TypeⅠinositol 1, 4, 5-triphosphate receptors increase in kidney of mice with fulminant hepatic failure

AIM： To delineate the mechanisms of renal vasoconstriction in hepatorenal syndrome （HRS）, we investigated the expression of type I inositol 1, 4, 5-triphosphate receptors （IP3R I） of kidney in mice with fulminant hepatic failure （FHF）. METHODS： FHF was induced by lipopolysaccharide （LPS） in D-galactosamine （GAIN） sensitized BALB/c mice. There were 20 mice in normal saline （NS）-treated group, 20 mice in LPS-treated group, 20 mice in GaIN- treated group, and 60 mice in GalN/LPS-treated group （FHF group）. Liver and kidney tissues were obtained at 2, 6, and 9 h after administration. The liver and kidney specimens were stained with hematoxylin-eosin for studying morphological changes under light microscope. The expression of IP3R I in kidney tissue was tested by immunohistochemistry, Western blot and reverse transcription （RT）-PCR. RESULTS： Kidney tissues were morphologically normal at all time points in all groups. IP3R I proteins were found localized in the plasma region of glomerular mesangial cells （GMC） and vascular smooth muscle cells （VSMC） in kidney by immunohistochemical staining. In kidney of mice with FHF at 6 h and 9 h IP3R I staining was upregulated. Results from Western blot demonstrated consistent and significant increment of IP3R I expression in mice with FHF at 6 h and 9 h （t = 3.16, P 〈 0.05; t = 5.43, P 〈 0.01）. Furthermore, we evaluated IP3R I mRNA expression by RT-PCR and observed marked upregulation of IP3R I mRNA in FHF samples at 2 h, 6 h and 9 h compared to controls （t = 2.97, P 〈 0.05; t = 4.42, P 〈 0.01; t = 3.81, P 〈 0.01）. CONCLUSION： The expression of IP3R I protein increased in GMC and renal VSMC of mice with FHF, possibly caused by up-regulation of IP3R I mRNA.

RNAi-Mediated Silencing of ITPK Gene Reduces Phytic Acid Content,Alters Transcripts of Phytic Acid Biosynthetic Genes,and Modulates Mineral Distribution in Rice Seeds

Phytic acid is the principal storage form of phosphorus in plant seeds and an essential signalling molecule in several regulatory processes of plant development.However,it is known as an anti-nutrient compound owing to its potent chelating property.Thus,reducing the phytic acid content in crops is desirable.Studies involving regulation of MIPS and IPK1 genes to generate low phytate rice have been reported earlier.However,the functional significance of OsITPK and the effect of its down-regulation on phytic acid content and the associated pleiotropic effects on rice have not yet been investigated.In this study,tissue specific RNA interference(RNAi)-mediated down-regulation of a major ITPK homolog(OsITP5/6K-1)resulted in 46.2%decrease in phytic acid content of T2 transgenic seeds with a subsequent 3-fold enhancement in the inorganic phosphorus content.Silencing of OsITP5/6K-1 altered the transcript levels of essential phytic acid pathway genes,without significantly affecting the transcript levels of other OsITPK homologs.Furthermore,the mapping of elements through X-ray microfluorescence analysis revealed significant changes in the spatial distribution pattern and translocation of elements in low phytate seeds.Additionally,low phytate polished seeds exhibited 1.3-fold and 1.6-fold enhancement in iron and zinc content in the grain endosperm,respectively.Silencing of OsITP5/6K-1 also altered the amino acid and myo-inositol content of the transgenic seeds.Our results successfully established that RNAi-mediated silencing of OsITP5/6K-1 gene significantly reduced the phytate levels in seeds without hampering the germination potential of seeds and plant growth.The present study provided an insight into the mechanism of phytic acid biosynthesis pathway.

Inositol 1,4,5-trisphosphate 3-kinases:functions and regulations

Inositol 1,4,5-trisphosphate 3-kinase (IP3 3-kinase/IP3K) plays an important role in signal transduction in animal cellsby phosphorylating inositol 1,4,5-trisphosphate (IP3) to inositol 1,3,4,5-tetrakisphosphate (IP4). Both IP3 and IP4 arecritical second messengers which regulate calcium (Ca2+) homeostasis. Mammalian IP3Ks are involved in many biologicalprocesses, including brain development, memory, learning and so on. It is widely reported that Ca2+ is a canonicalsecond messenger in higher plants. Therefore, plant IP3K should also play a crucial role in plant development. Recently,we reported the identification of plant IP3K gene (AtIpk2β/AtIP3K) from Arabidopsis thaliana and its characterization.Here, we summarize the molecular cloning, biochemical properties and biological functions of IP3Ks from animal, yeastand plant. This review also discusses potential functions of IP3Ks in signaling crosstalk, inositol phosphate metabolism,gene transcriptional control and so on.

The Role and Mechanism of Unfolded Protein Response Pathway in Tumor Drug Resistance

In the process of tumor proliferation and metastasis,tumor cells encounter hypoxia,low glucose,acidosis,and other stressful environments.These conditions prompt tumor cells to generate endoplasmic reticulum stress(ERS).As a signal mechanism that mitigates ERS in eukaryotic cells,the unfolded protein response(UPR)pathway can activate cells and tissues,regulating pathological activities in various cells,and maintaining ER homeostasis.It forms the most crucial adaptive and defensive mechanism for cells.However,under the continuous influence of chemotherapy drugs,the quantity of unfolded proteins and erroneous proteins produced by tumor cells significantly increases,surpassing the normal regulatory range of UPR.Consequently,ERS fails to function properly,fostering tumor cell proliferation and the development of drug resistance.This review delves into the study of three UPR pathways(PERK,IRE1,and ATF6),elucidating the mechanisms of drug resistance and research progress in the signal transduction pathway of UPR related to cancers.It provides a profound understanding of the role and relationship between UPR and anti-tumor drugs,offering a new direction for effective clinical treatment.

Effect of acupuncture on the endoplasmic reticulum stress IRE1-CHOP pathway and the expression levels of Bax and Bcl-2 protein as well as genes in pancreatic tissue of rats with diabetes mellitus

Objective To explore the effect of acupuncture on the endoplasmic reticulum stress IRE l-CHOP signal pathway and the expression levels of related apoptosis genes in pancreatic tissue of rats with STZ-induced diabetes mellitus. Methods Eighty SD rats were selected, among which, 10 were fed with normal diet and taken as blank control group （＂blank group＂ for short）, the other 70 rats were fed with high fat and high glucose food and injected with small dosage of STZ intraperitoneally, and 30 models were established successfully. The models were randomly divided into acupuncture treatment group （~＇acupuncture group＂ for short）, model control group （＂model group＂ for short） and western medicine group （metformin） with 10 rats in each group. After treatment for 4 weeks, RBG, and the expression levels of CHOP, IRE 2, Bax, Bcl-2 protein and mRNA in pancreatic tissue of rats were determined. Result Compared with the conditions before treatment, RBG reduced obviously in the acupuncture group and western medicine group （P〈0.05）, and there was no statistical difference in RBG in the model group and blank group （P〉0.05）; the expression levels of CHOP, IRE 1 and Bax proteins in pancreatic tissue of rats in the model group were significantly higher than those in the blank group （P〈0.05）, the expression results in the acupuncture group and western medicine group were significantly lower than those in model group （P〈0.05）; the expression levels of CHOP, IRE 1 and Bax mRNAs in pancreatic tissue of rats in the model group were significantly higher than those in the blank group （P〈0.01）, the expression results in the acupuncture group and western medicine group were significantly lower than those in the model group （P〈0.01）; the expression level of Bcl-2 protein in the model group was significantly lower than that in the blank group （P〈0.05）, the expression results in the acupuncture group and western medicine group were significantly higher than that in the model group （P〈0.02）; there was no statistical difference between the acupuncture group and western medicine group （P〉0.05）; the expression level of Bcl-2 mRNA in the model group was significantly lower than that in the blank group （P〈0.02）, the expression results in the acupuncture group and western medicine group were significantly higher than that in the model group （P〈0.01）; there was no statistical difference between the acupuncture group and western medicine group （P〉0.05）. Conclusion There was endoplasmic reticulum stress in the pancreatic tissue of rats with STZ-induced diabetes mellitus, and IRE 1-CHOP signal pathway was the main pathway for inhibiting the endoplasmic reticulum stress in the pancreatic tissue. Acupuncture can improve the endoplasmic reticulum stress in pancreatic tissue, inhibit apoptosis genes, and protect the pancreatic tissue through IRE 1-CHOP signal pathway.

ERp44 C160S/C212S mutants regulate IP_(3)R_(1) channel activity

Previous studies have indicated that ERp44 inhibits inositol 1,4,5-trisphosphate(IP3)-induced Ca2+release(IICR)via IP3R1,but the mechanism remains largely unexplored.Using extracellular ATP to induce intracellular calcium transient as an IICR model,Ca2+image,pull down assay,and Western blotting experiments were carried out in the present study.We found that extracellular ATP induced calcium transient via IP3Rs(IICR)and the IICR were markedly decreased in ERp44 overexpressed Hela cells.The inhibitory effect of C160S/C212S but not C29S/T396A/ΔT(331–377)mutants of ERp44 on IICR were significantly decreased compared with ERp44.However,the binding capacity of ERp44 to L3V domain of IP3R1(1L3V)was enhanced by ERp44 C160S/C212S mutation.Taken together,these results suggest that the mutants of ERp44,C160/C212,can more tightly bind to IP3R1 but exhibit a weak inhibition of IP3R1 channel activity in Hela cells.

Effect of TheoPolyphenols(茶多酚)on Function of TransMembranous Signal System of Acute Ischemic Myocardium in Rats

Objective: To observe the effect of theo polyphenols(TP)on function of trans membranous signal of acute ischemic myocardium in rats. Methods: Model of myocardial ischemia was established. Thirty five male rats were randomly divided into 5 groups, 7 rats in each group. Non ischemic group:the anterior descending branch of left coronary artery was not ligated;Ischemic group:the time of ischemia continued for 10 min;TP groups:the groups were divided into 3 subgroups, TP dose was respectively 1 mg/kg, 4 mg/kg, 16 mg/kg, TP was administered through celiac injection 20 min before the anterior descending branch of left coronary artery was ligated. Results: The levels of phosphatidylinositol 4, 5 biphosphate(PIP 2), inositol 1, 4, 5 triphosphate(IP 3)in the ischemic group were markedly higher than those in the non ischemic group. The raise of the levels of PIP 2, IP 3caused by acute myocardial ischemia were markedly inhibited by the TP. The relationship of dose effect was observed. Conclusion: TP has inhibitory effect of trans membranous signal system of acute ischemic myocardium. It has protective effect on myocardium.

The role of TRPP2 in agonist-induced gallbladder smooth muscle contraction

TRPP2 channel protein belongs to the superfamily of transient receptor potential(TRP) channels and is widely expressed in various tissues, including smooth muscle in digestive gut. Accumulating evidence has demonstrated that TRPP2 can mediate Ca^(2+) release from Ca^(2+) stores. However, the functional role of TRPP2 in gallbladder smooth muscle contraction still remains unclear. In this study, we used Ca^(2+) imaging and tension measurements to test agonist-induced intracellular Ca^(2+) concentration increase and smooth muscle contraction of guinea pig gallbladder, respectively. When TRPP2 protein was knocked down in gallbladder muscle strips from guinea pig, carbachol(CCh)-evoked Ca^(2+) release and extracellular Ca^(2+) influx were reduced significantly, and gallbladder contractions induced by endothelin 1 and cholecystokinin were suppressed markedly as well. CCh-induced gallbladder contraction was markedly suppressed by pretreatment with U73122, which inhibits phospholipase C to terminate inositol 1,4,5-trisphosphate receptor(IP3) production, and 2-aminoethoxydiphenyl borate(2APB), which inhibits IP3 recepor(IP3R) to abolish IP3R-mediated Ca^(2+) release. To confirm the role of Ca^(2+) release in CCh-induced gallbladder contraction, we used thapsigargin(TG)-to deplete Ca^(2+) stores via inhibiting sarco/endoplasmic reticulum Ca^(2+)-ATPase and eliminate the role of store-operated Ca^(2+) entry on the CCh-induced gallbladder contraction. Preincubation with 2 μmol L^(-1) TG significantly decreased the CCh-induced gallbladder contraction. In addition, pretreatments with U73122, 2APB or TG abolished the difference of the CCh-induced gallbladder contraction between TRPP2 knockdown and control groups. We conclude that TRPP2 mediates Ca^(2+) release from intracellular Ca^(2+) stores, and has an essential role in agonist-induced gallbladder muscle contraction.

ITPK1 is an InsP_(6)/ADP phosphotransferase that controls phosphate signaling in Arabidopsis.

In plants, phosphate (Pi) homeostasis is regulated by the interaction of PHR transcription factors with stand-alone SPX proteins, which act as sensors for inositol pyrophosphates. Here, we combined different methods to obtain a comprehensive picture of how inositol (pyro)phosphate metabolism is regulated by Pi and dependent on the inositol phosphate kinase ITPK1. We found that inositol pyrophosphates are more responsive to Pi than lower inositol phosphates, a response conserved across kingdoms. With CE-ESI-MS we could separate different InsP7 isomers in Arabidopsis and rice, and identify 4/6-InsP7 and a PP-InsP4 isomer hitherto not reported in plants. We found that the inositol pyrophosphates 1/3-InsP7, 5-InsP7 and InsP8 increase severalfold in shoots after Pi resupply and that tissue-specific accumulation of inositol pyrophosphates relies on ITPK1 activities and MRP5-dependent InsP6 compartmentalization. Notably, ITPK1 is critical for Pi-dependent 5-InsP7 and InsP8 synthesis in planta and its activity regulates Pi starvation responses in a PHR-dependent manner. Furthermore, we demonstrate that ITPK1-mediated conversion of InsP6 to 5-InsP7 requires high ATP concentrations and that Arabidopsis ITPK1 has an ADP phosphotransferase activity to dephosphorylate specifically 5-InsP7 under low ATP. Collectively, our study provides deeper insights into Pi-dependent changes in nutritional and energetic states with the synthesis of regulatory inositol pyrophosphates.