Protective effect of salidroside on cardiac apoptosis in mice with chronic intermittent hypoxia

Endoplasmic reticulum stress: molecular mechanism and therapeutic targets

The endoplasmic reticulum (ER) functions as a quality-control organelle for protein homeostasis, or "proteostasis". The protein quality control systems involve ER-associated degradation, protein chaperons, and autophagy. ER stress is activated when proteostasis is broken with an accumulation of misfolded and unfolded proteins in the ER. ER stress activates an adaptive unfolded protein response to restore proteostasis by initiating protein kinase R-like ER kinase, activating transcription factor 6, and inositol requiring enzyme 1. ER stress is multifaceted, and acts on aspects at the epigenetic level, including transcription and protein processing. Accumulated data indicates its key role in protein homeostasis and other diverse functions involved in various ocular diseases, such as glaucoma, diabetic retinopathy, age-related macular degeneration, retinitis pigmentosa, achromatopsia, cataracts, ocular tumors, ocular surface diseases, and myopia. This review summarizes the molecular mechanisms underlying the aforementioned ocular diseases from an ER stress perspective. Drugs (chemicals, neurotrophic factors, and nanoparticles), gene therapy, and stem cell therapy are used to treat ocular diseases by alleviating ER stress. We delineate the advancement of therapy targeting ER stress to provide new treatment strategies for ocular diseases.

Salidroside ameliorates pathological cardiac hypertrophy via TLR4-TAK1-dependent signaling

Salidroside, a prominent active ingredient in traditional Chinese medicines, is garnering increased attention because of its unique pharmacological effects against ischemic heart disease via MAPK signaling, which plays a critical role in regulating the evolution of ventricular hypertrophy. However, the function of Salidroside on myocardial hypertrophy has not yet been elucidated. C57BL/6 mice were subjected to transverse aortic constriction (TAC), and treated with Salidroside (100 mg kg-1  day-1 ) by oral gavage for 3 weeks starting 1 week after surgery. Four weeks after TAC surgery, the mice were subjected to echocardiography and then sacrificed to harvest the hearts for analysis. For in vitro study, neonatal rat cardiomyocytes were used to validate the protective effects of Salidroside in response to Angiotensin II (Ang II, 1 μM) stimulation. Here, we proved that Salidroside dramatically inhibited hypertrophic reactions generated by pressure overload and isoproterenol (ISO) injection. Salidroside prevented the activation of the TAK1-JNK/p38 axis. Salidroside pretreatment of TAK1-inhibited cardiomyocytes shows no additional attenuation of Ang II-induced cardiomyocytes hypertrophy and signaling pathway activation. The overexpression of constitutively active TAK1 removed the protective effects of Salidroside on myocardial hypertrophy. TAC-induced increase of TLR4 protein expression was reduced considerably in the Salidroside treated mice. Transient transfection of small interfering RNA targeting TLR4 (siTLR4) in cardiomyocytes did not further decrease the activation of the TAK1/JNK-p38 axis. In conclusion, Salidroside functioned as a TLR4 inhibitor and displayed anti-hypertrophic action via the TAK1/JNK-p38 pathway.

Therapeutic potential and molecular mechanisms of salidroside in ischemic diseases

Rhodiola is an ancient wild plant that grows in rock areas in high-altitude mountains with a widespread habitat in Asia, Europe, and America. From empirical belief to research studies, Rhodiola has undergone a long history of discovery, and has been used as traditional medicine in many countries and regions for treating high-altitude sickness, anoxia, resisting stress or fatigue, and for promoting longevity. Salidroside, a phenylpropanoid glycoside, is the main active component found in all species of Rhodiola. Salidroside could enhance cell survival and angiogenesis while suppressing oxidative stress and inflammation, and thereby has been considered a potential compound for treating ischemia and ischemic injury. In this article, we highlight the recent advances in salidroside in treating ischemic diseases, such as cerebral ischemia, ischemic heart disease, liver ischemia, ischemic acute kidney injury and lower limb ischemia. Furthermore, we also discuss the pharmacological functions and underlying molecular mechanisms. To our knowledge, this review is the first one that covers the protective effects of salidroside on different ischemia-related disease.

Salidroside Ameliorated Intermittent Hypoxia-Aggravated Endothelial Barrier Disruption and Atherosclerosis via the cAMP/PKA/RhoA Signaling Pathway

Background: Endothelial barrier dysfunction plays a key role in atherosclerosis progression. The primary pathology of obstructive sleep apnea-hypopnea syndrome is chronic intermittent hypoxia (IH), which induces reactive oxygen species (ROS) overproduction, endothelial barrier injury, and atherosclerosis. Salidroside, a typical pharmacological constituent of Rhodiola genus, has documented antioxidative, and cardiovascular protective effects. However, whether salidroside can improve IH-aggravated endothelial barrier dysfunction and atherosclerosis has not been elucidated.

Methods and results: In normal chow diet-fed ApoE^−/− mice, salidroside (100 mg/kg/d, p. o.) significantly ameliorated the formation of atherosclerotic lesions and barrier injury aggravated by 7-weeks IH (21%–5%–21%, 120 s/cycle). In human umbilical vein endothelial cells (HUVECs), exposure to IH (21%–5%–21%, 40 min/cycle, 72 cycles) decreased transendothelial electrical resistance and protein expression of vascular endothelial cadherin (VE-cadherin) and zonula occludens 1. In addition, IH promoted ROS production and activated ras homolog gene family member A (RhoA)/Rho-associated protein kinase (ROCK) pathway. All of these effects of IH were reversed by salidroside. Similar to salidroside, ROCK-selective inhibitors Y26732, and Fasudil protected HUVECs from IH-induced ROS overproduction and endothelial barrier disruption. Furthermore, salidroside increased intracellular cAMP levels, while the PKA-selective inhibitor H-89 attenuated the effects of salidroside on IH-induced RhoA/ROCK suppression, ROS scavenging, and barrier protection.

Conclusion: Our findings demonstrate that salidroside effectively ameliorated IH-aggravated endothelial barrier injury and atherosclerosis, largely through the cAMP/PKA/RhoA signaling pathway.

Salidroside: A review of its recent advances in synthetic pathways and pharmacological properties

Salidroside has been identified as one of the most potent compounds isolated from various Rhodiola plants, which have been used for a long time as adaptogens in traditional Chinese medicine. However, due to the severe growing environment of herbal medicine and large-scale excavation, the content of natural salidroside is extremely small. Most of the previous studies focused on herbal medicine, and there were few reviews on the synthesis of its main active ingredient salidroside. This paper presents different synthetic routes of salidroside to resolve the contradiction between supply and demand and lays the foundation for new drug research and development. Furthermore, emerging evidence indicates that salidroside, a promising environmentally-adapted drug with low toxicity and few side effects, possesses a wide spectrum of pharmacological properties, including activities on the cardiovascular system and central nervous system, anti-hypoxia, anti-fatigue and anti-aging activities, anticancer activity, anti-inflammatory activity, antioxidant activity, antivirus and immune stimulation activities, antidiabetic activity, anti-osteoporotic activity, and so on. Although the former researches have summarized the pharmacological effects of salidroside, focusing on the central nervous system, diabetes, and cancer, the overall pharmacological aspects of it have not been analyzed. This review highlights biological characteristics and mechanisms of action from 2009 to now as well as toxicological and pharmacokinetic data of the analyzed compound reported so far, with a view to providing a reference for further development and utilization of salidroside.

Sodium Tanshinone IIA Sulfonate Attenuates Tumor Oxidative Stress and Promotes Apoptosis in an Intermittent Hypoxia Mouse Model

Objective:

Intermittent hypoxia, a significant feature of obstructive sleep apnea, has pro-tumorigenic effects. Here, we investigated the effect of sodium tanshinone IIA sulfonate on oxidative stress and apoptosis in a mouse model of Lewis lung carcinoma with intermittent hypoxia.

Methods:

Mice were randomly assigned to normoxia (control), normoxia plus sodium tanshinone IIA sulfonate (control + sodium tanshinone IIA sulfonate), intermittent hypoxia, and intermittent hypoxia + sodium tanshinone IIA sulfonate groups. Intermittent hypoxia administration lasted 5 weeks in the intermittent hypoxia groups. Lewis lung carcinoma cells were injected into the right flank of each mouse after 1 week of intermittent hypoxia exposure. Sodium tanshinone IIA sulfonate was injected intraperitoneally in the control + sodium tanshinone IIA sulfonate and intermittent hypoxia + sodium tanshinone IIA sulfonate groups. Tumor oxidative stress was evaluated by detection of malondialdehyde and superoxide dismutase. The apoptosis of tumor cells was evaluated by the terminal deoxynucleotidyl transferase dUTP nick-end labeling assay as well as by Western blot analysis of B-cell lymphoma 2-associated X protein and cleaved caspase-3 expression. Additionally, the expression of hypoxia-induced factor-1α, nuclear factor erythroid 2-related factor 2, and nuclear factor kappa B was also evaluated by Western blot.

Results:

Compared with the control group, the intermittent hypoxia treatment significantly increased Lewis lung carcinoma tumor growth and oxidative stress (serum malondialdehyde) but decreased serum levels of SOD and pro-apoptotic markers (terminal deoxynucleotidyl transferase dUTP nick-end labeling staining, B-cell lymphoma 2-associated X protein, and cleaved caspase-3). These changes were significantly attenuated by intraperitoneal injection of sodium tanshinone IIA sulfonate. Lower nuclear factor erythroid 2-related factor 2 and higher nuclear factor kappa B levels in the intermittent hypoxia group were clearly reversed by sodium tanshinone IIA sulfonate treatment. In addition, sodium tanshinone IIA sulfonate administration decreased the high expression of hypoxia-induced factor-1α induced by intermittent hypoxia.

Conclusion:

Intermittent hypoxia treatment resulted in high oxidative stress and low apoptosis in Lewis lung carcinoma–implanted mice, which could be attenuated by sodium tanshinone IIA sulfonate administration possibly through a mechanism mediated by the nuclear factor erythroid 2-related factor 2/nuclear factor kappa B signaling pathway.

Contribution of salidroside to the relieve of symptom and sign in the early acute stage of osteoarthritis in rat model

ETHNOPHARMACOLOGICAL RELEVANCE

The genus Rhodiola has been used to treat cough, hemoptysis, fever, pain, bruise and other symptoms which are related to injury and inflammation over a thousand years in traditional Tibetan medicine. Salidroside (p-hydroxyphenethyl-β-D-glucoside) is one of the most potent bioactive ingredients of the genus Rhodiola.

AIM OF STUDY

The present study aimed to explore whether salidroside could alleviate the clinical symptom and sign in the early acute stage of osteoarthritis (OA) in monosodium iodoacetate (MIA) rat model, and its underlying mechanisms.

MATERIALS AND METHODS

Osteoarthritis (OA) was induced in rat knees by intra-articular injection of MIA; simultaneously salidroside was administered by intravenous injection. Pain behaviors were evaluated by knee-bend test, hind limb weight-bearing asymmetry and hind paw mechanical withdrawal threshold. The joint swelling was determined by the difference of knee joint diameter. Inflammatory exudates in synovial fluid were evaluated by leukocyte counting and protein content. Cytokines, chemokines, reactive oxygen species (ROS) and reactive nitrogen species (RNS) markers were determined by Enzyme-linked immunosorbent assay (ELISA) and colorimetric assay in synovial fluid. Pro-inflammatory gene expressions in synovial tissue were detected by quantitative real time RT-PCR (qRT-PCR). Nuclear factor kappa-B (NF-κB) DNA binding assay and western blot were used to determine NF-κB activation and ROS marker protein expression in synovial tissue. Glycosaminoglycan (GAG) content in the cartilage was measured by dimethylmethylene blue method. Hematoxylin and eosin (H&E), Safranin O-fast green and a modified Mankin grading system were used to evaluate the histology of articular cartilage.

RESULTS

Salidroside could alleviate pain and joint swelling in the early acute stage of OA in rat model, reduced the number of leukocytes, total protein content, proinflammatory mediators and ROS/RNS markers in synovial fluid, down regulated the expression of proinflammatory genes in synovium, inhibited the activation of NF- κ B and oxidative stress response in synovium, promoted the synthesis of cartilage GAG, prevented the loss of proteoglycan and chondrocyte degeneration.

CONCLUSIONS

Salidroside effectively alleviates acute symptom and sign of OA in rat model by its anti-inflammatory and antioxidant affects to inhibit synovial inflammation, which provides a new strategy to prevent the onset and progression of OA.

Injury and Apoptosis in the Palatopharyngeal Muscle in Patients with Obstructive Sleep Apnea-Hypopnea Syndrome

Background

This study aimed to elucidate the possible activity of the mitochondrial-mediated apoptotic pathway (MMAP) in obstructive sleep apnea-hypopnea syndrome (OSAHS).

Material/Methods

A control group, a mild OSAHS group, a moderate OSAHS group, and a severe OSAHS group were included. Masson staining, hematoxylin and eosin staining, and terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay were performed to assess collagen fiber hyperplasia, pathological morphology, and cell apoptosis, respectively, in muscle samples.

Results

In the OSAHS groups, the palatopharyngeal muscle fibers were larger, with apparent hypertrophy and increased elastic fiber content. The proportions of type I fibers were markedly higher in the control group than in the moderate and severe OSAHS groups (P<0.05). Moreover, apoptosis was significantly enhanced in the muscle cells of the OSAHS groups. The Bax expression levels gradually increased across the 4 groups (lowest in the control group and highest in the severe OSAHS group) (P<0.05); conversely, the p38 and p62 expression levels did not significantly differ among groups (P>0.05).

Conclusions

A decrease in the proportion of the different fiber types can result in collapse of the upper airway. The pathogenesis of OSAHS appears to involve muscle cell apoptosis via MMAP.

Pathogenesis and Prevention of Worsening Axial Elongation in Pathological Myopia

PURPOSE

This review discusses the etiology and pathogenesis of myopia, prevention of disease progression and worsening axial elongation, and emerging myopia treatment modalities.

INTRODUCTION

Pediatric myopia is a public health concern that impacts young children worldwide and is associated with numerous future ocular diseases such as cataract, glaucoma, retinal detachment and other chorioretinal abnormalities. While the exact mechanism of myopia of the human eye remains obscure, several studies have reported on the role of environmental and genetic factors in the disease development.

METHODS

A review of literature was conducted. PubMed and Medline were searched for combinations and derivatives of the keywords including, but not limited to, "pediatric myopia", "axial elongation", "scleral remodeling" or "atropine." The PubMed and Medline database search were performed for randomized control trials, systematic reviews and meta-analyses using the same keyword combinations.

RESULTS

Studies have reported that detection of genetic correlations and modification of environmental influences may have a significant impact in myopia progression, axial elongation and future myopic ocular complications. The conventional pharmacotherapy of pediatric myopia addresses the improvement in visual acuity and prevention of amblyopia but does not affect axial elongation or myopia progression. Several studies have published varying treatments, including optical, pharmacological and surgical management, which show great promise for a more precise control of myopia and preservation of ocular health.

DISCUSSION

Understanding the role of factors influencing the onset and progression of pediatric myopia will facilitate the development of successful treatments, reduction of disease burden, arrest of progression and improvement in future of the management of myopia.

Neuroprotective Effect of Rhodiola crenulata in D-Galactose-Induced Aging Model

The medicinal plant Rhodiola crenulata grows at high altitudes in the Arctic and mountainous regions and is commonly used in phytotherapy in Eastern European and Asian countries. In the present study, we investigated the anti-apoptotic effect of Rhodiola crenulata and its neuroprotective mechanism of action in a rat model of D-galactose-induced aging. Two groups of twelve-week-old male Wistar rats received a daily injection of D-galactose (150mg/kg/day, i.p.) and orally administered Rhodiola crenulata (0, 248mg/kg/day) for eight weeks, while a control group received a saline injection (1ml/kg/day, i.p.). We examined apoptosis in the cortex and hippocampus of three groups of rats based on a terminal deoxynucleotide transferase-mediated deoxy uridine triphosphate nick-end labeling (TUNEL) positive assay. The expression levels of apoptotic and anti-apoptotic proteins in excised brains were analyzed by Western blotting. Our findings indicated that D-galactose caused marked neuronal apoptosis via activation of both extrinsic-dependent and mitochondrial-dependent apoptotic pathways. When compared to the control group, the protein levels of Fas receptor, Fas ligand, Fas-associated death domain (FADD), and activated caspase-8 (Fas-dependent apoptotic pathways), as well as those of t-Bid, Bax, cytochrome c, activated caspase-9, and activated caspase-3 (mitochondrial-dependent apoptotic pathways), were significantly increased in the D-galactose treated group. In addition, D-galactose impaired the phosphorylation of PI3K/Akt, an important survival signaling event in neurons. Rhodiola crenulata, however, protected against all these neurotoxicities in aging brains. The present study suggests that neuronal survival promoted by Rhodiola crenulata may be a potentially effective method to enhance the resistance of neurons to age-related disorders.

Salidroside ameliorates diabetic nephropathy in rats by activating renal AMPK/SIRT1 signaling pathway

This study investigated if the nephroprotective effect of Salidroside T1DM rats involves activation of AMPK/SIRT1. Rats were divided into control or T1DM and treated with vehicle or Salidroside (100 mg/kg) for 56 days. Mesangial cells were cultured in LG or HG media with or without Salidroside (100 µM/L) for 24 hr. Also, HG + Salidroside-treated cells were pre-incubated with EX-527 or compound C (CC) for 1 hr. With reducing glucose levels, Salidroside improved kidney structure/function in the T1DM rat. It also increased GSH and Bcl-2 levels in control and T1DM rats and inhibited ROS, increased activation of AMPK and nuclear SIRT1, and lowered acetylation of P53 and FOXO-1 in control and T1DM rats and in LG and HG-treated cells. These effects were abolished by EX-527 and CC. Also, CC decreased the nuclear levels of SIRT1. In conclusion, Salidroside attenuates DN in T1DM rats by activation of AMPK and subsequently, SIRT1. PRACTICAL APPLICATIONS: This animal and pre-clinical study shows that Salidroside is able to ameliorate DN in T1DM-induced rats and showed that it mainly acts by a hypoglycemic effect and activation of renal AMPK/SIRT1 axis. Given the wide tissue stimulatory effect of AMPK on peripheral glucose utilization, lipogenesis, and other cell signaling pathways, these data are encouraging to investigate the anti-diabetic effect of glycoside in more clinical trials.

Salidroside Attenuates Hypoxia-Induced Expression of Connexin 43 in Corpus Cavernosum Smooth Muscle Cells

<b><i>Introduction:</i></b> Connexin 43 (Cx43) is the major component of gap junction in corpus cavernosum smooth muscle, which allows rapid intercellular communication. Cx43 coordinates corpus cavernosum smooth muscle cells and ensures erectile function. The role of hypoxia in Cx43 dysfunction resulting in erectile dysfunction has not been well studied, and salidroside has shown cell protective effects under hypoxia. <b><i>Objective:</i></b> We aimed to investigate the protective role of salidroside and the underlying mechanisms in hypoxia-induced dysfunction of Cx43. <b><i>Methods:</i></b> Corpus cavernosum smooth muscle cells prepared from young male Sprague-Dawley rats were pretreated with or without salidroside and exposed to hypoxic condition for 48 h. The cell viability, expression of hypoxia-inducible factor-1α (HIF-1α) and Cx43, and Ca²⁺ signals were investigated. <b><i>Results:</i></b> Pretreatment with salidroside attenuated loss of hypoxia-induced cell viability markedly and could downregulate the HIF-1α protein expression under hypoxia. Moreover, the expression of Cx43 was significantly increased by hypoxia but was decreased with salidroside pretreatment. The salidroside pretreated group exhibited enhanced release of intracellular Ca²⁺ in corpus cavernosum smooth muscle cells compared with the hypoxia group after stimulation. <b><i>Conclusion:</i></b> Salidroside has a protective effect against hypoxia-induced damage to corpus cavernosum smooth muscle cells.

Protective effects of Salidroside on cardiac function in mice with myocardial infarction

Salidroside (SAL) is the major ingredient of Rhodiola rosea, and has been traditionally used in Chinese medicine for decades. Numerous studies have demonstrated the protective effects of SAL for myocardial ischemia. However, it is yet to be deciphered whether SAL has cardioprotective effects after myocardial infarction (MI) in vivo. In the present study, we established a mouse MI model via coronary artery ligation. The aim was to investigate whether SAL treatment could reduce mortality, improve cardiac function and attenuate myocardial remodeling in MI mice. Post-surgery, mice were randomly administered SAL or normal saline. After 21 days, SAL was found to significantly reduce mortality, improve cardiac function, reduce fibrosis and infarct size compared to normal saline. In addition, oral administration of SAL could attenuate myocardial inflammation and apoptosis and promote angiogenesis. SAL down-regulated the expression levels of TNF-α, TGF-β1, IL-1β, Bax and up-regulate the expression of Bcl-2, VEGF, Akt and eNOS. These results indicated that SAL could alleviate the pathological processes of myocardial remodeling in MI mice, and may be a potentially effective therapeutic approach for the management of clinical ischemic cardiovascular diseases.

Salidroside Suppresses IL-1β-Induced Apoptosis in Chondrocytes via Phosphatidylinositol 3-Kinases (PI3K)/Akt Signaling Inhibition

Background

Salidroside, a natural dietary isothiocyanate, has been widely studied for its multiple effects, including promoting proliferation, anti-inflammation, and anti-apoptosis. In the present study, these effects of Salidroside were explored to assess whether it could prevent osteoarthritis (OA) in vitro.

Material/Methods

The cytotoxic and proliferating effects of Salidroside on chondrocytes were detected by use of the Cell Counting Kit 8 assay. The expression levels of proteins were detected by Western blot. The cell apoptosis level was assessed by flow cytometry, and the levels of ROS, NO, caspase 3, and caspase 9 were assessed to evaluate the level of apoptosis. The expression level of pro-inflammatory factors was detected by ELISA.

Results

Our results demonstrated that Salidroside promotes chondrocytes proliferation, inhibits IL-1β-induced apoptosis and inflammation, and scavenges reactive oxygen species (ROS) and NO of chondrocytes. Salidroside upregulates the level of Bcl-2 and downregulates the level of Bax. Salidroside also inhibits the production of caspase 3/9 and suppresses the phosphorylation of PI3K and AKT.

Conclusions

Our results suggest that Salidroside prevents OA by its powerful pro-proliferating, anti-phlogistic, and anti-apoptotic effects by inhibiting PI3K/AKT.

Role of Chinese Herbal Medicines in Regulation of Energy Metabolism in Treating Cardiovascular Diseases

Recently, studying myocardial energy metabolism pathways or improving myocardial metabolism through drugs is another effective strategy for treating ischemic heart disease. Many active components of Chinese herbal medicines (CHMs) have been found to modulate energy metabolism in myocardial cells, cerebral vascular cells, endothelial cells and tumour cells. This paper reviews the advances in studies on the active components of CHMs that modulating energy metabolism in treating cardiovascular diseases over the past five years.

Recombinant human glucagon-like peptide-1 protects against chronic intermittent hypoxia by improving myocardial energy metabolism and mitochondrial biogenesis

BACKGROUND AND AIMS

Obstructive sleep apnea syndrome is a chronic disease associated with intermittent hypoxia (IH) and is an important risk factor for cardiovascular disease. Glucagon-like peptide (GLP-1) is a naturally occurring incretin used as a promising therapeutic agent in the treatment of acute myocardial infarction, dilated cardiomyopathy, and advanced heart failure. However, whether GLP-1 can protect against IH-induced cardiac injury is still unclear. Accordingly, in this study, we evaluated the effects of recombinant human GLP-1 (rhGLP-1) on cardiac health in mice.

METHODS

Mice were subjected to repetitive 5% O₂ for 30 s and 21% O₂ for 30 s, for a total of 8 h/day for 4 weeks. Subsequently, mice received subcutaneous injection of saline or rhGLP-1 (100 μg/kg, three times per day). Cardiac function, myocardial apoptosis and fibrosis, energy metabolism, and mitochondrial biogenesis were examined for evaluation of cardiac injury.

RESULTS

A reduction in diastolic function (E/A ratio) in mice exposed to IH was significantly reversed by rhGLP-1. IH induced marked cardiomyocyte apoptosis and myocardial fibrosis. Additionally, IH resulted in a shift from fatty acid to glucose metabolism in the myocardium with downregulation of peroxisome proliferator-activated receptor (PPAR) α and PPARγ. Moreover, IH caused a reduction in mitochondrial DNA (mtDNA) replication and transcription, together with reduced mtDNA content and impaired mitochondrial ultrastructure. These changes were abolished by rhGLP-1 via activation of PGC-1α and Akt signaling.

CONCLUSIONS

rhGLP-1 protects against IH-induced cardiac injury by improving myocardial energy metabolism and enhancing the early adaptive changes of mitochondrial biogenesis.

Expression profile of long non-coding RNAs in rat models of OSA-induced cardiovascular disease: new insight into pathogenesis

PURPOSE

Long non-coding RNAs (lncRNAs) are a recently identified class of regulatory molecules involved in the regulation of numerous biological processes, but their functions in a rat model of chronic intermittent hypoxia (CIH) remain largely unknown. Therefore, for further investigation, we aimed to explore lncRNA expression profiles and reveal their potential functional roles in rat models of CIH.

METHODS

We used a well-established CIH rat model and conducted lncRNA microarray experiments on the heart samples of rats with CIH and under normoxia control. Differentially expressed lncRNAs and mRNAs were identified via fold-change filtering and verified by quantitative reverse transcription polymerase chain reaction (qRT-PCR). Bioinformatics analyses were applied to reveal the potential roles of key lncRNAs. Co-expression analysis was conducted to determine the transcriptional regulatory relationship of lncRNAs and mRNAs between the two groups.

RESULTS

Our data indicated that 157 lncRNAs and 319 mRNAs were upregulated, while 132 lncRNAs and 428 mRNAs were downregulated in the rat model of CIH compared with sham control. Pathway analyses showed that 31 pathways involved in upregulated transcripts and 28 pathways involved in downregulated transcripts. Co-expression networks were also constructed to explore the potential roles of differentially expressed lncRNAs on mRNAs. LncRNAs, namely, XR_596701, XR_344474, XR_600374, ENSRNOT00000065561, XR_590196, and XR_597099, were validated by the use of qRT-PCR.

CONCLUSIONS

The present study first revealed lncRNAs expression profiles in a rat model of CIH, providing new insight into the pathogenesis of obstructive sleep apnea-induced cardiovascular disease.

Salidroside mitigates hypoxia/reoxygenation injury by alleviating endoplasmic reticulum stress‑induced apoptosis in H9c2 cardiomyocytes

Endoplasmic reticulum (ER) stress-induced apoptosis serves a crucial role in the development of myocardial ischemia/reperfusion (I/R) injury. Salidroside is a phenylpropanoid glycoside isolated from Rhodiola rosea L., which is a plant often used in traditional Chinese medicine. It possesses multiple pharmacological actions and protects against myocardial I/R injury in vitro and in vivo. However, it is not yet clear whether ER stress or ER stress-induced apoptosis contributes to the cardioprotective effects of salidroside against myocardial I/R injury. Hence, hypoxia/reoxygenation (H/R)-treated H9c2 cardiomyocytes were used in the current study to mimic myocardium I/R injury in vivo. It was hypothesized that salidroside alleviates ER stress and ER stress-induced apoptosis, thereby reducing H/R injury in H9c2 cells. The results demonstrated that salidroside attenuated H/R-induced H9c2 cardiomyocyte injury, as cell viability was increased, lactate dehydrogenase release was decreased, morphological changes in apoptotic cells were ameliorated and the apoptosis ratio was reduced compared with the H/R group. ER stress was reversed, indicated by the downregulation of glucose regulated protein 78 and C/EBP homologous protein following pretreatment with salidroside. In addition, salidroside attenuated ER stress-induced apoptosis, as the expression of cleaved caspase-12 and pro-apoptotic protein Bcl-2 associated X protein and activity of caspase-3 was decreased, while the expression of anti-apoptotic protein Bcl-2 was increased following pretreatment with salidroside. Furthermore, the results indicated that salidroside decreases the activation of the ER stress-associated signaling pathway, as the expression of phosphorylated protein kinase RNA (PKR)-like ER kinase (p-PERK) and phosphorylated inositol-requiring enzyme-1α (p-IRE1α) proteins were decreased following pretreatment with salidroside. These results demonstrate that salidroside protects against H/R injury via regulation of the PERK and IRE1α pathways, resulting in alleviation of ER stress or ER stress-induced apoptosis in H9c2 cardiomyocytes.

Salidroside alleviates ischemic brain injury in mice with ischemic stroke through regulating BDNK mediated PI3K/Akt pathway

There is evidence suggesting that inhibition of apoptosis plays a critical role in preventing neurons from damage and even death, after brain ischemia/reperfusion, which shows therapeutic potential for clinical treatment of brain injury. In this study, We preformed MCAO model in C57BL/6J wild-type (BDNK+/+) and BDNK knockout (BDNF-/-) mice respectively, and investigated the neuroprotective effect of Salidroside (Sal) and its underlying mechanisms. The results showed that Sal reversed brain infarct size, reduced cerebral edema, decreased the neurological deficit score and diminished TUNEL positive cells significantly. However, BDNK deficiency inhibited the neuroprotective effect of Sal. In addition, Sal increased cell viability, ameliorated neuron cell injury by decreasing LDH activity, and inhibited cell apoptotic rate. Sal suppressed apoptotic signaling via DNA-binding-dependent and -independent mechanisms. Furthermore, the neuroprotective effect of Sal on BDNK was mediated by PI3K/Akt pathway, which was proved by the use of PI3K knockout (PI3K-/-) mice and siRNA-PI3K. In summary, these data strongly suggested that Sal could be used as an effective neuroprotective agent to protect against ischemic stroke after cerebral I/R injury through regulating BDNK-mediated PI3K/Akt apoptotic pathway in DNA-binding-dependent and -independent manners.

Scleral hypoxia is a target for myopia control

Worldwide, myopia is the leading cause of visual impairment. It results from inappropriate extension of the ocular axis and concomitant declines in scleral strength and thickness caused by extracellular matrix (ECM) remodeling. However, the identities of the initiators and signaling pathways that induce scleral ECM remodeling in myopia are unknown. Here, we used single-cell RNA-sequencing to identify pathways activated in the sclera during myopia development. We found that the hypoxia-signaling, the eIF2-signaling, and mTOR-signaling pathways were activated in murine myopic sclera. Consistent with the role of hypoxic pathways in mouse model of myopia, nearly one third of human myopia risk genes from the genome-wide association study and linkage analyses interact with genes in the hypoxia-inducible factor-1α (HIF-1α)-signaling pathway. Furthermore, experimental myopia selectively induced HIF-1α up-regulation in the myopic sclera of both mice and guinea pigs. Additionally, hypoxia exposure (5% O₂) promoted myofibroblast transdifferentiation with down-regulation of type I collagen in human scleral fibroblasts. Importantly, the antihypoxia drugs salidroside and formononetin down-regulated HIF-1α expression as well as the phosphorylation levels of eIF2α and mTOR, slowing experimental myopia progression without affecting normal ocular growth in guinea pigs. Furthermore, eIF2α phosphorylation inhibition suppressed experimental myopia, whereas mTOR phosphorylation induced myopia in normal mice. Collectively, these findings defined an essential role of hypoxia in scleral ECM remodeling and myopia development, suggesting a therapeutic approach to control myopia by ameliorating hypoxia.

Salidroside induces apoptosis in human ovarian cancer SKOV3 and A2780 cells through the p53 signaling pathway

Salidroside is one of the most potent compounds extracted from the plant Rhodiola rosea, and its cardiovascular protective effects have been studied extensively. However, the role of salidroside in human ovarian carcinoma remains unknown. The aim of the current study was to investigate the effects of salidroside on the proliferation and apoptosis of SKOV3 and A2780 cells using MTT assay and acridine orange/ethidium bromide staining. Salidroside activated caspase-3 and upregulated the levels of apoptosis-inducing factor, Bcl-2-associated X and Bcl-2-associated death promoter (Bad) proteins. Furthermore, salidroside downregulated the levels of Bcl-2, p-Bad and X-linked inhibitor of apoptosis proteins. Salidroside activated the caspase-dependent pathway in SKOV3 and A2780 cells, upregulating p53, p21^Cip1/Waf1 and p16^INK4a. These results suggest that the p53/p21^Cip1/Waf1/p16^INK4a pathway may serve a key function in salidroside-mediated effects on SKOV3 and A2780 cells. The current findings indicate that salidroside may be a promising novel drug candidate for ovarian cancer therapy.

Short-term hypoxia upregulated Mas receptor expression to repress the AT1 R signaling pathway and attenuate Ang II-induced cardiomyocyte apoptosis

Hypertension-stimulated cardiac hypertrophy and apoptosis play critical roles in the progression of heart failure. Our previous study suggested that hypertensive angiotensin II (Ang II) enhanced insulin-like growth factor receptor II (IGF-IIR) expression and cardiomyocyte apoptosis, which are involved JNK activation, sirtuin1 (SIRT1) degradation, and heat-shock transcription factor 1 (HSF1) acetylation. Moreover, previous studies have implied that short-term hypoxia (STH) might exert cardioprotective effects. However, the effects of STH on Ang II-induced cardiomyocyte apoptosis remain unknown. In this study, we found that STH reduced myocardial apoptosis caused by Ang II via upregulation of the Mas receptor (MasR) to inhibit the AT₁ R signaling pathway. STH activates MasR to counteract the Ang II pro-apoptotic signaling cascade by inhibiting IGF-IIR expression via downregulation of JNK activation and reduction of SIRT1 degradation. Hence, HSF could remain deacetylated, and repress IGF-IIR expression. These effects decrease the activation of downstream pro-apoptotic and hypertrophic cascades and protect cardiomyocytes from Ang II-induced injury. In addition, we also found that silencing MasR expression enhanced Ang II-induced cardiac hypertrophy and the apoptosis signaling pathway. These findings suggest a critical role for MasR in cardiomyocyte survival. Altogether, our findings indicate that STH protects cardiomyocytes from Ang II-stimulated apoptosis. The protective effects of STH are associated with the upregulation of MasR to inhibit AT₁ R signaling. STH could be a potential therapeutic strategy for cardiac diseases in hypertensive patients.

Salidroside ameliorates sepsis-induced acute lung injury and mortality via downregulating NF-κB and HMGB1 pathways through the upregulation of SIRT1

Sepsis is a life-threatening medical condition. Salidroside, a substance isolated from Rhodiola rosea, possesses antioxidant and anti-inflammatory properties. The effect and mechanism of salidroside on sepsis-induced acute lung injury still remains to be well clarified. Here, we investigated the effect and mechanism of salidroside on septic mouse models and explored the role of salidroside-upregulated SIRT1. Salidroside inhibited the inflammatory responses and HMGB1 productions in bacterial lipopolysaccharide (LPS)-treated macrophages and mice. Salidroside could also reverse the decreased SIRT1 protein expression in LPS-treated macrophages and mice. Salidroside also alleviated the sepsis-induced lung edema, lipid peroxidation, and histopathological changes and the mortality, and improved the lung PaO₂/FiO₂ ratio in cecal ligation and puncture (CLP)-induced septic mice. Salidroside significantly decreased the serum TNF-α, IL-6, NO, and HMGB1 productions, pulmonary inducible NO synthase (iNOS) and phosphorylated NF-κB-p65 protein expressions, and pulmonary HMGB1 nuclear translocation in CLP septic mice. Moreover, sepsis decreased the SIRT1 protein expression in the lungs of CLP septic mice. Salidroside significantly upregulated the SIRT1 expression and inhibited the inflammatory responses in CLP septic mouse lungs. These results suggest that salidroside protects against sepsis-induced acute lung injury and mortality, which might be through the SIRT1-mediated repression of NF-κB activation and HMGB1 nucleocytoplasmic translocation.

Tauroursodeoxycholic acid attenuates endoplasmic reticulum stress and protects the liver from chronic intermittent hypoxia induced injury

Obstructive sleep apnea that characterized by chronic intermittent hypoxia (CIH) has been reported to associate with chronic liver injury. Tauroursodeoxycholic acid (TUDCA) exerts liver-protective effects in various liver diseases. The purpose of this study was to test the hypothesis that TUDCA could protect liver against CIH injury. C57BL/6 mice were subjected to intermittent hypoxia for eight weeks and applied with TUDCA by intraperitoneal injection. The effect of TUDCA on liver histological changes, liver function, oxidative stress, inflammatory response, hepatocyte apoptosis and endoplasmic reticulum (ER) stress were investigated. The results showed that administration of TUDCA attenuated liver pathological changes, reduced serum alanine aminotransferase and aspartate aminotransferase level, suppressed reactive oxygen species activity, decreased tumor necrosis factor-α and interleukin-1β level and inhibited hepatocyte apoptosis induced by CIH. TUDCA also inhibited CIH-induced ER stress in liver as evidenced by decreased expression of ER chaperone 78 kDa glucose-related protein, unfolded protein response transducers and ER proapoptotic proteins. Altogether, the present study described a liver-protective effect of TUDCA in CIH mice model, and this effect seems at least partly through the inhibition of ER stress.

The Protective Effect of Salidroside on Hypoxia-Induced Corpus Cavernosum Smooth Muscle Cell Phenotypic Transformation

Salidroside, a major active ingredient isolated from Rhodiola rosea, has a long application in Chinese medical history. It has widely demonstrated effects on fatigue, psychological stress, and depression and exhibits potential antihypoxia activity. Emerging evidence shows that hypoxia is an important independent risk factor for erectile dysfunction (ED). The aim of this study was to clarify the effect of salidroside on hypoxia-induced phenotypic transformation of corpus cavernosum smooth muscle cells (CCSMCs). Our results showed that salidroside decreased the hypoxia-induced expression of collagen and content of vimentin, a corpus cavernosum smooth muscle synthetic protein, in vitro. Simultaneously, salidroside increased expression of the CCSMC contractile proteins, α-smooth muscle actin (α-SMA) and desmin. In vivo, similarly, the expressions of collagen and hypoxia-inducible factor-1α were increased in bilateral cavernous neurectomy (BCN) rats while they were decreased in the salidroside group. Among the phenotypic proteins, α-SMA and desmin increased and vimentin decreased after treating BCN rats with salidroside compared with the BCN alone group. Overall, our results demonstrate that salidroside has the ability to oppose hypoxia and can inhibit the CCSMC phenotypic transformation induced by hypoxia. Salidroside may provide a new treatment method for ED.

Content Determination of Phenylpropanoids and Enhancing Exercise Ability of Effective Fractions in Pedicularis densispica

BACKGROUND

Most researches were focused on chemical constituents and bioactivities of Pedicularis. However, there were a few reports on simultaneous determination of the series phenylpropanoids compounds in Pedicularis by High Performance Liquid Chromatography (HPLC).

OBJECTIVE

To establish an HPLC method for simultaneous determination of salidroside, verbascoside, iso-verbascoside, leucoseptoside A, jionoside D and martynoside in Pedicularis densispica (PD), and to assess the enhancing exercise ability of effective fractions of phenylpropanoids (EFP).

MATERIALS AND METHODS

The separation was performed on C18 column with step-wise gradient elution with water (A)-methanol (B) as the mobile phase at a flow rate of 1.0 mL/min, with detection wavelength at 275 nm (0-4 min) and 330 nm (4-40 min). The EFP were obtained from extracts of PD by resin gradient dilution. The enhancing exercise ability of EFP was exerted in exhaustive swimming and anoxia endurance tests in vivo.

RESULTS

The contents of six marker compounds had good linear relationship in the ranges of 2.10-8.40, 13.60-54.40, 0.93-3.72, 0.53-2.12, 1.50-6.00, 0.37-1.28, respectively, and the average recoveries of the six phenylpropanoids were all in the range of 98-103%. Total contents of phenylpropanoids in EFP were more than 60%. Three medicine groups of exhaustive swimming and anoxia endurance time were higher than those of the water group.

CONCLUSION

The analytical method is reliable, simple and accurate, and can be used for the comprehensive quality control of PD. This experiment suggests that PD has the effect of promoting the recovery and elimination of fatigue and improving the exercise capacity.

SUMMARY

A simple, practical and low-cost RP-HPLC method has been developed for the simultaneous determination of six marker phenylpropanoids in Pedicularis densispica.Three effective fractions of phenylpropanoids groups of exhaustive swimming and anoxia endurance time were higher than those of the water group.The separation was performed on C18 column with stepwise gradient elution with water-methanol. The enhancing exercise ability was exerted in exhaustive swimming and anoxia endurance tests in vivo.This plant has the effect of promoting the recovery and elimination of fatigue and improving the exercise capacity. Abbreviation used: PD: Pedicularis densispica, EFP: Effective fractions of phenylpropanoids, DAD: Diode array detector, HPLC: High performance liquid chromatography, LOD: Limits of detection, LOQ: Limits of quantification, RSD: Relative standard deviation, BV: Bed volumes.

Establishment of a Rabbit Model of Chronic Obstructive Sleep Apnea and Application in Cardiovascular Consequences

Background:

Although obstructive sleep apnea (OSA) has been recognized as a major risk factor for cardiovascular complications and its clinical features are well characterized, it is difficult to replicate the OSA hypoxic model in humans. We aimed to establish an experimental rabbit model for chronic OSA and to explore its application to measure blood pressure (BP), myocardial systolic function, and oxidative stress.

Methods:

The rabbit model for OSA was established by repeatedly closing the airway and then reopening it. A tube specially designed with a bag that could be alternately inflated and deflated according to a predetermined time schedule, resulting in recurrent airway occlusions and chronic intermittent hypoxia (CIH) imitating OSA patterns in humans, was used. Twenty-four rabbits were randomly divided into obstruction, sham, and control groups, and their upper airways were alternately closed for 15 s and then reopened for 105 s in a 120-s-long cycle, for 8 h each day over 12 consecutive weeks. Before and after the experiment, the BP of each rabbit was monitored. Levels of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) in the serum, superoxide dismutase (SOD) activity, malondialdehyde (MDA) and reactive oxygen species (ROS) contents, as well as Na⁺-K⁺-ATPase/Ca²⁺-ATPase activities in cardiac muscle were examined. In addition, cardiac functional parameters were measured using echocardiography.

Results:

After 3 months, all rabbits in the obstruction group manifested sleepiness performance similar to that observed in OSA patients. Traces of airflow and SpO₂ showed that this model mimicked the respiratory events involved in OSA, including increased respiratory effort and decreased oxygen saturation. Gradually, the BP rose each month. CIH led to obvious oxidative stress and injured myocardial systolic performance. The serum levels of IL-6 and TNF-α increased significantly (64.75 ± 9.05 pg/ml vs. 147.00 ± 19.24 pg/ml and 59.38 ± 8.21 pg/ml vs. 264.75 ± 25.54 pg/ml, respectively, both P < 0.001). Compared with the sham and the control groups, myocardial activities of Na⁺-K⁺-ATPase/Ca²⁺-ATPase and SOD in the obstruction group decreased markedly, while ROS and MDA content increased.

Conclusions:

These results show that the rabbit model for OSA simulates the pathophysiological characteristics of OSA in humans, which implies that this animal model is feasible and useful to study the mechanisms involved in the cardiovascular consequences of OSA.

Rhodiola crenulata extract counteracts the effect of hypobaric hypoxia in rat heart via redirection of the nitric oxide and arginase 1 pathway

BACKGROUND

Rhodiola crenulata is traditionally used as a folk medicine in Tibet for preventing high-altitude illnesses, including sudden cardiac death (SCD). The cardio-protective effects of Rhodiola crenulata root extract (RCE) against hypoxia in vivo have been recently confirmed. However, the way in which RCE produces these effects remains unclear. The present study is designed to confirm the protective effects of RCE on the heart in acute hypobaric hypoxia exposure and examine the mechanisms by which this occurs.

METHODS

Sprague-Dawley (SD) rats were pretreated with or without RCE and then exposed to a simulated altitude of 8000 m in a hypobaric hypoxia chamber for 9 h. The expression of cardiac arginase 1 (Arg-1) and endothelial nitric oxide synthase (eNOS) and the activity of associated signaling pathways was examined.

RESULTS

Hypoxia reduced cardiac eNOS phosphorylation and increased Arg-1 expression, but both responses were reversed by RCE pre-treatment. In addition, RCE decreased the hypoxia-induced oxidative stress markers of reactive oxygen species (ROS) production, malondialdehyde (MDA) level, and protein carbonyl content. Furthermore, RCE protected cardiomyocytes from hypoxia-induced cardiac apoptosis and restored the phosphorylation level of AKT and p38 MAPK as well as the superoxide dismutase 2 (SOD2) content in hypoxic animals.

CONCLUSION

The findings provide evidence that the effects of Rhodiola crenulata against altitude illness are partially mediated by modulation of eNOS and Arg-1 pathways in the heart.

Effect of superoxide anion scavenger on rat hearts with chronic intermittent hypoxia

Only very limited information regarding the protective effects of the superoxide anion scavenger on chronic intermittent hypoxia-induced cardiac apoptosis is available. The purpose of this study is to evaluate the effects of the superoxide anion scavenger on cardiac apoptotic and prosurvival pathways in rats with sleep apnea. Forty-two Sprague-Dawley rats were divided into three groups, rats with normoxic exposure (Control, 21% O2, 1 mo), rats with chronic intermittent hypoxia exposure (Hypoxia, 3-7% O2vs. 21% O2per 40 s cycle, 8 h per day, 1 mo), and rats with pretreatment of the superoxide anion scavenger and chronic intermittent hypoxia exposure (Hypoxia-O2 (-)-Scavenger, MnTMPyP pentachloride, 1 mg/kg ip per day; 3-7% O2vs. 21% O2per 40 s cycle, 8 h per day, 1 mo) at 5-6 mo of age. After 1 mo, the protein levels and apoptotic cells of excised hearts from three groups were measured by Western blotting and terminal deoxynucleotide transferase-mediated dUTP nick end labeling (TUNEL) assay. The superoxide anion scavenger decreased hypoxia-induced myocardial architecture abnormalities, left ventricular hypertrophy, and TUNEL-positive apoptosis. The superoxide anion scavenger decreased hypoxia-induced Fas ligand, Fas death receptors, Fas-associated death domain (FADD), activated caspase-8, and activated caspase-3 (Fas-dependent apoptotic pathway) as well as Bad, activated caspase-9 and activated caspase-3 (mitochondria-dependent apoptotic pathway), endonuclease G (EndoG), apoptosis-inducing factor (AIF), and TUNEL-positive apoptosis. The superoxide anion scavenger increased IGF-1, IGF-1R, p-PI3k, p-Akt, p-Bad, Bcl-2, and Bcl-xL (survival pathway). Our findings imply that the superoxide anion scavenger might prevent cardiac Fas-mediated and mitochondrial-mediated apoptosis and enhance the IGF-1-related survival pathway in chronic intermittent hypoxia. The superoxide anion scavenger may prevent chronic sleep apnea-enhanced cardiac apoptotic pathways and enhances cardiac survival pathways.

Effects of rhodiola crenulata on mice hearts under severe sleep apnea

BACKGROUND

The goal of this study is to determine if Rhodiola Crenulata (RC) has protective effects on mice hearts with severe sleep apnea model.

METHODS

Sixty-four C57BL/6 J mice 5-6 months old were distributed into 4 groups i.e. Control group (21% O2, 24 h per day, 8 weeks, n=16); Hypoxia group (Hypoxia: 7% O2 60 s, 20% O2 alternating 60 s, 8 h per day, 8 weeks, n=16); Hypoxia+90RC and Hypoxia+270RC group (Hypoxia for 1st 4 weeks and hypoxia pretreated 90 mg/Kg and 270 mg/Kg Rhodiola Crenulata by oral gavage per day for 2nd 4 weeks, each n=16). Excised hearts from 4 groups of mice were analyzed for heart weight index changes using H&E staining, TUNEL-positive assays and Western Blotting protein.

RESULTS

Cardiac widely dispersed TUNEL-positive apoptotic cells in mice hearts were less in Hypoxia+RC90 and Hypoxia+RC270 than those in Hypoxia. Compared with Hypoxia, the protein levels of Fas ligand, Fas death receptors, Fas-Associated Death Domain (FADD), activated caspase 8, and activated caspase 3 (Fas dependent apoptotic pathways) were decreased in Hypoxia+RC90, Hypoxia+RC270. The protein levels of Bad, Bax, t-Bid, activated caspase 9, activated caspase 3 (mitochondria dependent apoptotic pathway) were less in Hypoxia+RC90, Hypoxia+RC270 than those in hypoxia. The protein levels of Bcl2, Bcl-xL, p-Bad (Bcl2-realted anti-apoptotic pathway) and VEGF, p-PI3k, p-AKT (VEGF-related pro-survival pathway) were higher in Hypoxia+RC90, Hypoxia+RC270 than those in hypoxia.

CONCLUSIONS

Our findings suggest that Rhodiola Crenulata have protective effects on chronic intermittent hypoxia-induced cardiac widely dispersed apoptosis via Fas-dependent and mitochondria-dependent apoptotic and VEGF-related pro-survival pathway.