Calcium-activated chloride channels and Na2S-induced relaxation of non-pregnant rat uteri in estrus
2015
Authors:
Mijušković, AnaTatalović, Nikola
Nikolić-Kokić, Aleksandra
Oreščanin Dušić, Zorana
Spasić, Mihajlo
Blagojević, Duško
Contributors
Spasić, MihajloDocument Type:
Conference object (Published version)
,
© 2015 by the Serbian Biochemical Society
Metadata
Show full item recordAbstract:
The uterus is a spontaneously active tissue, whose contractions have to be controlled and
regulated for successful pregnancy and parturition. Spontaneous contractions might be initiated
by spontaneous pacemaker activity, although pacemaker cells are not fully defined. Myometrial
membrane potential changes are essential for uterine activity which is a function of ion movement
across the membrane governed by ion channel activity [1]. Changes in membrane potential are
achieved by coordinated actions of two classes of channels: those that exert hyperpolarizing
current and those that exert depolarizing currents. Calcium-activated chloride channels (CaCCs)
are important contributors to depolarizing currents 1,2. However, the molecular identity of CaCCs
is still not known. Several candidates have been proposed including bestrophins (BEST), CLCA
and the anoctamin (ANO or TMEM) family of proteins 3.
Improper or irregular uterine activity may underlie the common pathological disorders such
as infertility, improper implantation, dysmenorrhea, weak uterine contraction during labor and
preterm labor. The contractile activity of the uterus is regulated by the complex electrophysiologic
network which is highly sensitive to various pharmacological and signaling molecules.
Hydrogen sulphide (H2S) appears to be an important signaling molecule in rat uterus. The
production of H2S and the presence of enzymes responsible for its endogenous production
(cystathionine beta-synthase and cystathionine gamma-lyase) have been demonstrated in rat
uterus 3,4. Hydrogen sulphide reduces uterine contractility, and it is recognized as a promising
treatment for uterine disorders. It decreases amplitude as well as frequency of uterine
contractions. H2S effect on the frequency of contractions appears to be mediated via pacemaker
channels. CaCCs channel inhibitors were shown to reduce the frequency of spontaneous
contractions in myometrial strips and were proposed to be the main pacemaker channels in
smooth muscles 1. Very little, however, is known about these channels in the myometrium.
The mechanism of the H2S -induced relaxation in non-pregnant uteri has not been examined.
Organ bath studies were employed to assess the pharmacological effects of sodium sulphide
(Na2S; hydrogen sulphide donor) in uterine strips by exposing them to Na2S with or without
Cl− channel blockers (DIDS, NFA, T16Ainh-A01, TA). Relaxation was not affected by
majority of CaCC modulators since T16Ainh-AO1, tannic acid and NFA failed to inhibit
Na2S induced relaxation but is DIDS sensitive 3. DIDS was recently found to be highly
selective for bestrophin (BEST-1) channels 5.
BEST proteins were shown to recapitulate the properties of native CaCCs. Although
both bestrophin and calcium-activated chloride channel families were proposed to be the
candidate genes for smooth muscle contraction their exact function and regulation remain
to be confirmed 6.
The aim of this study was to explore the expression of bestrophins channels (BEST-1
and BEST-2) in rat uterus in estrus. Expression studies of the BEST-1 and BEST-2 were
performed by Western blotting, RT-PCR and immunohistochemistry. BEST-1 and BEST-2
are expresses at the mRNA level and at protein level in rat uterus in estrus, suggesting a role
for BESTs in the control of uterine contractility. However, expression of BEST-1 is higher
comparing to BEST-2. Moreover, BEST-1 seems to be major mediators of Na2S induced
uterine relaxation. Mechanistic insights of possible Na2S-induced modulation od BEST-1
were performed by molecular docking studies.
Taken together, work undertaken strengthens the evidence of a physiologically important
role for bestrophin channels in the normal physiology of uterine contractions. Moreover, is
an important modulator of uterine contractions and bestrophins appear to be main modulator
of its effects. This research add to our understanding of molecular mechanisms of H2S effects
and will be beneficial in designing future in vivo studies, and ultimately identifying new
therapeutic targets to treat uterine disorders that are associated with disturbed contractility.
Funding / projects:
- Molecular mechanisms of redox signalling in homeostasis: adaptation and pathology (RS-MESTD-Basic Research (BR or ON)-173014)
In:
- Spasić M, editor. Integrated Research in Life Science. Serbian Biochemical Society Fifth Conference; 2015 Nov 13; Belgrade, Serbia. Belgrade: Faculty of Chemistry; 2015. p. 111-2.