Notoginsenoside R1 protects human keratinocytes HaCaT from LPS-induced inflammatory injury by downregulation of Myd88.

Burn injury is a gigantic challenge in public health which brings multiple negative effects to patients both in physical and spiritual aspects. Inflammation plays vital roles in the progression of burn injury, and our study investigated whether notoginsenoside R1 (NGR1) alleviated lipopolysaccharide (LPS)-induced human keratinocyte HaCaT cell inflammatory injury. Inflammatory injury was induced by LPS in HaCaT cells. Stimulated cells were then treated by NGR1 in different concentrations. Cell viability and cell apoptosis were detected by Cell Counting Kit-8 and flow cytometry, respectively. The concentration of tumor necrosis factor α (TNF-α) and interleukin-6 (IL-6) was measured by enzyme-linked immunosorbent assay (ELISA). The accumulated levels of apoptosis-related proteins (caspase-3 and caspase-9), nuclear factor κB (NF-κB), p38 mitogen-activated protein kinase (p38MAPK) signal pathways-related proteins (p65, IκBα, and p38MAPK), and myeloid differentiation primary response 88 (MyD88) were examined by western blot. Transfection was used to alter the expression of MyD88. We found that LPS stimulated HaCaT cells and induced cell inflammation, evidenced by decreasing cell viability, increasing cell apoptosis, and elevating TNF-α and IL-6 expressions. Then, we found that NGR1 reversed the results by enhancing cell viability, inhibiting cell apoptosis, and reducing TNF-α and IL-6 expressions. In addition, NGR1 decreased the phosphorylation of p65, IκBα, and p38MAPK, which increased by LPS. Moreover, NGR1 negatively regulated the expression of MyD88, and transfection with pMyD88 led to the opposite results with what showed by NGR1 in LPS-stimulated HaCaT cells. To sum up, NGR1 alleviates LPS-induced HaCaT cell inflammatory injury by downregulation of MyD88, as well as inactivation of NF-κB and p38MAPK signal pathways.

Transcriptional regulation of stress kinase JNK2 in pro-arrhythmic CaMKIIδ expression in the aged atrium.

Aims: c-jun N-terminal kinase (JNK) is a critical stress response kinase that activates in a wide range of physiological and pathological cellular processes. We recently discovered a pivotal role of JNK in the development of atrial arrhythmias in the aged heart, while cardiac CaMKIIδ, another pro-arrhythmic molecule, was also known to enhance atrial arrhythmogenicity. Here, we aimed to reveal a regulatory role of the stress kinase JNK2 isoform on CaMKIIδ expression. Methods and results: Activated JNK2 leads to increased CaMKIIδ protein expression in aged human and mouse atria, evidenced from the reversal of CaMKIIδ up-regulation in JNK2 inhibitor treated wild-type aged mice. This JNK2 action in CaMKIIδ expression was further confirmed in HL-1 myocytes co-infected with AdMKK7D-JNK2, but not when co-infected with AdMKK7D-JNK1. JNK2-specific inhibition (either by a JNK2 inhibitor or overexpression of inactivated dominant-negative JNK2 (JNK2dn) completely attenuated JNK activator anisomycin-induced CaMKIIδ up-regulation in HL-1 myocytes, whereas overexpression of JNK1dn did not. Moreover, up-regulated CaMKIIδ mRNA along with substantially increased phosphorylation of JNK downstream transcription factor c-jun [but not activating transcription factor2 (ATF2)] were exhibited in both aged atria (humans and mice) and transiently JNK activated HL-1 myocytes. Cross-linked chromatin-immunoprecipitation assays (XChIP) revealed that both c-jun and ATF2 were bound to the CaMKIIδ promoter, but significantly increased binding of c-jun only occurred in the presence of anisomycin and JNK inhibition alleviated this anisomycin-elevated c-jun binding. Mutated CaMKII consensus c-jun binding sites impaired its promoter activity. Enhanced transcriptional activity of CaMKIIδ by anisomycin was also completely reversed to the baseline by either JNK2 siRNA or c-jun siRNA knockdown. Conclusion: JNK2 activation up-regulates CaMKIIδ expression in the aged atrium. This JNK2 regulation in CaMKIIδ expression occurs at the transcription level through the JNK downstream transcription factor c-jun. The discovery of this novel molecular mechanism of JNK2-regulated CaMKII expression sheds new light on possible anti-arrhythmia drug development.

Nebivolol suppresses cardiac ryanodine receptor-mediated spontaneous Ca2+ release and catecholaminergic polymorphic ventricular tachycardia.

ß-Blockers are a standard treatment for heart failure and cardiac arrhythmias. There are ∼30 commonly used ß-blockers, representing a diverse class of drugs with different receptor affinities and pleiotropic properties. We reported that among 14 ß-blockers tested previously, only carvedilol effectively suppressed cardiac ryanodine receptor (RyR2)-mediated spontaneous Ca2+ waves during store Ca2+ overload, also known as store overload-induced Ca2+ release (SOICR). Given the critical role of SOICR in arrhythmogenesis, it is of importance to determine whether there are other ß-blockers that suppress SOICR. Here, we assessed the effect of other commonly used ß-blockers on RyR2-mediated SOICR in HEK293 cells, using single-cell Ca2+ imaging. Of the 13 ß-blockers tested, only nebivolol, a ß-1-selective ß-blocker with nitric oxide synthase (NOS)-stimulating action, effectively suppressed SOICR. The NOS inhibitor (N-nitro-l-arginine methyl ester) had no effect on nebivolol's SOICR inhibition, and the NOS activator (histamine or prostaglandin E2) alone did not inhibit SOICR. Hence, nebivolol's SOICR inhibition was independent of NOS stimulation. Like carvedilol, nebivolol reduced the opening of single RyR2 channels and suppressed spontaneous Ca2+ waves in intact hearts and catecholaminergic polymorphic ventricular tachycardia (CPVT) in the mice harboring a RyR2 mutation (R4496C). Interestingly, a non-ß-blocking nebivolol enantiomer, (l)-nebivolol, also suppressed SOICR and CPVT without lowering heart rate. These data indicate that nebivolol, like carvedilol, possesses a RyR2-targeted action that suppresses SOICR and SOICR-evoked VTs. Thus, nebivolol represents a promising agent for Ca2+-triggered arrhythmias.

Non-ß-blocking R-carvedilol enantiomer suppresses Ca2+ waves and stress-induced ventricular tachyarrhythmia without lowering heart rate or blood pressure.

Carvedilol is the current ß-blocker of choice for suppressing ventricular tachyarrhythmia (VT). However, carvedilol's benefits are dose-limited, attributable to its potent ß-blocking activity that can lead to bradycardia and hypotension. The clinically used carvedilol is a racemic mixture of ß-blocking S-carvedilol and non-ß-blocking R-carvedilol. We recently reported that novel non-ß-blocking carvedilol analogues are effective in suppressing arrhythmogenic Ca(2+) waves and stress-induced VT without causing bradycardia. Thus, the non-ß-blocking R-carvedilol enantiomer may also possess this favourable anti-arrhythmic property. To test this possibility, we synthesized R-carvedilol and assessed its effect on Ca(2+) release and VT. Like racemic carvedilol, R-carvedilol directly reduces the open duration of the cardiac ryanodine receptor (RyR2), suppresses spontaneous Ca(2+) oscillations in human embryonic kidney (HEK) 293 cells, Ca(2+) waves in cardiomyocytes in intact hearts and stress-induced VT in mice harbouring a catecholaminergic polymorphic ventricular tachycardia (CPVT)-causing RyR2 mutation. Importantly, R-carvedilol did not significantly alter heart rate or blood pressure. Therefore, the non-ß-blocking R-carvedilol enantiomer represents a very promising prophylactic treatment for Ca(2+)- triggered arrhythmia without the bradycardia and hypotension often associated with racemic carvedilol. Systematic clinical assessments of R-carvedilol as a new anti-arrhythmic agent may be warranted.

The cardiac ryanodine receptor luminal Ca2+ sensor governs Ca2+ waves, ventricular tachyarrhythmias and cardiac hypertrophy in calsequestrin-null mice.

CASQ2 (cardiac calsequestrin) is commonly believed to serve as the SR (sarcoplasmic reticulum) luminal Ca2+ sensor. Ablation of CASQ2 promotes SCWs (spontaneous Ca2+ waves) and CPVT (catecholaminergic polymorphic ventricular tachycardia) upon stress but not at rest. How SCWs and CPVT are triggered by stress in the absence of the CASQ2-based luminal Ca2+ sensor is an important unresolved question. In the present study, we assessed the role of the newly identified RyR2 (ryanodine receptor 2)-resident luminal Ca2+ sensor in determining SCW propensity, CPVT susceptibility and cardiac hypertrophy in Casq2-KO (knockout) mice. We crossbred Casq2-KO mice with RyR2 mutant (E4872Q+/-) mice, which lack RyR2-resident SR luminal Ca2+ sensing, to generate animals with both deficiencies. Casq2+/- and Casq2-/- mice showed stress-induced VTs (ventricular tachyarrhythmias), whereas Casq2+/-/E4872Q+/- and Casq2-/-/E4872Q+/- mice displayed little or no stress-induced VTs. Confocal Ca2+ imaging revealed that Casq2-/- hearts frequently exhibited SCWs after extracellular Ca2+ elevation or adrenergic stimulation, whereas Casq2-/-/E4872Q+/- hearts had few or no SCWs under the same conditions. Cardiac hypertrophy developed and CPVT susceptibility increased with age in Casq2-/- mice, but not in Casq2-/-/E4872Q+/- mice. However, the amplitudes and dynamics of voltage-induced Ca2+ transients in Casq2-/- and Casq2-/-/E4872Q+/- hearts were not significantly different. Our results indicate that SCWs, CPVT and hypertrophy in Casq2-null cardiac muscle are governed by the RyR2-resident luminal Ca2+ sensor. This implies that defects in CASQ2-based lumi-nal Ca2+ sensing can be overridden by the RyR2-resident luminal Ca2+ sensor. This makes this RyR2-resident sensor a promising molecular target for the treatment of Ca2+-mediated arrhythmias.

Generation and characterization of a mouse model harboring the exon-3 deletion in the cardiac ryanodine receptor.

A large genomic deletion in human cardiac ryanodine receptor (RYR2) gene has been detected in a number of unrelated families with various clinical phenotypes, including catecholaminergic polymorphic ventricular tachycardia (CPVT). This genomic deletion results in an in-frame deletion of exon-3 (Ex3-del). To understand the underlying disease mechanism of the RyR2 Ex3-del mutation, we generated a mouse model in which the RyR2 exon-3 sequence plus 15-bp intron sequences flanking exon-3 were deleted. Heterozygous Ex3-del mice (Ex3-del+/-) survived, but no homozygous Ex3-del mice were born. Unexpectedly, the Ex3-del+/- mice are not susceptible to CPVT. Ex3-del+/- cardiomyocytes exhibited similar amplitude but altered dynamics of depolarization-induced Ca2+ transients compared to wild type (WT) cells. Immunoblotting analysis revealed markedly reduced expression of RyR2 protein in the Ex3-del+/- mutant heart, indicating that Ex3-del has a major impact on RyR2 protein expression in mice. Cardiac specific, conditional knockout of the WT RyR2 allele in Ex3-del+/- mice led to bradycardia and death. Thus, the absence of CPVT and other phenotypes in Ex3-del+/- mice may be attributable to the predominant expression of the WT RyR2 allele as a result of the markedly reduced expression of the Ex3-del mutant allele. The effect of Ex3-del on RyR2 protein expression is discussed in relation to the phenotypic variability in individuals with the RyR2 exon-3 deletion.

The ryanodine receptor store-sensing gate controls Ca2+ waves and Ca2+-triggered arrhythmias.

Spontaneous Ca(2+) release from intracellular stores is important for various physiological and pathological processes. In cardiac muscle cells, spontaneous store overload-induced Ca(2+) release (SOICR) can result in Ca(2+) waves, a major cause of ventricular tachyarrhythmias (VTs) and sudden death. The molecular mechanism underlying SOICR has been a mystery for decades. Here we show that a point mutation, E4872A, in the helix bundle crossing region (the proposed gate) of the cardiac ryanodine receptor (RyR2) completely abolishes luminal, but not cytosolic, Ca(2+) activation of RyR2. The introduction of metal-binding histidines at this site converts RyR2 into a luminal Ni(2+)-gated channel. Mouse hearts harboring a heterozygous RyR2 mutation at this site (E4872Q) are resistant to SOICR and are completely protected against Ca(2+)-triggered VTs. These data show that the RyR2 gate directly senses luminal (store) Ca(2+), explaining the regulation of RyR2 by luminal Ca(2+), the initiation of Ca(2+) waves and Ca(2+)-triggered arrhythmias. This newly identified store-sensing gate structure is conserved in all RyR and inositol 1,4,5-trisphosphate receptor isoforms.

Novel carvedilol analogues that suppress store-overload-induced Ca2+ release.

Carvedilol is a uniquely effective drug for the treatment of cardiac arrhythmias in patients with heart failure. This activity is in part because of its ability to inhibit store-overload-induced calcium release (SOICR) through the RyR2 channel. We describe the synthesis, characterization, and bioassay of ca. 100 compounds based on the carvedilol motif to identify features that correlate with and optimize SOICR inhibition. A single-cell bioassay was employed on the basis of the RyR2-R4496C mutant HEK-293 cell line in which calcium release from the endoplasmic reticulum through the defective channel was measured. IC50 values for SOICR inhibition were thus obtained. The compounds investigated contained modifications to the three principal subunits of carvedilol, including the carbazole and catechol moieties, as well as the linker chain containing the ß-amino alcohol functionality. The SAR results indicate that significant alterations are tolerated in each of the three subunits.

Carvedilol and its new analogs suppress arrhythmogenic store overload-induced Ca2+ release.

Carvedilol is one of the most effective beta blockers for preventing ventricular tachyarrhythmias in heart failure, but the mechanisms underlying its favorable antiarrhythmic benefits remain unclear. Spontaneous Ca(2+) waves, also called store overload-induced Ca(2+) release (SOICR), evoke ventricular tachyarrhythmias in individuals with heart failure. Here we show that carvedilol is the only beta blocker tested that effectively suppresses SOICR by directly reducing the open duration of the cardiac ryanodine receptor (RyR2). This unique anti-SOICR activity of carvedilol, combined with its beta-blocking activity, probably contributes to its favorable antiarrhythmic effect. To enable optimal titration of carvedilol's actions as a beta blocker and as a suppressor of SOICR separately, we developed a new SOICR-inhibiting, minimally beta-blocking carvedilol analog, VK-II-86. VK-II-86 prevented stress-induced ventricular tachyarrhythmias in RyR2-mutant mice and did so more effectively when combined with either of the selective beta blockers metoprolol or bisoprolol. Combining SOICR inhibition with optimal beta blockade has the potential to provide antiarrhythmic therapy that can be tailored to individual patients.

[Carbon sequestration of young Robinia pseudoacacia plantation in Loess Plateau].

In order to understand the carbon sequestration of ecological forests in Loess Plateau, a comparative study was made on the organic carbon density (OCD) of soil, litter, and plant organs in an 8-year-old Robinia pseudoacacia plantation and nearby barren land. Comparing with the barren land, the young R. pseudoacacia plantation had a decrease (0.26 kg x m(-2)) of soil OCD, but the OCD in its litter, root system, and aboveground organs increased by 121.1%, 202.0%, and 656. 7%, respectively, with a total carbon sequestration increased by 3.3% annually, which illustrated that R. pseudoacacia afforestation on Loess Plateau had an obvious positive effect on carbon sequestration.

[Effects of RNA interference targeting angiotensin 1a receptor on the blood pressure and cardiac hypertrophy of rats with 2K1C hypertension].

OBJECTIVE: To investigate the effects of RNA interference (RNAi) targeting angiotensin 1a (AT1a) receptor on the blood pressure and cardiac hypertrophy of rats with 2K1C (2-kidney, 1-clip) hypertension. METHODS: Two kinds of RNAi plasmids, pAT1a-shRNA1 carrying an U6 promoter and an AT1a-specific shRNA-coding template sequence corresponding the sites 928 - 946 and pAT1a-shRNA2 carrying an U6 promoter and an AT1a-specific shRNA-coding template sequence corresponding the sites 978 - 996, and a blank plasmid pCon carrying a nonspecific shRNA-coding sequence were constructed. Thirty Sprague-Dawley rats underwent clipping of the left renal artery so as to establish two-kidney, one-clip (2K1C) hypertension models and then were randomly divided into 5 equal groups: pAT1a-shRNA1 group (injected with pAT1a-shRNA1 4 mg/kg only one time), pAT1a-shRNA2 group (injected with pAT1a-shRNA2 4 mg/kg only one time), pCon group (injected with pCon 4 mg/kg only one time), valsartan group (perfused into the stomach with valsartan, a AT1 receptor inhibitor 30 mg.kg(-1).d(-1), for 3 weeks), and control blank group (without any treatment). Three weeks later, the systolic pressure of the caudal artery was measured, catheterization through carotid artery was conducted to measure the systolic blood pressure (SBP) and diastolic blood pressure (DBP), and the left ventricular pressure curve was drawn. Then the rats were killed; the weight of the heart was measured, the ratio of left ventricle weight to body weight (LV/BW) was calculated, and pathological examination of the heart and thoracic aorta was performed. Western blotting was used to detect the protein expression of AT21 in the ventricle and aorta. Six age-matched healthy rats were used as normal controls. RESULTS: There was no significant difference in the caudal artery pressure among the 5 groups (all P > 0.05) before intervention. Three weeks later the caudal artery pressures of the blank control group and pCon group continued to significantly increase by about 25 mm Hg compared to the values before the intervention (both P < 0.001) and without significant difference between these 2 groups; however, the caudal artery pressures of the pAT1a-shRNA1, pAT1a-shRNA2, and valsartan groups were 15.1 mm Hg +/- 5.4 mm Hg, 16.4 mm Hg +/- 8.4 mm Hg, and 30.6 mm Hg +/- 18.2 mm Hg lower than those before the intervention respectively (all P < 0.01); and were also significantly lower than those of the blank groups (P < 0.01 or P < 0.05). There was no significant differences in the +/- dp/dt value and indicators of renal function among these groups. The carotid artery pressure of the pAT1a-shRNA1, pAT1a-shRNA2, and valsartan groups were 194 mm Hg +/- 5 mm Hg, 200 mm Hg +/- 5 mm Hg, and 164 mm Hg +/- 5 mm Hg, all significantly lower than those of the blank and pCon groups (234 mm Hg +/- 10 mm Hg and 232 mm Hg +/- 7 mm Hg respectively, all P < 0.01). The LV/BW of the pAT1a-shRNA1, pAT1a-shRNA2, and valsartan groups were 2.27 +/- 0.37, 2.31 +/- 0.26, and 2.26 +/- 0.39, all significantly lower than that of the blank and pCon groups (3.24 +/- 0.38 and 2.94 +/- 0.06, respectively, all P < 0.01), similar to that of the normal control group (P > 0.05). The myocardiocytes were significantly hypertrophic and the arterial tunica media was significantly thickened in the blank group and such changes were all improved to different degrees in the pAT1a-shRNA1, pAT1a-shRNA2, and valsartan groups. The protein expression levels of AT1 receptor in the myocardium of the pAT1a-shRNA and pAT1a-shRNA2 groups were lower by 53.3% and 47.8% respectively than that of the blank group, and the protein expression levels of AT1 receptor in the thoracic aorta of the pAT1a-shRNA and pAT1a-shRNA2 groups were lower by 58.7% and 49.3% respectively than that of the blank group (all P < 0.01); however, there were no significant difference in the protein expression levels of AT1 receptor in the myocardium and thoracic aorta between the valsartan and blank groups (both P > 0.05). CONCLUSION: RNA interference targeting AT1a receptor inhibits the development of renovascular hypertension and the accompanying cardiac hypertrophy. The RNAi technology may become a new strategy of gene therapy for hypertension.

[Selective knockdown of Angiotensin II receptor subtype 1a in rat vascular smooth muscle cells by RNA interference].

OBJECTIVE: To selectively knockdown the expression of Angiotensin II receptor subtype 1a (AT1aR) in rat vascular smooth muscle cells (VSMCs) by RNA interference and the sequential effects on cellular viability and proliferation. METHODS: The primary cultured rat aortic VSMCs were transfected by plasmids pAT1a-shRNA1 and pAT1a-shRNA2, each carrying an U6 promoter and an AT1a-specific shRNA-coding template sequence, or by a control plasmid pGenesil-Control (pCon) carrying a nonspecific shRNA-coding sequence. The mRNA and protein expressions of AT1a, AT2 were analyzed by semi-quantified RT-PCR and Western blot, respectively and normalized to the internal control gene beta-actin. Cellular viability and proliferation were determined with methylthiazoletetrazolium (MTT) assay. RESULTS: AT1a mRNA and protein were reduced by 82% and 69% by pAT1a-shRNA1, 77% and 56% by pAT1a-shRNA2, respectively while no change was found in pCon treated VSMCs. AT2 receptor level in VSMCs remains unchanged after various treatments. The A(490nm) values obtained by MTT measurements were similar among groups in the absence of Ang II but decreased significantly in pAT1a-shRNA1 and pAT1a-shRNA2 treated VSMCs in the presence of Ang II. CONCLUSION: RNA interference can selectively knockdown AT1a expression in cultured VSMCs and attenuate the Ang II induced cell proliferation. Future studies are warranted to explore the potential role of RNA interference on AT1 function and as a new gene therapy tool for cardiovascular diseases.