Interactions of PPAR-alpha and adenosine receptors in hypoxia-induced angiogenesis

The emerging role of PPAR-alpha in breast cancer

Breast cancer has been confirmed to have lipid disorders in the tumour microenvironment. Peroxisome proliferator-activated receptor alpha (PPARα) is a ligand-activated transcriptional factor that belongs to the family of nuclear receptors. PPARα regulates the expression of genes involved in fatty acid homeostasis and is a major regulator of lipid metabolism. Because of its effects on lipid metabolism, an increasing number of studies have investigated the relationship of PPARα with breast cancer. PPARα has been shown to impact the cell cycle and apoptosis in normal cells and tumoral cells through regulating genes of the lipogenic pathway, fatty acid oxidation, fatty acid activation, and uptake of exogenous fatty acids. Besides, PPARα is involved in the regulation of the tumour microenvironment (anti-inflammation and inhibition of angiogenesis) by modulating different signal pathways such as NF-κB and PI3K/AKT/mTOR. Some synthetic PPARα ligands are used in adjuvant therapy for breast cancer. PPARα agonists are reported to reduce the side effects of chemotherapy and endocrine therapy. In addition, PPARα agonists enhance the curative effects of targeted therapy and radiation therapy. Interestingly, with the emerging role of immunotherapy, attention has been focused on the tumour microenvironment. The dual functions of PPARα agonists in immunotherapy need further research. This review aims to consolidate the operations of PPARα in lipid-related and other ways, as well as discuss the current and potential applications of PPARα agonists in tackling breast cancer.

DNMT1-mediated PPARα methylation aggravates damage of retinal tissues in diabetic retinopathy mice

Background

Peroxisome proliferator-activated receptor alpha (PPARα) is associated with diabetic retinopathy (DR), and the underlying mechanism is still unclear. Aim of this work was to investigate the mechanism of PPARα in DR.

Methods

Human retinal capillary pericytes (HRCPs) were treated with high glucose (HG) to induce DR cell model. DR mouse model was established by streptozotocin injection, and then received 5-Aza-2-deoxycytidine (DAC; DNA methyltransferase inhibitor) treatment. Hematoxylin–eosin staining was performed to assess retinal tissue damage. PPARα methylation was examined by Methylation-Specific PCR. Flow cytometry and DCFH-DA fluorescent probe was used to estimate apoptosis and reactive oxygen species (ROS). The interaction between DNA methyltransferase-1 (DNMT1) and PPARα promoter was examined by Chromatin Immunoprecipitation. Quantitative real-time PCR and western blot were performed to assess gene and protein expression.

Results

HG treatment enhanced the methylation levels of PPARα, and repressed PPARα expression in HRCPs. The levels of apoptotic cells and ROS were significantly increased in HRCPs in the presence of HG. Moreover, DNMT1 was highly expressed in HG-treated HRCPs, and DNMT1 interacted with PPARα promoter. PPARα overexpression suppressed apoptosis and ROS levels of HRCPs, which was rescued by DNMT1 up-regulation. In DR mice, DAC treatment inhibited PPARα methylation and reduced damage of retinal tissues.

Conclusion

DNMT1-mediated PPARα methylation promotes apoptosis and ROS levels of HRCPs and aggravates damage of retinal tissues in DR mice. Thus, this study may highlight novel insights into DR pathogenesis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40659-021-00347-1.

BK channel-forming slo1 proteins mediate the brain artery constriction evoked by the neurosteroid pregnenolone

Pregnenolone is a neurosteroid that modulates glial growth and differentiation, neuronal firing, and several brain functions, these effects being attributed to pregnenolone actions on the neurons and glial cells themselves. Despite the vital role of the cerebral circulation for brain function and the fact that pregnenolone is a vasoactive agent, pregnenolone action on brain arteries remain unknown. Here, we obtained in vivo concentration response curves to pregnenolone on middle cerebral artery (MCA) diameter in anesthetized male and female C57BL/6J mice. In both male and female animals, pregnenolone (1 nM-100 μM) constricted MCA in a concentration-dependent manner, its maximal effect reaching ~22-35% decrease in diameter. Pregnenolone action was replicated in intact and de-endothelialized, in vitro pressurized MCA segments with pregnenolone evoking similar constriction in intact and de-endothelialized MCA. Neurosteroid action was abolished by 1 μM paxilline, a selective blocker of Ca2+ - and voltage-gated K+ channels of large conductance (BK). Cell-attached, patch-clamp recordings on freshly isolated smooth muscle cells from mouse MCAs demonstrated that pregnenolone at concentrations that constricted MCAs in vitro and in vivo (10 μM), reduced BK activity (NPo), with an average decrease in NPo reaching 24.2%. The concentration-dependence of pregnenolone constriction of brain arteries and inhibition of BK activity in intact cells were paralleled by data obtained in cell-free, inside-out patches, with maximal inhibition reached at 10 μM pregnenolone. MCA smooth muscle BKs include channel-forming α (slo1 proteins) and regulatory β1 subunits, encoded by KCNMA1 and KCNMB1, respectively. However, pregnenolone-driven decrease in NPo was still evident in MCA myocytes from KCNMB1-/- mice. Following reconstitution of slo1 channels into artificial, binary phospholipid bilayers, 10 μM pregnenolone evoked slo1 NPo inhibition which was similar to that seen in native membranes. Lastly, pregnenolone failed to constrict MCA from KCNMA1-/- mice. In conclusion, pregnenolone constricts MCA independently of neuronal, glial, endothelial and circulating factors, as well as of cell integrity, organelles, complex membrane cytoarchitecture, and the continuous presence of cytosolic signals. Rather, this action involves direct inhibition of SM BK channels, which does not require β1 subunits but is mediated through direct sensing of the neurosteroid by the channel-forming α subunit.

Acute hypoxia changes the mode of glucose and lipid utilization in the liver of the largemouth bass (Micropterus salmoides)

Dissolved oxygen (DO) undountedly affects fish distribution, metabolism, and evern survival. Intensive aquaculture and environmental changes will inevitably lead to hypoxic stress for largemouth bass (Micropterus salmoides). The different metabolic responses and mechanism still remains relatively unknown during acute hypoxia exposure. In this study, largemouth bass were subjected to hypoxic stress (3.0 ± 0.2 mg/L and 1.2 ± 0.2 mg/L) for 24 h and 12 h reoxygenation to systemically evaluate indicators of glucose and lipid metabolism. A regulatory network was constructed using RNA-seq to further elucidate the transcriptional regulation of glucose and lipid metabolism. During hypoxia for 4 h, the liver glycogen, glucose and pyruvic acid contents significantly decreased, whereas plasma glucose content and liver lactic acid content increased significantly. The accumulation of liver triglycerides and non-esterified fatty acids was enhanced during hypoxia for 8 h. The activity of key enzymes revealed the different metabolic responses to hypoxia exposure for 4 h, including the enhancement of glycolysis, and inhibition of gluconeogenesis. Furthermore, hypoxia exposure for 8 h increased lipid mobilization, and inhibited the β-oxidation. In addition, an integrated regulatory network of 9 major pathways involved in the response to hypoxia exposure was constructed, including HIF signaling pathway, VEGF signaling pathway, AMPK signaling pathway, insulin signaling pathway and PPAR signaling pathway; glycolysis/gluconeogenesis, pyruvate metabolism, fatty acid degradation and fatty acid biosynthesis. Additionally, reoxygenation inhibited glycolysis, and promoted gluconeogenesis and lipid oxidation, but energy deficits persisted. In short, although the mobilization and activation of fatty acid in liver were enhanced in the early stage of hypoxia, glycolysis was the main energy source under acute hypoxia. The extent and duration of hypoxia determine the degree of change in energy metabolism.

Fenofibrate Rescues Diabetes-Related Impairment of Ischemia-Mediated Angiogenesis by PPARα-Independent Modulation of Thioredoxin-Interacting Protein

Fenofibrate, a peroxisome proliferator-activated receptor α (PPARα) agonist, reduces lower limb amputations in patients with type 2 diabetes. The mechanism is, however, unknown. In this study, we demonstrate that fenofibrate markedly attenuates diabetes-related impairment of ischemia-mediated angiogenesis. In a murine model of hindlimb ischemia, daily oral fenofibrate treatment restored diabetes-impaired blood flow recovery, foot movement, hindlimb capillary density, vessel diameter, and vascular endothelial growth factor signaling to nondiabetic levels in both wild-type and PPARα-knockout mice, indicating that these fenofibrate effects are largely PPARα independent. In vitro, fenofibric acid (FFA) rescued high glucose-induced (25 mmol/L) impairment of endothelial cell migration, tubulogenesis, and survival in a PPARα-independent manner. Interestingly, fenofibrate in vivo and FFA in vitro reversed high glucose-induced expression of thioredoxin-interacting protein (TXNIP), an exquisitely glucose-inducible gene previously identified as a critical mediator of diabetes-related impairment in neovascularization. Conversely, adenoviral overexpression of TXNIP abrogated the restorative effects of FFA on high glucose-impaired endothelial cell function in vitro, indicating that the effects of FFA are mediated by TXNIP. We conclude that fenofibrate rescues diabetic impairment in ischemia-mediated angiogenesis, in large part, by PPARα-independent regulation of TXNIP. These findings may therefore explain the reduction in amputations seen in patients with diabetes treated with fenofibrate.

Inflammation-coagulation response and thrombotic effects induced by silica nanoparticles in zebrafish embryos

Nowadays, nanotechnology environmental health and safety (nanoEHS) is gaining attention. We previously found that silica nanoparticles (SiNPs) could induce vascular endothelial damage. However, the subsequent toxicologic response to SiNPs-induced endothelial damage was still largely unknown. In this study, we explored the inflammation–coagulation response and thrombotic effects of SiNPs in endothelial cells and zebrafish embryos. For in vitro study, swollen mitochondria and autophagosome were observed in ultrastructural analysis. The cytoskeleton organization was disrupted by SiNPs in vascular endothelial cells. The release of proinflammatory and procoagulant cytokines including IL-6, IL-8, MCP-1, PECAM-1, TF and vWF, were markedly elevated in a dose-dependent manner. For in vivo study, based on the NOAEL for dosimetry selection, and using two transgenic zebrafish, Tg(mpo:GFP) and Tg(fli-1:EGFP), SiNPs-induced neutrophil-mediated inflammation and impaired vascular endothelial cells. With the dosage higher than NOAEL, SiNPs significantly decreased blood flow and velocity, exhibiting a blood hypercoagulable state in zebrafish embryos. The thrombotic effect was assessed by o-dianisidine staining, showed that an increasing of erythrocyte aggregation occurred in SiNPs-treated zebrafish. Microarray analysis was used to screen the possible genes for inflammation–coagulation response to SiNPs in zebrafish, and the JAK1/TF signaling pathway was further verified by qRT-PCR and Western blot assays. For in-deepth study, il6st was knocked down with specific morpholinos. The whole-mount in situ hybridization and qRT-PCR analysis showed that the expression jak1 and f3b were attenuated in il6st knockdown groups. In summary, our data demonstrated that SiNPs could induce inflammation–coagulation response and thrombotic effects via JAK1/TF signaling pathway.

Therapeutic potency of pharmacological adenosine receptor agonist/antagonist in angiogenesis, current status and perspectives

OBJECTIVES

Adenosine concentration significantly increases in tumour microenvironment contributing to tumorigenic processes including cell proliferation, survival, invasion and of special interest in this review angiogenesis.

KEY FINDINGS

This review summarizes the role of pharmacological adenosine receptor agonist and antagonist in regulating angiogenesis for a better understanding and hence a better management of angiogenesis-associated disorders.

SUMMARY

Depending upon the pharmacological characteristics of adenosine receptor subtypes, adenosine elicits anti- or pro-angiogenic responses in stimulated cells. Inhibition of the stimulatory effect of adenosine signalling on angiogenesis using specific pharmacological adenosine receptor agonist, and antagonist is a potentially novel strategy to suppress angiogenesis in tumours.

Silica nanoparticles inhibit macrophage activity and angiogenesis via VEGFR2-mediated MAPK signaling pathway in zebrafish embryos

The safety evaluation of silica nanoparticles (SiNPs) are getting great attention due to its widely-used in food sciences, chemical industry and biomedicine. However, the adverse effect and underlying mechanisms of SiNPs on cardiovascular system, especially on angiogenesis is still unclear. This study was aimed to illuminate the possible mechanisms of SiNPs on angiogenesis in zebrafish transgenic lines, Tg(fli-1:EGFP) and Albino. SiNPs caused the cardiovascular malformations in a dose-dependent manner via intravenous microinjection. The incidences of cardiovascular malformations were observed as: Pericardial edema > Bradycardia > Blood deficiency. The area of subintestinal vessels (SIVs) was significant reduced in SiNPs-treated groups, accompanied with the weaken expression of vascular endothelial cells in zebrafish embryos. Using neutral red staining, the quantitative number of macrophage was declined; whereas macrophage inhibition rate was elevated in a dose-dependent way. Furthermore, SiNPs significantly decreased the mRNA expression of macrophage activity related gene, macrophage migration inhibitory factor (MIF) and the angiogenesis related gene, vascular endothelial growth factor receptor 2 (VEGFR2). The protein levels of p-Erk1/2 and p-p38 MAPK were markedly decreased in zebrafish exposed to SiNPs. Our results implicate that SiNPs inhibited the macrophage activity and angiogenesis via the downregulation of MAPK singaling pathway.

Multi-organ toxicity induced by fine particulate matter PM2.5 in zebrafish (Danio rerio) model

The fine particulate matter (PM_2.5) in air pollution is a major public health concern and now known to contribute to severe diseases, therefore, a comprehensive understanding of PM_2.5-induced adverse effects in living organisms is needed urgently. This study was aimed to evaluate the toxicity of PM_2.5 on multi-organ systems in a zebrafish (Danio rerio) model. The embryonic toxicity induced by PM_2.5 was demonstrated by an increase in mortality and inhibition of hatching rate, in a dose- and time-dependent manner. PM_2.5 caused the pericardial edema, as well as reducing heart rate and cardiac output. The area of sub-intestinal vessels (SIVs) was significant reduced in Tg(fli-1:EGFP) transgenic zebrafish lines. Morphological defects and yolk sac retention were associated with hepatocyte injury. In addition, PM_2.5 disrupted the axonal integrity, altering of axon length and pattern in Tg(NBT:EGFP) transgenic lines. Genes involved in cardiac function (spaw, supt6h, cmlc1), angiogenesis (vegfr2a, vegfr2b), and neural function (gabrd, chrna3, npy8br) were markedly down-regulated; while genes linked to hepatic metabolism (cyp1a, cyp1b1, cyp1c1) were significantly up-regulated by PM_2.5. In summary, our data showed that PM_2.5 induced the cardiovascular toxicity, hepatotoxicity and neurotoxicity in zebrafish, suggested that PM_2.5 could cause multi-organ toxicity in aquatic organism.

Nuclear receptor research in zebrafish

Nuclear receptors (NRs) form a superfamily of transcription factors that can be activated by ligands and are involved in a wide range of physiological processes. NRs are well conserved between vertebrate species. The zebrafish, an increasingly popular animal model system, contains a total of 73 NR genes, and orthologues of almost all human NRs are present. In this review article, an overview is presented of NR research in which the zebrafish has been used as a model. Research is described on the three most studied zebrafish NRs: the estrogen receptors (ERs), retinoic acid receptors (RARs) and peroxisome proliferator-activated receptors (PPARs). The studies on these receptors illustrate the versatility of the zebrafish as a model for ecotoxicological, developmental and biomedical research. Although the use of the zebrafish in NR research is still relatively limited, it is expected that in the next decade the full potential of this animal model will be exploited.

Multifaceted Mechanisms of WY-14643 to Stabilize the Blood-Brain Barrier in a Model of Traumatic Brain Injury

The blood-brain barrier (BBB) is damaged during ischemic insults such as traumatic brain injury or stroke. This contributes to vasogenic edema formation and deteriorate disease outcomes. Enormous efforts are pursued to understand underlying mechanisms of ischemic insults and develop novel therapeutic strategies. In the present study the effects of PPARα agonist WY-14643 were investigated to prevent BBB breakdown and reduce edema formation. WY-14643 inhibited barrier damage in a mouse BBB in vitro model of traumatic brain injury based on oxygen/glucose deprivation in a concentration dependent manner. This was linked to changes of the localization of tight junction proteins. Furthermore, WY-14643 altered phosphorylation of kinases ERK1/2, p38, and SAPK/JNK and was able to inhibit proteosomal activity. Moreover, addition of WY-14643 upregulated PAI-1 leading to decreased t-PA activity. Mouse in vivo experiments showed significantly decreased edema formation in a controlled cortical impact model of traumatic brain injury after WY-14643 application, which was not found in PAI-1 knockout mice. Generally, data suggested that WY-14643 induced cellular responses which were dependent as well as independent from PPARα mediated transcription. In conclusion, novel mechanisms of a PPARα agonist were elucidated to attenuate BBB breakdown during traumatic brain injury in vitro.

Cortical Thickness of Native Tibetans in the Qinghai-Tibetan Plateau

BACKGROUND AND PURPOSE

High-altitude environmental factors and genetic variants together could have exerted their effects on the human brain. The present study was designed to investigate the cerebral morphology in high-altitude native Tibetans.

MATERIALS AND METHODS

T1-weighted brain images were obtained from 77 Tibetan adolescents on the Qinghai-Tibetan Plateau (altitude, 2300-5300 m) and 80 matched Han controls living at sea level. Cortical thickness, curvature, and sulcus were analyzed by using FreeSurfer.

RESULTS

Cortical thickness was significantly decreased in the left posterior cingulate cortex, lingual gyrus, superior parietal cortex, precuneus, and rostral middle frontal cortex and the right medial orbitofrontal cortex, lateral occipital cortex, precuneus, and paracentral lobule. Curvature was significantly decreased in the left superior parietal cortex and right superior marginal gyrus; the depth of the sulcus was significantly increased in the left inferior temporal gyrus and significantly decreased in the right superior marginal gyrus, superior temporal gyrus, and insular cortex. Moreover, cortical thickness was negatively correlated with altitude in the left superior and middle temporal gyri, rostral middle frontal cortex, insular cortex, posterior cingulate cortex, precuneus, lingual gyrus, and the right superior temporal gyrus. Curvature was positively correlated with altitude in the left rostral middle frontal cortex, insular cortex, and middle temporal gyrus. The depth of the sulcus was negatively correlated with altitude in the left lingual gyrus and right medial orbitofrontal cortex.

CONCLUSIONS

Differences in cortical morphometry in native Tibetans may reflect adaptations related to high altitude.

Hypoxia inhibits lymphatic thoracic duct formation in zebrafish

Hypoxia promotes blood vessel growth through up-regulation of pro-angiogenic pathways but its role on the lymphatic system remains unclear. The homeobox transcription factor Prox1 is a master control gene for generating lymphatic endothelial cells (LECs) and is up-regulated by hypoxia-inducible factors in mammals. While vascular endothelial growth factor A (VEGFA) is critical for angiogenesis, VEGFC and its receptor VEGF receptor-3 (VEGFR-3) are essential for the initial sprouting and directed migration as well as for the subsequent survival of LECs. The aim of this study was to determine the effects of hypoxia on the development of the lymphatic system in zebrafish. Zebrafish embryos were obtained from Tg(SAGFF27C; UAS:GFP) animals carrying a lymphatic reporter gene coupled to green fluorescent protein (GFP). Exposure of 1-day old zebrafish embryos to hypoxic conditions (5% O2) for 24 h inhibited thoracic duct formation (-27%, p < 0.0001). Hypoxia inhibited the expression of pro-lymphangiogenic factors prox1a, vegfc and vegfr-3. This inhibition was relieved after re-oxygenation. On the other hand, hypoxia increased the expression of vegfa, a pro-angiogenic factor. In conclusion, hypoxia has opposite effects on vascular development in zebrafish, inhibiting the development of the lymphatic vascular system while promoting the development of the blood vascular system.

Combined toxicity of silica nanoparticles and methylmercury on cardiovascular system in zebrafish (Danio rerio) embryos

This study was to investigate the combined toxicity of silica nanoparticles (SiNPs) and methylmercury (MeHg) on cardiovascular system in zebrafish (Danio rerio) embryos. Ultraviolet absorption analysis showed that the co-exposure system had high absorption and stability. The dosages used in this study were based on the NOAEL level. Zebrafish embryos exposed to the co-exposure of SiNPs and MeHg did not show any cardiovascular malformation or atrioventricular block, but had an inhibition effect on bradycardia. Using o-Dianisidine for erythrocyte staining, the cardiac output of zebrafish embryos was decreased gradually in SiNPs, MeHg, co-exposure groups, respectively. Co-exposure of SiNPs and MeHg enhanced the vascular endothelial damage in Tg(fli-1:EGFP) transgenic zebrafish line. Moreover, the co-exposure significantly activated the oxidative stress and inflammatory response in neutrophils-specific Tg(mpo:GFP) transgenic zebrafish line. This study suggested that the combined toxic effects of SiNPs and MeHg on cardiovascular system had more severe toxicity than the single exposure alone.

Divergent evolution of cis-acting peroxisome proliferator-activated receptor elements that differentially control the tandemly duplicated fatty acid-binding protein genes, fabp1b.1 and fabp1b.2, in zebrafish

Gene duplication is thought to facilitate increasing complexity in the evolution of life. The fate of most duplicated genes is nonfunctionalization: functional decay resulting from the accumulation of mutations. According to the duplication-degeneration-complementation (DDC) model, duplicated genes are retained by subfunctionalization, where the functions of the ancestral gene are sub-divided between duplicate genes, or by neofunctionalization, where one of the duplicates acquires a new function. Here, we report the differential regulation of the zebrafish tandemly duplicated fatty acid-binding protein genes, fabp1b.1 and fabp1b.2, by peroxisome proliferator-activated receptors (PPAR). fabp1b.1 mRNA levels were induced in tissue explants of liver, but not intestine, by PPAR agonists. fabp1b.1 promoter activity was induced to a greater extent by rosiglitazone (PPARγ-selective agonist) compared to WY 14,643 (PPARα-selective agonist) in HEK293A cells. Mutation of a peroxisome proliferator response element (PPRE) at -1232 bp in the fabp1b.1 promoter reduced PPAR-dependent activation. fabp1b.2 promoter activity was not affected by PPAR agonists. Differential regulation of the duplicated fabp1b promoters may be the result of PPRE loss in fabp1b.2 during a meiotic crossing-over event. Retention of PPAR inducibility in fabp1b.1 and not fabp1b.2 suggests unique regulation and function of the fabp1b duplicates.

Transcriptomic signatures of peroxisome proliferator-activated receptor α (PPARα) in different mouse liver models identify novel aspects of its biology

Background

The peroxisome proliferator-activated receptor alpha (PPARα) is a ligand-activated transcription factor that regulates lipid catabolism and inflammation and is hepatocarcinogenic in rodents. It is presumed that the functions of PPARα in liver depend on cross-talk between parenchymal (hepatocytes) and non-parenchymal (Kupffer and endothelial cells) fractions as well as inter-organ interactions. In order to determine how cellular composition and inter-organ interactions influence gene expression upon pharmacological activation of PPARα, we performed a meta-analysis of transcriptomics data obtained from mouse hepatocytes (containing only the parenchymal fraction), mouse liver slices (containing both fractions), and mouse livers exposed to a PPARα agonist. The aim was to obtain a comprehensive view of common and model-specific PPARα-dependent genes and biological processes to understand the impact of cross-talk between parenchymal and non-parenchymal fractions as well as the effect of inter-organ interactions on the hepatic PPARα transcriptome.

To this end we analyzed microarray data of experiments performed in mouse primary hepatocytes treated with the PPARα agonist Wy14643 for 6 or 24 h (in vitro), mouse precision cut liver slices treated with Wy14643 for 24 h (ex vivo), and livers of wild type and Ppara knockout mice treated with Wy14643 for 6 h or 5 days (in vivo).

Results

In all models, activation of PPARα significantly altered processes related to various aspects of lipid metabolism. In ex vivo and in vivo models, PPARα activation significantly regulated processes involved in inflammation; these processes were unaffected in hepatocytes. Only in vivo models showed significant regulation of genes involved in coagulation, carcinogenesis, as well as vesicular trafficking and extracellular matrix.

Conclusions

PPARα-dependent regulation of genes/processes involved in lipid metabolism is mostly independent of the presence of non-parenchymal cells or systemic factors, as it was observed in all liver models. PPARα-dependent regulation of inflammatory genes requires the presence of non-parenchymal cells, as it was observed only ex vivo and in vivo. However, the full spectrum of PPARα biology at the level of lipid metabolism, immunity, carcinogenesis, as well as novel aspects of PPARα signaling such as coagulation, vesicular trafficking and the extracellular matrix, seems to require systemic factors, as it was observed exclusively in vivo.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-1106) contains supplementary material, which is available to authorized users.

Modulation of membrane lipid composition and homeostasis in salmon hepatocytes exposed to hypoxia and perfluorooctane sulfonamide, given singly or in combination

The relative importance of environmental hypoxia due to global climate change on organismal ability to adapt to chemical insult and/or mechanisms of these responses is not well understood. Therefore, we have studied the effects of combined exposure to perfluorooctane sulfonamide (PFOSA) and chemically induced hypoxia on membrane lipid profile and homeostasis. Primary salmon hepatocytes were exposed to PFOSA at 0, 25 and 50 µM singly or in combination with either cobalt chloride (CoCl2: 0 and 150 µM) or deferroxamine (DFO: 0 and 100 µM) for 24 and 48 h. CoCl2 and DFO were used to induce cellular hypoxia because these two chemicals have been commonly used in animal experiments for this purpose and have been shown to increase hypoxia-inducible factor 1-alpha (HIF-1α) and vascular endothelial growth factor (VEGF) levels. Fatty acid (FA) profiles were determined by GC-MS, while gene expression patterns were determined by quantitative PCR. Hypoxic condition was confirmed with time-related increases of HIF-1α mRNA levels in CoCl2 and DFO exposed cells. In general, significant alterations of genes involved in lipid homeostasis were predominantly observed after 48 h exposure. Gene expression analysis showed that biological responses related to peroxisome proliferation (peroxisome proliferator-activated receptors (PPARs) and acyl coenzyme A (ACOX)) and FA desaturation (Δ5- and Δ6-desaturases: FAD5 and FAD6, respectively) and elongation (FAE) were elevated slightly by single exposure (i.e. either PFOSA, CoCl2 or DFO exposure alone), and these responses were potentiated in combined exposure conditions. Principal component analysis (PCA) showed a clustering of peroxisome proliferation responses at transcript levels and FA desaturation against membrane FAs levels whose changes were explained by PFOSA and chemically induced hypoxia exposures. Overall, our data show that most of the observed responses were stronger in combined stressor exposure conditions, compared to individual stressor exposure. In general, our data show that hypoxia may, singly or in combination with PFOSA produce deleterious health, physiological and developmental consequences through the alteration of membrane lipid profile in organisms.

Divergent roles for adiponectin receptor 1 (AdipoR1) and AdipoR2 in mediating revascularization and metabolic dysfunction in vivo

Adiponectin is a well described anti-inflammatory adipokine that is highly abundant in serum. Previous reports have found that adiponectin deficiency promotes cardiovascular and metabolic dysfunction in murine models, whereas its overexpression is protective. Two candidate adiponectin receptors, AdipoR1 and AdipoR2, are uncharacterized with regard to cardiovascular tissue homeostasis, and their in vivo metabolic functions remain controversial. Here we subjected AdipoR1- and AdipoR2-deficient mice to chronic hind limb ischemic surgery. Blood flow recovery in AdipoR1-deficient mice was similar to wild-type; however, revascularization in AdipoR2-deficient mice was severely attenuated. Treatment with adiponectin enhanced the recovery of wild-type mice but failed to rescue the impairment observed in AdipoR2-deficient mice. In view of this divergent receptor function in the hind limb ischemia model, AdipoR1- and AdipoR2-deficient mice were also evaluated in a model of diet-induced obesity. Strikingly, AdipoR1-deficient mice developed severe metabolic dysfunction compared with wild type, whereas AdipoR2-deficient mice were protected from diet-induced weight gain and metabolic perturbations. These data show that AdipoR2, but not AdipoR1, is functionally important in an in vivo model of ischemia-induced revascularization and that its expression is essential for the revascularization actions of adiponectin. These data also show that, in contrast to revascularization responses, AdipoR1, but not AdipoR2 deficiency, leads to diet-induced metabolic dysfunction, revealing that these receptors have highly divergent roles in vascular and metabolic homeostasis.