Heme oxygenase-1 enhances autophagy in podocytes as a protective mechanism against high glucose-induced apoptosis

SB202190 inhibits endothelial cell apoptosis via induction of autophagy and heme oxygenase-1

Activation of the p38 mitogen-activated protein kinase (MAPK) pathway has been implicated in various detrimental events finally leading to endothelial dysfunction. The present study therefore investigates the impact of the p38 MAPK inhibitor SB202190 on the expression of the cytoprotective enzyme heme oxygenase-1 (HO-1) as well as metabolic activity, apoptosis and autophagy of endothelial cells. Using human umbilical vein endothelial cells (HUVEC) SB202190 was found to cause a time- and concentration-dependent induction of HO-1 protein. Induction of HO-1 protein expression was mimicked by SB203580, another p38 MAPK inhibitor, but not by SB202474, an inactive structural analogue of p38 MAPK inhibitors. HO-1 induction by both SB202190 and SB203580 was also demonstrated by analysis of mRNA expression. On the functional level, SB202190 was shown to increase metabolic activity and autophagy of HUVEC along with diminishing basal apoptosis. Treatment of cells with tin protoporphyrin IX (SnPPIX), a well-characterised HO-1 enzymatic inhibitor, or HO-1 siRNA left SB202190-modulated metabolic activity and autophagy virtually unaltered but caused a significant reversal of the anti-apoptotic action of SB202190. Conversely, however, HO-1 expression by SB202190 became completely suppressed by the autophagy inhibitor bafilomycin A1. Bafilomycin A1 likewise fully reversed effects of SB202190 on metabolic activity and apoptosis, albeit significantly inducing apoptosis per se. Collectively, this work demonstrates SB202190 to confer upstream induction of autophagy followed by HO-1 induction resulting in potential protective effects against apoptosis. On the other hand, our data oppose HO-1 to contribute to SB202190-mediated increases in metabolic activity and autophagy, respectively.

A novel heme oxygenase-1 splice variant, 14kDa HO-1, promotes cell proliferation and increases relative telomere length

Alternative splicing is a routine phenomenon which greatly increases the diversity of proteins in eukaryotic cells. In humans, most multi-exonic genes are alternatively spliced and their splice variants confer distinct functions. Heme oxygenase-1 (HO-1, 32 kDa) is an inducible stress responsive protein, which possesses multiple functions in many cellular processes. In the current study, we identified a novel alternative splice isoform of 14 kDa HO-1 generated through exclusion of exon 3, and it is highly expressed in immortalized cells. In contrast to nuclear accumulation of the full-length 32 kDa HO-1, the novel 14 kDa HO-1 isoform is retained in the cytoplasm under ultraviolet (UV) irradiation. Interestingly, the 14 kDa HO-1 is shown to promote cell proliferation and an increase in relative telomere lengths in vivo and in vitro. Thus, we are pioneer to report and confirm the presence of a novel splice form of HO-1 and its distinct role in modulating telomere length and tumor growth.

Resveratrol Potently Counteracts Quercetin Starvation-Induced Autophagy and Sensitizes HepG2 Cancer Cells to Apoptosis

SCOPE

Resveratrol (RSV) has been described as a potent antioxidant, antisteatotic, and antitumor compound, and it has also been identified as a potent autophagy inducer. On the other hand, quercetin (QCT) is a dietary flavonoid with known antitumor, anti-inflammatory, and antidiabetic effects. Additionally, QCT increases autophagy. To study the hypothetical synergistic effect of both compounds, we test the combined effect of QCT and RSV on the autophagy process in HepG2 cells.

METHODS AND RESULTS

Autophagy is studied by western blotting, real-time RT-PCR, and cellular staining. Our results clearly indicate a bifunctional molecular effect of RSV. Both polyphenols are individually able to promote autophagy. Strikingly, when RSV is combined with QCT, it promotes a potent reduction of QCT-induced autophagy and influences proapoptotic signaling.

CONCLUSION

RSV acts differentially on the autophagic process depending on the cellular energetic state. We further characterize the molecular mechanisms related to this effect, and we observe that AMP-activated protein kinase (AMPK) phosphorylation, heme oxygenase 1 (HO-1) downregulation, lysosomal membrane permeabilization (LMP), and Zinc (Zn²⁺ ) dynamics could be important modulators of such RSV-related effects and could globally represent a promising strategy to sensitize cancer cells to QCT treatment.

Heme oxygnease-1 induction by methylene blue protects RAW264.7 cells from hydrogen peroxide-induced injury

Although methylene blue (MB) has showed strong antioxidant effect, its effect related with heme oxygenase-1 (HO-1) is still unclear. Thus, we investigated the effects of MB on HO-1 protein content and enzyme activity, and its protective effect against hydrogen peroxide (H₂O₂)-induced oxidative damage in RAW264.7 macrophage. The cell viability and the release of lactate dehydrogenase of RAW264.7 were determined. The mitochondrial functions were valuated through these indexes: content of adenosine triphosphate, superoxide dismutase, concentration of reactive oxygen species and mitochondrial membrane potential. Meanwhile, high content screening tested generation of ROS, MMP and intracellular concentration of calcium ion. qRT-PCR valuated macrophage phenotype markers expression. Lastly, flow cytometry and caspase-3 detection analyzed RAW264.7 apoptosis. Our data showed that (1) Both pretreatment and posttreatment of MB increased HO-1 protein content and enzyme activity; (2) MB rescued cells from H₂O₂-induced mitochondrial dysfunction; (3) High content screening revealed that MB alleviated the changes including generation of reactive oxygen species, mitochondrial membrane potential and intracellular concentration of calcium ion in H₂O₂ exposed RAW264.7; (4) MB attenuated H₂O₂-induced apoptosis; (5) MB pretreatment decreased the expression of M1 macrophage markers (Tnf and Nos2) while increasing the expression of M2 macrophage markers (Mrc1 and Il10); (6) The beneficial effect of MB was abolished by zinc protoporphyrin IX (HO-1 activity inhibitor) or HO-1 siRNA. In summary, MB protects RAW264.7 cells from H2O2-induced injury through up-regulation HO-1.

The cellular selection between apoptosis and autophagy: roles of vitamin D, glucose and immune response in diabetic nephropathy

BACKGROUND AND AIMS

Apoptosis, autophagy and cell cycle arrest are cellular responses to injury which are supposed to play fundamental roles in initiation and progression of diabetic nephropathy (DN). The aims of the present study is to shed light on the potential effects of vitamin D analog 22-oxacalcitriol (OCT) on different cell responses during DN, and the possible interplay between both glucose, immune system and vitamin D in determining the cell fate.

METHOD

All rats were randomly allocated into one of three groups: control, vehicle-treated DN group and OCT-treated DN group. Eight weeks after induction of diabetes, the rats were killed. Fasting blood glucose levels, serum 25 (OH) D, renal functions, cytokines and gene expression of autophagy, apoptotic and cell cycle arrest markers were assessed. In addition, the histological assessment of renal architecture was done.

RESULTS

OCT treatment remarkably improved the renal functions and albuminuria. The reductions in mesangial cell hypertrophy, extracellular matrix as well as cell loss were significantly associated with upregulation of pro-autophagy gene expressions and downregulation of both pro-apoptotic and G1-cell cycle arrest genes expression. The reno-protective effects of OCT treatment were associated with significant attenuation of the fasting blood glucose, serum IL-6, renal TLR-4 and IFN-g gene expression.

CONCLUSION

Modulator effects of OCT on glucose and immune system play important roles in renal cell fate decision and chronic kidney disease progression.

Apelin involved in progression of diabetic nephropathy by inhibiting autophagy in podocytes

Podocyte autophagy dysfunction has been reported to be responsible for the progression of diabetic nephropathy (DN), however, the factors contributed to autophagy dysfunction in type 2 diabetes are not fully understood. Among promoting factors in DN, an adipokine, apelin, had been showed to trigger podocyte dysfunction. Therefore, it is hypothesized that apelin, which is increased in plasma in type 2 diabetes, lead to podocyte apoptosis through inhibiting podocyte autophagy, which resulted in podocyte dysfunction followed by DN. KkAy mice (diabetic mice) and cultured podocytes (MPC5 cells and native podocytes) were treated with high glucose (HG) and apelin or its antagonist F13A. Renal function, podocyte autophagy, podocyte apoptosis and corresponding cell signaling pathways in podocytes were detected. The results showed that apelin aggravated the renal dysfunction and foot process injuries in kkAy mice, which is positively correlated to podocyte apoptosis and negatively correlated to podocyte autophagy. Apelin induced podocyte apoptosis and inhibited podocyte autophagy in both normal glucose and HG conditions while F13A reversed these effects. Investigations by western blot found that apelin inhibits podocyte autophagy through ERK-, Akt- and mTOR-dependent pathways. In conclusion, increased apelin concentration in plasma inhibited podocyte autophagy, which would lead to podocyte apoptosis and renal dysfunction in diabetes. These effects would contribute to the progression of DN.

Salidroside Reduces High-Glucose-Induced Podocyte Apoptosis and Oxidative Stress via Upregulating Heme Oxygenase-1 (HO-1) Expression

Background

Hyperglycemia is one of the most dangerous factors causing diabetic nephropathy. Salidroside is considered to have the effects of reducing oxidative stress damage and improving cell viability. This study was performed to investigate whether and how salidroside reduces high-glucose (HG)-induced apoptosis in mouse podocytes.

Material/Methods

We examined whether salidroside could decrease HG-induced podocyte oxidative stress and podocyte apoptosis in vitro. The potential signaling pathways were also investigated. Podocytes (immortalized mouse epithelial cells) were treated with normal glucose (5.5 mM) as control or HG (30 mM), and then exposed to salidroside treatment.

Results

HG enhanced the generation of intracellular reactive oxygen species (ROS) and apoptosis in podocytes. Salidroside reduced HG-induced apoptosis-related consequences via promoting HO-1 expression. Salidroside increased the expression level of phosphorylated Akt (p-Akt) and phosphorylated ILK (p-ILK), p-JNK, and p-ERK and localization of Nrf-2. JNK inhibitor and ILK inhibitor decreased HO-1 expression to different degrees. Moreover, specific siRNAs of ILK, Nrf-2, and HO-1, and inhibitors of HO-1 and ILK significantly increased ROS generation and Caspase9/3 expression in the presence of salidroside and HG.

Conclusions

The results suggest that salidroside reduces HG-induced ROS generation and apoptosis and improves podocytes viability by upregulating HO-1 expression. ILK/Akt, JNK, ERK1/2, p38 MAPK, and Nrf-2 are involved in salidroside-decreased podocyte apoptosis in HG condition.

Ursolic acid improves podocyte injury caused by high glucose

BACKGROUND

Autophagy plays an important role in the maintenance of podocyte homeostasis. Reduced autophagy may result in limited renal cell function during exposure to high glucose conditions. In this study we investigated the effects of ursolic acid (UA) on autophagy and podocyte injury, which were induced by high glucose.

METHODS

Conditionally immortalized murine podocytes were cultured in media supplemented with high glucose and the effects of the PI3K inhibitor LY294002 and UA on protein expression were determined. miR-21 expression was detected by real-time RT-PCR. Activation of the PTEN-PI3K/Akt/mTOR pathway, expression of autophagy-related proteins and expression of podocyte marker proteins were determined by western blot. Immunofluorescence was used to monitor the accumulation of LC3 puncta. Autophagosomes were also observed by transmission electron microscopy.

RESULTS

During exposure to high glucose conditions, the normal level of autophagy was reduced in podocytes, and this defective autophagy induced podocyte injury. Increased miR-21 expression, decreased PTEN expression and abnormal activation of the PI3K/Akt/mTOR pathway were observed in cells that were cultured in high glucose conditions. UA and LY294002 reduced podocyte injury through the restoration of defective autophagy. Our data suggest that UA inhibits miR-21 expression and increases PTEN expression, which in turn inhibits Akt and mTOR and restores normal levels of autophagy.

CONCLUSIONS

Our data suggest that podocyte injury is associated with reduced levels of autophagy during exposure to high glucose conditions, UA attenuated podocyte injury via an increase in autophagy through miR-21 inhibition and PTEN expression, which inhibit the abnormal activation of the PI3K/Akt/mTOR pathway.

Retraction statement: ‘Urotensin II inhibits autophagy in renal tubular epithelial cells and induces extracellular matrix production in early diabetic mice’ by Guan‐Jong Chen, Fei Wu, Xin‐Xin Pang, Ai‐Hua Zhang, Jun‐Bao Shi, Min Lu and Chao‐Shu Tang

AIMS/INTRODUCTION

Urotensin II (UII) and autophagy have been considered as important components in the pathogenesis of diabetic nephropathy. The present study explores whether UII can regulate autophagy in the kidney, and its effect in diabetes.

MATERIALS AND METHODS

Immunohistochemistry and western blot were carried out on the kidney tissues of diabetic UII receptor (UT) gene knockout mice, wild-type diabetic mice and normal control mice. For the in vitro experiment, HK-2 cells were treated with UII (10-7 mol/L) in the presence or absence of UT antagonist, SB-657510, (10-6 mol/L) or autophagy inducer, rapamycin (10-3 mol/L), for 12 h. Markers for autophagy (LC3-II, p62/SQSTM1) and extracellular matrix (fibronectin, collagen IV) were analyzed.

RESULTS

In diabetic UT knockout mice, expression of LC3-II is increased and p62 was reduced in comparison with that of the normal diabetic mice. Fibronectin and collagen IV were downregulated in diabetic UT knockout mice when compared with that of the normal diabetic mice. For the in vitro cell experiment, UII was shown to inhibit expression LC3-II and increase expression of p62 in comparison with that of the normal control. Treatment with SB-657510 can block UII-induced downregulation of LC3-II and upregulation of p62 while inhibiting UII-induced upregulation of fibronectin and collagen IV. Adding autophagy inducer, rapamycin, also inhibited UII-induced upregulation of fibronectin and collagen IV.

CONCLUSIONS

The present study is the first to show that UII can downregulate autophagy in the kidney while accompanying the increased production of extracellular matrix in early diabetes. Our in vitro study also showed that upregulation of autophagy can decrease UII-induced production of extracellular matrix in HK-2 cells.

Beneficial effects of Huaiqihuang on hyperglycemia-induced MPC5 podocyte dysfunction through the suppression of mitochondrial dysfunction and endoplasmic reticulum stress

The present study was performed to investigate the effect of Huaiqihuang (HQH) on hyperglycemia (HG)-induced mitochondrial dysfunction and endoplasmic reticulum (ER) stress in MPC5 podocytes. The effects of HQH and HG on cell viability were assessed using an MTT assay. mRNA and protein expression levels were evaluated using reverse transcription-quantitative polymerase chain reaction and western blot analysis, respectively. Cell apoptosis was assessed using terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick end labeling, whereas reactive oxygen species production and alterations in mitochondrial membrane potential were assessed using flow cytometry. DNA damage was evaluated using a comet assay. The results demonstrated that treatment of podocytes with HQH markedly suppressed the HG‑induced generation of reactive oxygen species. HQH also significantly improved mitochondrial membrane potential in podocytes exposed to HG. When the podocytes were treated with HG, Ca2+ levels were significantly increased, compared with those in the control group, whereas treatment of the podocytes with HQH significantly reversed the HG‑induced upregulation of Ca2+ secretion. Treatment of the podocytes with HQH significantly reversed the HG‑induced upregulation of glucose‑related protein 78 (GRP78) and C/EBP‑homologous protein, which were used as indicators of ER stress. Furthermore, GRP78 loss‑of‑function attenuated HG‑induced podocyte dysfunction, including cell apoptosis and DNA damage. In conclusion, beneficial effects of HQH on HG‑induced MPC5 podocyte dysfunction were observed, and occurred through the suppression of mitochondrial dysfunction and ER stress.

Dietary fat may modulate adipose tissue homeostasis through the processes of autophagy and apoptosis

PURPOSE

Obesity increases the risk of cardiovascular disease, type 2 diabetes mellitus and cancer development. Autophagy and apoptosis are critical processes for development and homeostasis in multicellular organisms and have been linked to a variety of disorders. We aimed to investigate whether the quantity and quality of dietary fat can influence these processes in the adipose tissue of obese people.

METHODS

A randomized, controlled trial within the LIPGENE study assigned 39 obese people with metabolic syndrome to 1 of 4 diets: (a) a high-saturated fatty acid diet, (b) a high-monounsaturated fatty acid (HMUFA) diet, and (c, d) two low-fat, high-complex carbohydrate diets supplemented with long-chain n-3 polyunsaturated fatty acids (LFHCC n-3) or placebo (LFHCC), for 12 weeks each.

RESULTS

We found an increase in the expression of autophagy-related BECN1 and ATG7 genes after the long-term consumption of the HMUFA diet (p = 0.001 and p = 0.004, respectively) and an increase in the expression of the apoptosis-related CASP3 gene after the long-term consumption of the LFHCC and LFHCC n-3 diets (p = 0.001 and p = 0.029, respectively). CASP3 and CASP7 gene expression changes correlated with HOMA index.

CONCLUSION

Our results suggest that the processes of autophagy and apoptosis in adipose tissue may be modified by diet and that the consumption of a diet rich in monounsaturated fat may contribute to adipose tissue homeostasis by increasing autophagy. They also reinforce the notion that apoptosis in adipose tissue is linked to insulin resistance.

CLINICAL TRIAL REGISTRATION NUMBER

ClinicalTrials.gov NCT00429195.

Resveratrol protects podocytes against apoptosis via stimulation of autophagy in a mouse model of diabetic nephropathy

Podocyte apoptosis coincides with albuminuria onset and precedes podocytopenia in diabetic nephropathy. However, there is a lack of effective therapeutic drugs to protect podocytes from apoptosis. Here, we demonstrated that resveratrol relieved a series of indicators of diabetic nephropathy and attenuated apoptosis of podocytes in db/db diabetic model mice. In addition, resveratrol induced autophagy in both db/db mice and human podocytes. Furthermore, inhibition of autophagy by 3-methyladenine (3-MA) and autophagy gene 5 (Atg5) short hairpin RNA (shRNA) reversed the protective effects of resveratrol on podocytes. Finally, we found that resveratrol might regulate autophagy and apoptosis in db/db mice and podocytes through the suppression of microRNA-383-5p (miR-383-5p). Together, our results indicate that resveratrol effectively attenuates high glucose-induced apoptosis via the activation of autophagy in db/db mice and podocytes, which involves miR-383-5p. Thus, this study reveals a new possible strategy to treat diabetic nephropathy.

[Autophagy in the kidney]

Autophagy is a highly conserved, physiological, catabolic process, involving the lysosomal degradation of cytosolic components, including macromolecules (such as proteins and lipids) and cytosolic organelles. Autophagy is believed to be essential for the maintenance of cellular homeostasis, for a number of fundamental biological activities, and an important component of the complex response of cells to multiple forms of stress. Autophagy is involved in the pathogenesis of a number of clinically important disorders but, until recently, little was known about its connection to kidney diseases. However, there is now growing evidence that autophagy is specifically linked to the pathogenesis of important renal diseases such as acute kidney injury, diabetic nephropathy and polycystic kidney disease. However, an understanding of the precise role of autophagy in the course of kidney diseases is still in its infancy. The review points out areas of particular interest for future research, and also discusses the importance of such information on whether the pharmacologic agents that modulate autophagy are potentially usable as novel forms of treatment for various kidney diseases.

Mitochondrial quality-control dysregulation in conditional HO-1-/- mice

The heme oxygenase-1 (Hmox1; HO-1) pathway was tested for defense of mitochondrial quality control in cardiomyocyte-specific Hmox1 KO mice (HO-1[CM]^-/-) exposed to oxidative stress (100% O₂). After 48 hours of exposure, these mice showed persistent cardiac inflammation and oxidative tissue damage that caused sarcomeric disruption, cardiomyocyte death, left ventricular dysfunction, and cardiomyopathy, while control hearts showed minimal damage. After hyperoxia, HO-1(CM)^-/- hearts showed suppression of the Pgc-1α/nuclear respiratory factor-1 (NRF-1) axis, swelling, low electron density mitochondria by electron microscopy (EM), increased cell death, and extensive collagen deposition. The damage mechanism involves structurally deficient autophagy/mitophagy, impaired LC3II processing, and failure to upregulate Pink1- and Park2-mediated mitophagy. The mitophagy pathway was suppressed through loss of NRF-1 binding to proximal promoter sites on both genes. These results indicate that cardiac Hmox1 induction not only prevents heme toxicity, but also regulates the timing and registration of genetic programs for mitochondrial quality control that limit cell death, pathological remodeling, and cardiac fibrosis.

Repression of miR-217 protects against high glucose-induced podocyte injury and insulin resistance by restoring PTEN-mediated autophagy pathway

Podocyte damage is the initial hallmark of diabetic nephropathy (DN), leading to the increasing morbidity and mortality in diabetic patients. Recent researches have corroborated the critical roles of miRNAs in the pathological progression of DN. Here, elevation of miR-217 was verified in high glucose (HG)-stimulated podocytes. Moreover, blocking miR-217 expression antagonized HG-induced cell injury by attenuating the adverse role of HG on cell viability and inhibiting ROS levels and cell apoptosis. Simultaneously, miR-217 repression restored HG-disrupted insulin resistance by elevating glucose uptake and nephrin expression, an essential component for insulin-induced glucose uptake. Mechanism assay substantiated the defective autophagy in HG-treated podocytes, which was resumed by miR-217 cessation. Importantly, suppressing autophagy pathway with 3-MA alleviated the protective roles of miR-217 down-regulation in podocyte injury and insulin resistance. Luciferase reporter analysis confirmed that PTEN was a target of miR-217 in podocytes. Additionally, blocking PTEN expression restrained autophagy restoration in miR-217-decreased cells. Furthermore, PTEN down-regulation attenuated the beneficial role of miR-217 suppression in HG-induced injury and insulin resistance. Together, this study manifests that miR-217inhibition can protectively antagonize HG-induced podocyte damage and insulin resistance by restoring the defective autophagy pathway via targeting PTEN, representing a novel and promising therapeutic target against diabetic nephropathy.

Berberine enhances the AMPK activation and autophagy and mitigates high glucose-induced apoptosis of mouse podocytes

High glucose concentration can induce injury of podocytes and berberine has a potent activity against diabetic nephropathy. However, whether and how berberine can inhibit high glucose-mediated injury of podocytes have not been clarified. This study tested the effect of berberine on high glucose-mediated apoptosis and the AMP-activated protein kinase (AMPK), mammalian target of rapamycin (mTOR) activation and autophagy in podocytes. The results indicated that berberine significantly mitigated high glucose-decreased cell viability, and nephrin and podocin expression as well as apoptosis in mouse podocytes. Berberine significantly increased the AMPK activation and mitigated high glucose and/or the AMPK inhibitor, compound C-mediated mTOR activation and apoptosis in podocytes. Berberine significantly enhanced the AMPK activation and protected from high glucose-induced apoptosis in the AMPK-silencing podocytes. Furthermore, berberine significantly increased the high glucose-elevated Unc-51-like autophagy-activating kinase 1 (ULK1) S317/S555 phosphorylation, Beclin-1 expression, the ratios of LC3II to LC3I expression and the numbers of autophagosomes, but reduced ULK1 S757 phosphorylation in podocytes. In addition, berberine significantly attenuated compound C-mediated inhibition of autophagy in podocytes. The protective effect of berberine on high glucose-induced podocyte apoptosis was significantly mitigated by pre-treatment with 3-methyladenine or bafilomycin A1. Collectively, berberine enhanced autophagy and protected from high glucose-induced injury in podocytes by promoting the AMPK activation. Our findings may provide new insights into the molecular mechanisms underlying the anti-diabetic nephropathy effect of berberine and may aid in design of new therapies for intervention of diabetic nephropathy.

5-Aminolevulinic acid with sodium ferrous citrate induces autophagy and protects cardiomyocytes from hypoxia-induced cellular injury through MAPK-Nrf-2-HO-1 signaling cascade

BACKGROUND

Hypoxia causes cardiac disease via oxidative stress and mitochondrial dysfunction. 5-Aminolevulinic acid in combination with sodium ferrous citrate (ALA/SFC) has been shown to up-regulate heme oxygenase-1 (HO-1) and decrease macrophage infiltration and renal cell apoptosis in renal ischemia injury mice. However, its underlying mechanism remains largely unknown. The aim of this study was to investigate whether ALA/SFC could protect cardiomyocytes from hypoxia-induced apoptosis by autophagy via HO-1 signaling.

MATERIALS & METHODS

Murine atrial cardiomyocyte HL-1 cells were pretreated with ALA/SFC and then exposed to hypoxia.

RESULTS

ALA/SFC pretreatment significantly attenuated hypoxia-induced cardiomyocyte apoptosis, reactive oxygen species production, and mitochondrial injury, while it increased cell viability and autophagy levels. HO-1 expression by ALA/SFC was associated with up-regulation and nuclear translocation of Nrf-2, whereas Nrf-2 siRNA dramatically reduced HO-1 expression. ERK1/2, p38, and SAPK/JNK pathways were activated by ALA/SFC and their specific inhibitors significantly reduced ALA/SFC-mediated HO-1 upregulation. Silencing of either Nrf-2 or HO-1and LY294002, inhibitor of autophagy, abolished the protective ability of ALA/AFC against hypoxia-induced injury and reduced ALA/SFC-induced autophagy.

CONCLUSION

Taken together, our data suggest that ALA/SFC induces autophagy via activation of MAPK/Nrf-2/HO-1 signaling pathway to protect cardiomyocytes from hypoxia-induced apoptosis.

Interferon gamma-induced apoptosis of head and neck squamous cell carcinoma is connected to indoleamine-2,3-dioxygenase via mitochondrial and ER stress-associated pathways

Background

Tumor response to immunotherapy is the consequence of a concerted crosstalk between cytokines and effector cells. Interferon gamma (IFNγ) is one of the common cytokines coordinating tumor immune response and the associated biological consequences. Although the role of IFNγ in the modulation of tumor immunity has been widely documented, the mechanisms regulating IFNγ-induced cell death, during the course of immune therapy, is not described in detail.

Results

IFNγ triggered apoptosis of CLS-354 and RPMI 2650 cells, enhanced the protein expression and activation of indoleamine 2,3-dioxygenase (IDO), and suppressed the basal expression of heme oxygenase-1(HO-1). Interestingly, IFNγ induced the loss of mitochondrial membrane potential (Δψm) and increased accumulation of reactive oxygen species (ROS). The cytokine also induced the activation of Janus kinase (JAK)/Signal Transducer and Activator of Transcription (STAT)1, apoptosis signal-regulating kinase 1 (ASK1), p38, c-jun-N-terminal kinase (JNK) and NF-κB pathways and the transcription factors STAT1, interferon regulatory factor 1 (IRF1), AP-1, ATF-2, NF-κB and p53, and expression of Noxa protein. Furthermore, IFNγ was found to trigger endoplasmic reticulum (ER) stress as evidenced by the cleavage of caspase-4 and activation of protein kinase RNA-like endoplasmic reticulum kinase (PERK) and inositol-requiring-1α (IRE1α) pathways. Using specific inhibitors, we identified a potential role for IDO as apoptotic mediator in the regulation of IFNγ-induced apoptosis of head and neck squamous cell carcinoma (HNSCC) cells via Noxa-mediated mitochondrial dysregulation and ER stress.

Conclusion

In addition to the elucidation of the role of IDO in the modulation of apoptosis, our study provides new insights into the molecular mechanisms of IFNγ-induced apoptosis of HNSCC cells during the course of immune therapy.

Withaferin A suppresses the growth of myelodysplasia and leukemia cell lines by inhibiting cell cycle progression

Treatment outcomes for acute myeloid leukemia and myelodysplastic syndromes (MDS) remain unsatisfactory despite progress in various types of chemotherapy and hematopoietic stem cell transplantation. Therefore, there is a need for the development of new treatment options. We investigated the growth‐suppressive effects of withaferin A (WA), a natural plant steroidal lactone, on myelodysplasia and leukemia cell lines. WA exhibited growth‐suppressive effects on the cell lines, MDS‐L, HL‐60, THP‐1, Jurkat and Ramos, and induction of cell cycle arrest at G2/M phase at relatively low doses. Evaluation by annexin V/PI also confirmed the induction of partial apoptosis. Gene expression profiling and subsequent gene set enrichment analysis revealed increased expression of heme oxygenase‐1 (HMOX1). HMOX1 is known to induce autophagy during anticancer chemotherapy and is considered to be involved in the treatment resistance. Our study indicated increased HMOX1 protein levels and simultaneous increases in the autophagy‐related protein LC3A/B in MDS‐L cells treated with WA, suggesting increased autophagy. Combined use of WA with chloroquine, an autophagy inhibitor, enhanced early apoptosis and growth suppression. Together with the knowledge that WA had no apparent suppressive effect on the growth of human normal bone marrow CD34‐positive cells in the short‐term culture, this drug may have a potential for a novel therapeutic approach to the treatment of leukemia or MDS.

Spironolactone promotes autophagy via inhibiting PI3K/AKT/mTOR signalling pathway and reduce adhesive capacity damage in podocytes under mechanical stress

Mechanical stress which would cause deleterious adhesive effects on podocytes is considered a major contributor to the early progress of diabetic nephropathy (DN). Our previous study has shown that spironolactone could ameliorate podocytic adhesive capacity in diabetic rats. Autophagy has been reported to have a protective role against renal injury. The present study investigated the underlying mechanisms by which spironolactone reduced adhesive capacity damage in podocytes under mechanical stress, focusing on the involvement of autophagy. Human conditional immortalized podocytes exposed to mechanical stress were treated with spironolactone, LY294002 or rapamycin for 48 h. The accumulation of LC3 puncta was detected by immunofluorescence staining. Podocyte expression of mineralocorticoid receptor (MR), integrin β1, LC3, Atg5, p85-PI3K, p-Akt, p-mTOR were detected by Western blotting. Podocyte adhesion to collagen type IV was also performed with spectrophotometry. Immunofluorescence staining showed that the normal level of autophagy was reduced in podocytes under mechanical stress. Decreased integrin β1, LC3, Atg5 and abnormal activation of the PI3K/Akt/mTOR pathway were also detected in podocytes under mechanical stress. Spironolactone up-regulated integrin β1, LC3, Atg5 expression, down-regulated p85-PI3K, p-Akt, p-mTOR expression and reduced podocytic adhesive capacity damage. Our data demonstrated that spironolactone inhibited mechanical-stress-induced podocytic adhesive capacity damage through blocking PI3K/Akt/mTOR pathway and restoring autophagy activity.

Myricitrin Attenuates High Glucose-Induced Apoptosis through Activating Akt-Nrf2 Signaling in H9c2 Cardiomyocytes

Hyperglycemia, as well as diabetes mellitus, has been shown to trigger cardiac cell apoptosis. We have previously demonstrated that myricitrin prevents endothelial cell apoptosis. However, whether myricitrin can attenuate H9c2 cell apoptosis remains unknown. In this study, we established an experiment model in H9c2 cells exposed to high glucose. We tested the hypothesis that myricitrin may inhibit high glucose (HG)-induced cardiac cell apoptosis as determined by TUNEL staining. Furthermore, myricitrin promoted antioxidative enzyme production, suppressed high glucose-induced reactive oxygen species (ROS) production and decreased mitochondrial membrane potential (MMP) in H9c2 cells. This agent significantly inhibited apoptotic protein expression, activated Akt and facilitated the transcription of NF-E2-related factor 2 (Nrf2)-mediated protein (heme oxygenase-1 (HO-1) and quinone oxidoreductase 1 (NQO-1) expression as determined by Western blotting. Significantly, an Akt inhibitor (LY294002) or HO-1 inhibitor (ZnPP) not only inhibited myricitrin-induced HO-1/NQO-1 upregulation but also alleviated its anti-apoptotic effects. In summary, these observations demonstrate that myricitrin activates Nrf2-mediated anti-oxidant signaling and attenuates H9c2 cell apoptosis induced by high glucose via activation of Akt signaling.

FGF21 represses cerebrovascular aging via improving mitochondrial biogenesis and inhibiting p53 signaling pathway in an AMPK-dependent manner

Cerebrovascular aging has a high relationship with stroke and neurodegenerative disease. In the present study, we evaluated the influence of fibroblast growth factor 21 (FGF21) on angiotensin (Ang II)-mediated cerebrovascular aging in human brain vascular smooth muscle cells (hBVSMCs). Ang II induced remarkable aging-phenotypes in hBVSMCs, including enhanced SA-β-gal staining and NBS1 protein expression. First, we used immunoblotting assay to confirm protein expression of FGF21 receptor (FGFR1) and the co-receptor β-Klotho in cultured hBVSMCs. Second, we found that FGF21 treatment partly prevented the aging-related changes induced by Ang II. FGF21 inhibited Ang II-enhanced ROS production/superoxide anion levels, rescued the Ang II-reduced Complex IV and citrate synthase activities, and suppressed the Ang II-induced meprin protein expression. Third, we showed that FGF21 not only inhibited the Ang II-induced p53 activation, but also blocked the action of Ang II on Siah-1-TRF signaling pathway which is upstream factors for p53 activation. At last, either chemical inhibition of AMPK signaling pathway by a specific antagonist Compound C or knockdown of AMPKα1/2 isoform using siRNA, successfully abolished the anti-aging action of FGF21 in hBVSMCs. These results indicate that FGF21 protects against Ang II-induced cerebrovascular aging via improving mitochondrial biogenesis and inhibiting p53 activation in an AMPK-dependent manner, and highlight the therapeutic value of FGF21 in cerebrovascular aging-related diseases such as stroke and neurodegenerative disease.

Targeting the lysosome in cancer

Lysosomes are membrane-bound intracellular organelles that receive macromolecules delivered by endocytosis, phagocytosis, and autophagy for degradation and recycling. Over the last decade, advances in lysosome research have established a broad role for the lysosome in the pathophysiology of disease. In this review, we highlight the recent discoveries in lysosome biology, with an emphasis on their implications for cancer therapy. We focus on targeting the lysosome in cancer by exploring lysosomal biogenesis and its role in the crosstalk between apoptosis and autophagy. We also discuss how lysosomal inhibition could emerge as a new therapeutic strategy to overcome drug resistance in cancer.

Heme oxygenase-1, a novel target for the treatment of diabetic complications: focus on diabetic peripheral neuropathy

Diabetic neuropathy is a complex disorder induced by long standing diabetes. Many signaling pathways and transcription factors have been proposed to be involved in the development and progression of related processes. Years of research points to critical role of oxidative stress, neuroinflammation and apoptosis in the pathogenesis of neuropathy in diabetes. Heme oxygenase-1 (HO-1) is heat-shock protein induced under conditions of different kinds of stress and has been implicated in cellular defense against oxidative stress. HO-1 degrades heme to biliverdin, carbon monoxide (CO) and free iron. Biliverdin and CO are gaining particular interest because these two have been found to mediate most of anti-inflammatory, antioxidant and anti-apoptotic effects of HO-1. Although extensively studied in different kinds of cancers and cardiovascular conditions, role of HO-1 in diabetic neuropathy is still under investigation. In this paper, we review the unique therapeutic potential of HO-1 and its role in mitigating various pathological processes that lead to diabetic neuropathy. This review also highlights the therapeutic approaches such as pharmacological and natural inducers of HO-1, gene delivery of HO-1 or its reaction products that in future, could lead to progression of HO-1 activators through the preclinical stages of drug development to clinical trials.