhagia). The median activity (pmol/mg protein/min) for the proliferative phase was 94.4 (normal subjects) and 56.6 (women with menorrhagia) and for the secretory phase 148.3 (normal subjects) and 142.5 (women with menorrhagia). The activity of phospholipase A2 type 2 was significantly lower in the proliferative phase of women with ovulatory menorrhagia compared with normal subjects (P less than 0.05). Phospholipase C activity (nmol/mg protein/min) was significantly higher in women with ovulatory menorrhagia (median 8.2) compared with women with normal blood loss (median 5.5) (P less than 0.01).

[Various indicators of the kallikrein-kinin system of the blood in patients of reproductive age with dysfunctional uterine hemorrhage]

Fifteen women with dysfunctional uterine hemorrhages [DUH] of the reproductive period and ten women aged 20 to 30 with normal two-phase menstrual cycle were examined. Measurements of the blood plasma kallikrein and prekallikrein activities in normal females have revealed a direct correlation between kallikrein level and colpocytologic data and an inverse correlation between prekallikrein level and these data. An incessant growth of kallikrein content was detected in DUH patients, whereas their prekallikrein levels were much lower than in the controls. A manifest activation of the kallikrein-kinin system was detected in the patients with DUH of the reproductive period, augmenting with the development of the proliferative processes in the endometrium.

The activity of calcium dependent and calcium independent phospholipase A2 in normal endometrium and in endometrium from women suffering from menorrhagia and polycystic ovary syndrome

The activity of 2 phospholipase A2 enzymes, PLA2(i) and PLA2(ii) was measured in endometrium in women with regular menstrual cycles without evidence of pathology and in those complaining of menstrual disturbances. There was a significant 4-fold increase in PLA2(i) activity in secretory phase endometrium (mean +/- SD: 32.7 +/- 9.5 pmol per mg protein/minute) compared to that of the proliferative and menstrual phases (9.5 +/- 4.9 and 6.1 +/- 2.6 pmol per mg protein/minute, respectively) but PLA2(ii) activity was variable and not related to the stage of the cycle (range: 4.0-97.0, 18.7-110.3 and 0.1-85.5 pmol per mg protein/minute for proliferative, secretory and menstrual phases, respectively). There was no significant difference between normal subjects and those with menorrhagia with respect to the mean activities of either isoenzyme at any stage of the cycle. Women with polycystic ovary syndrome (PCO) had markedly higher endometrial PLA2(ii) activity than normal subjects. The evidence of this study suggests that PLA2(ii) is not implicated in unexplained menorrhagia, but our preliminary findings indicate that the high level of PLA2(ii) activity found in the endometrium of women with PCO might be a marker of abnormal endometrial function.

Endometrial prostaglandins and menorrhagia: influence of a prostaglandin synthetase inhibitor in vivo

Prostaglandin levels in the human endometrium were determined on day 2 of the menstrual cycle in eumenorrheic subjects and in patients with menorrhagia, dysmenorrhea, or both. Menorrhagic subjects had significantly higher levels of endometrial prostaglandins of the E and F series when compared with eumenorrheics. Prostaglandin E levels were markedly higher than prostaglandin F. In 10 menorrhagic subjects who completed a double-blind clinical study on the effectiveness of mefenamic acid in lowering menstrual blood loss, 9 exhibited statistically significant reduction in endometrial prostaglandin levels. A decrease in menstrual blood loss was also noted during mefenamic acid treatment in these patients. These findings are consistent with the concept that abnormally high uterine prostaglandin levels may be an important etiologic factor in menorrhagia and support the notion that one of the mechanisms of action of nonsteroidal anti-inflammatory agents in the treatment of this menstrual disorder is inhibition of endometrial prostaglandin production.

Phospholipase C activity in human endometrium: its significance in endometrial pathology

Phospholipase C activity was measured in human endometrium using an assay based on the release of total labelled water soluble products (inositol, inositol phosphates) from L-3-phosphatidyl-[2-3H] inositol. The enzyme was shown to be calcium dependent and to have an optimum pH of 5.5. There was no difference between proliferative phase and secretory phase endometrium with respect to phospholipase C activity either in women with normal menstrual blood loss (proliferative phase: 3.7 +/- 0.7 (mean +/- SD), secretory phase: 4.5 +/- 2.0 nmol/mg protein/min) or in those complaining of severe menorrhagia (proliferative phase: 5.8 +/- 2.8, secretory phase: 7.0 +/- 2.8 nmol/mg protein/min). However, women complaining of severe menorrhagia had significantly higher endometrial phospholipase C activity than those in the normal group (P less than 0.01 and P less than 0.02 for proliferative and secretory phases respectively). Endometrial phospholipase C activity was also elevated in the presence of other gynaecological disorders, e.g. dysmenorrhoea, adenocarcinoma of the cervix and endometrial hyperplasia. The results indicate that phospholipase C activity in human endometrium is not related to the stage of the menstrual cycle but that in the presence of menorrhagia and other gynaecological disorders, activity is increased. Phospholipase C could be implicated in the generation of arachidonic acid for prostaglandin synthesis which may in turn be associated with these abnormalities.

The fibrinolytic enzyme system in normal menstruation and excessive uterine bleeding and the effect of tranexamic acid

The fibrinolytic enzyme system of menstrual and peripheral blood was studied in three groups of women: Group 1, 20 subjects (mean age 37.2 years) with normal menstrual loss; Group 2, 20 patients (mean age 39 years) with dysfunctional uterine bleeding studied before treatment, and Group 3, during treatment with a fibrinolytic inhibitor, tranexamic acid (AMCA) (1 g 8-hourly). The fibrinolytic activity (plasminogen activator and plasmin) of menstrual blood was significantly higher than that of peripheral blood in the three groups (p less than 0.001). Both plasminogen activator and plasmin were higher in the menstrual blood of patients with menorrhagia (Group 2) compared with the control subjects (Group 1) (p less than 0.001 and p less than 0.1 respectively). Treatment with AMCA significantly reduced both plasminogen activator (p less than 0.01) and plasmin (p less than 0.05) in the menstrual blood of patients with menorrhagia (Group 3). No significant differences in fibrinolytic activity were found in peripheral blood between Groups 1 and 2; however, both plasminogen activator and plasmin were significantly lower (p less than 0.01) in Group 3 than in Group 2. Plasmin activity was also significantly lower (p less than 0.05) in Group 3 compared to Group 1. These findings confirm the presence of increased fibrinolytic activity in the uterus in excessive (dysfunctional) bleeding.