The association of prostaglandins E2 and F2α with erythropoiesis regulatory factors

Prostaglandins E₂ and F_2α have regulatory roles, respectively, in the potentiation and inhibition of erythropoietin. Antisera to PGF_2α and EIF, an erythropoiesis inhibitory factor, can be used to resolve the reason for improvement in erythropoiesis following renal dialysis. Concurrent loss of PGE₂ with Ep during treatment with neuraminidase suggests that PGE₂ is bound to Ep by way of sialic acid.     

Protein phosphatase-1α interacts with and dephosphorylates polycystin-1

Polycystin signaling is likely to be regulated by phosphorylation. While a number of potential protein kinases and their target phosphorylation sites on polycystin-1 have been identified, the corresponding phosphatases have not been extensively studied. We have now determined that polycystin-1 is a regulatory subunit for protein phosphatase-1α (PP1α). Sequence analysis has revealed the presence of a highly conserved PP1-interaction motif in the cytosolic, C-terminal tail of polycystin-1; and we have shown that transfected PP1α specifically co-immunoprecipitates with a polycystin-1 C-tail construct. To determine whether PP1α dephosphorylates polycystin-1, a PKA-phosphorylated GST-polycystin-1 fusion protein was shown to be dephosphorylated by PP1α but not by PP2B (calcineurin). Mutations within the PP1-binding motif of polycystin-1, including an autosomal dominant polycystic kidney disease (ADPKD)-associated mutation, significantly reduced PP1α-mediated dephosphorylation of polycystin-1. The results suggest that polycystin-1 forms a holoenzyme complex with PP1α via a conserved PP1-binding motif within the polycystin-1 C-tail, and that PKA-phosphorylated polycystin-1 serves as a substrate for the holoenzyme.     

Copper Deficiency Leads to Anemia,Duodenal Hypoxia,Upregulation of HIF-2α and Altered Expression of Iron Absorption Genes in Mice

Iron and copper are essential trace metals, actively absorbed from the proximal gut in a regulated fashion. Depletion of either metal can lead to anemia. In the gut, copper deficiency can affect iron absorption through modulating the activity of hephaestin - a multi-copper oxidase required for optimal iron export from enterocytes. How systemic copper status regulates iron absorption is unknown. Mice were subjected to a nutritional copper deficiency-induced anemia regime from birth and injected with copper sulphate intraperitoneally to correct the anemia. Copper deficiency resulted in anemia, increased duodenal hypoxia and Hypoxia inducible factor 2α (HIF-2α) levels, a regulator of iron absorption. HIF-2α upregulation in copper deficiency appeared to be independent of duodenal iron or copper levels and correlated with the expression of iron transporters (Ferroportin - Fpn, Divalent Metal transporter – Dmt1) and ferric reductase – Dcytb. Alleviation of copper-dependent anemia with intraperitoneal copper injection resulted in down regulation of HIF-2α-regulated iron absorption genes in the gut. Our work identifies HIF-2α as an important regulator of iron transport machinery in copper deficiency.     

Maresin-1 resolution with RORα and LGR6

Maresin-1, a pro-resolving lipid mediator, is drawing a great deal of attention in receptor pharmacology, largely because two distinct types of receptor molecules have been reported as the targets of maresin-1. One is retinoic acid-related orphan receptor α (RORα) and the other is leucine-rich repeat domain-containing G protein-coupled receptor 6 (LGR6). RORα is a nuclear receptor and LGR6 is a plasma membrane GPCR. Identification of two different molecular targets raises the following question: What are the pro-resolving functions of each receptor in inflammation resolution, host defense, tissue homeostasis, and wound healing? In this article, I review the new targets from the point of view of pharmacology and maresin-1 resolution along with intracellular signaling molecules.     

The expression of HIF-1α in primary hepatocellular carcinoma and its correlation with radiotherapy response and clinical outcome

The purpose of this study was to evaluate the relationship between hypoxia-inducible factor-1α (HIF-1α) protein expression in hepatocellular carcinoma (HCC), and responses of abdominal metastatic lymph nodes (LNs) from HCC patients treated with external beam radiotherapy (EBRT). HIF-1α immunohistochemical staining was performed on tissue microarrays (TMAs) of primary HCC specimens from 69 HCC patients with abdominal LN metastases. All patients received abdominal metastatic LN EBRT at the Department of Radiation Oncology at Zhongshan Hospital. A receiver-operating characteristic (ROC)-based approach and logistical regression analysis were used to determine the predictive value of HIF-1α expression in primary tumors with HCC metastatic LN EBRT response. Kaplan–Meier curves and log-rank tests were used to analyze patient survival. Cox proportional hazards regression model was used to analyze independent prognostic factors. HIF-1α expression was correlated with blood hemoglobin (Hb: r = −0.280, P = 0.020), response of abdominal metastatic LNs to EBRT (r = 0.286, P = 0.017), locoregional recurrence (r = 0.278, P = 0.021), and cancer-specific deaths (r = 0.298, P = 0.013). HIF-1α expression was predictive of EBRT response of metastatic LNs [area under the curve (AUC): 0.646; 95% confidence interval (CI): 0.499–0.793; P = 0.047], locoregional recurrence (AUC: 0.657; 95% CI: 0.509–0.805; P = 0.049) and cancer-specific deaths (AUC: 0.671; 95% CI: 0.531–0.812; P = 0.035). Patients with tumors exhibiting high HIF-1α expression had significantly poorer overall survival (OS) than those with low tumor expression of HIF-1α (P = 0.016). Multivariate analysis showed that Hb (P = 0.035), vascular invasion (P = 0.026), Child-Pugh score (P < 0.001), intrahepatic tumor control (P < 0.001), and HIF-1α (P = 0.020) were independent prognosis factors for OS of HCC patients after receiving abdominal metastatic LN EBRT. HIF-1α expression in primary HCCs was associated with EBRT response of abdominal metastatic LNs and poor prognosis.     

Inverse Regulation of the Cytosolic Ca2+ Buffer Parvalbumin and Mitochondrial Volume in Muscle Cells via SIRT1/PGC-1α Axis

Skeletal muscles show a high plasticity to cope with various physiological demands. Different muscle types can be distinguished by the force, endurance, contraction/relaxation kinetics (fast-twitch vs. slow-twitch muscles), oxidative/glycolytic capacity, and also with respect to Ca²⁺-signaling components. Changes in Ca²⁺ signaling and associated Ca²⁺-dependent processes are thought to underlie the high adaptive capacity of muscle fibers. Here we investigated the consequences and the involved mechanisms caused by the ectopic expression of the Ca²⁺-binding protein parvalbumin (PV) in C2C12 myotubes in vitro, and conversely, the effects caused by its absence in in fast-twitch muscles of parvalbumin null-mutant (PV−/−) mice in vivo. The absence of PV in fast-twitch muscle tibialis anterior (TA) resulted in an increase in the peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) and of its positive regulator, the deacetylase sirtuin 1 (SIRT1). TA muscles from PV−/− mice also have an increased mitochondrial volume. Mild ionophore treatment of control (PV-devoid) C2C12 myotubes causing a moderate elevation in [Ca²⁺]_c resulted in an increase in mitochondrial volume, together with elevated PGC-1α and SIRT1 expression levels, whilst it increased PV expression levels in myotubes stably transfected with PV. In PV-expressing myotubes the mitochondrial volume, PGC-1α and SIRT1 were significantly lower than in control C2C12 myotubes already at basal conditions and application of ionophore had no effect on either one. SIRT1 activation causes a down-regulation of PV in transfected myotubes, whilst SIRT1 inhibition has the opposite effect. We conclude that PV expression and mitochondrial volume in muscle cells are inversely regulated via a SIRT1/PGC-1α signaling axis.     

MMP-2, TNF-α and NLRP1 polymorphisms in Chinese patients with ankylosing spondylitis and rheumatoid arthritis

Rheumatoid arthritis (RA) and ankylosing spondylitis (AS) are autoimmune, inflammatory diseases with substantial genetic contributions. Matrix metalloproteinase (MMP)-2, tumor necrosis factor (TNF)-α and NLR family pyrin domain-containing 1 (NLRP1) play important roles in the immune response. We studied the MMP-2 rs243865 C/T, TNF-α rs1800629 A/G, NLRP1 rs878329 C/G and NLRP1 rs6502867 C/T polymorphisms in a Chinese cohort of 520 patients with RA, 100 with AS and 520 controls. Genotyping was performed using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Using the MMP-2 rs243865 CC homozygote genotype as the reference group, the CT and TT/CT genotypes were associated with significantly reduced risks of AS. However, logistic regression analyses revealed that the MMP-2 rs243865 C/T polymorphism was not associated with risk of RA. TNF-α rs1800629 A/G, NLRP1 rs878329 C/G and NLRP1 rs6502867 C/T polymorphisms were not associated with risk of RA or AS. These findings suggest that the MMP-2 rs243865 C/T polymorphism is associated with AS development.     

Differential roles of Sirt1 in HIF-1α and HIF-2α mediated hypoxic responses

Hypoxia-inducible factors 1α and 2α (HIF-1α and HIF-2α) determine cancer cell fate under hypoxia. Despite the similarities of their structures, HIF-1α and HIF-2α have distinct roles in cancer growth under hypoxia, that is, HIF-1α induces growth arrest whereas HIF-2α promotes cell growth. Recently, sirtuin 1 (Sirt1) was reported to fine-tune cellular responses to hypoxia by deacetylating HIF-1α and HIF-2α. Yet, the roles of Sirt1 in HIF-1α and HIF-2α functions have been controversial. We here investigated the precise roles of Sirt1 in HIF-1α and HIF-2α regulations. Immunological analyses revealed that HIF-1α K674 and HIF-2α K741 are acetylated by PCAF and CBP, respectively, but are deacetylated commonly by Sirt1. In the Gal4 reporter systems, Sirt1 was found to repress HIF-1α activity constantly in ten cancer cell-lines but to regulate HIF-2α activity cell type-dependently. Moreover, Sirt1 determined cell growth under hypoxia depending on HIF-1α and HIF-2α. Under hypoxia, Sirt1 promoted cell proliferation of HepG2, in which Sirt1 differentially regulates HIF-1α and HIF-2α. In contrast, such an effect of Sirt1 was not shown in HCT116, in which Sirt1 inactivates both HIF-1α and HIF-2α because conflicting actions of HIF-1α and HIF-2α on cell growth may be offset. Our results provide a better understanding of the roles of Sirt1 in HIF-mediated hypoxic responses and also a basic concept for developing anticancer strategy targeting Sirt1.     

Excretion of 6-keto-PGF1α and PGE2 in rats with hereditary hypothalamic diabetes insipidus

We measured the urinary excretion of a stable metabolite of prostacyclin, 6-keto-PGF_1α, and of PGE₂ in homozygous Brattleboro rats, a strain with hereditary hypothalamic diabetes insipidus. Excretion of both prostaglandins was largely increased compared to both heterozygous Brattleboro rats and Long-Evans rats. These results are in contrast to previously published observations demonstrating a subnormal excretion of PGE₂ in Brattleboro rats. It is suggested that prostaglandin synthesis may be under tonic inhibitory control by vasopressin both in the kidney and in the endothelial cells of blood vessels. The findings further support the view that prostaglandins play an important role in the regulation of water excretion and in the pathogenesis of polyuric conditions.     

The concentrations of urinary prostaglandins E and plasma prostaglandins F2α and E during induction of ovulation with human gonadotropins

Plasma prostaglandins F₂α and E (PGF₂α, PGE) and urinary PGE were measured in 10 women treated with human gonadotropins (HMG) and subsequently with human chorionic gonadotropins (HCG). Five women became pregnant (6 pregnancies). There was no correlation between concentrations of plasma PGF₂α or PGE and plasma estradiol or progesterone. Urinary PGE concentrations showed a positive correlation with estradiol before HCG and a negative correlation with progesterone after HCG, only in women who subsequently became pregnant.Higher urinary PGE concentrations before HCG suggest that either HMG or rising estradiol levels stimulate PGE renal production. The significant negative correlation.between urinary PGE and progesterone concentrations, after HCG, in those patients who became pregnant suggests that ovarian production of progesterone may decrease renal production of PGE.