Peptidylarginine Deiminase in Rat Pituitary: Sex Difference, Estrous Cycle-Related Changes, and Estrogen Dependence*

Abstract

We have found notable sex difference in peptidylarginine deiminase (EC 3.5.3.15) in rat pituitaries. Pituitaries collected from 3-week to 6-month-old male rats, and those from 3-week-old females showed negligible enzyme activities. The enzyme activity of female pituitaries increased markedly by 2 months, and even further by 6 months of age. Measurements of the enzyme activity around the estrous cycle revealed its characteristic change, being high in the proestrus and estrus, and low in the metestrus and diestrus. These changes of the enzyme activity were shown to reflect changes of the actual amount of a single type of peptidylarginine deiminase by immunoprecipitation and immunoblotting analyses using an antiserum raised to an enzyme sample purified from rat skeletal muscle. The amount of pituitary enzyme was impoverished by ovariectomy. Repeated injections of 17 beta-estradiol to ovariectomized rats substantially restored the pituitary enzyme level. The above data suggest involvement of peptidylarginine deiminase in the female pituitary function.

cDNA nucleotide sequence and primary structure of mouse uterine peptidylarginine deiminase

“…Furthermore, our recent studies have demonstrated that the expression of this enzyme in the uterus is controlled by steroid hormones [ 151. Estrous-cycle-dependent changes of this enzyme in the rat pituitary gland have also been reported by Senshu et al [16], and they showed that such changes were partly under the control of estrogen [16-181. Among the tissues so far tested, only the uterus [lS] and the pituitary gland [16, 181 display changes in the level of this enzyme in response to steroid hormone administration, indicating that the hormonal regulation is not systemic. Thus, peptidylarginine deiminase is of considerable interest for studies on the regulatory mechanisms involved in the tissue-specific expression of genes.…”

Role for Peptidylarginine Deiminase Enzymes in Disease and Female Reproduction

“…Using pituitary lysates, investigators noticed a strong sexual dimorphism with a high level of PAD activity in the female rat pituitary, while little enzymatic activity was seen in the pituitary gland from males. Negligible PAD enzymatic activity was detected in 3-week old female pituitary, but by about 4 months of age, activity increased substantially, suggesting that sexual maturation contributes to PAD expression [58]. In rats, serum estrogen (17β-estradiol) concentration varies during the estrous cycle, gradually increasing during metestrus, peaking at proestrus, followed by a sharp decrease during estrus [59].…”

“…Estrous cycle-staged rats showed a two-fold higher PAD activity level in pituitary lysates during proestrus and estrus than during metestrus and diestrus stages. Thus, the rise in 17β-estradiol serum levels just prior to increased PAD activity levels suggests that the fluctuations of the hormone during the estrous cycle plays an important role in PAD expression in the pituitary [58].…”

“…First, Senshu et al showed that ovariectomy of rats causes a severe drop in pituitary PAD activity; however, this activity could be restored by repeated injections of 17β-estradiol [58,60]. Interestingly, they also found that, in the pituitary, PAD mRNA levels did not directly correlate with enzymatic activity, leading the authors to speculate that PAD mRNA might be regulated at the translational and stability levels [60].…”

Citrullination: the loss of tolerance and development of autoimmunity in rheumatoid arthritis

“…In vitro citrullination is only detectable in the presence of high calcium concentration (11) but in healthy conditions, its concentration range is 10 -8 -10 -6 M, so PADs are inactive (12).This suggests that the citrullination process happens only under 'extreme' conditions, such as during apoptosis or terminal differentiation of the epidermis. PADs are enzymes primarily involved in apoptotic and differentiation events in physiological conditions and recently they have also been involved in other cellular processes, such as gene regulation (13,14).…”