Hypoxia-Mediated Down-Regulation of OCTN2 and PPARα Expression in Human Placentas and in BeWo Cells

The Role of Peroxisome Proliferator-Activated Receptors in Preeclampsia

Preeclampsia is a common pregnancy-related hypertensive disorder. Often presenting as preexisting or new-onset hypertension complicated by proteinuria and/or end-organ dysfunction, preeclampsia significantly correlates with maternal and perinatal morbidity and mortality. Peroxisome proliferator-activated receptors (PPARs) are nuclear receptor proteins that regulate gene expression. In order to investigate the role of PPARs in the pathophysiology of preeclampsia, we conducted a literature review using the MEDLINE and LIVIVO databases. The search terms "peroxisome proliferator-activated receptor", "PPAR", and "preeclampsia" were employed and we were able to identify 35 relevant studies published between 2002 and 2022. Different study groups reached contradictory conclusions in terms of PPAR expression in preeclamptic placentae. Interestingly, PPARγ agonists alone, or in combination with well-established pharmaceutical agents, were determined to represent novel, potent anti-preeclamptic treatment alternatives. In conclusion, PPARs seem to play a significant role in preeclampsia.

Maternal Serum and Placental Metabolomes in Association with Prenatal Phthalate Exposure and Neurodevelopmental Outcomes in the MARBLES Cohort

Prenatal exposure to phthalates, a family of endocrine-disrupting plasticizers, is associated with disruption of maternal metabolism and impaired neurodevelopment. We investigated associations between prenatal phthalate exposure and alterations of both the maternal third trimester serum metabolome and the placental metabolome at birth, and associations of these with child neurodevelopmental outcomes using data and samples from the Markers of Autism Risk in Babies Learning Early Signs (MARBLES) cohort. The third trimester serum (n = 106) and placental (n = 132) metabolomes were investigated using 1H nuclear magnetic resonance spectroscopy. Children were assessed clinically for autism spectrum disorder (ASD) and cognitive development. Although none of the urinary phthalate metabolite concentrations were associated with maternal serum metabolites after adjustment for covariates, mixture analysis using quantile g-computation revealed alterations in placental metabolites with increasing concentrations of phthalate metabolites that included reduced concentrations of 2-hydoxybutyrate, carnitine, O-acetylcarnitine, glucitol, and N-acetylneuraminate. Child neurodevelopmental outcome was not associated with the third trimester serum metabolome, but it was correlated with the placental metabolome in male children only. Maternal phthalate exposure during pregnancy is associated with differences in the placental metabolome at delivery, and the placental metabolome is associated with neurodevelopmental outcomes in males in a cohort with high familial ASD risk.

Predicting Human Fetal Drug Exposure Through Maternal-Fetal PBPK Modeling and In Vitro or Ex Vivo Studies

Medication (drug) use in human pregnancy is prevalent. Determining fetal safety and efficacy of drugs is logistically challenging. However, predicting (not measuring) fetal drug exposure (systemic and tissue) throughout pregnancy is possible through maternal-fetal physiologically based pharmacokinetic (PBPK) modeling and simulation. Such prediction can inform fetal drug safety and efficacy. Fetal drug exposure can be quantified in 2 complementary ways. First, the ratio of the steady-state unbound plasma concentration in the fetal plasma (or area under the plasma concentration-time curve) to the corresponding maternal plasma concentration (ie, Kp,uu ). Second, the maximum unbound peak (Cu,max,ss,f ) and trough (Cu,min,ss,f ) fetal steady-state plasma concentrations. We (and others) have developed a maternal-fetal PBPK model that can successfully predict maternal drug exposure. To predict fetal drug exposure, the model needs to be populated with drug specific parameters, of which transplacental clearances (active and/or passive) and placental/fetal metabolism of the drug are critical. Herein, we describe in vitro studies in cells/tissue fractions or the perfused human placenta that can be used to determine these drug-specific parameters. In addition, we provide examples whereby this approach has successfully predicted systemic fetal exposure to drugs that passively or actively cross the placenta. Apart from maternal-fetal PBPK models, animal studies also have the potential to estimate fetal drug exposure by allometric scaling. Whether such scaling will be successful is yet to be determined. Here, we review the above approaches to predict fetal drug exposure, outline gaps in our knowledge to make such predictions and map out future research directions that could fill these gaps.

Study of serum miR-518 and its correlation with inflammatory factors in patients with gestational diabetes mellitus complicated with hypertensive disorder complicating pregnancy

OBJECTIVE

Gestational diabetes mellitus (GDM) and hypertensive disorder complicating pregnancy (HDCP) are common complications during pregnancy. This study estimated the correlation of serum miR-518 and inflammatory factors in GDM complicated with HDCP patients (GDM&HDCP).

METHODS

Total 240 pregnant women were enrolled, including 118 cases with GDM alone, 57 cases with GDM&HDCP, and 65 healthy pregnant women. The expressions of serum miR-518 and PPARα were detected by RT-qPCR. The clinical diagnostic efficacy of miR-518 for GDM and GDM&HDCP was analyzed via ROC curve. Pearson coefficient was used to analyze the correlation between miR-518 and serum inflammatory factors (hs-CRP, IL-6, and TNF-α), and the relevance between peroxisome proliferator-activated receptor α (PPARα) and serum inflammatory factors. The targeted binding of miR-518 and PPARα was verified using dual-luciferase assay.

RESULTS

Serum miR-518 was highly-expressed in GDM and GDM&HDCP patients, but far higher in GDM&HDCP patients. Serum miR-518 level > 1.815 could assist the diagnosis of GDM (81.53% sensitivity and 100% specificity). Serum miR-518 expression was positively-correlated with serum inflammatory factors. miR-518 targeted PPARα and PPARα was lowly-expressed in the serum of GDM and GDM&HDCP patients. PPARα was negatively-linked with serum inflammatory factors.

CONCLUSION

High expression of miR-518 assists the diagnosis of GDM and GDM&HDCP, and miR-518 regulates the serum inflammatory factors by inhibiting PPARα.

Erythrocyte transglutaminase-2 combats hypoxia and chronic kidney disease by promoting oxygen delivery and carnitine homeostasis

Due to lack of nuclei and de novo protein synthesis, post-translational modification (PTM) is imperative for erythrocytes to regulate oxygen (O₂) delivery and combat tissue hypoxia. Here, we report that erythrocyte transglutminase-2 (eTG2)-mediated PTM is essential to trigger O₂ delivery by promoting bisphosphoglycerate mutase proteostasis and the Rapoport-Luebering glycolytic shunt for adaptation to hypoxia, in healthy humans ascending to high altitude and in two distinct murine models of hypoxia. In a pathological hypoxia model with chronic kidney disease (CKD), eTG2 is critical to combat renal hypoxia-induced reduction of Slc22a5 transcription and OCNT2 protein levels via HIF-1α-PPARα signaling to maintain carnitine homeostasis. Carnitine supplementation is an effective and safe therapeutic approach to counteract hypertension and progression of CKD by enhancing erythrocyte O₂ delivery. Altogether, we reveal eTG2 as an erythrocyte protein stabilizer orchestrating O₂ delivery and tissue adaptive metabolic reprogramming and identify carnitine-based therapy to mitigate hypoxia and CKD progression.

Overview of Drug Transporters in Human Placenta

The transport of drugs across the placenta is a point of great importance in pharmacotherapy during pregnancy. However, the knowledge of drug transport in pregnancy is mostly based on experimental clinical data, and the underlying biological mechanisms are not fully understood. In this review, we summarize the current knowledge of drug transporters in the human placenta. We only refer to human data since the placenta demonstrates great diversity among species. In addition, we describe the experimental models that have been used in human placental transport studies and discuss their availability. A better understanding of placental drug transporters will be beneficial for the health of pregnant women who need drug treatment and their fetuses.

Hypoxia causes sex-specific hepatic toxicity at the transcriptome level in marine medaka (Oryzias melastigma)

Hypoxia, a low environmental oxygen level, is a common problem in the ocean globally. Hypoxia has been known to cause disruption to the endocrine system of marine organisms in both laboratory and field studies. Our previous studies have demonstrated the sex-specific response to hypoxia in the neural and reproductive systems of marine fish. In the current report, we aim to study the sex-specific hepatic response of fish at the transcriptome level to hypoxic stress. By using a comparative transcriptome analysis, followed by a systematic bioinformatics analysis including Database for Annotation, Visualization and Integrated Discovery (DAVID) and Ingenuity Pathway Analysis (IPA), we found that hypoxia altered expression of genes related to cell proliferation and apoptosis of hepatocytes, which are associated with human pathologies, such as liver inflammation hepatic steatosis and steatohepatitis. Furthermore, we observed sex-specific responses in the livers of fish through different cell signaling pathways. In female fish, hypoxia causes dysregulation of expression of genes related to impairment in endoplasmic reticulum structure and liver metabolism. In male fish, genes associated with redox homeostasis and fatty acid metabolism were altered by hypoxic stress. The findings of this study support the notion that hypoxia could cause sex-specific changes (hepatic toxicity and changes) in marine fish.

Contributions of Drug Transporters to Blood-Placental Barrier

The placenta is the only organ linking two different individuals, mother and fetus, termed as blood-placental barrier. The functions of the blood-placental barrier are to regulate material transfer between the maternal and fetal circulation. The main functional units are the chorionic villi within which fetal blood is separated by only three or four cell layers (placental membrane) from maternal blood in the surrounding intervillous space. A series of drug transporters such as P-glycoprotein (P-GP), breast cancer resistance protein (BCRP), multidrug resistance-associated proteins (MRP1, MRP2, MRP3, MRP4, and MRP5), organic anion-transporting polypeptides (OATP4A1, OATP1A2, OATP1B3, and OATP3A1), organic anion transporter 4 (OAT4), organic cation transporter 3 (OCT3), organic cation/carnitine transporters (OCTN1 and OCTN2), multidrug and toxin extrusion 1 (MATE1), and equilibrative nucleoside transporters (ENT1 and ENT2) have been demonstrated on the apical membrane of syncytiotrophoblast, some of which also expressed on the basolateral membrane of syncytiotrophoblast or fetal capillary endothelium. These transporters are involved in transport of most drugs in the placenta, in turn, affecting drug distribution in fetus. Moreover, expressions of these transporters in the placenta often vary along with the gestational ages and are also affected by pathophysiological factor. This chapter will mainly illustrate function and expression of these transporters in placentas, their contribution to drug distribution in fetus, and their clinical significance.

Drug Transporters Expressed in the Human Placenta and Models for Studying Maternal-Fetal Drug Transfer

Tremendous efforts have been directed to investigate the ontogeny of drug transporters in fetuses, neonates, infants, and children based on their importance for understanding drug pharmacokinetics. During development (ie, in the fetus and newborn infant), there is special interest in transporters expressed in the placenta that modulate placental drug transfer. Many of these transporters can decrease or increase drug concentrations in the fetus and at birth, stressing the relevance of elucidating expression in the placenta and potential gestational age-dependent changes therein. Hence, the main objective of this review was to summarize the current knowledge about expression and ontogeny of transporters in the human placenta in healthy pregnant women. In addition, various in vitro, ex vivo, and in silico models that can be used to investigate placental drug transfer, namely, placental cancer cell lines, ex vivo cotyledon perfusion experiments, and physiologically based pharmacokinetic (PBPK) models, are discussed together with their advantages and shortcomings. A particular focus was placed on PBPK models because these models can integrate different types of information, such as expression data, ontogeny information, and observations obtained from the ex vivo cotyledon perfusion experiment. Such a mechanistic modeling framework may leverage the available information and ultimately help to improve knowledge about the adequacy and safety of pharmacotherapy in pregnant women and their fetuses.

High-fat diet intake modulates maternal intestinal adaptations to pregnancy and results in placental hypoxia, as well as altered fetal gut barrier proteins and immune markers

KEY POINTS

Maternal obesity has been associated with shifts in intestinal microbiota, which may contribute to impaired barrier function Impaired barrier function may expose the placenta and fetus to pro-inflammatory mediators We investigated the impacts of diet-induced obesity in mice on maternal and fetal intestinal structure and placental vascularization Diet-induced obesity decreased maternal intestinal short chain fatty acids and their receptors, impaired gut barrier integrity and was associated with fetal intestinal inflammation. Placenta from obese mothers showed blood vessel immaturity, hypoxia, increased transcript levels of inflammation, autophagy and altered levels of endoplasmic reticulum stress markers. These data suggest that maternal intestinal changes probably contribute to adverse placental adaptations and also impart an increased risk of obesity in the offspring via alterations in fetal gut development.

ABSTRACT

Shifts in maternal intestinal microbiota have been implicated in metabolic adaptations to pregnancy. In the present study, we generated cohorts of female C57BL/6J mice fed a control (17% kcal fat, n = 10-14) or a high-fat diet (HFD 60% kcal from fat, n = 10-14; ad libitum) aiming to investigate the impact on the maternal gut microbiota, intestinal inflammation and gut barrier integrity, placental inflammation and fetal intestinal development at embryonic day 18.5. HFD was associated with decreased relative abundances of short-chain fatty acid (SCFA) producing genera during pregnancy. These diet-induced shifts paralleled decreased maternal intestinal mRNA levels of SCFA receptor Gpr41, modestly decreased cecal butyrate, and altered mRNA levels of inflammatory cytokines and immune cell markers in the maternal intestine. Maternal HFD resulted in impaired gut barrier integrity, with corresponding increases in circulating maternal levels of lipopolysaccharide (LPS) and tumour necrosis factor. Placentas from HFD dams demonstrated blood vessel immaturity and hypoxia; decreased free carnitine, acylcarnitine derivatives and trimethylamine-N-oxide; and altered mRNA levels of inflammation, autophagy, and ER stress markers. HFD exposed fetuses had increased activation of nuclear factor-kappa B and inhibition of the unfolded protein response in the developing intestine. Taken together, these data suggest that HFD intake prior to and during pregnancy shifts the composition of the maternal gut microbiota and impairs gut barrier integrity, resulting in increased maternal circulating LPS, which may ultimate contribute to changes in placental vascularization and fetal gut development.

Effect of Acetyl-L-carnitine Used for Protection of Neonatal Hypoxic-Ischemic Brain Injury on Acute Kidney Changes in Male and Female Rats

Neonatal hypoxia-ischemia (HI) is a common cause of brain injury in infants. Acute kidney injury frequently occurs after birth asphyxia and is associated with adverse outcome. Treatment with acetyl-L-carnitine (ALCAR) after HI protects brain and improves outcome. Rat pups underwent carotid ligation and 75 min hypoxia on postnatal day 7 to determine effects of HI on kidney which is understudied in this model. HI + ALCAR pups were treated at 0, 4 and 24 h after HI. The organic cation/carnitine transporter 2 (OCTN2), transports ALCAR and functions to reabsorb carnitine and acylcarnitines from urine. At 24 h after injury OCTN2 levels were significantly decreased in kidney from HI pups, 0.80 ± 0.04 (mean ± SEM, p < 0.01), compared to sham controls 1.03 ± 0.04, and HI + ALCAR pups 1.11 ± 0.06. The effect of HI on the level of pyruvate dehydrogenase (PDH) was determined since kidney has high energy requirements. At 24 h after HI, kidney PDH/β-actin ratios were significantly lower in HI pups, 0.98 ± 0.05 (mean ± SEM, p < 0.05), compared to sham controls 1.16 ± 0.06, and HI + ALCAR pups 1.24 ± 0.03, p < 0.01. Treatment of pups with ALCAR after HI prevented the decrease in renal OCTN2 and PDH levels at 24 h after injury. Protection of PDH and OCTN2 after HI would improve energy metabolism in kidney, maintain tissue carnitine levels and overall carnitine homeostasis which is essential for neonatal health.

The role of various transporters in the placental uptake of ofloxacin in an in vitro model of human villous trophoblasts

Introduction

Six years after the US Food and Drug Administration approval of the broad-spectrum antibiotic ofloxacin (OFLX), the chiral switching of this racemic mixture resulted in a drug composed of the L-optical isomer levofloxacin (LVFX). Since both fluoroquinolones (FQs) were introduced to the pharmaceutical market, they have been widely prescribed by physicians, with careful administration during pregnancy and breastfeeding. Therefore, the role of the influx and efflux placental transporters in the concentrations of these drugs that permeate through human placental barrier model was investigated in this study.

Methods

The contribution of major carriers on the transplacental flux of OFLX and LVFX uptake into choriocarcinoma BeWo cells was evaluated in the presence vs absence of well-known inhibitors.

Results

Our results reveal that neither the influx transporters such as organic cation transporters, organic anion transporters, and monocarboxylate transporters nor the efflux transporters such as P-glycoprotein or breast cancer resistance protein significantly affected the transport of OFLX. In contrast, multiple transporters revealed pronounced involvement in the transfer of the levorotatory enantiomer in and out of the in vitro placental barrier. These data suggest a non-carrier-mediated mechanism of transport of the racemic mixture, while LVFX is subjected to major influx and efflux passage through the placental brush border membranes.

Conclusion

This study provides underlying insights to elucidate the governing factors that influence the flux of these FQs through organ barriers, in view of the controversial safety profile of these drugs in pregnant population.

Characterization of Maternal and Neonatal Pharmacokinetic Behavior of Ceftazidime

Ceftazidime is a parenteral cephalosporin frequently used in pregnant women for treatment of urinary tract or intrauterine infections. Despite its regular use in pregnant women, ceftazidime disposition in both mother and fetus is not well understood, and a pharmacokinetic (PK) model that allows characterization and simulation of both maternal and preterm neonatal ceftazidime disposition is not available. In this study, 10 pregnant women with suspected or proven intrauterine infections in the late second and early third trimester were treated with 1 g of ceftazidime intravenously every 6 hours. During ceftazidime treatment, one maternal and umbilical cord blood sample was taken at delivery to quantify ceftazidime concentrations in the mother and preterm neonate. Data showed that ceftazidime concentrations in the mother were comparable to those observed in the neonate. Based on these data, a PK model was developed to describe maternal disposition, ceftazidime distribution over the placenta, and elimination in the neonate. The maternal substructure of the model was parameterized according to a previously reported ceftazidime model with minor adjustments to account for pregnancy-related effects on renal elimination of ceftazidime. The expanded population PK model with an additional neonatal compartment was fitted to measured drug concentrations in the neonate. The neonatal elimination rate constant at delivery was close to that estimated for the mother. The presented results show that ceftazidime readily crosses the placenta and indicate that perinatal PK behavior of ceftazidime in preterm neonates can be expected to be similar to those observed in their mothers.

Placental control of drug delivery

The placenta serves as the interface between the maternal and fetal circulations and regulates the transfer of oxygen, nutrients, and waste products. When exogenous substances are present in the maternal bloodstream-whether from environmental contact, occupational exposure, medication, or drug abuse-the extent to which this exposure affects the fetus is determined by transport and biotransformation processes in the placental barrier. Advances in drug delivery strategies are expected to improve the treatment of maternal and fetal diseases encountered during pregnancy.

Decreased expression of organic cation transporters, Oct1 and Oct2, in brain microvessels and its implication to MPTP-induced dopaminergic toxicity in aged mice

This study was to investigate the influence of age on the expression of organic cation transporters (OCTs) that belong to the SLC22 family in brain microvessels (BMVs) and its implications for 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced dopaminergic toxicity in mice. Here, we showed that Oct1 and Oct2, but not Oct3, mRNAs were detected and enriched (compared with cerebral cortex) in BMVs of C57BL/6 (B6) mice using reverse transcription-quantitative PCR (RT-qPCR), and immunofluorescence analysis further revealed that Oct1 and Oct2 proteins were colocalized with endothelial markers. Both the mRNA and protein levels of Oct1 and Oct2 were reduced in aged mice. After an intraperitoneal administration of MPTP, brain extracellular levels of MPTP and 1-methyl-4-phenyl-pyridinium (MPP(+)) were much lower in aged mice and in Oct1/2(-/-) mice compared with younger mice and wild-type control mice, respectively. Knockout of Oct1/Oct2 protected Oct1/2(-/-) mice from MPTP-induced neurotoxicity, whereas the loss of tyrosine hydroxylase (TH)-positive neurons was slightly greater in aged than in younger mice. However, intrastriatal infusion of low-dose MPTP caused more severe dopaminergic toxicity in the substantia nigra of both aged mice and Oct1/2(-/-) mice. These findings show that age-dependent downregulation or knockout of Oct1/Oct2 in BMVs may reduce the transport of MPTP, which, in part, affects its dopaminergic toxicity.

Downregulation of duodenal SLC transporters and activation of proinflammatory signaling constitute the early response to high altitude in humans

Solute carrier (SLC) transporters mediate the uptake of biologically active compounds in the intestine. Reduced oxygenation (hypoxia) is an important factor influencing intestinal homeostasis. The aim of this study was to investigate the pathophysiological consequences of hypoxia on the expression and function of SLCs in human intestine. Hypoxia was induced in human intestinal epithelial cells (IECs) in vitro (0.2; 1% O2 or CoCl2). For human in vivo studies, duodenal biopsies and serum samples were obtained from individuals (n = 16) acutely exposed to 4,554 meters above sea levels. Expression of relevant targets was analyzed by quantitative PCR, Western blotting, or immunofluorescence. Serum levels of inflammatory mediators and nucleosides were determined by ELISA and LC/MS-MS, respectively. In the duodenum of volunteers exposed to high altitude we observed decreased mRNA levels of apical sodium-dependent bile acid transporter (ASBT), concentrative nucleoside transporters 1/2 (CNT1/2), organic anion transporting polypeptide 2B1 (OATP2B1), organic cation transporter 2 (OCTN2), peptide transporter 1 (PEPT1), serotonin transporter (SERT), and higher levels of IFN-γ, IL-6, and IL-17A. Serum levels of IL-10, IFN-γ, matrix metalloproteinase-2 (MMP-2), and serotonin were elevated, whereas the levels of uridine decreased upon exposure to hypoxia. Hypoxic IECs showed reduced levels of equilibrative nucleoside transporter 2 (ENT2), OCTN2, and SERT mRNAs in vitro, which was confirmed on the protein level and was accompanied by activation of ERK1/2, increase of hypoxia-inducible factor (HIF) proteins, and production of IL-8 mRNA. Costimulation with IFN-γ and IL-6 during hypoxia further decreased the expression of SERT, ENT2, and CNT2 in vitro. Reduced oxygen supply affects the expression pattern of duodenal SLCs that is accompanied by changes in serum levels of proinflammatory cytokines and biologically active compounds demonstrating that intestinal transport is affected during systemic exposure to hypoxia in humans.

Hypoxia alters ocular drug transporter expression and activity in rat and calf models: implications for drug delivery

Chronic hypoxia, a key stimulus for neovascularization, has been implicated in the pathology of proliferative diabetic retinopathy, retinopathy of prematurity, and wet age related macular degeneration. The aim of the present study was to determine the effect of chronic hypoxia on drug transporter mRNA expression and activity in ocular barriers. Sprague-Dawley rats were exposed to hypobaric hypoxia (PB = 380 mmHg) for 6 weeks, and neonatal calves were maintained under hypobaric hypoxia (PB = 445 mmHg) for 2 weeks. Age matched controls for rats, and calves were maintained at ambient altitude and normoxia. The effect of hypoxia on transporter expression was analyzed by qRT-PCR analysis of transporter mRNA expression in hypoxic and control rat choroid-retina. The effect of hypoxia on the activity of PEPT, OCT, ATB(0+), and MCT transporters was evaluated using in vitro transport studies of model transporter substrates across calf cornea and sclera-choroid-RPE (SCRPE). Quantitative gene expression analysis of 84 transporters in rat choroid-retina showed that 29 transporter genes were up regulated or down regulated by ≥1.5-fold in hypoxia. Nine ATP binding cassette (ABC) families of efflux transporters including MRP3, MRP4, MRP5, MRP6, MRP7, Abca17, Abc2, Abc3, and RGD1562128 were up-regulated. For solute carrier family transporters, 11 transporters including SLC10a1, SLC16a3, SLC22a7, SLC22a8, SLC29a1, SLC29a2, SLC2a1, SLC3a2, SLC5a4, SLC7a11, and SLC7a4 were up regulated, while 4 transporters including SLC22a2, SLC22a9, SLC28a1, and SLC7a9 were down-regulated in hypoxia. Of the three aquaporin (Aqp) water channels, Aqp-9 was down-regulated, and Aqp-1 was up-regulated during hypoxia. Gene expression analysis showed down regulation of OCT-1, OCT-2, and ATB(0+) and up regulation of MCT-3 in hypoxic rat choroid-retina, without any effect on the expression of PEPT-1 and PEPT-2. Functional activity assays of PEPT, OCT, ATB(0+), and MCT transporters in calf ocular tissues showed that PEPT, OCT, and ATB(0+) functional activity was down-regulated, whereas MCT functional activity was up-regulated in hypoxic cornea and SCRPE. Gene expression analysis of these transporters in rat tissues was consistent with the functional transport assays except for PEPT transporters. Chronic hypoxia results in significant alterations in the mRNA expression and functional activity of solute transporters in ocular tissues.

Activation of peroxisome proliferator-activated receptor α (PPARα) suppresses hypoxia-inducible factor-1α (HIF-1α) signaling in cancer cells

Activation of peroxisome proliferator-activated receptor α (PPARα) has been demonstrated to inhibit tumor growth and angiogenesis, yet the mechanisms behind these actions remain to be characterized. In this study, we examined the effects of PPARα activation on the hypoxia-inducible factor-1α (HIF-1α) signaling pathway in human breast (MCF-7) and ovarian (A2780) cancer cells under hypoxia. Incubation of cancer cells under 1% oxygen for 16 h significantly induced HIF-1α expression and activity as assayed by Western blotting and reporter gene analysis. Treatment of the cells with PPARα agonists, but not a PPARγ agonist, prior to hypoxia diminished hypoxia-induced HIF-1α expression and activity, and addition of a PPARα antagonist attenuated the suppression of HIF-1α signaling. Activation of PPARα attenuated hypoxia-induced HA-tagged HIF-1α protein expression without affecting the HA-tagged HIF-1α mutant protein level, indicating that PPARα activation promotes HIF-1α degradation in these cells. This was further confirmed using proteasome inhibitors, which reversed PPARα-mediated suppression of HIF-1α expression under hypoxia. Using the co-immunoprecipitation technique, we found that activation of PPARα enhances the binding of HIF-1α to von Hippel-Lindau tumor suppressor (pVHL), a protein known to mediate HIF-1α degradation through the ubiquitin-proteasome pathway. Following PPARα-mediated suppression of HIF-1α signaling, VEGF secretion from the cancer cells was significantly reduced, and tube formation by endothelial cells was dramatically impaired. Taken together, these findings demonstrate for the first time that activation of PPARα suppresses hypoxia-induced HIF-1α signaling in cancer cells, providing novel insight into the anticancer properties of PPARα agonists.

Effects of SAC on oxidative stress and NO availability in placenta: potential benefits to preeclampsia

Preeclampsia (PE) is a major cause of fetal growth restriction and perinatal mortality, which involves oxidative stress and vasodilator signaling disorder. S-allyl-L-cysteine (SAC) is one of the most abundant compounds in garlic extracts, and possesses several biological activities. This research was designed to investigate the protective effects of SAC against H(2)O(2)-induced oxidative insults, as well as the effects on NO/cGMP signaling pathway in placenta. We used TEV-1 cells and placental explants to detect the effects of SAC. TEV-1 cells and human placental explants were separately exposed to SAC, H(2)O(2), or a combination of H(2)O(2) and SAC. Intracellular ROS was detected by flow cytometry; the NO level was detected by an NO metabolites (NOx) assay; the cGMP level was simultaneously measured by the method of radioimmunoassay; the expression of eNOS in TEV-1 cells was measured by immunochemistry and Western blot. Our findings showed that H(2)O(2) treatment increased ROS productions in TEV-1 cells and significantly decreased cGMP and NO level either in TEV-1 cells or explants compared to the control groups (p < 0.05). The expression of eNOS in TEV-1 cells also significantly decreased in H(2)O(2) treated group compared to the control group (p < 0.05). Co-treatment of H(2)O(2) and SAC significantly decreased ROS productions, and increased NO, cGMP and eNOS level compared to the H(2)O(2) treated alone groups (p < 0.05), which were all reverted back to near control levels. Further more, SAC treatment increased NO and cGMP level of TEV-1 cells and explants in a dose-dependent manner even at non-oxidative stress status (p < 0.05). However, when the TEV-1 cells were cultured in the presence of NOS inhibitor (L-NAME) and NO donor (SNP), additional SAC treatment still significantly increased the NO level in comparison with SAC non-treated group (p < 0.05). In conclusion, these results demonstrate that ROS (H(2)O(2)-mediated) can induce insults to NO/cGMP pathway, while SAC could antagonize this insult. And SAC also possesses the ability to increase NO and cGMP level at non-oxidative stress status in TEV-1 cells and placenta explants. SAC is therefore hypothesized to be a potential drug for PE treatment.