RNA Therapeutics for the Cardiovascular System

RNA therapeutics hold significant promise in the treatment of cardiovascular diseases. RNAs are biologically diverse and functionally specific and can be used for gain- or loss-of-function purposes. The effectiveness of mRNA-based vaccines in the recent COVID-19 pandemic has undoubtedly proven the benefits of an RNA-based approach. RNA-based therapies are becoming more common as a treatment modality for cardiovascular disease. This is most evident in hypertension where several small interfering RNA-based drugs have proven to be effective in managing high blood pressure in several clinical trials. As befits a rapidly burgeoning field, there is significant interest in other classes of RNA. Revascularization of the infarcted heart through an mRNA drug is under clinical investigation. mRNA technology may provide the platform for the expression of paracrine factors for myocardial protection and regeneration. Emergent technologies on the basis of microRNAs and gene editing are tackling complex diseases in a novel fashion. RNA-based gene editing offers hope of permanent cures for monogenic cardiovascular diseases, and long-term control of complex diseases such as essential hypertension, as well. Likewise, microRNAs are proving effective in regenerating cardiac muscle. The aim of this review is to provide an overview of the current landscape of RNA-based therapies for the treatment of cardiovascular disease. The review describes the large number of RNA molecules that exist with a discussion of the clinical development of each RNA type. In addition, the review also presents a number of avenues for future development.

Trypanosoma cruzi Dysregulates piRNAs Computationally Predicted to Target IL-6 Signaling Molecules During Early Infection of Primary Human Cardiac Fibroblasts

Trypanosoma cruzi, the etiological agent of Chagas disease, is an intracellular protozoan parasite, which is now present in most industrialized countries. About 40% of T. cruzi infected individuals will develop severe, incurable cardiovascular, gastrointestinal, or neurological disorders. The molecular mechanisms by which T. cruzi induces cardiopathogenesis remain to be determined. Previous studies showed that increased IL-6 expression in T. cruzi patients was associated with disease severity. IL-6 signaling was suggested to induce pro-inflammatory and pro-fibrotic responses, however, the role of this pathway during early infection remains to be elucidated. We reported that T. cruzi can dysregulate the expression of host PIWI-interacting RNAs (piRNAs) during early infection. Here, we aim to evaluate the dysregulation of IL-6 signaling and the piRNAs computationally predicted to target IL-6 molecules during early T. cruzi infection of primary human cardiac fibroblasts (PHCF). Using in silico analysis, we predict that piR_004506, piR_001356, and piR_017716 target IL6 and SOCS3 genes, respectively. We validated the piRNAs and target gene expression in T. cruzi challenged PHCF. Secreted IL-6, soluble gp-130, and sIL-6R in condition media were measured using a cytokine array and western blot analysis was used to measure pathway activation. We created a network of piRNAs, target genes, and genes within one degree of biological interaction. Our analysis revealed an inverse relationship between piRNA expression and the target transcripts during early infection, denoting the IL-6 pathway targeting piRNAs can be developed as potential therapeutics to mitigate T. cruzi cardiomyopathies.

Mechanism underlying the effect of Liujunzi decoction on advanced-stage non-small cell lung cancer in patients after first-line chemotherapy

OBJECTIVE

To further clarify the anticancer mechanisms of Liujunzi decoction and provide possible targets for the treatment of advanced-stage nonsmall cell lung cancer (NSCLC) by re-analyzing differential gene expression profile of peripheral blood mononuclear cells (PBMCs) from Liujunzi decoctiontreated NSCLC patients receiving first-line chemotherapy.

METHODS

The PBMC gene expression microarray data set GSE61926 was retrieved from a high throughput gene expression database. Differentially expressed genes (DEGs) were screened by paired sample t-test and the multiple ratio method. Gene ontology and Kyoto encyclopedia of genes and genomes (KEGG) pathway analyses were performed using the DAVID database. The protein-protein interaction (PPI) network was constructed using interaction gene library retrieval tools and Cytoscape software.

RESULTS

A total of 162 DEGs were identified, with 67 upregulated genes and 95 downregulated genes. The functional distribution of Gene Oncology (GO) genes showed that DEGs were mostly concentrated in extracellular regions, calcium ion binding, and transcriptase activity. KEGG pathway analysis showed that cytokine-cytokine receptor interactions were significantly enriched. PPI network analysis screened out the top 10 central protein-coding genes with the highest nodal degree: IL2, PIWIL4, DICER1, PIWIL2, SAA1, XCL1, IL22RA1, ARHGAP11A, DCP1A, and GDNF. Among them, the central protein-coding gene with the highest node degree was IL2. In addition, the central protein-coding genes with high node degrees and high molecular complex detection (MCODE) scores were PIWIL4, DICER1, PIWIL2, and DCP1A, all of which are related to tumor development.

CONCLUSIONS

One signaling pathway and 10 central protein-coding genes related to anticancer mechanisms were screened by re-analysis of GSE61926 data. IL2, PIWIL4, DICER1, PIWIL2, and DCP1A may have important roles in the mechanism of Liujunzi decoction treatment against NSCLC. Our results suggest that the anticancer mechanism of Liujunzi decoction may be related to gene silencing by RNA and the biological processes of piwi-interacting RNA and other small RNAs.

Novel Mechanisms of Exosome-Mediated Phagocytosis of Dead Cells in Injured Heart

[Figure: see text].

Teprasiran, a Small Interfering RNA, for the Prevention of Acute Kidney Injury in High-Risk Patients Undergoing Cardiac Surgery: A Randomized Clinical Study

Supplemental Digital Content is available in the text.

Acute kidney injury (AKI) affects up to 30% of patients undergoing cardiac surgery, leading to increased in-hospital and long-term morbidity and mortality. Teprasiran is a novel small interfering RNA that temporarily inhibits p53-mediated cell death that underlies AKI.

Role of PCSK9 Inhibitors in Patients with Familial Hypercholesterolemia

Patients with familial hypercholesterolemia (FH) are at high or very high risk for cardiovascular disease. Those with heterozygous FH (HeFH) often do not reach low-density lipoprotein cholesterol (LDL-C) targets with statin and ezetimibe therapy, and those with homozygous FH (HoFH) usually require additional lipid-modifying therapies. Drugs that inhibit proprotein convertase subtilisin/kexin type 9 (PCSK9) offer a novel approach to reduce LDL-C. The monoclonal antibodies, alirocumab and evolocumab, given by subcutaneous injection every 2 or 4 weeks produce reductions in LDL-C of 50% to 60% in patients with HeFH, allowing many of them to achieve their LDL-C goals. Patients with HoFH show a reduced and more variable LDL-C response, which appears to depend on residual LDL receptor activity, and those with receptor-negative mutations may show no response. Inclisiran is a long-acting small interfering RNA therapeutic agent that inhibits the synthesis of PCSK9. Subcutaneous doses of 300 mg can reduce LDL-C by more than 50% for at least 6 months and the responses in HeFH and HoFH patients are similar to those achieved with monoclonal antibodies. These PCSK9 inhibitors are generally well tolerated and they provide a new opportunity for effective treatment for the majority of patients with FH.

Renoprotective Effects of Small Interfering RNA Targeting Liver Angiotensinogen in Experimental Chronic Kidney Disease

[Figure: see text].

[Influenza virus activates toll-like receptor 7/nuclear factor-κB signaling pathway to regulate airway inflammatory response in patients with acute exacerbation of chronic obstructive pulmonary diseases]

Objective: To explore how influenza A virus (IAV) regulates airway inflammation via activating Toll-like receptor 7(TLR7)/nuclear factor of κB (NF-κB) signaling pathway in patients with acute exacerbation of chronic obstructive pulmonary disease (COPD). Methods: Primary bronchial epithelial cells were isolated and cultured from normal controls and COPD patients. Samples were divided into 6 groups according to different in vitro treatment, including normal epithelial cell group (A), normal cells+IAV group (B), COPD epithelial cell group (C), COPD cells+IAV group (D), normal cells+TLR7 small interference RNA (si-RNA) group (E), COPD cells+TLR7 siRNA group (F). Protein expressions of TLR7 and NF-κB were detected by Western blot after 24h co-culture with IAV and TLR7 siRNA. Interleukin-6 (IL-6) and tumor necrosis factor α (TNF α) were detected by enzyme-linked immunosorbent assay (ELISA). Results: (1) Compared with group A [0.350±0.075 and 0.470±0.034, (53.000±6.532)pg/ml and (17.000±1.625)pg/ml],TLR7, NF-κB protein expression and IL-6, TNF α levels were significantly increased in group B[0.950±0.075 and 1.090±0.078,(185.000±7.874)pg/ml and (32.000±0.838)pg/ml], group C[0.780±0.056 and 0.910±0.045,(138.000±5.100)pg/ml and 29.000±1.323)pg/ml) and group D[1.280±0.031 and 1.540±0.051,(432.000±5.734)pg/ml and (52.000±3.453)pg/ml] (all P<0.01). Compared with group C TLR7, NF-κB protein expression and IL-6, TNF α levels were significantly increased in group D (P<0.01). (2) Compared with the group A[0.530±0.023 and 0.800±0.046,(51.000±0.327)pg/ml and (14.000±0.314)pg/ml], TLR7, NF-κB protein expression and IL-6, TNF α levels were significantly decreased in the group E[0.350±0.047 and 0.510±0.067,(26.000±1.081)pg/ml and(8.000±0.526)pg/ml] (P<0.05). Compared with group C[1.080±0.078 and 1.280±0.034,(125.000±2.249)pg/ml and (28.000±1.010)pg/ml], TLR7, NF-κB protein expression and IL-6, TNF α levels decreased in the group F[0.880±0.056 and 1.040±0.029,(83.000±1.125)pg/ml and (21.000±0.429)pg/ml] (P<0.05). Conclusion: Influenza viruses activate TLR7/NF-κB signaling pathway to regulate airway inflammation storms in patients with acute exacerbation of COPD. New therapeutic targets of acute exacerbation COPD may be studied based on these inflammation responses to influenza viruses.

[Expression of circular RNA hsa_circ_0014130 in lung adenocarcinoma cell lines and its effect on proliferation and invasion of lung adenocarcinoma cell line]

Objective: To investigate the function and mechanism of hsa_circ_0014130 in lung adenocarcinoma cell line and to find potential molecular inhibitors. Methods: The hsa_circ_0014130 expression level detection and overexpression and subtraction experiments were performed using common cell lines of lung cancer (PC9, H1299, A549, HCC827, and BEAS-2B). qPCR was used to verify the proliferation and invasion of lung cancer cells by MTS and invasion assay, and then the targeted microRNA was searched through the database. Western blot was used to detect the downstream signaling pathways, and finally the effect of small molecule inhibitors was investigated on proliferation and invasion of non-small cell lung cancer. Results: The expression level of hsa_circ_0014130 was up-regulated in the three cell lines, and both the overexpression plasmid and the subtractive siRNA were effectively transfected into the cells. Overexpression of hsa_circ_0014130 was able to promote the proliferation and invasion of tumor cells, and knockdown of hsa_circ_0014130 inhibited the proliferation and invasion of tumor cells. hsa_circ_0014130 was capable to target hsa-miR-566 to reduce its expression level and to inhibit epithelial-to-mesenchymal transition. The use of the small molecule inhibitor SB-431542 and simultaneous reduction of hsa_circ_0014130 significantly inhibited the proliferation and invasion of tumor cells. Conclusions: The hsa_circ_0014130 promotes the invasion and proliferation of lung cancer cells by targeting hsa-miR-566 to enhance the expression of TWIST1, and its expression level can be significantly inhibited by the small molecule inhibitor SB-431542, which significantly inhibits the proliferation and invasion of lung cancer cells. Therefore,hsa_circ_0014130 is a potential lung cancer treatment target.

Allele-Specific Silencing Ameliorates Restrictive Cardiomyopathy Attributable to a Human Myosin Regulatory Light Chain Mutation

BACKGROUND

Restrictive cardiomyopathy is a rare heart disease associated with mutations in sarcomeric genes and with phenotypic overlap with hypertrophic cardiomyopathy. There is no approved therapy directed at the underlying cause. Here, we explore the potential of an interfering RNA (RNAi) therapeutic for a human sarcomeric mutation in MYL2 causative of restrictive cardiomyopathy in a mouse model.

METHODS

A short hairpin RNA (M7.8L) was selected from a pool for specificity and efficacy. Two groups of myosin regulatory light chain N47K transgenic mice were injected with M7.8L packaged in adeno-associated virus 9 at 3 days of age and 60 days of age. Mice were subjected to treadmill exercise and echocardiography after treatment to determine maximal oxygen uptake and left ventricular mass. At the end of treatment, heart, lung, liver, and kidney tissue was harvested to determine viral tropism and for transcriptomic and proteomic analysis. Cardiomyocytes were isolated for single-cell studies.

RESULTS

A one-time injection of AAV9-M7.8L RNAi in 3-day-old humanized regulatory light chain mutant transgenic mice silenced the mutated allele (RLC-47K) with minimal effects on the normal allele (RLC-47N) assayed at 16 weeks postinjection. AAV9-M7.8L RNAi suppressed the expression of hypertrophic biomarkers, reduced heart weight, and attenuated a pathological increase in left ventricular mass. Single adult cardiac myocytes from mice treated with AAV9-M7.8L showed partial restoration of contraction, relaxation, and calcium kinetics. In addition, cardiac stress protein biomarkers, such as calmodulin-dependent protein kinase II and the transcription activator Brg1 were reduced, suggesting recovery toward a healthy myocardium. Transcriptome analyses further revealed no significant changes of argonaute (AGO1, AGO2) and endoribonuclease dicer (DICER1) transcripts, and endogenous microRNAs were preserved, suggesting that the RNAi pathway was not saturated.

CONCLUSIONS

Our results show the feasibility, efficacy, and safety of RNAi therapeutics directed towards human restrictive cardiomyopathy. This is a promising step toward targeted therapy for a prevalent human disease.

[Effects of human leucocyte antigen-G expression on invasion and proliferation of chorionic trophoblastic cell line JEG-3]

Objective: To investigate the effects of human leukocyte-associated antigen-G (HLA-G) expression in silencing trophoblast cell line JEG-3 under normal and hypoxic conditions on invasion and proliferation of JEG-3 cells. Methods: Inhibition of HLA-G expression in JEG-3 cells by transfection of small interfering RNA (siRNA),the transfected JEG-3 cells were divided into 4 groups: normoxia control group, hypoxia control group, normoxia inhibition group and hypoxia inhibition group. The levels of HLA-G mRNA and protein in 4 groups of cells were detected by real-time quantitive PCR and western blot. The proliferation activity and invasion ability of 4 groups of cells were determined by methylthiazolyl tetrazolium (MTT) assay and invasion assay. Results: (1) Real-time quantitive PCR technology showed: the level of HLA-G mRNA in the hypoxic inhibition group (0.220±0.050) was significantly different (P<0.05), when compared with that in the hypoxic control group (0.630±0.030) and normoxic inhibition group (0.400±0.020). (2) Western blot analysis showed: the expression level of HLA-G protein in the hypoxic inhibition group was 0.260±0.010, statistically different from that in the hypoxic control group (0.850±0.100) and the normoxic inhibition group (0.560±0.020; P<0.05).(3) MTT showed: proliferative activity of JEG-3 cells in the normoxic inhibition group was 0.490±0.070, the ability of cell proliferation was reduced. When compared with that in the normoxic control group (0.850±0.050), the differences was statistically significant (P<0.05). The proliferative activity of JEG-3 cells in the hypoxic inhibition group (0.330±0.070) was lower than that in the normoxic inhibition group (0.490±0.070), and there was a significant difference (P<0.05). (4) Invasion assay showed: compared with the normoxic control group (98±7), the invasive ability of JEG-3 cells in the normoxic inhibition group (73±7) was weakened, and the difference was statistically significant (P<0.05). The number of transmembrane cells (52±11) of JEG-3 cells in the hypoxic inhibition group was lower than that in the hypoxic control group (72±7), and the difference was statistically significant (P<0.05). Compared with the normoxic inhibition group, the invasion ability of JEG-3 cells in the hypoxic inhibition group decreased, and the difference was statistically significant (P<0.05). Conclusion: Under hypoxia, using siRNA technology to down-regulate the expression of HLA-G may affect the proliferation and invasion ability of trophoblast cells, which may be involved in the occurrence of hypertensive disorder of pregnancy.

[Establishment of myocardial targeted nanoparticles and preliminary evaluation of its effects on prevention and treatment of myocardial injury]

Objective: To establish 3-{4-[2-hydroxyl-(1-methylethylamino) propoxy] phenyl} propionic acid cetylesters (PAC) modified nanoparticles, and preliminarily explore its cardiomyocyte-targeting function and protection effects on myocardium. Methods: (1) HL-1 myocardial cells were divided into cyanidin-3 (Cy3) marked non-targeted small interference RNA (Cy3-siNC) group and Cy3 marked small interference RNA designed for the nuclear factor kappa B (NF-κB)-p65 gene (Cy3-si435) group according to the random number table, with 3 wells in each group. Cells in Cy3-siNC group were transfected with Cy3-siNC, while cells in Cy3-si435 group were transfected with Cy3-si435. At transfection hour 24, the mRNA expression of NF-κB-p65 of cells was determined by real-time fluorescent quantitative polymerase chain reaction. (2) Multiple emulsificating solvent evaporating method was adopted to prepare PAC modified nanoparticles carried with Cy3-siNC (Cy3-siNC-PAC) and PAC modified nanoparticles carried with Cy3-si435 (Cy3-si435-PAC). The morphology of Cy3-si435-PAC nanoparticles was observed with scanning electron microscope, and the size and potential of Cy3-si435-PAC nanoparticles were detected by nanometer particle size and zeta potential analyzer. The entrapment efficiency and drug loadings of Cy3-si435-PAC nanoparticle were determined with ultraviolet spectrophotometer. The release of Cy3-si435 of Cy3-si435-PAC nanoparticles was determined by dialysis method. (3) Another batch of HL-1 cells were divided into 4 groups according to the random number table, with 9 wells in each group. Cells in negative control group were added with 5 μL phosphate buffer. Cells in 25, 50, and 100 mg/mL Cy3-si435-PAC nanoparticles groups were added with 5 μL 25, 50, and 100 mg/mL Cy3-si435-PAC nanoparticles, respectively. At transfection hour 6, 12, and 24, proliferation activity of cells in 3 wells of each group was detected by methyl thiazolyl tetrazolium method, respectively. (4) Another batch of HL-1 cells were cultured for 24 h, and then treated with 100 μL Cy3-si435-PAC nanoparticles. At transfection hour 0, 4, 8, 12, and 24, the percentage of cells uptaking Cy3-si435-PAC nanoparticles in 3 wells were detected by flow cytometry, respectively. (5) Another batch of HL-1 cells were divided into 2 groups according to the random number table, with 3 wells in each group. Cells in Cy3-siNC-PAC group were added with 100 μL Cy3-siNC-PAC nanoparticles, while cells in Cy3-si435-PAC group were added with 100 μL Cy3-si435-PAC nanoparticles. At transfection hour 24, the mRNA expression of NF-κB-p65 of cells was determined by real-time fluorescent quantitative polymerase chain reaction. (6) Six male C57BL/6J mice were divided into 2 groups according to the random number table, with 3 mice in each group. Mice in Cy3-siNC-lipopolysaccharide (LPS) group and Cy3-si435-LPS group were respectively injected with 500 μL Cy3-siNC-PAC nanoparticles and Cy3-si435-PAC nanoparticles (50 mg/mL) in the tail vein. At injection hour 24, mice in the two groups were intraperitoneally injected with 10 mg/kg LPS to induce myocardial injury. At post injury hour 24, the distribution of nanoparticles in mice was detected with small animal imager. (7) Another 9 male C57BL/6J mice were divided into 3 groups according to the random number table, with 3 mice in each group. Mice in Cy3-siNC-normal saline (NS) group and Cy3-siNC-LPS group were injected with 500 μL 50 mg/mL Cy3-siNC-PAC nanoparticles in the tail vein, while mice in Cy3-si435-LPS group were injected with 500 μL 50 mg/mL Cy3-si435-PAC nanoparticles. At injection hour 24, mice in Cy3-siNC-NS group were intraperitoneally injected with NS, while mice in Cy3-siNC-LPS group and Cy3-si435-LPS group were injected with 10 mg/kg LPS to induce myocardial injury. At post injury hour 24, pathological changes of myocardium of mice in each group were observed with HE staining. Data were processed with t test and one-way analysis of variance. Results: (1) The mRNA expression of NF-κB-p65 of cells in Cy3-si435 group was 0.183±0.004, significantly lower than 1.003±0.092 in Cy3-siNC group (t=15.46, P<0.01). (2) The form of prepared Cy3-si435-PAC nanoparticles was good, with particle size of 146.0 nm, potential of -29.2 mV, entrapment efficiency of (86.9±1.1) %, drug loadings of (25.4±0.9) %, and stable Cy3-si435 release. (3) At transfection hour 6, 12, and 24, there were no statistically significant differences in proliferation activity of cells in the 4 groups (with F values from 0.129 to 2.512, P values above 0.05). (4) At transfection hour 0, 4, 8, 12, and 24, the percentages of cells uptaking Cy3-si435-PAC nanoparticles were (0.79±0.06)%, (31.04±1.59)%, (51.64±2.67)%, (68.15±2.60)%, and (83.68±4.67)%, respectively. (5) The mRNA expression of NF-κB-p65 of cells in Cy3-si435-PAC group was 0.286±0.015, significantly lower than 1.002±0.073 in Cy3-siNC-PAC group (t=16.62, P<0.01). (6) At post injury hour 24, uniform distribution of nanoparticles could be observed in cardiomyocytes of mice in Cy3-siNC-LPS group and Cy3-si435-LPS group. (7) The structure of myocardial fibers of mice in Cy3-siNC-NS group was dense, with no inflammatory cells infiltration and uniform distribution of cytoplasm. The structure of myocardial fibers of mice in Cy3-siNC-LPS group were loose, with inflammatory cells infiltration and scattered distribution of cytoplasm. The structure of myocardial fibers of mice in Cy3-si435-LPS group was denser, with no obvious inflammatory cells infiltration and uniform distribution of cytoplasm. Conclusions: Cy3-si435-PAC nanoparticles have good morphology, uniform particle size, normal potential distribution, and no cell cytotoxicity. Cy3-si435-PAC nanoparticles can be effectively uptaked by HL-1 cells and suppress NF-κB-p65 mRNA expression. They also can effectively target to mice cardiomyocytes to reduce inflammatory cells infiltration and alleviate the myocardial injury of mice induced by LPS.

Pregnancy Reprograms Large-Conductance Ca2+-Activated K+ Channel in Uterine Arteries: Roles of Ten-Eleven Translocation Methylcytosine Dioxygenase 1-Mediated Active Demethylation

The large-conductance Ca²⁺-activated K⁺ (BK_Ca) channel is of critical importance in pregnancy-mediated increase in uterine artery vasodilation and blood flow. The present study tested the hypothesis that active DNA demethylation plays a key role in pregnancy-induced reprogramming and upregulation of BK_Ca channel β1 subunit (BKβ1) in uterine arteries. Uterine arteries were isolated from nonpregnant and near-term pregnant sheep. Pregnancy significantly increased the expression of ten-eleven translocation methylcytosine dioxygenase 1 (TET1) in uterine arteries. A half-palindromic estrogen response element was identified at the TET1 promoter, and estrogen treatment increased TET1 promoter activity and TET1 expression in uterine arteries. In accordance, pregnancy and steroid hormone treatment resulted in demethylation of BKβ1 promoter by increasing 5-hydroxymethylcytosine and decreasing 5-methylcytosine at the CpG in the Sp1_-380 binding site that is of critical importance in the regulation of the promoter activity and BKβ1 expression. Inhibition of TET1 with fumarate significantly decreased BKβ1 expression in uterine arteries of pregnant animals and blocked steroid hormone-induced upregulation of BKβ1. Functionally, fumarate treatment inhibited pregnancy and steroid hormone-induced increases in BK_Ca channel current density and BK_Ca channel-mediated relaxations. In addition, fumarate blocked pregnancy and steroid hormone-induced decrease in pressure-dependent myogenic tone of the uterine artery. The results demonstrate a novel mechanism of estrogen-mediated active DNA demethylation in reprogramming of BK_Ca channel expression and function in the adaption of uterine circulation during pregnancy.

Adenylyl cyclase 5 links changes in calcium homeostasis to cAMP-dependent cyst growth in polycystic liver disease

BACKGROUND & AIMS

Genetic defects in polycystin-1 or -2 (PC1 or PC2) cause polycystic liver disease associated with autosomal dominant polycystic kidney disease (PLD-ADPKD). Progressive cyst growth is sustained by a cAMP-dependent Ras/ERK/HIFα pathway, leading to increased vascular endothelial growth factor A (VEGF-A) signaling. In PC2-defective cholangiocytes, cAMP production in response to [Ca²⁺]_ER depletion is increased, while store-operated Ca²⁺ entry (SOCE), intracellular and endoplasmic reticulum [Ca²⁺]_ER levels are reduced. We investigated whether the adenylyl cyclases, AC5 and AC6, which can be inhibited by Ca²⁺, are activated by the ER chaperone STIM1. This would result in cAMP/PKA-dependent Ras/ERK/HIFα pathway activation in PC2-defective cells, in response to [Ca²⁺]_ER depletion.

METHODS

PC2/AC6 double conditional knockout (KO) mice were generated (Pkd2/AC6 KO) and compared to Pkd2 KO mice. The AC5 inhibitor SQ22,536 or AC5 siRNA were used in isolated cholangiocytes while the inhibitor was used in biliary organoid and animals; liver tissues were harvested for histochemical analysis.

RESULTS

When comparing Pkd2/AC6 KO to Pkd2 KO mice, no decrease in liver cyst size was found, and cellular cAMP after [Ca²⁺]_ER depletion only decreased by 12%. Conversely, in PC2-defective cells, inhibition of AC5 significantly reduced cAMP production, pERK1/2 expression and VEGF-A secretion. AC5 inhibitors significantly reduced growth of biliary organoids derived from Pkd2 KO and Pkd2/AC6 KO mice. In vivo treatment with SQ22,536 significantly reduced liver cystic area and cell proliferation in PC2-defective mice. After [Ca²⁺]_ER depletion in PC2-defective cells, STIM1 interacts with AC5 but not with Orai1, the Ca²⁺ channel that mediates SOCE.

CONCLUSION

[Ca²⁺]_ER depletion in PC2-defective cells activates AC5 and results in stimulation of cAMP/ERK1-2 signaling, VEGF production and cyst growth. This mechanism may represent a novel therapeutic target.

LAY SUMMARY

Polycystic liver diseases are characterized by progressive cyst growth until their complications mandate surgery or liver transplantation. In this manuscript, we demonstrate that inhibiting cell proliferation, which is induced by increased levels of cAMP, may represent a novel therapeutic target to slow the progression of the disease.

Bone morphogenetic proteins protect pulmonary microvascular endothelial cells from apoptosis by upregulating α-B-crystallin

OBJECTIVE

To investigate the role of bone morphogenetic proteins (BMPs) on α-B-crystallin (CRYAB) expression and its physiological consequences on endothelial cells (ECs).

APPROACH AND RESULTS

We report that the gene encoding for the small heat shock protein, CRYAB, is a transcriptional target of the BMP signaling pathway. We demonstrate that CRYAB expression is upregulated strongly by BMPs in an EC line and in human lung microvascular ECs and human umbilical vein ECs. We show that BMP signals through the BMPR2-ALK1 pathway to upregulate CRYAB expression through a transcriptional indirect mechanism involving Id1. We observed that the known antiapoptotic effect of the BMPs is, in part, because of the upregulation of CRYAB expression in EC. We also show that cryab is downregulated in vivo, in a mouse model of pulmonary arterial hypertension induced by chronic hypoxia where the BMP pathway is downregulated.

CONCLUSIONS

We demonstrate a cross-talk between BMPs and CRYAB and a major effect of this regulatory interaction on resistance to apoptosis.

Monocyte-directed RNAi targeting CCR2 improves infarct healing in atherosclerosis-prone mice

BACKGROUND

Exaggerated and prolonged inflammation after myocardial infarction (MI) accelerates left ventricular remodeling. Inflammatory pathways may present a therapeutic target to prevent post-MI heart failure. However, the appropriate magnitude and timing of interventions are largely unknown, in part because noninvasive monitoring tools are lacking. Here, we used nanoparticle-facilitated silencing of CCR2, the chemokine receptor that governs inflammatory Ly-6C(high) monocyte subset traffic, to reduce infarct inflammation in apolipoprotein E-deficient (apoE(-/-)) mice after MI. We used dual-target positron emission tomography/magnetic resonance imaging of transglutaminase factor XIII (FXIII) and myeloperoxidase (MPO) activity to monitor how monocyte subset-targeted RNAi altered infarct inflammation and healing.

METHODS AND RESULTS

Flow cytometry, gene expression analysis, and histology revealed reduced monocyte numbers and enhanced resolution of inflammation in infarcted hearts of apoE(-/-) mice that were treated with nanoparticle-encapsulated siRNA. To follow extracellular matrix cross-linking noninvasively, we developed a fluorine-18-labeled positron emission tomography agent ((18)F-FXIII). Recruitment of MPO-rich inflammatory leukocytes was imaged with a molecular magnetic resonance imaging sensor of MPO activity (MPO-Gd). Positron emission tomography/magnetic resonance imaging detected anti-inflammatory effects of intravenous nanoparticle-facilitated siRNA therapy (75% decrease of MPO-Gd signal; P<0.05), whereas (18)F-FXIII positron emission tomography reflected unimpeded matrix cross-linking in the infarct. Silencing of CCR2 during the first week after MI improved ejection fraction on day 21 after MI from 29% to 35% (P<0.05).

CONCLUSION

CCR2-targeted RNAi reduced recruitment of Ly-6C(high) monocytes, attenuated infarct inflammation, and curbed post-MI left ventricular remodeling.