Study on the characteristics of genetic diversity of different populations of Guizhou endemic plant Rhododendron pudingense based on microsatellite markers

BACKGROUND

Rhododendron pudingense, firstly discovered in Puding county of Guizhou province in 2020, have adapted to living in rocky fissure habitat, which has important ornamental and economic values. However, the genetic diversity and population structure of this species have been rarely described, which seriously affects the collection and protection of wild germplasm resources.

RESULTS

In the present study, 13 pairs of primers for polymorphic microsatellite were used to investigate the genetic diversity of 65 R. pudingense accessions from six different geographic populations. A total of 254 alleles (Na) were obtained with an average of 19.5 alleles per locus. The average values of polymorphic information content (PIC), observed heterozygosity (Ho), and expected heterozygosity (He) were 0.8826, 0.4501, and 0.8993, respectively, These results indicate that the microsatellite primers adopted demonstrate good polymorphism, and the R. pudingense exhibits a high level of genetic diversity at the species level. The average genetic differentiation coefficient (Fst) was 0.1325, suggested that moderate divergence occurred in R. pudingense populations. The average values of genetic differentiation coefficient and gene flow among populations were 0.1165 and 3.1281, respectively. The analysis of molecular variance (AMOVA) indicated that most of the population differences (88%) were attributed to within-population variation. The PCoA results are consistent with the findings of the UPGMA clustering analysis, supporting the conclusion that the six populations of R. pudingense can be clearly grouped into two separate clusters. Based on Mantel analysis, we speculate that the PD population may have migrated from WM-1 and WM-2. Therefore, it is advised to protect the natural habitat of R. pudingense in situ as much as possible, in order to maximize the preservation of its genetic diversity.

CONCLUSIONS

This is the first comprehensive analysis of genetic diversity and population structure of R. pudingense in Guizhou province. The research results revealed the high genetic diversity and moderate population diferentiation in this horticulture plant. This study provide a theoretical basis for the conservation of wild resources of the R. pudingense and lay the foundation for the breeding or cultivation of this new species.

Corrigendum to "Connexin 43 dephosphorylation at serine 282 induces spontaneous arrhythmia and increases susceptibility to ischemia/reperfusion injury" [Heliyon 9 (5), May 2023 Article e15879]

[This corrects the article DOI: 10.1016/j.heliyon.2023.e15879.].

Connexin 43 dephosphorylation at serine 282 induces spontaneous arrhythmia and increases susceptibility to ischemia/reperfusion injury

Background

Connexin 43 (Cx43), the predominant gap junction protein in hearts, is modified by specific (de)phosphorylation events under physiological and pathological states to affect myocardium function and structure. Previously we found that deficiency in Cx43 S282 phosphorylation could impair intercellular communication and contribute to cardiomyocyte apoptosis by activating p38 mitogen-activated protein kinase (p38 MAPK)/factor-associated suicide (Fas)/Fas-associating protein with a novel death domain (FADD) pathway, which is involved in myocardium injury in ischemia/reperfusion (I/R) heart. In addition, mutant at Cx43 S282 substituted with alanine heterozygous mice (S282A+/-) exhibited different degrees of ventricular arrhythmias and only some underwent myocardium apoptosis. In this study, we aimed to investigate the role of Cx43 pS282 in different cardiac pathological phenotypes.

Methods

We examined cardiac function, structure, and relevant protein expression in S282A+/- mice (aged 2, 10 and 30 weeks) by electrocardiograph, echocardiography, histological staining, and co-immunoprecipitation followed by Western blot. Intraperitoneal isoprenaline injection and I/R surgery were applied in S282A+/- mice as external stimulus. 2,3,5-triphenyltetrazolium chloride staining was used for myocardium infarction evaluation.

Results

Adult S282A+/- mice (aged 10 and 30 weeks) still exhibited spontaneous arrhythmia. Unlike neonatal stage (aged around 2 weeks), no apoptosis-related manifestations and the activation of p38 MAPK-Fas-FADD apoptotic pathway were observed in adult S282A+/- hearts. S282A+/- neonatal mice with cardiomyocytes apoptosis exhibited more than 60% dephosphorylation at Cx43 S282 than WT mice, while less than 40% S282 dephosphorylation were found in adult S282A+/- mice. In addition, although S282A+/- mice displayed normal cardiac function, they were highly susceptible to isoproterenol-induced ECG alternans and prone to cardiac injury and deaths upon I/R attack.

Conclusions

These results reinforce that Cx43 S282 dephosphorylation acts as a susceptibility factor in regulating cardiomyocyte survival and cardiac electrical homeostasis in basal conditions and contributes to myocardium injury in the setting of I/R. Cx43 S282 phosphorylation was competent to induce spontaneous arrhythmias, cardiomyocyte apoptosis and deaths based on the degree of S282 dephosphorylation.

Connexin 43 hyper-phosphorylation at serine 282 triggers apoptosis in rat cardiomyocytes via activation of mitochondrial apoptotic pathway

Cx43 is the major connexin in ventricular gap junctions, and plays a pivotal role in control of electrical and metabolic communication among adjacent cardiomyocytes. We previously found that Cx43 dephosphorylation at serine 282 (pS282) caused cardiomyocyte apoptosis, which is involved in cardiac ischemia/reperfusion injury. In this study we investigated whether Cx43-S282 hyper-phosphorylation could protect cardiomyocytes against apoptosis. Adenovirus carrying rat full length Cx43 gene (Cx43-wt) or a mutant gene at S282 substituted with aspartic acid (S282D) were transfected into neonatal rat ventricular myocytes (NRVMs) or injected into rat ventricular wall. Rat abdominal aorta constriction model (AAC) was used to assess Cx43-S282 phosphorylation status. We showed that Cx43 phosphorylation at S282 was increased over 2-times compared to Cx43-wt cells at 24 h after transfection, while pS262 and pS368 were unaltered. S282D-transfected cells displayed enhanced gap junctional communication, and increased basal intracellular Ca²⁺ concentration and spontaneous Ca²⁺ transients compared to Cx43-wt cells. However, spontaneous apoptosis appeared in NRVMs transfected with S282D for 34 h. Rat ventricular myocardium transfected with S282D in vivo also exhibited apoptotic responses, including increased Bax/Bcl-xL ratio, cytochrome c release as well as caspase-3 and caspase-9 activities, while factor-associated suicide (Fas)/Fas-associated death domain expression and caspase-8 activity remained unaltered. In addition, AAC-induced hypertrophic ventricles had apoptotic injury with Cx43-S282 hyper-phosphorylation compared with Sham ventricles. In conclusion, Cx43 hyper-phosphorylation at S282, as dephosphorylation, also triggers cardiomyocyte apoptosis, but through activation of mitochondrial apoptosis pathway, providing a fine-tuned Cx43-S282 phosphorylation range required for the maintenance of cardiomyocyte function and survival.

Design, synthesis, and biological evaluation of novel triazoloquinazolinone derivatives as SHP2 protein inhibitors

A novel series of triazoloquinazolinone derivatives were designed, synthesised, and evaluated for their in vitro biological activities against the SHP2 protein. Moreover, some compounds were evaluated against A375 cells. The results revealed that target compounds possessed moderate to excellent inhibitory activity against SHP2 protein, whereas compounds 12f, 12l, 12j, 17e, and 17f have strong antiproliferative activity on A375 cells. The compound 12l showed remarkable cytotoxicity against A375 cells and a strong inhibitory effect against SHP2 protein when compared with SHP244. The structure-activity relationships (SARs) indicated that electron-donating groups (EDGs) on phenyl rings are beneficial for improving the antitumor activity; compounds with a hydroxyl substituent at the 2-position of phenyl ring exhibited superior activities than compounds with a substituent at the 4-position. In addition, compound 12l displayed improved physicochemical properties as well as metabolic stability compared to SHP244. Our efforts identified 12l as a promising SHP2 protein inhibitor, warranting its further investigation.

Functional Calsequestrin-1 Is Expressed in the Heart and Its Deficiency Is Causally Related to Malignant Hyperthermia-Like Arrhythmia

Background: Calsequestrins (Casqs), comprising the Casq1 and Casq2 isoforms, buffer Ca²⁺ and regulate its release in the sarcoplasmic reticulum (SR) of skeletal and cardiac muscle, respectively. Human inherited diseases associated with mutations in CASQ1 or CASQ2 include malignant hyperthermia/environmental heat stroke (MH/EHS) and catecholaminergic polymorphic ventricular tachycardia. However, patients with an MH/EHS event often suffer from arrhythmia for which the underlying mechanism remains unknown. Methods: Working hearts from conventional (Casq1-KO) and cardiac-specific (Casq1-CKO) Casq1 knockout mice were monitored in vivo and ex vivo by electrocardiogram and electrical mapping, respectively. MH was induced by 2% isoflurane and treated intraperitoneally with dantrolene. Time-lapse imaging was used to monitor intracellular Ca²⁺ activity in isolated mouse cardiomyocytes or neonatal rat ventricular myocytes (NRVMs) with knockdown, over-expression or truncation of the Casq1 gene. Conformational change in both Casqs was determined by crosslinking Western blot analysis. Results: Like MH/EHS patients, Casq1-KO and Casq1-CKO mice had faster basal heart rate, and ventricular tachycardia upon exposure to 2% isoflurane, which could be relieved by dantrolene. Basal sinus tachycardia and ventricular ectopic electrical triggering also occurred in Casq1-KO hearts ex vivo. Accordingly, the ventricular cardiomyocytes from Casq1-CKO mice displayed dantrolene-sensitive increased Ca²⁺ waves and diastole premature Ca²⁺ transients/oscillations upon isoflurane. NRVMs with Casq1-knockdown had enhanced spontaneous Ca2+ sparks/transients upon isoflurane, while cells over-expressing Casq1 exhibited decreased Ca2+ sparks/transients that were absent in cells with truncation of 9 amino acids at the C-terminus of Casq1. Structural evaluation showed that most of the Casq1 protein was present as a polymer and physically interacted with RyR2 in the ventricular SR. The Casq1 isoform was also expressed in human myocardium. Mechanistically, exposure to 2% isoflurane or heating at 41ºC induced Casq1 oligomerization in mouse ventricular and skeletal muscle tissues, leading to a reduced Casq1/RyR2 interaction and increased RyR2 activity in the ventricle. Conclusions: Casq1 is expressed in the heart, where it regulates SR Ca²⁺ release and heart rate. Casq1 deficiency independently causes MH/EHS-like ventricular arrhythmia by trigger-induced Casq1 oligomerization and a relief of its inhibitory effect on RyR2-mediated Ca²⁺ release, thus revealing a new inherited arrhythmia and a novel mechanism for MH/EHS arrhythmogenesis.

[-a]

Objective: To investigate the clinicopathological features, treatment and prognosis of fibrin-associated diffuse large B cell lymphoma (DLBCL) arising within concurrent atrial myxoma. Methods: Six cases of fibrin-associated DLBCL arising within concurrent atrial myxoma diagnosed at the Department of Pathology, Guangdong General Hospital, from 2006 to 2019 were included. The histology, immunophenotype, treatment and prognoses were analyzed. Results: The patients' age ranged from 46 to 78 years (mean 59 years). There were 3 males and 3 females. The tumors were all discovered incidentally on histological examination of surgical pathology specimens excised for atrial myxoma. All patients appeared to have morphological features of DLBCL, B lineage immunophenotype, high proliferative index and latency type III of Epstein-Barr viral infection. They had complete tumor resections without adjuvant chemotherapy and were healthy at 5- to 120-month follow-ups. Conclusions: Fibrin-associated DLBCL arising within concurrent atrial myxoma is an unusual form of DLBCL associated with chronic inflammation, and its clinical outcome is indolent. The findings suggest that this type of lymphoma does not warrant excessive or unnecessary treatments after complete resection.

Connexin 43-serine 282 modulates serine 279 phosphorylation in cardiomyocytes

Connexin 43 (Cx43) phosphorylation plays a pivotal role in cardiac electrical and contractile performance. In a previous study we have found that Cx43 phosphorylation at serine 282 (pS282) regulates cardiomyocyte survival. Considering that both sites are altered simultaneously in many studies, we designed this study to identify the status of S279 phosphorylation upon pS282 manipulation. In heterozygous mice with S282 gene substituted with alanine (S282A), we found ventricular arrhythmias with inhibition of Cx43 phosphorylation at both S282 and S279 in the hearts. In cultured neonatal rat ventricular myocytes (NRVMs), transfection of virus carrying S282A mutant also blocked Cx43 phosphorylation at both S279/282 and gap junction coupling, while expression of wild-type Cx43 or S279A did not. Further, NRVMs transfected with S282 phospho-mimicking mutant substituted with aspartate or treated with ATP exhibited promotions of Cx43 phosphorylation at S279/282 and intercellular communication. Therefore, this study demonstrated a regulatory role of Cx43-S282 on S279 phosphorylation in cardiomyocytes, and suggested an involvement of S279 in the Cx43-S282 mediated cardiomyocyte homeostasis.

[Diagnostic and prognostic implications of MAML2 gene translocation in primary pulmonary mucoepidermoid carcinoma]

Objective: To investigate MAML2 gene-translocation in primary pulmonary mucoepidermoid carcinoma (PMEC) and pulmanary adenosquamous carcinoma, and the optimal diagnostic immunohistiochemical (IHC) panel in distinguishing PMEC from adenosqumous carcinoma. Methods: Twenty-four cases of PMEC and 44 adenosqumous carcinoma diagnosed in the Guangdong General Hospital were tested for MAML2 translocation by fluorescent in-situ hybridization (FISH) using tissue array. An IHC panel including TTF1, Napsin A, CK5/6, p63, p40 and Ki-67 was performed on the cohort. The clinical data for all cases were collected and all PMEC patients had follow-up information. Results: The patients' age ranged form 6 to 73 years, with a median age of 32 years. The male to female ratio was 1.4∶1.0. MAML2 translocation was found in 16/24 (66.7%) cases of PMEC whereas all 44 cases adenosqumous carcinoma were negative for translocation. All the cases of the PMEC were negative for TTF1 and Napsin A but positive for CK5/6, p63 and p40 in the intermediate cells and epidermal-like cells. In most PMEC cases, the Ki-67 expression index was lower than 10%. In contrast, most cases of adenosqumous carcinomas expressed TTF1 and Napsin A in the adenomatous component and CK5/6, p63 and p40 in the squamous component, which expression pattern was different from that of PMEC. Based on IHC staining, 2 cases of highly invasive ALK-positive adenocarcinoma mimicing PMEC were also found in the study. Conclusions: MAML2 gene translocation can be detected in about two-third of PMEC. Translocation of MAML2 gene and lower morphology grading are associated with good prognosis. The combined use of IHC antibodies panel is helpful to distinguish PMEC from the adenosqumous carcinoma and adenocarcinoma mimicing PMEC.

[Pathological features of duodenal-type follicular lymphoma]

Objective: To investigate the clinicopathological features, treatment and prognosis of duodenal-type follicular lymphoma. Methods: Four cases of duodenal-type follicular lymphoma diagnosed at Guangdong General Hospital from 2014 to 2015 with detailed clinical data were included. The histomorphology, immunophenotype, treatment and prognoses were analyzed. Results: The patients' age ranged from 51 to 57 years (mean 54 years), and there were 2 males and 2 females. The involved sites were gastric fundus in one case, second portion of the duodenum in two cases and terminal ileum in one case. All patients presented with multiple mucosal granules or nodules at endoscopy. Microscopically, there were multiple mucosal neoplastic follicles, constituting grade 1-2 disease based on nodal follicular lymphoma grading system. The tumor cells were positive for CD20, CD10, bcl-6 and bcl-2. CD21 highlighted the follicular dendritic meshwork mainly at the periphery of the follicles. Proliferation index was low. Three patients received rituximab monotherapy for 4 cycles, leading to complete remission. One patient refused therapy and the disease progressed to systemic lymphoma 15 months after the initial diagnosis. Conclusions: Duodenal-type follicular lymphoma is a special variant of follicular lymphoma with indolent clinical course. The tumor exhibits morphology of low grade follicular lymphoma with characteristic dendritic meshwork at the periphery of the follicles and a low proliferation index. Prognosis is excellent. Rituximab monotherapy is treatment of choice, but a small minority of patients may progress to systemic disease.

Low molecular-weight fucoidan protects against hindlimb ischemic injury in type 2 diabetic mice through enhancing endothelial nitric oxide synthase phosphorylation

BACKGROUND

Diabetes mellitus (DM) complications are associated with ischemic injury. Angiogenesis is a therapeutic strategy for diabetic foot. The aim of this study was to investigate the possible angiogenic effect of low molecular weight fucoidan (LMWF) in diabetic peripheral arterial disease (PAD).

METHODS

Diabetic db/db mice and age-matched C57BL/6 mice underwent femoral artery ligation followed by LMWF (30, 60, 80 mg/kg per day, p.o.) or cilostazol (30 mg/kg/day, p.o.) treatment for 6 weeks. Endothelium-dependent vasodilation and blood flow of the hindlimb were measured. Histological and western blot analyses of CD34, vascular endothelial growth factor (VEGF), eNOS, and inflammatory factors in the gastrocnemius were performed. The effects of LMWF were confirmed in human umbilical vein endothelial cells (HUVEC).

RESULTS

Diabetic mice with ligation exhibited hindlimb ulceration, hydrosarca, and necrosis, increased expression of inflammatory factors, and decreased levels of VEGF and eNOS phosphorylation. Treatment with LMWF markedly ameliorated foot lesions, suppressed expression of inflammatory factors, and improved plantar perfusion by promoting endothelium-dependent vasodilation and revascularization in diabetic PAD mice. In high-glucose treated HUVEC, LMWF (40 μg/mL) reversed blunted endothelial cell proliferation, migration, and tube formation, and promoted eNOS phosphorylation and VEGF expression, whereas HUVEC pretreatment with 100 μmol/L N^G -nitro-l-arginine methyl ester, an eNOS antagonist, markedly inhibited the effects of LMWF.

CONCLUSION

This study demonstrates that LMWF alleviates hindlimb ischemic damage, at least in part by promoting eNOS phosphorylation, nitric oxide production, and VEGF expression, resulting in enhanced angiogenesis in the ischemic region.

Orai1 downregulation impairs lymphocyte function in type 2 diabetes mellitus

BACKGROUND/AIMS

It has been suggested that diabetes is associated with immune dysfunction, in which Ca²⁺ signaling malfunction in lymphocyte may contributes most. However, the pattern of the Ca²⁺ signal disorder and the mechanism(s) that explains the change are unclear. Here, in this study we aimed to investigate possible changes and mechanism(s) accounting for the internal Ca²⁺ signals in diabetic T lymphocyte upon stimulation.

METHODS AND RESULTS

Using Fura-2-AM, we found a significant decrease in Ca²⁺ influx induced by thapsigargin (TG) and anti-CD3 antibody (OKT3) in T lymphocytes from blood of both diabetes patients and animals. Furthermore, a downregulated Orai1 protein expression, but not mRNA, was also observed in these cells using western blot and qRT-PCR, respectively. In addition, in high-glucose and agonist treated Jurkat T cells, Ca²⁺ entry and the release of interleukin-2 (IL-2) were also decreased. Orai1 expression reduced, while stromal interaction molecule 1 (STIM1) and other downstream proteins remained unchanged.

CONCLUSION

This study demonstrates that the declined Orai1 expression, at least partly, contributes to the downregulated Ca²⁺ entry during lymphocyte excitation, providing an important mechanism for T lymphocyte malfunction in diabetes.

CaMKII Potentiates Store-Operated Ca2+ Entry Through Enhancing STIM1 Aggregation and Interaction with Orai1

BACKGROUND/AIMS

Upon Ca2+ store depletion, stromal interaction molecule 1 (STIM1) oligomerizes, redistributes near plasmalemma to interact with Ca2+ selective channel-forming subunit (Orai1) and initiates store-operated Ca2+ entry (SOCE). Ca2+/calmodulin-dependent protein kinase II (CaMKII) is a regulator of SOCE, but how CaMKII regulates SOCE remains obscure.

METHODS

Using Fura2, confocal microscopy, co-immunoprecipitation, specific blocker and overexpression/knockdown approaches, we evaluated STIM1 aggregation and its interaction with Orai1, and SOCE upon Ca2+ store depletion in thapsigargin (TG) treated HEK293 and HeLa cells.

RESULTS

Overexpression of CaMKIIδ enhanced TG-induced STIM1 co-localization and interaction with Orai1 as well as SOCE. In contrast, CaMKIIδ knockdown and a specific inhibitor of CaMKII suppressed them. In addition, overexpression or knockdown of CaMKIIδ in TG treated cells exhibited increased or reduced STIM1 clustering and plasmalemma redistribution, respectively.

CONCLUSION

CaMKII up-regulates SOCE by increasing STIM1 aggregation and interaction with Orai1. This study provides an additional insight into SOCE regulation and a potential mechanism for CaMKII involvement in some pathological situations through crosstalk with SOCE.

[Expression of βF1 and T cell receptor γ in T lymphoblastic lymphoma/leukemia]

Objective: To evaluate the expression of βF1 and T cell receptor (TCR)γ in T lymphoblastic lymphoma/leukemia(T-LBL/ALL), and investigate the clinicopathological features. Methods: Fifty-one cases of T-LBL/ALL were collected at Guangdong General Hospital from 2010 to 2016, the expression of βF1 and TCRγ was assessed by immunohistochemistry. Results: There were 13 cases of children and adolescents, and 38 cases of adults. The expression rates of βF1 and TCRγ were 27.5%(14/51) and 15.7%(8/51) respectively. The proportion of adults in αβ T-LBL/ALL, TCR-silent T-LBL/ALL and γδ T-LBL/ALL was 7/14, 79.3%(23/29)and 8/8 respectively, and the difference was significant (P=0.023). There was no statistical difference in sex, LDH, bone marrow involvement and Ann arbor stage among these three groups(P>0.05). γδ T-LBL/ALLs included 6 cases of CD4(-)/CD8(-) phenotype, whereas αβ T-LBL/ALL included 7 cases of CD4(+) /CD8(+) phenotype. There was significant difference in CD4/CD8 expression among these three groups(P<0.01). Conclusions: γδ T-LBL/ALL occurred only in adults, with predominantly CD4(-)/CD8(-) phenotype. αβ T-LBL/ALL occurred more common in children and adolescents, with predominantly CD4(+) /CD8(+) phenotype.

Low molecular weight fucoidan ameliorates hindlimb ischemic injury in type 2 diabetic rats

ETHNOPHARMACOLOGICAL RELEVANCE

Low molecular weight fucoidan (LMWF), extracted from Laminaria japonica Areschoug, is a traditional Chinese medicine, commonly used to alleviate edema, particularly for feet with numbness and pain.

AIM OF THE STUDY

Diabetic mellitus (DM) patients are at high risk of developing peripheral arterial disease (PAD). Individuals with DM and PAD co-morbidity have a much higher risk of critical limb ischemia. LMWF showed several beneficial effects, such as anti-inflammation, anti-thrombosis, and enhancing revascularization. Therefore, we hypothesized that LMWF might be beneficial to diabetes-induced PAD, and investigated the therapeutic potential of LMWF on diabetic PAD rats.

MATERIALS AND METHODS

Type 2 diabetic Goto-Kakizaki (GK) rats were made PAD by injection of sodium laurate into femoral artery. LMWF (20, 40 or 80mg/kg/day) or cilostazol (100mg/kg/day) were given to diabetic PAD rats for 4 weeks, respectively. The effects of LMWF on foot ulceration and claudication, plantar blood flow, collateral vessel formation, endothelium morphology, gastrocnemius injury, platelet aggregation, vessel vasodilation, and the expressions of inflammation factors, VEGF, eNOS, and nitric oxide were measured.

RESULTS

We found that LMWF markedly ameliorated foot ulceration and claudication, and improved the plantar perfusion by reversing hyperreactive platelet aggregation, ameliorating endothelium-dependent vasodilation and revascularization on diabetic PAD rats. In addition, upregulation of several inflammatory factors, such as ICAM-1 and IL-1β in the gastrocnemius muscles of ischemic hindlimb were suppressed by LMWF administration. And eNOS phosphorylation at Ser1177 and NO production were significantly enhanced in LMWF-treated diabetic PAD rats.

CONCLUSIONS

Taken together, our findings demonstrated that LMWF exhibits therapeutic effect on hindlimb ischemia in type 2 diabetic rats likely through ameliorating endothelium eNOS dysfunction and enhancing revascularization, thus, providing a potential supplementary non-invasive treatment for diabetes-induced PAD.

[Serum uric acid is associated with disease severity and an important predictor for clinical outcome in patients with pulmonary hypertension]

Objective: The growing body of literature showed a link between uric acid and pulmonary hypertension (PH), but the impact of hyperuremia on outcome of patients with PH has not been well defined. Therefore, the present study was performed to analyze the impact of uric acid on outcome of PH patients. Methods: One hundred seventy-three PH patients (112 females, mean age 38 years old), who were hospitalized in our department between January 2010 and December 2015, were included in our study, the PH diagnosis was made based on right heart catheterization examination result (mean pulmonary artery pressure≥25 mmHg(1 mmHg=0.133 kPa)). PH patients were divided into mild to moderate PH group (Rp/Rs≤0.6, n=97) and severe PH group (Rp/Rs>0.6, n=76). Fifty-one patients (33 females, mean age 45 years old) without PH based on right heart catheterization were included as control subjects. All participants were followed up for a median of 24 months(6-71 months). Clinical endpoints were defined as cardiogenic death or heart-and-lung transplantation. Results: Uric acid was positively correlated with pulmonary vascular resistance(r=0.398, P<0.01), systemic vascular resistance(r=0.244, P<0.01) and mean right atrial pressure (r=0.26, P<0.01), and was negatively correlated with cardiac index(r=-0.278, P<0.01)and mixed venous oxygen saturation (r=-0.322, P<0.01)in PH patients. Serum uric acid level was significantly higher in patients with severe PH than in patients with mild-to-moderate PH and the control subjects (both P<0.05). According to the receiver operating characteristic curve (ROC), 425.5 μmol/L was found to be the best cut-off value of serum uric acid level to predict the outcome of PH patients (sensitivity 50%, specificity 72%). During follow-up, patients with higher level of uric acid (>425.5 μmol/L) were linked with poorer clinical outcome compared to patients with uric acid <425.5 μmol/L(P=0.027). Conclusion: Our findings suggests that uric acid is associated with the severity of PH and higher uric acid level serves as an important predictor for poor clinical outcome of PH patients.

Low molecular weight fucoidan modulates P-selectin and alleviates diabetic nephropathy

Diabetic nephropathy (DN) is a serious microvascular complication that can lead to chronic and end-stage renal failure. It is understood that inflammation is associated with the onset and process of DN. Low molecular weight fucoidan (LMWF) isolated from Saccharina japonica has anti-inflammatory properties. Therefore, this study aimed to explore the mechanism of LMWF in DN model induced by streptozotocin. The biochemical indices levels showed LMWF reduced the DN diagnostic indices to protect renal function. The HE stained sections exhibited LMWF protected normal morphological structures and reduced inflammatory cell infiltration in the kidneys of DN rats. Furthermore, the levels of P-selectin and selectin-dependent inflammatory cytokines resulting from LMWF were obviously decreased at both the transcriptional and protein levels. Thus, our results found that LMWF protected the renal function in DN rats and alleviated inflammation through the modulation of P-selectin and inflammatory cytokines. LMWF may have therapeutic potential against DN.

Low molecular weight fucoidan ameliorates streptozotocin-induced hyper-responsiveness of aortic smooth muscles in type 1 diabetes rats

ETHNOPHARMACOLOGICAL RELEVANCE

Low molecular weight fucoidan (LMWF) was prepared from Laminaria japonica Areschoug, a popular seafood and medicinal plant consumed in Asia. Chinese have long been using it as a traditional medicine for curing hypertension and edema.

AIM OF THE STUDY

This study was intent to investigate the possible beneficial effect of LMWF on hyper-responsiveness of aortic smooth muscles instreptozotocin (STZ)-induced type 1 diabetic rats.

MATERIALS AND METHODS

Sprague-Dawley rats were made diabetic by injection of STZ, followed by the administration of LMWF (50 or 100mg/kg/day) or probucol (100mg/kg/day) for 12 weeks. Body weight, blood glucose level, basal blood pressure, serum lipid profiles, oxidative stress, prostanoids production, and vasoconstriction response of endothelium-denuded aorta rings to phenylephrine were measured by Real time-PCR, Western blots, ELISA assay, and force myograph, respectively.

RESULTS

LMWF (100mg/kg/day)-treated group showed robust improvements on STZ-induced body weight-loss, hypertension, and hyperlipidaemia as indicated by decreased serum level of total cholesterol, triglyceride, and low density lipoprotein cholesterol; while probucol, a lipid-modifying drug with antioxidant properties, displayed mild effects. In addition, LMWF appreciably ameliorated STZ-elicited hyper-responsiveness and oxidative stress in aortic smooth muscles as indicated by decreased superoxide level, increased glutathione content and higher superoxide dismutase activity. Furthermore, administration with LMWF dramatically prevented cyclooxygenase-2 stimulation and restored the up-regulation of thromboxane synthase and down-regulation of 6-keto-PGF1α (a stable metabolic product of prostaglandin I2) in the STZ-administered rats.

CONCLUSION

This study demonstrates for the first time that LMWF can protect against hyperlipidaemia, hypertension, and hyper-responsiveness of aortic smooth muscles in type 1 diabetic rat via, at least in part, amelioration of oxidative stress and restoration of prostanoids levels in aortic smooth muscles. Therefore, LMWF can be a potential adjuvant treatment against cardiovascular complications in type 1 diabetes.

Calsequestrin-1 Regulates Store-Operated Ca2+ Entry by Inhibiting STIM1 Aggregation

BACKGROUND/AIMS

Stromal interacting molecule-1 (STIM1) aggregation and redistribution to plasma membrane to interact with Orai1 constitute the core mechanism of store-operated Ca2+ entry (SOCE). Previous study has revealed that calsequestrin-1 (CSQ1) regulates SOCE in HEK293 cells through interacting with STIM1 and inhibiting STIM1/Orai1 interaction. Here, we further investigate how CSQ1/STIM1 interaction affects SOCE.

METHODS

Using confocal microscopy, STIM1 aggregation and co-localizations with CSQ1 or Orai1 upon Ca2+ store depletion by thapsigargin were measured and quantified by Imaris software in HeLa cells transfected with different CSQ1 mutants. The interactions of CSQ1/STIM1 and STIM1/Orai1, and internal Ca2+ changes were detected by co-immunoprecipitation and Fura2, respectively.

RESULTS

Wt-CSQ1 overexpression significantly reduced STIM1 clustering in the perimembrane and cytosolic regions, whereas over-expression of a C-terminal amino acid 362-396 deletion mutant (C35) did not. Consistently, a significant depression of SOCE, increased CSQ1 monomerization and CSQ1/STIM1 interaction, and a reduced STIM1/Orai1 association were observed in wt-CSQ1 but not in C35-transfected cells. Additionally, mutant lacking C-terminal AA 388-396 deletion exerted weaker potency in inhibiting STIM1 aggregation and association with Orai1 than wt-CSQ1.

CONCLUSIONS

Our results demonstrate that CSQ1 monomers suppress SOCE by interacting with STIM1 and attenuating STIM1 aggregation via its C-terminal amino acid 362-396.

Retrograde regulation of STIM1-Orai1 interaction and store-operated Ca2+ entry by calsequestrin

Interaction between the endoplasmic reticulum (ER)-located stromal interaction molecue1 (STIM1) and the plasma membrane-located Ca²⁺ channel subunit, Orai1, underlies store-operated Ca²⁺ entry (SOCE). Calsequestrin1 (CSQ1), a sarcoplasmic reticulum Ca²⁺ buffering protein, inhibits SOCE, but the mechanism of action is unknown. We identified an interaction between CSQ1 and STIM1 in HEK293 cells. An increase in monomeric CSQ1 induced by depleted Ca²⁺ stores, or trifluoperazine (TFP), a blocker of CSQ folding and aggregation, enhanced the CSQ1-STIM1 interaction. In cells with Ca²⁺ stores depleted, TFP further increased CSQ1 monomerization and CSQ1-STIM1 interaction, but reduced the association of STIM1 with Orai1 and SOCE. Over-expression of CSQ1 or a C-terminal (amino acid 388–396) deletion mutant significantly promoted the association of CSQ1 with STIM1, but suppressed both STIM1-Orai1 interaction and SOCE, while over-expression of the C-terminal (amino acid 362–396) deletion mutant had no effect. The physical interaction between low polymeric forms of CSQ1 and STIM1 likely acts by interfering with STIM1 oligimerization and inhibits STIM1-Orai1 interaction, providing a brake to SOCE under physiological conditions. This novel regulatory mechanism for SOCE may also contribute to the pathological Ca²⁺ overload in calsequestrin deficient diseases, such as malignant hyperthermia and ventricular tachycardia.

Cx43 phosphorylation on S279/282 and intercellular communication are regulated by IP3/IP3 receptor signaling

Background

Inositol 1,4,5-trisphosphate receptor (IP₃R) plays a pivotal role in the Ca²⁺ release process in a variety of cell types. Additionally, IP₃R is distributed in ventricular intercalated discs, but its function(s) in this particular site remains unknown. Connexin (Cx43), the predominant gap junction (GJ) protein in ventricular myocardium, is linked to several signaling pathways that regulate Cx43 properties by (de)phosphorylation on multiple residues. Here, we investigated the regulatory role of IP₃R in cell-cell communication and the mechanism(s) underlying this effect.

Results

In neonatal rat and adult mouse ventricular myocytes IP₃R co-localized and co-immunoprecipitated with Cx43 in GJ plaques detected by immunostaining and western blot assays. Blocking IP₃R with antagonists or silencing pan-IP₃R expression with shRNA hindered the 6-carboxyfluorescein (6-CFDA) diffusion through GJs and desynchronized Ca²⁺ transients among confluent neonatal myocytes in culture, whereas stimulation of IP₃R with IP₃ ester or ATP exerted the opposite effect. Likewise, 6-CFDA propagation through GJs was modulated by IP₃R activation or inhibition in cell pairs of isolated adult cardiomyocytes. Furthermore, IP₃R activation or IP₃R suppression promoted or suppressed, respectively, Cx43 phosphorylation on S279/282. Site-directed mutagenesis indicated that expression of a mutant Cx43-S282A (alanine) inhibited S279/282 phosphorylation and GJ permeability, while the S279A mutant showed the opposite effect in ventricular myocytes. Expression of these mutants in HEK293 cells revealed that cells with a dual S279/282 mutation failed to express exogenous Cx43, whereas cells with a single S279 or S282 mutation displayed Cx43 overexpression with increased phosphorylation of S279/282 and promotion of intercellular communication.

Conclusions

These results demonstrated, for the first time, that IP₃R physically interacts with Cx43 and participates in the regulation of Cx43 phosphorylation on S279/282, thereby affecting GJ intercellular communication in ventricular myocytes.

Electronic supplementary material

The online version of this article (doi:10.1186/s12964-014-0058-6) contains supplementary material, which is available to authorized users.

Role of Inositol-1,4,5-Trisphosphate Receptor in the Regulation of Calcium Transients in Neonatal Rat Ventricular Myocytes

This study determined the regulatory effect of inositol 1,4,5-trisphosphate receptors (IP3Rs) on the basal Ca2+ transients in cardiomyocytes. In cultured neonatal rat ventricular myocytes (NRVMs) at different densities, we used confocal microscopy to assess the effect of IP3Rs on the endogenous spontaneous Ca2+ oscillations through specific activation of IP3Rs with myo-IP3 hexakis (butyryloxymethyl) ester (IP3BM), a membrane permeable IP3, and interference of IP3R expression with shRNA. We found that NRVMs at the monolayer state displayed coordinated Ca2+ transients with less rate, shorter duration, and higher amplitude compared to single NRVMs. In addition, monolayer NRVMs exhibited 4 or 10 times more increased Ca2+ transients in response to phenylephrine, an α-adrenergic receptor agonist, or IP3BM than single NRVMs did, while the transient pattern remained unaltered, suggesting that the sensitivity of intracellular Ca2+ response to IP3R activation is different between single and monolayer NRVMs. However, interference of IP3R expression with shRNA reduced the frequency and amplitude of the spontaneous Ca2+ fluctuates similarly in both densities of NRVMs, resembling the effects of ryanodine receptor inhibition by ryanodine or tetracaine. Our findings suggest that IP3Rs are involved, in part, in the regulation of native Ca2+ transients, in profiles of their initiation and Ca2+ release extent, in developing cardiomyocytes. In addition, caution should be paid in evaluating the behavior of Ca2+ signaling in primary cultured cardiomyocytes at different densities.

Role of inositol-1,4,5-trisphosphate receptor in the regulation of calcium transients in neonatal rat ventricular myocytes

This study determined the regulatory effect of inositol 1,4,5-trisphosphate receptors (IP3Rs) on the basal Ca(2+) transients in cardiomyocytes. In cultured neonatal rat ventricular myocytes (NRVMs) at different densities, we used confocal microscopy to assess the effect of IP3Rs on the endogenous spontaneous Ca(2+) oscillations through specific activation of IP3Rs with myo-IP3 hexakis (butyryloxymethyl) ester (IP3BM), a membrane permeable IP3, and interference of IP3R expression with shRNA. We found that NRVMs at the monolayer state displayed coordinated Ca(2+) transients with less rate, shorter duration, and higher amplitude compared to single NRVMs. In addition, monolayer NRVMs exhibited 4 or 10 times more increased Ca(2+) transients in response to phenylephrine, an α-adrenergic receptor agonist, or IP3BM than single NRVMs did, while the transient pattern remained unaltered, suggesting that the sensitivity of intracellular Ca(2+) response to IP3R activation is different between single and monolayer NRVMs. However, interference of IP3R expression with shRNA reduced the frequency and amplitude of the spontaneous Ca(2+) fluctuates similarly in both densities of NRVMs, resembling the effects of ryanodine receptor inhibition by ryanodine or tetracaine. Our findings suggest that IP3Rs are involved, in part, in the regulation of native Ca(2+) transients, in profiles of their initiation and Ca(2+) release extent, in developing cardiomyocytes. In addition, caution should be paid in evaluating the behavior of Ca(2+) signaling in primary cultured cardiomyocytes at different densities.

Altered platelet calsequestrin abundance, Na⁺/Ca²⁺ exchange and Ca²⁺ signaling responses with the progression of diabetes mellitus

INTRODUCTION

Downregulation of calsequestrin (CSQ), a major Ca(2+) storage protein, may contribute significantly to the hyperactivity of internal Ca(2+) ([Ca(2+)]i) in diabetic platelets. Here, we investigated changes in CSQ-1 abundance, Ca(2+) signaling and aggregation responses to stimulation with the progression of diabetes, especially the mechanism(s) underlying the exaggerated Ca(2+) influx in diabetic platelets.

MATERIALS AND METHODS

Type 1 diabetes was induced by streptozotocin in rats. Platelet [Ca(2+)]i and aggregation responses upon ADP stimulation were assessed by fluorescence spectrophotometry and aggregometry, respectively. CSQ-1 expression was evaluated using western blotting.

RESULTS

During the 12-week course of diabetes, the abundance of CSQ-1, basal [Ca(2+)]i and ADP-induced Ca(2+) release were progressively altered in diabetic platelets, while the elevated Ca(2+) influx and platelet aggregation were not correlated with diabetes development. 2-Aminoethoxydiphenyl borate, the store-operated Ca(2+) channel blocker, almost completely abolished ADP-induced Ca(2+) influx in normal and diabetic platelets, whereas nifedipine, an inhibitor of the nicotinic acid adenine dinucleotide phosphate receptor, showed no effect. Additionally, inhibition of Na(+)/Ca(2+) exchange induced much slower Ca(2+) extrusion and more Ca(2+) influx in normal platelets than in diabetic platelets. Furthermore, under the condition of Ca(2+)-ATPase inhibition, ionomycin caused greater Ca(2+) mobilization and Ca(2+) influx in diabetic platelets than in normal platelets.

CONCLUSIONS

These data demonstrate that platelet hyperactivity in diabetes is caused by several integrated factors. Besides the downregulation of CSQ-1 that mainly disrupts basal Ca(2+) homeostasis, insufficient Na(+)/Ca(2+) exchange also contributes, at least in part, to the hyperactive Ca(2+) response to stimulation in diabetic platelets.

Low molecular weight fucoidan alleviates cardiac dysfunction in diabetic Goto-Kakizaki rats by reducing oxidative stress and cardiomyocyte apoptosis

Diabetic cardiomyopathy (DCM) is characterized by cardiac dysfunction and cardiomyocyte apoptosis. Oxidative stress is suggested to be the major contributor to the development of DCM. This study was intended to evaluate the protective effect of low molecular weight fucoidan (LMWF) against cardiac dysfunction in diabetic rats. Type 2 diabetic goto-kakizaki rats were untreated or treated with LMWF (50 and 100 mg/kg/day) for three months. The establishment of DCM model and the effects of LMWF on cardiac function were evaluated by echocardiography and isolated heart perfusion. Ventricle staining with H-E or Sirius Red was performed to investigate the structural changes in myocardium. Functional evaluation demonstrated that LMWF has a beneficial effect on DCM by enhancing myocardial contractility and mitigating cardiac fibrosis. Additionally, LMWF exerted significant inhibitory effects on the reactive oxygen species production and myocyte apoptosis in diabetic hearts. The depressed activity of superoxide dismutase in diabetic heart was also improved by intervention with LMWF. Moreover, LMWF robustly inhibited the enhanced expression of protein kinase C β, an important contributor to oxidative stress, in diabetic heart and high glucose-treated cardiomyocytes. In conclusion, LMWF possesses a protective effect against DCM through ameliorations of PKCβ-mediated oxidative stress and subsequent cardiomyocyte apoptosis in diabetes.

Regulation of basal lateral membrane mobility and permeability to divalent cations by membrane associated-protein kinase C

Biological membrane stabilization is essential for maintenance of cellular homeostasis, functionality and appropriate response to various stimuli. Previous studies have showed that accumulation of PKCs in the cell membrane significantly downregulates the membrane fluidity and Ca²⁺ influxes through the membranes in activated cells. In addition, membrane-inserted form of PKCs has been found in a variety of resting mammalian cells and tissues. This study is aimed to investigate possible role of the endogenous membrane-associated PKCs in the modulation of basal membrane fluidity. Here, we showed that interfering PKC expression by chronic activation of PKC with phorbol myristate acetate (PMA) or shRNA targeting at PKCα lowered the levels of PKCα in cytosol, peripheral membrane and integral membrane pools, while short-term activation of PKC with PMA induced accumulation of PKCα in the membrane pool accompanied by a dramatic decrease in the cytosol fraction. The lateral membrane mobility increased or decreased in accordance with the abundance alterations in the membrane-associated PKCα by these treatments. In addition, membrane permeability to divalent cations including Ca²⁺, Mn²⁺ and Ba²⁺ were also potentiated or abrogated along with the changes in PKC expression on the plasma membrane. Membrane stabilizer ursodeoxycholate abolished both of the enhanced lateral membrane mobility and permeability to divalent cations due to PKCα deficiency, whereas Gö6983, a PKC antagonist, or Gd³⁺ and 2-aminoethyoxydipheyl borne, two Ca²⁺ channels blockers, showed no effect, suggesting that this PKC-related regulation is independent of PKC activation or a modulation of specific divalent cation channel. Thus, these data demonstrate that the native membrane-associated PKCα is involved in the maintenance of basal membrane stabilization in resting cells.

Regulatory effect of connexin 43 on basal Ca2+ signaling in rat ventricular myocytes

Background

It has been found that gap junction-associated intracellular Ca²⁺ [Ca²⁺]_i disturbance contributes to the arrhythmogenesis and hyperconstriction in diseased heart. However, whether functional gaps are also involved in the regulation of normal Ca²⁺ signaling, in particular the basal [Ca²⁺]_i activities, is unclear.

Methods and Results

Global and local Ca²⁺ signaling and gap permeability were monitored in cultured neonatal rat ventricular myocytes (NRVMs) and freshly isolated mouse ventricular myocytes by Fluo4/AM and Lucifer yellow (LY), respectively. The results showed that inhibition of gap communication by heptanol, Gap 27 and flufenamic acid or interference of connexin 43 (Cx43) with siRNA led to a significant suppression of LY uptake and, importantly, attenuations of global Ca²⁺ transients and local Ca²⁺ sparks in monolayer NRVMs and Ca²⁺ sparks in adult ventricular myocytes. In contrast, overexpression of rat-Cx43 in NRVMs induced enhancements in the above measurements, and so did in HEK293 cells expressing rat Cx43. Additionally, membrane-permeable inositol 1,4,5-trisphosphate (IP₃ butyryloxymethyl ester) and phenylephrine, an agonist of adrenergic receptor, could relieve the inhibited Ca²⁺ signal and LY uptake by gap uncouplers, whereas blockade of IP₃ receptor with xestospongin C or 2-aminoethoxydiphenylborate mimicked the effects of gap inhibitors. More importantly, all these gap-associated effects on Ca²⁺ signaling were also found in single NRVMs that only have hemichannels instead of gap junctions. Further immunostaining/immunoblotting single myocytes with antibody against Cx43 demonstrated apparent increases in membrane labeling of Cx43 and non-junctional Cx43 in overexpressed cells, suggesting functional hemichannels exist and also contribute to the Ca²⁺ signaling regulation in cardiomyocytes.

Conclusions

These data demonstrate that Cx43-associated gap coupling plays a role in the regulation of resting Ca²⁺ signaling in normal ventricular myocytes, in which IP₃/IP₃ receptor coupling is involved. This finding may provide a novel regulatory pathway for mediation of spontaneous global and local Ca²⁺ activities in cardiomyocytes.

Possible mechanisms underlying the biphasic regulatory effects of arachidonic acid on Ca2+ signaling in HEK293 cells

Arachidonic acid (AA), an endogenous lipid signal molecule released from membrane upon cell activation, modulates intracellular Ca(2+) ([Ca(2+)](i)) signaling positively and negatively. However, the mechanisms underlying the biphasic effects of AA are rather obscure. Using probes for measurements of [Ca(2+)](i) and fluidity of plasma membrane (PM)/endoplasmic reticulum (ER), immunostaining, immunoblotting and shRNA interference approaches, we found that AA at low concentration, 3 μM, reduced the PM fluidity by activating PKCα and PKCβII translocation to PM and also the ER fluidity directly. In accordance, 3 μM AA did not impact the basal [Ca(2+)](i) but significantly suppressed the thapsigargin-induced Ca(2+) release and Ca(2+) influx. Inhibition of PKC with Gö6983 or knockdown of PKCα or PKCβ using shRNA significantly attenuated the inhibitory effects of 3 μM AA on PM fluidity and agonist-induced Ca(2+) signal. However, AA at high concentration, 30 μM, caused robust release and entry of Ca(2+) accompanied by a facilitated PM fluidity but decreased ER fluidity and dramatic PKCβI and PKCβII redistribution in the ER. Compared with ursodeoxycholate acid, a membrane stabilizing agent that only inhibited the 30 μM AA-induced Ca(2+) influx by 45%, Gd(3+) at concentration of 10 μM could completely abolish both release and entry of Ca(2+) induced by AA, suggesting that the potentiated PM fluidity is not the only reason for AA eliciting Ca(2+) signal. Therefore, the study herein demonstrates that a lowered PM fluidity by PKC activation and a direct ER stabilization contribute significantly for AA downregulation of [Ca(2+)](i) response, while Gd(3+)-sensitive 'pores' in PM/ER play an important role in AA-induced Ca(2+) signal in HEK293 cells.

Induction of cell proliferation and survival genes by estradiol-repressed microRNAs in breast cancer cells

Background

In estrogen responsive MCF-7 cells, estradiol (E₂) binding to ERα leads to transcriptional regulation of genes involved in the control of cell proliferation and survival. MicroRNAs (miRNAs) have emerged as key post-transcriptional regulators of gene expression. The aim of this study was to explore whether miRNAs were involved in hormonally regulated expression of estrogen responsive genes.

Methods

Western blot and QPCR were used to determine the expression of estrogen responsive genes and miRNAs respectively. Target gene expression regulated by miRNAs was validated by luciferase reporter assays and transfection of miRNA mimics or inhibitors. Cell proliferation was evaluated by MTS assay.

Results

E₂ significantly induced bcl-2, cyclin D1 and survivin expression by suppressing the levels of a panel of miRNAs (miR-16, miR-143, miR-203) in MCF-7 cells. MiRNA transfection and luciferase assay confirmed that bcl-2 was regulated by miR-16 and miR-143, cyclinD1 was modulated by miR-16. Importantly, survivin was found to be targeted by miR-16, miR-143, miR-203. The regulatory effect of E₂ can be either abrogated by anti-estrogen ICI 182, 780 and raloxifene pretreatment, or impaired by ERα siRNA, indicating the regulation is dependent on ERα. In order to investigate the functional significance of these miRNAs in estrogen responsive cells, miRNAs mimics were transfected into MCF-7 cells. It revealed that overexpression of these miRNAs significantly inhibited E₂-induced cell proliferation. Further study of the expression of the miRNAs indicated that miR-16, miR-143 and miR-203 were highly expressed in triple positive breast cancer tissues, suggesting a potential tumor suppressing effect of these miRNAs in ER positive breast cancer.

Conclusions

These results demonstrate that E₂ induces bcl-2, cyclin D1 and survivin by orchestrating the coordinate downregulation of a panel of miRNAs. In turn, the miRNAs manifest growth suppressive effects and control cell proliferation in response to E₂. This sheds a new insight into the integral post-transcriptional regulation of cell proliferation and survival genes by miRNAs, a potential therapeutic option for breast cancer.

Potential regulatory role of calsequestrin in platelet Ca(2+) homeostasis and its association with platelet hyperactivity in diabetes mellitus

BACKGROUND

Altered Ca(2+) homeostasis contributes significantly to platelet hyperactivity in diabetes mellitus. Calsequestrin (CSQ), as a Ca(2+) buffer protein in the sarcoplasmic reticulum, also regulates the Ca(2+) release process in muscles. We hypothesized that CSQ may be expressed in platelets, but is altered and involved in diabetic platelet Ca(2+) abnormalities and hyperaggregability.

METHODS

CSQ expression in platelets from streptozotocin-induced type 1 diabetes rats, type 2 diabetes volunteers and Goto-Kakizaki rats were analyzed by western blotting and RT-qPCR. Platelet Ca(2+) and aggregation were evaluated with Fura2 and an aggregometer, respectively.

RESULTS

Platelets from diabetic patients and rats exhibited increased resting Ca(2+) levels, and hyperactive Ca(2+) and aggregation responses to agonists. This enhanced basal Ca(2+) was largely dependent on intracellular Ca(2+) and insensitive to inositol 1,4,5-trisphosphate receptor (IP(3)R) antagonism. Additionally, the expression of the skeletal CSQ isotype (CSQ-1) was detected in both rat and human platelets, but its levels were significantly lowered in diabetic platelets as compared with normal platelets. Impairment of CSQ by trifluoperazine caused concentration-dependent Ca(2+) release in normal platelets and HEK293 cells. Knocking down CSQ-1 in HEK293 cells resulted in increased leakage of Ca(2+), which was also insensitive to IP(3)R inhibition, and exaggerated Ca(2+) release following carbachol treatment.

CONCLUSIONS

Downregulation of CSQ-1 in diabetic platelets and impairment of CSQ-1 in normal cells leads to disturbed Ca(2+) release, demonstrating a potential role for CSQ-1 in the regulation of the platelet Ca(2+) release process and a possible causal contribution to diabetic platelet hyperactivity.

Perivascular epithelioid cell tumor (PEComa) of gynecologic origin: a clinicopathological study of three cases

Perivascular epithelioid cell tumors (PEComas), occasionally associated with the tuberous sclerosis complex, are characterized by varying amounts of spindle and epithelioid cells with clear to eosinophilic cytoplasm that display immunoreactivity for melanocytic markers, most frequently HMB-45. Perivascular epithelioid cell tumor of gynecologic origin is very rare, and there have been only a few reported cases. This study describes the clinical, histological, and immunohistochemical features and prognoses of three cases of gynecologic origin. Two of the three tumors were confined to the uterus and one to the vagina. None of the patients had tuberous sclerosis complex. Immunohistochemistry indicated that all three cases expressed at least one melanocytic marker, and HMB45 was a positive marker for all of them. These markers can be found in both epithelial cells and spindle cells. Except for MiTF, which was located in the nucleus, all the other antibodies were located in the cytoplasm. The three cases have been followed up for 26, 22, and three months, respectively, with disease-free survival in all cases. We conclude that PEComas of gynecologic origin have morphological and immunohistochemical features of the PEComa family, which are rare and should be included in the differential diagnosis with other tumors. Until more cases of this rare tumor are evaluated with longer follow-up, firm criteria for malignancy remain uncertain.

Higher specificity of the activity of low molecular weight fucoidan for thrombin-induced platelet aggregation

Algal fucoidans possess a wide variety of biological activities, including anticoagulation and antithrombosis, making them potential candidates for clinical use. We assessed the antiaggregant, anticoagulant and antithrombotic activities and the underlying mechanism of the low- and high-molecular weight fucoidans from the seaweed Laminaria japonica of Qingdao, China (F-Q and HMWF-Q). In the platelets of rats and humans, HMWF-Q demonstrated a pro-aggregation response, whereas F-Q (like the commercially purchased fucoidan (F-S) and heparin), showed an inhibitory effect on thrombin-induced aggregation with an IC(50) of 8 microg/mL, approximately five times lower than those of F-S and heparin. In the activated partial thromboplastin time test, F-Q (40 microg/mL) demonstrated less potent effect than F-S (40 microg/mL) and heparin (7mug/mL); 162+/-2.4s vs. 250+/-13.2s and >300s, p<0.01, respectively. It was also less effective than F-S on inhibiting thrombin catalyzed fibrinogen cleavage (IC(50) 10 microg/mL vs. 2.8 microg/mL) in vitro and rat thrombosis in vivo at 3mg/kg (i.v.). The inhibitory effects of F-Q and heparin on thrombin activity were strikingly enhanced by either antithrombin (AT) or heparin cofactor II (HCII). A direct interaction of F-S with thrombin, and F-Q or heparin with AT was demonstrated in both fluorescence quenching and PAGE analysis. Additionally, a pro-aggregation effect and an enhancement of thrombin activity were also observed with F-S, but not with F-Q or heparin, treatment. These results indicate that F-Q inhibits thrombin via activation of AT and HCII, whereas F-S mainly interacts directly with thrombin. Importantly, F-Q shows a higher specificity for hypoaggregation and a weaker effect for anticoagulant profiles than heparin and F-S. Therefore, F-Q could be a promising candidate for the treatment of thrombosis-related cardiovascular diseases.

A novel association of mGluR1a with the PDZ scaffold protein CAL modulates receptor activity

Metabotropic glutamate receptor subtype 1a (mGluR1a) associates with the proteins mediating its receptor activity, suggesting a complex-controlled function of mGluR1a. Here, using glutathione-S-transferase pull-down, co-immunoprecipitation and immunofluorescence assays in vitro and in vivo, we have found CFTR-associated ligand (CAL) to be a novel binding partner of mGluR1a, through its PSD95/discslarge/ZO1homology domain. Deletion of mGluR1a-carboxyl terminus (CT) or mutation of Leu to Ala in the CT of mGluR1a reduces the association, indicating the essential binding region of mGluR1a for CAL. Functionally, the interaction of mGluR1a with CAL was shown to inhibit mGluR1a-mediated ERK1/2 activation, without an apparent effect, via the C-terminal-truncated receptor. These findings might provide a novel mechanism for the regulation of mGluR1a-mediated signaling through the interaction with CAL.

Nuclear Ca2+ sparks and waves mediated by inositol 1,4,5-trisphosphate receptors in neonatal rat cardiomyocytes

Dynamic nuclear Ca(2+) signals play pivotal roles in diverse cellular functions including gene transcription, cell growth, differentiation, and apoptosis. Here we report a novel nuclear Ca(2+) regulatory mechanism mediated by inositol 1,4,5-trisphosphate receptors (IP(3)Rs) around the nucleus in developing cardiac myocytes. Activation of IP(3)Rs by alpha(1)-adrenergic receptor (alpha(1)AR) stimulation or by IP(3) application (in saponin-permeabilized cells) increases Ca(2+) spark frequency preferentially in the region around the nucleus in neonatal rat ventricular myocytes. A nuclear enrichment of IP(3)R distribution supports the higher responsiveness of Ca(2+) release in this particular region. Strikingly, we observed "nuclear Ca(2+)waves" that engulf the entire nucleus without spreading into the bulk cytosol. alpha(1)AR stimulation enhances the occurrence of nuclear Ca(2+) waves and confers them the ability to trigger cytosolic Ca(2+) waves via IP(3)R-dependent pathways. This finding accounts, at least partly, for a profound frequency-dependent modulation of global Ca(2+) oscillations during alpha(1)AR stimulation. Thus, IP(3)R-mediated Ca(2+) waves traveling in the nuclear region provide active, autonomous regulation of nuclear Ca(2+) signaling, which provides for not only the local signal transduction, but also a pacemaker to drive global Ca(2+) transient in the context of alpha(1)AR stimulation in developing cardiac myocytes.

Receptor subtype involved in alpha 1-adrenergic receptor-mediated Ca2+ signaling in cardiomyocytes

AIM

The enhancement of intracellular Ca2+ signaling in response to alpha 1-adrenergic receptor (alpha 1-AR) stimulation is an essential signal transduction event in the regulation of cardiac functions, such as cardiac growth, cardiac contraction, and cardiac adaptation to various situations. The present study was intended to determine the role(s) of the alpha 1-AR subtype(s) in mediating this response.

METHODS

We evaluated the effects of subtype-specific agonists and antagonists of the alpha 1- AR on the intracellular Ca2+ signaling of neonatal rat ventricular myocytes using a confocal microscope.

RESULTS

After being cultured for 48 h, the myocytes exhibited spontaneous local Ca2+ release, sparks, and global Ca2+ transients. The activation of the alpha 1-AR with phenylephrine, a selective agonist of the alpha 1-AR, dose-dependently increased the frequency of Ca2+ transients with an EC50 value of 2.3 micromol/L. Blocking the alpha 1A-AR subtype with 5-methylurapidil (5-Mu) inhibited the stimulatory effect of phenylephrine with an IC(50) value of 6.7 nmol/L. In contrast, blockade of the alpha 1B-AR and alpha 1D-AR subtypes with chloroethylclonidine and BMY 7378, respectively, did not affect the phenylephrine effect. Similarly, the local Ca2+ spark numbers were also increased by the activation of the alpha 1-AR, and this effect could be abolished selectively by 5-Mu. More importantly, A61603, a novel selective alpha 1A-AR agonist, mimicked the effects of phenylephrine, but with more potency (EC(50) value =6.9 nmol/L) in the potentiation of Ca2+ transients, and blockade of the alpha 1A-AR by 5-Mu caused abolishment of its effects.

CONCLUSION

These results indicate that alpha 1-adrenergic stimulation of intracellular Ca2+ activity is mediated selectively by the alpha 1A-AR.

Role of inositol 1,4,5-trisphosphate receptors in alpha1-adrenergic receptor-induced cardiomyocyte hypertrophy

AIM

Intracellular Ca2+ plays pivotal roles in diverse cellular functions, including gene transcription that underlies cardiac remodeling during stress responses. However, the role of inositol 1,4,5-trisphosphate receptors (IP3Rs) in the mediation of cardiac intracellular Ca2+ and hypertrophic growth remains elusive. Prior work with neonatal rat ventricular myocytes suggests that activation of IP3Rs may be linked to a1 adrenergic receptor (alpha1AR) increased stereotyped Ca2+ spark occurrence and global Ca2+ oscillations. Thus, we hypothesized that Ca2+ release through IP3Rs was necessary for alpha1AR-stimulated cardiac hypertrophy.

METHODS

We used myoinositol 1,4,5-trisphosphate hexakis (butyryloxymethyl) ester (IP3BM), a membrane-permeant ester of IP3, to activate IP3Rs directly, and Fluo 4/AM to measure intracellular Ca2+ signaling.

RESULTS

IP3BM (10 micromol x L(-1)) mimicked the effects of phenylephrine, a selective agonist of alpha1AR, in increments in local Ca2+ spark release (especially in the perinuclear area) and global Ca2+ transient frequencies. More importantly, IP3R inhibitors, 2-aminoethoxydiphenyl borate and Xestospongin C, abolished the IP3BM-induced Ca2+ responses, and significantly suppressed alpha1AR-induced cardiomyocyte hypertrophy assayed by cell size, [3H] leucine incorporation and atrial natriuretic factor gene expression, during sustained (48 h) phenylephrine stimulation.

CONCLUSION

These results, therefore, provide cellular mechanisms that link IP3R signaling to alpha1AR-stimulated gene expression and cardiomyocyte hypertrophy.

Defect complexes in Re3+-doped magnesium sulphate phosphors

A series of magnesium sulphate phosphors MgSO4:RE3+,X ( RE = Dy, Tm, Eu and X = P, Mn) have been prepared and studied. Based on the experimental results of thermoluminescence (TL) emission spectra and dose responses studies, it is proposed that in these phosphors large defect complexes are formed, which include intrinsic imperfections and dopants. These defect complexes were formed in the course of preparation of phosphors and could be regarded as basic elements in the TL multi-stage processes. This defect model might be applicable to the most of TL materials.

TL and OSL of SrSO4 phosphors doped with Eu

The thermoluminescence (TL) and optically stimulated luminescence (OSL) of SrSO4:Eu (0.1 mol%) powder sample were studied. The TL and OSL emission spectrum are measured after irradiation (absorbed dose 100 Gy) of 90Sr source; both of them showed that the emission wavelength is at approximately 375 nm, which indicates that TL and OSL have the same luminescence centres, and the luminescence comes from transitions between the energy levels of Eu2+. The TL glow curves and OSL decay curves illustrate that there is only one main TL peak but two main components in OSL curves. By a comparative study of TL and OSL it is concluded that OSL traps are different from TL traps. The TL and OSL dose responses of SrSO4:Eu phosphor were measured, and it showed that phosphor has similar dose responses for OSL and TL.

Thermoluminescence glow curves and optical stimulated luminescence of undoped alpha-Al2O3 crystals

The characteristics of thermoluminescence (TL) and optical stimulated luminescence (OSL) in undoped alpha-Al2O3 single crystals were studied. The TL glow curves of the crystal samples irradiated at various dose levels were measured by RisØ TL/OSL-DA-15B/C reader with U-340 or 7-59 filters at different heating rates. The glow peaks measured with U-340 at approximately 210 degrees C of the undoped alpha-Al2O3 can be well fitted by first-order kinetic equation whereas the glow peaks measured with 7-59 filters are a composite of two first-order glow peaks. It indicates that the TL glow curves are dependent upon the filter used in the reader that is related to the emission spectra of luminescence materials. The OSL were also measured and fitted by two exponential functions to get the luminescence intensities. The TL and OSL dose responses of the undoped alpha-Al2O3 crystal were obtained in the dose range of 0.12-248 Gy and fitted by the composite action dose-response function to get nonlinear characteristic parameters. The TL and OSL dose responses are linear-sublinear.

Direct coupling between arachidonic acid-induced Ca2+ release and Ca2+ entry in HEK293 cells

Arachidonic acid (AA) modulates intracellular Ca2+ signaling via Ca2+ release or/and Ca2+ entry. However, the mechanism underlies either process is unknown; nor is it clear as to whether the two processes are mechanistically linked. By using Fura2/AM, we found that AA induced mobilization of internal Ca2+ store and an increment in Ca2+, Mn2+ and Ba2+ influx in HEK293 cells. The AA-mediated Ca2+ signaling was not due to AA metabolites, and insensitive to capacitative Ca2+ entry inhibitors. Interestingly, isotetrandrine and Gd3+ inhibited both AA-induced Ca2+ release and Ca2+ entry in a concentration-dependent manner without affecting Ca2+ discharge caused by carbachol, caffeine, or thapsigargin. Additionally, similar pattern of inhibition was observed with tetracaine treatment. More importantly, the three compounds exhibited almost equal potent inhibition of AA-initiated Ca2+ release as well as Ca2+ influx. Therefore, this study, for the first time, provides evidence for a direct coupling between AA-mediated Ca2+ release and Ca2+ entry.

Caffeine induced Ca2+ release and capacitative Ca2+ entry in human embryonic kidney (HEK293) cells

The potential role of endogenous ryanodine receptor (RyR) in modulating Ca2+ handling in HEK293 cells is controversial. Using Fura2/AM, here we provide evidence that caffeine can induce Ca2+ release from inositol 1,4,5-trisphosphate receptor-sensitive stores and Ca2+ entry in early passage numbers of HEK293 cells, but not in late passage ones. Ryanodine blocks caffeine-mediated effect, whereas 4-chloro-m-cresol can mimic these effects. In contrast, an increase in cyclic AMP or activation of voltage-dependent Ca2+ channels does not induce detectable alteration in intracellular Ca2+. Importantly, immunoblotting and staining have revealed that endogenous RyR expression is more abundant in the early than in the late passage cells. Additionally, similar to carbachol, Ca2+ entry in response to caffeine is blocked by capacitative Ca2+ entry inhibitors. These results indicate that the endogenous RyR in HEK293 cells can function as Ca2+ release channels and mediate capacitative Ca2+ entry, but they may be reduced due to cell passage.