Patrick R. Cammarata

Regulation of Mitochondrial Respiratory Chain Biogenesis by Estrogens/Estrogen Receptors and Physiological, Pathological and Pharmacological Implications

There has been increasing evidence pointing to the mitochondrial respiratory chain (MRC) as a novel and important target for the actions of 17beta-estradiol (E(2)) and estrogen receptors (ER) in a number of cell types and tissues that have high demands for mitochondrial energy metabolism. This novel E(2)-mediated mitochondrial pathway involves the cooperation of both nuclear and mitochondrial ERalpha and ERbeta and their co-activators on the coordinate regulation of both nuclear DNA- and mitochondrial DNA-encoded genes for MRC proteins. In this paper, we have: 1) comprehensively reviewed studies that reveal a novel role of estrogens and ERs in the regulation of MRC biogenesis; 2) discussed their physiological, pathological and pharmacological implications in the control of cell proliferation and apoptosis in relation to estrogen-mediated carcinogenesis, anti-cancer drug resistance in human breast cancer cells, neuroprotection for Alzheimers disease and Parkinsons disease in brain, cardiovascular protection in human heart and their beneficial effects in lens physiology related to cataract in the eye; and 3) pointed out new research directions to address the key questions in this important and newly emerging area. We also suggest a novel conceptual approach that will contribute to innovative regimens for the prevention or treatment of a wide variety of medical complications based on E(2)/ER-mediated MRC biogenesis pathway.

Role of wild-type estrogen receptor-β in mitochondrial cytoprotection of cultured normal male and female human lens epithelial cells

The influence of sexual category as a modifier of cellular function is underinvestigated. Whether sex differences affect estrogen-mediated mitochondrial cytoprotection was determined using cell cultures of normal human lens epithelia (nHLE) from postmortem male and female donors. Experimental indicators assessed included differences in estrogen receptor-beta (ERbeta) isoform expression, receptor localization in mitochondria, and estrogen-mediated prevention of loss of mitochondrial membrane potential using the potentiometric fluorescent compound JC-1 after nHLE were exposed to peroxide. The impact of wild-type ERbeta (wtERbeta1) was also assessed using wtERbeta1 siRNA to suppress expression. A triple-primer PCR assay was employed to determine the proportional distribution of the receptor isoforms (wtERbeta1, -beta2, and -beta5) from the total ERbeta message pool in male and female cell cultures. Irrespective of sex, nHLE express wtERbeta1 and the ERbeta2 and ERbeta5 splice variants in similar ratios. Confocal microscopy and immunofluorescence revealed localization of the wild-type receptor in peripheral mitochondrial arrays and perinuclear mitochondria as well as nuclear staining in both cell populations. The ERbeta2 and ERbeta5 isoforms were distributed primarily in the nucleus and cytosol, respectively; no association with the mitochondria was detected. Both male and female nHLE treated with E(2) (1 muM) displayed similar levels of protection against peroxide-induced oxidative stress. In conjunction with acute oxidative insult, RNA suppression of wtERbeta1 elicited the collapse of mitochondrial membrane potential and markedly diminished the otherwise protective effects of E(2). Thus, whereas the estrogen-mediated prevention of mitochondrial membrane permeability transition is sex independent, the mechanism of estrogen-induced mitochondrial cytoprotection is wtERbeta1 dependent.

RNA suppression of ERK2 leads to collapse of mitochondrial membrane potential with acute oxidative stress in human lens epithelial cells

17beta-Estradiol (E(2)) reduces oxidative stress-induced depolarization of mitochondrial membrane potential (MMP) in cultured human lens epithelial cells (HLE-B3). The mechanism by which the nongenomic effects of E(2) contributed to the protection against mitochondrial membrane depolarization was investigated. Mitochondrial membrane integrity is regulated by phosphorylation of BAD, and it is known that phosphorylation of Ser(112) inactivates BAD and prevents its participation in the mitochondrial death pathway. We found that E(2) rapidly increased both the phosphorylation of ERK2 and Ser(112) in BAD. Ser(112) is phosphorylated by p90 ribosomal S6 kinase (RSK), a Ser/Thr kinase, which is a downstream effector of ERK1/2. Inhibition of RSK by the RSK-specific inhibitor SL0101 did not reduce the level of E(2)-induced phosphorylation of Ser(112). Silencing BAD using small interfering RNA did not alter mitochondrial membrane depolarization elicited by peroxide insult. However, under the same conditions, silencing ERK2 dramatically increased membrane depolarization compared with the control small interfering RNA. Therefore, ERK2, functioning through a BAD-independent mechanism regulates MMP in humans lens epithelial cells. We propose that estrogen-induced activation of ERK2 acts to protect cells from acute oxidative stress. Moreover, despite the fact that ERK2 plays a regulatory role in mitochondrial membrane potential, estrogen was found to block mitochondrial membrane depolarization via an ERK-independent mechanism.

Effect of TNF-α on SMIT mRNA levels andmyo-inositol accumulation in cultured endothelial cells

Previously we have shown that hyperosmolarity increases Na+- myo-inositol cotransporter (SMIT) activity and mRNA levels in cultured endothelial cells. Because hyperosmolarity and cytokines, such as tumor necrosis factor-α (TNF-α), activate similar signal transduction pathways, we examined the effect of TNF-α on SMIT mRNA levels and myo-inositol accumulation. In contrast to the effect of hyperosmolarity, TNF-α caused a time- and concentration-dependent decrease in SMIT mRNA levels and myo-inositol accumulation. The effect of TNF-α on myo-inositol accumulation was found in large-vessel endothelial cells (derived from the aorta and pulmonary artery) and cerebral microvessel endothelial cells. In bovine aorta and bovine pulmonary artery endothelial cells, TNF-α activated nuclear factor (NF)-κB. TNF-α also increased ceramide levels, and C2-ceramide mimicked the effect of TNF-α on SMIT mRNA levels and myo-inositol accumulation in bovine aorta endothelial cells. Pyrrolidinedithiocarbamate, genistein, and 7-amino-1-chloro-3-tosylamido-2-hepatanone, compounds that can inhibit NF-κB activation, partially prevented the TNF-α-induced decrease in myo-inositol accumulation. The effect of TNF-α on myo-inositol accumulation was also partially prevented by the protein kinase C inhibitor calphostin C but not by staurosporine. These studies demonstrate that TNF-α causes a decrease in SMIT mRNA levels and myo-inositol accumulation in cultured endothelial cells, which may be related to the activation of NF-κB.

Sorbinil prevents the hypergalactosemic-induced reduction in [3H]-myo-inositol uptake and decreased [3H]-myo-inositol incorporation into the phosphoinositide cycle in bovine lens epithelial cells in vitro.

The synthesis of phosphatidylinositol, phosphatidylinositol-4-phosphate and phosphatidylinositol-4-5-bisphosphate was studied using 3H-myo-inositol (3H-MI) as precursor in cultured bovine lens epithelial cells (BLECs) maintained in galactose-free, physiological medium or 40 mM galactose (Gal) +/- sorbinil for six days. The formation of inositol polyphosphates from phosphoinositides was also shown. Galactitol did not exceed 2mM in Gal-incubated cells after six days of exposure; no galactitol was observed in BLECs maintained in galactose-free, physiological medium or Gal supplemented with sorbinil. Uptake of 3H-myo-inositol(3H-MI) into BLECs was significantly reduced in cells exposed to Gal. A concomitant reduction in 3H-MI incorporation was observed in the phosphoinositides, as well as with the released inositol phosphates. The simultaneous addition of sorbinil to the Gal medium corrected the drop in 3H-MI uptake and normalized 3H-MI incorporation into the phosphoinositides and inositol phosphates. While an apparent decrease in the three inositol-containing lipids was observed with the Gal-incubated cells, based on 3H-MI incorporation, there was no change in total membrane phosphatidylinositol content when compared to cells maintained in physiological medium as determined by the microgram Pl PO4 per microgram total membrane PO4. The apparent loss of radiolabeled phosphoinositides was attributed to the decreased specific activity resulting from the lower internal pool of 3H-MI in the Gal-exposed cells available for incorporation into the phosphoinositides.(ABSTRACT TRUNCATED AT 250 WORDS)

Lenticular cytoprotection. Part 1: the role of hypoxia inducible factors-1α and -2α and vascular endothelial growth factor in lens epithelial cell survival in hypoxia.

Two new phenolic compounds, epicaesalpin J and 7,10,11-trihydroxydracaenone, were isolated from the heartwood of Caesalpinia sappan L. Their structures were identified by spectroscopic analysis methods, such as 1D and 2D NMR, along with the high resolution mass spectral data. The NO inhibition activities of two new compounds and six known compounds were tested.

Uncoupling of Attenuated myo-[3H]Inositol Uptake and Dysfunction in Na+-K+-ATPase Pumping Activity in Hypergalactosemic Cultured Bovine Lens Epithelial Cells

Attenuation of both the active transport of myo-inositol and Na+-K+-ATPase pumping activity has been implicated in the onset of sugar cataract and other diabetic complications in cell culture and animal models of the disease. Cultured bovine lens epithelial cells (BLECs) maintained in galactose-free Eagles minimal essential medium (MEM) or 40 mM galactose with and without sorbinil for up to 5 days were examined to determine the temporal effects of hypergalactosemia on Na+-K+-ATPase and myo-inositol uptake. The Na+-K+-ATPase pumping activity after 5 days of continuous exposure to galactose did not change, as demonstrated by 86Rb uptake. The uptake of myo-[3H]inositol was lowered after 20 h of incubation in galactose and remained significantly below that of the control throughout the 5-day exposure period. The coadministration of sorbinil to the galactose medium normalized the myo-[3H]inositol uptake. No significant difference in the rates of passive efflux of myo-[3H]inositol or 86Rb from preloaded galactose-treated and control cultures was observed. Culture-media reversal studies were also carried out to determine whether the galactose-induced dysfunction in myo-inositol uptake could be corrected. BLECs were incubated in galactose for 5 days, then changed to galactose-free physiological medium with and without sorbinil for a 1-day recovery period. myo-Inositol uptake was reduced to 34% of control after 6 days of continuous exposure to galactose. Within 24 h of media reversal, myo-inositol uptake returned to or exceeded control values in BLECs switched to either MEM or MEM with sorbinil. These observations support the contention that the aldose reductase reaction or formation of the product of the aldose reductase reaction disrupted lens cell myo-inositol uptake. Although the coadministration of sorbinil to the galactose medium protected against the attendant decrease in transport activity, the cessation of exposure of BLECs to galactose was sufficient stimulus to normalize myo-inositol uptake. Moreover, these observations suggested that the deficit in myoinositol uptake elicited by exposure to galactose was reversible and occurred independently of changes in Na+-K+-ATPase pumping activity in cultured lens epithelium, indicating that the two parameters are not strictly associated and that the deficit in myo-inositol uptake occurs rapidly during hypergalactosemia.

DEPLETION OF GLUTATHIONE BY L-BUTHIONINE SULFOXIMINE DOES NOT PROMOTE INACTIVATION OF MYO-INOSITOL TRANSPORT IN CULTURED BOVINE LENS EPITHELIAL CELLS

Exposure of cultured bovine lens epithelial cells (BLECs) to minimal essential medium (MEM) containing 40 mM galactose (Gal) promotes a decrease in the cellular content of reduced glutathione (GSH) as galactitol increases. Incubation of BLECs with Gal also leads to a reduction in 3H-myo-inositol (3H-MI) concentrating capability. Studies were therefore initiated to determine the nature of the relationship between polyol accumulation, GSH content and the attenuation of the active transport of myo-inositol. The inhibitor of glutathione biosynthesis, L-buthionine sulfoximine (L-BSO) was used in order to lower the intracellular pool of GSH in MEM-maintained cells to a concentration below that characteristically observed in Gal-treated cells, under conditions whereby no galactitol accumulation could or had occurred. L-BSO (0.5 mM) was simultaneously administered to BLECs maintained in either MEM or Gal for up to five days. The cellular content of GSH after five days of continuous incubation was 3.3 micrograms GSH/micrograms PO4 in MEM alone and 0.45 microgram GSH/microgram PO4 in MEM + BSO. Moreover, the GSH content in BLECs exposed to Gal for five days was 1.9 micrograms GSH/micrograms PO4 and was not detectable in the Gal + BSO-treated cells. However, the ability to concentrate 3H-MI in MEM + BSO-treated BLECs was equivalent to that observed with MEM-maintained cells regardless of the significant difference in GSH content. Likewise, L-BSO addition to Gal-treated cells, while virtually depleting the intracellular GSH content, did not further decrease the ability of the cells to accumulate 3H-MI compared to that observed with BLECs in Gal alone. Indeed, supplementation of Gal-treated cells with exogenous GSH failed to correct the Gal-induced attenuation in myo-inositol concentrating ability. These studies demonstrate that the Gal-induced depletion of cellular GSH and the Gal-induced deficit in ability to concentrate myo-inositol are not associated and represent independent events. That is, depletion of lens cell GSH does not lead to the attenuation of myo-inositol uptake in cultured lens epithelial cells.

Protein kinase C activity and its relationship to myo-inositol uptake during hyperglycemic conditions in cultured bovine lens epithelial cells

Incubation of cultured bovine lens epithelial cells (BLECs) in minimal essential medium (MEM) containing 40 mM galactose for 20 hr results in an attenuation of 3H-myo-inositol (3H-MI) concentrating ability. Decreased MI uptake could negatively impact on normal phosphoinositide turnover and diacylglycerol production, and presumably, protein kinase C (PKC) activation. The present report examines the relationship between PKC activity, myo-inositol transport and hyperglycemic conditions. PKC activities in the cytosol and particulate fractions of bovine lens epithelial cells in culture were quantitated using a mixed micelle assay following DEAE-cellulose (DE52) and Sephadex G-25 chromatography. Protein kinase C activity was assessed as Ca2+ and phospholipid-dependent Ac-myelin basic protein substrate peptide phosphorylation and confirmed using a PKC pseudosubstrate inhibitor peptide (PKC 19-36). Total PKC activity was similar in galactose-incubated cells (871 +/- 64 pmol/mg total protein/min) and control cells (881 +/- 8 pmol/mg total protein/min) after 20 hr. In unstimulated cells, approximately 90% of the total cellular PKC activity was recovered in the cytosolic fraction. Enzyme translocation was induced with the tumor promoting phorbol ester, phorbol 12-myristate 13-acetate (PMA), resulting in a 6-fold increase in membrane-associated PKC activity. A similar PMA-induced translocation was observed in BLECs incubated with 40 mM galactose MEM-maintained cells briefly treated with PMA or the non-phorbol PKC activators, SC-10 and mezerein, displayed a rate of 3H-MI uptake similar to the untreated control cells.(ABSTRACT TRUNCATED AT 250 WORDS)