Dopamine stimulates Cl− absorption coupled with HCO3− secretion in rat late distal colon

Freshly isolated rat colonic mucosa close to anus (the late distal colonic mucosa) was used to investigate the effect of dopamine on the rat late distal colonic ion transport by means of short-circuit current (I(SC)) recording and reverse transcription PCR (RT-PCR) analysis. The results showed that the basolateral addition of dopamine (0.1-1000 micromol/l) produced a concentration-dependent downward deflection in I(SC) with an apparent EC(50) of 20.06 micromol/l in the late distal colon. The dopamine-induced I(SC) decrease was abolished by bilateral removal of Cl(-) or HCO(3)(-), apical Cl(-) replacement and apical pretreatment with non-specific Cl(-) channel blocker/transporter inhibitor, DPC (1 mmol/l) or glibenclamide (1 mmol/l), and reversed by subsequent addition of glibenclamide. Removal of basolateral Na(+) or reducing basolateral HCO(3)(-) (3 mmol/l) as well as basolateral pretreatment with DIDS (4,4'-didsothio- cyanostilbene-2, 2'-disulfonic acid) (250 micromol/l), an inhibitor of NBC or AE, could also inhibit the dopamine-induced I(SC) response. However, apical pretreatment with epithelial Na(+) channel blocker, amiloride (10 micromol/l), Ca(2+)-dependent Cl(-) channel blocker/anion exchanger, DIDS (100 micromol/l), or putative K(+) blockers such as Ba(2+) (5 mmol/l), TEA (tetraethylammonium) (5 mmol/l) or 293B (trans-6-cyano-4- (N-ethylsulfonyl-N-methylamino)-3-hydroxy-2,2-dimethyl-chromane) (10 micromol/l) did not significantly affect the dopamine-induced I(SC) response. RT-PCR results showed the expression of anion exchanger, SLC26A3, but not SLC26A6, in rat late distal colon. In conclusion, the present results suggest that dopamine may promote rat late distal colonic epithelial Cl(-) absorption coupled with HCO(3)(-) secretion, which may be mediated by apical electrogenic anion exchanger, SLC26A3, and require basolateral entry of HCO(3)(-) through Na(+)-HCO(3)(-) cotransporter. The present findings reveal a previously unreported dopamine-regulated anion transport process in rat late distal colon, which may have implication in Parkinson's disease.

Cystic fibrosis transmembrane conductance regulator is vital to sperm fertilizing capacity and male fertility

Cystic fibrosis transmembrane conductance regulator (CFTR) is an anion channel, mutations of which cause cystic fibrosis, a disease characterized by defective Cl(-) and HCO(3)(-) transport. Although >95% of all CF male patients are infertile because of congenital bilateral absence of the vas deferens (CBAVD), the question whether CFTR mutations are involved in other forms of male infertility is under intense debates. Here we report that CFTR is detected in both human and mouse sperm. CFTR inhibitor or antibody significantly reduces the sperm capacitation, and the associated HCO(3)(-)-dependent events, including increases in intracellular pH, cAMP production and membrane hyperpolarization. The fertilizing capacity of the sperm obtained from heterozygous CFTR mutant mice is also significantly lower compared with that of the wild-type. These results suggest that CFTR in sperm may be involved in the transport of HCO(3)(-) important for sperm capacitation and that CFTR mutations with impaired CFTR function may lead to reduced sperm fertilizing capacity and male infertility other than CBAVD.

YWK-II protein as a novel Go-coupled receptor for Müllerian inhibiting substance in cell survival

Müllerian inhibiting substance (MIS) has recently been implicated in multiple cellular functions including promotion of cell survival, but the receptor(s) and signaling pathways involved remain elusive. We have investigated the possibility of YWK-II protein, previously shown to interact physically with MIS and Go protein, being a receptor mediating the cell survival effect of MIS. In YWK-II-overexpressing CHO cells, MIS activates the Go-coupled ERK1/2 signaling pathway and promotes cell survival with altered levels of p53 and caspase-3. YWK-II antibody is found to interfere with the ability of MIS to promote viability of mouse sperm and affect MIS-activated ERK1/2 phosphorylation. In vivo studies involving injection of YWK-II antibody into the seminiferous tubule of the mouse testis, where MIS is known to be produced, show significant reduction in the sperm count with accumulation of p53 and cleaved caspase-3 in testicular nuclei. Taken together, the present study has demonstrated a new Go-coupled receptor for MIS in mediating ERK1/2 activation leading to anti-apoptotic activity or cell survival.

Establishment of a mouse primary co-culture of endometrial epithelial cells and peripheral blood leukocytes: Effect on epithelial barrier function and leukocyte survival

This study aimed to establish an in vitro co-culture model that would allow us to study the interaction between endometrial epithelial cells and immune cells. Flow cytometry analysis and cell surface marker staining were used to identify suitable immune leukocytes from a range of sources, such as intraepithelial lymphocytes (IEL), thymocytes, splenocytes and peripheral blood leukocytes. Optimizing culture conditions such as cell viabilities, cell seeding ratios and densities and co-culture methods were examined and determined. Results showed that co-culture of mouse endometrial epithelial cells (EEC) with peripheral blood leukocytes (PBL) at seeding densities of 3.0 x 10(6) and 1.0 x 10(6)cells/ml, respectively, appeared to affect both the survival of leukocytes and epithelial barrier function. Cell viability counts of immune cells showed 95% and 72.5% cell survival after isolation and after 4 days in co-culture with EEC, respectively, but only 11% cell survival when cultured alone for 4 days without EEC. Short-circuit current (I(sc)) results also showed that EEC and PBL co-culture exhibited a four-fold increase in the transepithelial resistance (TER) as compared to EEC culture alone, indicating enhanced protective barrier function. Taken together, the currently established in vitro co-culture model of endometrial epithelial cells and immune cells may provide a means to investigate local cellular immune responses upon uterine infections.

Effect of NYD-SP27 down-regulation on ATP-induced Ca2+-dependent pancreatic duct anion secretion in cystic fibrosis cells

Our previous study demonstrated that NYD-SP27 is a novel inhibitory PLC isoform expressed endogenously in human pancreas and upregulated in CFPAC-1 cells. The present study investigated the effect of NYD-SP27 down-regulation on the ATP-stimulated and Ca(2+)-dependent pancreatic anion secretion by CFPAC-1 cell line using short-circuit current (I(SC)) recording. NYD-SP27 antisense-transfected CFPAC-1 (AT-CF) cells exhibited a significantly higher basal transmembrane potential difference and current than those of empty vector-transfected CFPAC-1 (VT-CF) cells. Cl(-) channel blocker, DPC or Glibenclamide (1mM), and inhibitor of Na(+)-K(+)-Cl(-) cotransporter, bumetanide (100 microM) significantly inhibited the basal current in AT-CF cells. The inhibitor of adenylate cyclase, MDL12330A (20 microM), and Ca(2+)-dependent Cl(-) channel (CaCC) blocker, DIDS (100 microM) also significantly reduced the basal current in AT-CF. Apical application of ATP (10 microM) stimulated a fast transient I(SC) increase in VT-CF cells, but a more sustained rise with slower decline in AT-CF cells. Pretreatment with BAPTA-AM (50 microM) reduced the ATP-induced I(SC) response in AT-CF cells by 77.9%. PMA (1 microM), a PKC activator, inhibited the ATP-stimulated current increase (the transient peak) in VT-CF cells, but had no effect on the AT-CF cells. However, PKC inhibitor, staurosporine (40 microM) could inhibit the ATP-induced I(SC) response in AT-CF cells. The present results confirm the previously proposed inhibitory role of NYD-SP27 in the PLC pathway and demonstrate that the suppression of its expression could result in an enhancement of ATP-stimulated Ca(2+) dependent pancreatic anion secretion.

Differentiation of adult rat bone marrow stem cells into epithelial progenitor cells in culture

We have previously obtained monoclonal bone marrow stem cells from adult rats (rMSCs) and induced them into phenotypic neurons. In the present study, we aimed to induce rMSCs into epithelial cells by culturing them onto compartmentalized permeable supports, which have been used for growing a variety of polarized epithelia in culture. Hematoxylin staining showed that after 4 days grown on permeable supports, rMSCs formed an epithelial-like monolayer. Immunofluorescence of the permeably-supported monolayers, but not the rMSCs grown in culture flasks, showed positive signals for epithelial markers, cytokeratin 5 & 8. RT-PCR results also showed the mRNA expression of epithelial sodium channel (ENaC) and cystic fibrosis transmembrane conductance regulator (CFTR) as well as tight junction protein ZO-1 in the rMSC-derived monolayers grown on permeable supports but absent from those grown in culture flasks. However, western blot only detected protein expression of ZO-1 but not ENaC nor CFTR. The short-circuit current measurements showed that the rMSC-derived monolayers grown on permeable supports exhibited a trans-monolayer resistance of 30-50 Omega cm(2); however, the monolayers did not respond to activators or blockers of CFTR or ENaC. The results suggest that compartmentalized or polarized culture conditions provide a suitable environment for rMSCs to differentiate into epithelial progenitor cells with tight junction formation; however, this condition is not sufficient for functional expression of epithelial ion channels associated with well-differentiated epithelia.

Critical role of CFTR in uterine bicarbonate secretion and the fertilizing capacity of sperm

Cystic fibrosis transmembrane conductance regulator (CFTR) is a cAMP-activated Cl- channel expressed in a wide variety of epithelial cells, mutations of which are responsible for hallmark defective Cl- and HCO3- secretion seen in cystic fibrosis (CF). However, the physiological role of CFTR in reproductive tracts is far from understood although infertility has been observed in CF patients of both sexes. Previously we have demonstrated the expression of CFTR in the female reproductive tract and the involvement of CFTR in mediating anion secretion by the endometrium. Our recent results show that endometrial epithelial cells possess a cAMP-activated HCO3- transport mechanism, which could be impaired with channel blockers known to block CFTR or antisense against CFTR. Co-culture of sperm with CFTR antisense-treated endometrial cells or HCO3- secretion-defective CF epithelial cells resulted in reduced sperm capacitation and egg-fertilizing ability. Addition of HCO3- to the culture media and transfection of wild-type CFTR into CF cells rescued the fertilizing capacity of sperm. Immunostaining and Western blot revealed that CFTR is expressed in rodent sperm and intracellular measurement of pH during sperm capacitation indicated that the entry of HCO3- into sperm could be inhibited by CFTR inhibitor. These results are consistent with a critical role of CFTR in controlling uterine HCO3- secretion and sperm fertilizing capacity, suggesting that CFTR may be a potential target for post-meiotic regulation of fertility.

Effect of sodium ferulate on human colonic anion secretion and the underlying signaling mechanism

The present study investigated the effect of ferulic acid, a compound purified from traditional Chinese herbal medicine Chuanxiong and Awei, on anion secretion by human colonic cells (T84) using the short circuit current (I(SC)) and microspectrofluorimetric technique. Basolateral administration of sodium ferulate (SF) produced a concentration-dependent increase of I(SC) in T84 cells with an EC50 of 1.2 mM. The SF-induced increase in I(SC) contained a transient peak followed by a sustained plateau. Removal of extracellular Cl-, basolateral addition of bumetanide, an inhibitor of the Na+ - K+ - Cl- cotransporter (NKCC) and apical pretreatment with DPC, a Cl- channels blocker, decreased the SF-induced increase in I(SC) by 94% (p < 0.001), 84% (p < 0.001) and 85% (p < 0.001) respectively. Pretreatment with thapsigargin, a specific microsomal Ca2+-ATPase inhibitor, in combination with EGTA, a Ca2+ chelator, decreased the SF-induced peak by 52% (p < 0.01) and inhibited the SF-induced plateau by 60% (p < 0.05). Pretreatment with MDL12330A, an adenylate cyclase inhibitor, blocked the SF-induced I(SC) plateau by 87% (p < 0.01) but did not affect the SF-induced I(SC) peak. Microspectrofluorimetric measurements show that SF induced a sustained increase in [Ca2+]i. The results suggested that SF could induce Cl- secretion in T84 cells via Ca2+ and cAMP-dependent pathways.

Anti-apoptotic activity of Bak Foong Pills and its ingredients on 6-hydroxydopamine-induced neurotoxicity in PC12 cells

Bak Foong Pills (BFP), a traditional Chinese medicine used for centuries for the enhancement of women's health, was shown to display neuro-protective activity in the 1-methyl-4-phenyl-1,2,4,6,-tetrahydro-pyridine (MPTP)-induced mouse model in a previous study. In order to elucidate its mechanism of action, we investigated the anti-apoptotic properties of Bak Foong Pills and its main ingredients, including Panax ginseng, Angelica sinensis, Glycyrrhiza uralensis, and Ligusticum chuanxiong, in the 6-hydroxydopamine (6-OHDA)-treated PC12 cell model. The addition of the neurotoxin could cause significant cell death and reduction of cell proliferation, as shown in the results determined by MTT assay, nitric oxide (NO) measurement and flow cytometric propidium iodine (PI) staining analysis, while pre-treatment of PC12 cell with either BFP or its main ingredients prevented the toxicity to some degree. In addition, the neurotoxin caused an elevated activation of caspase-3, the key enzyme for activation of the cellular apoptotic cascade, whereas BFP or its main ingredients inhibited the activation of caspase-3. These results strongly indicate that BFP and its main ingredients may provide a useful therapeutic strategy for the treatment of neurodegenerative diseases, such as Parkinson's disease.