Norepinephrine-induced oxidative stress causes PC-12 cell apoptosis by both endoplasmic reticulum stress and mitochondrial intrinsic pathway: inhibition of phosphatidylinositol 3-kinase survival pathway

Neuroprotective actions of norepinephrine in neurological diseases

Precise control of norepinephrine (NE) levels and NE-receptor interaction is crucial for proper function of the brain. Much evidence for this view comes from experimental studies that indicate an important role for NE in the pathophysiology and treatment of various conditions, including cognitive dysfunction, Alzheimer's disease, Parkinson's disease, multiple sclerosis, and sleep disorders. NE provides neuroprotection against several types of insults in multiple ways. It abrogates oxidative stress, attenuates neuroinflammatory responses in neurons and glial cells, reduces neuronal and glial cell activity, promotes autophagy, and ameliorates apoptotic responses to a variety of insults. It is beneficial for the treatment of neurodegenerative diseases because it improves the generation of neurotrophic factors, promotes neuronal survival, and plays an important role in the regulation of adult neurogenesis. This review aims to present the evidence supporting a principal role for NE in neuroprotection, and molecular mechanisms of neuroprotection.

Insulin reduces endoplasmic reticulum stress-induced apoptosis by decreasing mitochondrial hyperpolarization and caspase-12 in INS-1 pancreatic β-cells

Pancreatic β-cell mass is a critical determinant of insulin secretion. Severe endoplasmic reticulum (ER) stress causes β-cell apoptosis; however, the mechanisms of progression and suppression are not yet fully understood. Here, we report that the autocrine/paracrine function of insulin reduces ER stress-induced β-cell apoptosis. Insulin reduced the ER-stress inducer tunicamycin- and thapsigargin-induced cell viability loss due to apoptosis in INS-1 β-cells. Moreover, the effect of insulin was greater than that of insulin-like growth factor-1 at physiologically relevant concentrations. Insulin did not attenuate the ER stress-induced increase in unfolded protein response genes. ER stress did not induce cytochrome c release from mitochondria. Mitochondrial hyperpolarization was induced by ER stress and prevented by insulin. The protonophore/mitochondrial oxidative phosphorylation uncoupler, but not the antioxidants N-acetylcysteine and α-tocopherol, exhibited potential cytoprotection during ER stress. Both procaspase-12 and cleaved caspase-12 levels increased under ER stress. The caspase-12 inhibitor Z-ATAD-FMK decreased ER stress-induced apoptosis. Caspase-12 overexpression reduced cell viability, which was diminished in the presence of insulin. Insulin decreased caspase-12 levels at the post-translational stages. These results demonstrate that insulin protects against ER stress-induced β-cell apoptosis in this cell line. Furthermore, mitochondrial hyperpolarization and increased caspase-12 levels are involved in ER stress-induced and insulin-suppressed β-cell apoptosis.

The role of hormones in sepsis: an integrated overview with a focus on mitochondrial and immune cell dysfunction

Sepsis is a dysregulated host response to infection that results in life-threatening organ dysfunction. Virtually every body system can be affected by this syndrome to greater or lesser extents. Gene transcription and downstream pathways are either up- or downregulated, albeit with considerable fluctuation over the course of the patient's illness. This multi-system complexity contributes to a pathophysiology that remains to be fully elucidated. Consequentially, little progress has been made to date in developing new outcome-improving therapeutics. Endocrine alterations are well characterised in sepsis with variations in circulating blood levels and/or receptor resistance. However, little attention has been paid to an integrated view of how these hormonal changes impact upon the development of organ dysfunction and recovery. Here, we present a narrative review describing the impact of the altered endocrine system on mitochondrial dysfunction and immune suppression, two interlinked and key aspects of sepsis pathophysiology.

Feline Uroepithelial Cell Culture as a Novel Model of Idiopathic Cystitis: Investigations on the Effects of Norepinephrine on Inflammatory Response, Oxidative Stress, and Barrier Function

Feline idiopathic cystitis (FIC) is one of the most common urinary tract disorders in domestic cats. As stress is suggested to play a key role in the pathogenesis of FIC, the effects of norepinephrine (NE) as a stress mediator were investigated on a novel feline primary uroepithelial cell culture, serving as an in vitro model of the disease. The uroepithelial cells gained from the mucosa of the bladder of a euthanized cat were cultured for 6 days and were acutely exposed to NE (10, 100, and 1000 µM) for 1 h. NE increased the metabolic activity of the cultured cells and elevated the extracellular concentrations of the pro-inflammatory mediators interleukin-6 (IL-6) and stromal cell derived factor 1 (SDF-1), confirming that NE can trigger an inflammatory response in the uroepithelium. Cellular protein carbonyl levels were increased by NE exposure, while malondialdehyde and glucose regulated protein 78 concentrations remained unchanged, indicating that NE may provoke the oxidative damage of proteins without inducing lipid peroxidation or endoplasmic reticulum stress. Further, it can be strongly suggested that an acute NE challenge might diminish the barrier function of uroepithelial cells, as reflected by the decreased glycosaminoglycan concentration, claudin-4 protein expression, and reduced TER values of the NE-treated cell cultures. Based on these results, short-term NE exposure mimicking acute stress can provoke an inflammatory response and decrease the barrier integrity of cultured feline uroepithelial cells. Hence, it is highly expected that stress-associated NE release may play an important mediatory role in the pathogenesis of FIC.

Live and let die: signaling AKTivation and UPRegulation dynamics in SARS-CoVs infection and cancer

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the pathogen responsible for the coronavirus disease 2019 (COVID-19) pandemic. Of particular interest for this topic are the signaling cascades that regulate cell survival and death, two opposite cell programs whose control is hijacked by viral infections. The AKT and the Unfolded Protein Response (UPR) pathways, which maintain cell homeostasis by regulating these two programs, have been shown to be deregulated during SARS-CoVs infection as well as in the development of cancer, one of the most important comorbidities in relation to COVID-19. Recent evidence revealed two way crosstalk mechanisms between the AKT and the UPR pathways, suggesting that they might constitute a unified homeostatic control system. Here, we review the role of the AKT and UPR pathways and their interaction in relation to SARS-CoV-2 infection as well as in tumor onset and progression. Feedback regulation between AKT and UPR pathways emerges as a master control mechanism of cell decision making in terms of survival or death and therefore represents a key potential target for developing treatments for both viral infection and cancer. In particular, drug repositioning, the investigation of existing drugs for new therapeutic purposes, could significantly reduce time and costs compared to de novo drug discovery.

Neuroprotective effects of allocryptopine-rich alkaloid extracts against oxidative stress-induced neuronal damage

BACKGROUND

Oxidative stress is a significant feature in the pathomechanism of neurodegenerative diseases. Thus, the search for an effective and safe novel antioxidant agent with neuroprotective properties has increased the interest in medicinal plant products as a bioactive phytochemical source. However, little is known about the potential effects of the medically important Glaucium corniculatum as a natural antioxidant.

OBJECTIVE

In the present study, it was aimed to investigate the anti-oxidative, anti-apoptotic, and cell cycle regulatory mechanisms underlying the neuroprotective effects of alkaloid extracts (chloroform, methanol, and water) from G. corniculatum, which was profiled for major alkaloid/alkaloids, against H₂O₂-induced neuronal damage in differentiated PC12 cells.

MATERIALS AND METHODS

The profiles of the alkaloid extracts were analyzed by GC-MS. The effects of the alkaloid extracts on intracellular ROS production, level of apoptotic cells, and cell cycle dysregulation were analyzed by flow cytometry; the effects on mRNA expression of apoptosis-related genes were also analyzed by qRT-PCR.

RESULTS

The same alkaloid components, allocryptopine, tetrahydropalmatine, and tetrahydroberberine N-oxide were obtained in all three solvents, but the ratios of the components differed according to the solvents. Allocryptopine was determined to be the major alkaloid ingredient in the alkaloid extracts, with the highest amount of allocryptopine (497 μg/mg) being found in the chloroform alkaloid extract (CAE) (*p < 0.05). The best results were obtained from CAE, which has the highest amount of allocryptopine among alkaloid extracts in all studies. CAE suppressed intracellular ROS production (5.7-fold), percentage of apoptotic cells (3.0-fold), and cells in the sub G1 phase (6.8-fold); additionally, it increased cells in the G1 phase (1.5-fold) (**p < 0.01). CAE remarkably reduced the expressions of Bax, Caspase-9/-3 mRNA (2.4-3.5-fold) while increasing the expression of Bcl-2 mRNA (3.0-fold) (*p < 0.05).

CONCLUSIONS

Our results demonstrated that alkaloid extracts from G. corniculatum, which contain allocryptopine, tetrahydropalmatine, and tetrahydroberberine N-oxide suppressed oxidative stress-induced neuronal apoptosis, possibly by suppressing the mitochondrial apoptotic pathway and regulating the cell cycle. These results are the first report that related alkaloids have played a neuroprotective role by regulating multiple mechanisms. Thus, our study indicated that these alkaloids especially allocryptopine could offer an efficient and novel strategy to explore novel drugs for neuroprotection and cognitive improvement.

Central venous pressure value can assist in adjusting norepinephrine dosage after the initial resuscitation of septic shock

BACKGROUND

New definitions for sepsis and septic shock (Sepsis-3) were published, but the strategy to adjust vasopressors after the initial guidelines is still unclear. We conducted a retrospective observational study to explore dosing strategy of norepinephrine (NE).

METHODS

A retrospective observational study in the 15-bed mixed intensive care unit of a tertiary care university hospital. The study was performed on septic shock patients after 30 mL/kg fluid resuscitation and mean arterial pressure (MAP) levels reached >65 mmHg requiring NE. We divided patients into NE dosage increase and decrease groups, and collected hemodynamic and tissue perfusion parameters before (T1) and after (T2) adjusting NE dosage.

RESULTS

In both NE increase and decrease groups, central venous pressure (CVP) and pressure difference between usual MAP and MAP (dMAP) at the T1 time point were associated with lactate clearance. In groups LC HM (CVP <10 mmHg, dMAP > 0 mmHg) and HC HM (CVP ≥ 10 mmHg, dMAP > 0 mmHg), decrease in NE dosage decreased lactate level, while in group HC LM (CVP ≥ 10 mmHg, dMAP ≤ 0 mmHg), both increase and decrease in NE dosage led to increase lactate level.

CONCLUSIONS

After patients with septic shock (Sepsis-3) resuscitated to reach the initial recovery target goals, combination of CVP and MAP refer to usual levels can help doctors make the next decision to make the correct choice of increase NE dosage or decrease NE dosage.

Atomoxetine produces oxidative stress and alters mitochondrial function in human neuron-like cells

Atomoxetine (ATX) is a non-stimulant drug used in the treatment of attention-deficit/hyperactivity disorder (ADHD) and is a selective norepinephrine reuptake inhibitor. It has been shown that ATX has additional effects beyond the inhibition of norepinephrine reuptake, affecting several signal transduction pathways and alters gene expression. Here, we study alterations in oxidative stress and mitochondrial function in human differentiated SH-SY5Y cells exposed over a range of concentrations of ATX. We found that the highest concentrations of ATX in neuron-like cells, caused cell death and an increase in cytosolic and mitochondrial reactive oxygen species, and alterations in mitochondrial mass, membrane potential and autophagy. Interestingly, the dose of 10 μM ATX increased mitochondrial mass and decreased autophagy, despite the induction of cytosolic and mitochondrial reactive oxygen species. Thus, ATX has a dual effect depending on the dose used, indicating that ATX produces additional active therapeutic effects on oxidative stress and on mitochondrial function beyond the inhibition of norepinephrine reuptake.

Repeated Glucose Deprivation/Reperfusion Induced PC-12 Cell Death through the Involvement of FOXO Transcription Factor

BACKGROUND

Cognitive impairment and brain damage in diabetes is suggested to be associated with hypoglycemia. The mechanisms of hypoglycemia-induced neural death and apoptosis are not clear and reperfusion injury may be involved. Recent studies show that glucose deprivation/reperfusion induced more neuronal cell death than glucose deprivation itself. The forkhead box O (FOXO) transcription factors are implicated in the regulation of cell apoptosis and survival, but their role in neuronal cells remains unclear. We examined the role of FOXO transcription factors and the involvement of the phosphatidylinositol 3-kinase (PI3K)/Akt and apoptosis-related signaling pathways in PC-12 cells exposed to repeated glucose deprivation/reperfusion.

METHODS

PC-12 cells were exposed to control (Dulbecco's Modified Eagle Medium [DMEM] containing 25 mM glucose) or glucose deprivation/reperfusion (DMEM with 0 mM glucose for 6 hours and then DMEM with 25 mM glucose for 18 hours) for 5 days. MTT assay and Western blot analysis were performed for cell viability, apoptosis, and the expression of survival signaling pathways. FOXO3/4',6-diamidino-2-phenylindole staining was done to ascertain the involvement of FOXO transcription factors in glucose deprivation/reperfusion conditions.

RESULTS

Compared to PC-12 cells not exposed to hypoglycemia, cells exposed to glucose deprivation/reperfusion showed a reduction of cell viability, decreased expression of phosphorylated Akt and Bcl-2, and an increase of cleaved caspase-3 expression. Of note, FOXO3 protein was localized in the nuclei of glucose deprivation/reperfusion cells but not in the control cells.

CONCLUSION

Repeated glucose deprivation/reperfusion caused the neuronal cell death. Activated FOXO3 via the PI3K/Akt pathway in repeated glucose deprivation/reperfusion was involved in genes related to apoptosis.

Hydrogen sulfide exhibits cardioprotective effects by decreasing endoplasmic reticulum stress in a diabetic cardiomyopathy rat model

Endoplasmic reticulum (ER) stress is critical in the occurrence and development of diabetic cardiomyopathy (DC). Hydrogen sulfide (H2S) has been found to be the third gaseous signaling molecule with anti‑ER stress effects. Previous studies have shown that H2S acts as a potent inhibitor of fibrosis in the heart of diabetic rats. This study aimed to demonstrate whether H2S exhibits protective effects on the myocardium of streptozotocin (STZ)‑induced diabetic rats by suppressing ER stress. In this study, diabetic models were established by intraperitoneal (i.p.) injection of 40 mg/kg STZ. The STZ‑treated mice were divided into three groups, and subsequently treated with normal saline, 30 µmol/kg or 100 µmol/kg NaHS, i.p., respectively, for 8 weeks. The extent of myocyte hypertrophy was measured using hematoxylin and eosin‑stained sections and collagen components were investigated using immunostaining. The expression of glucose-regulated protein (Grp78), C/EBP‑homologous protein (CHOP) and caspase‑12 in the heart tissue of each group was detected by western blot analysis. It was demonstrated that H2S could improve myocardial hypertrophy and myocardial collagen deposition in diabetic rats. In addition, it could reduce the expression of Grp78, caspase-12 and CHOP. In conclusion, these findings demonstrate that H2S suppresses STZ‑induced ER stress in the hearts of rats, and it may serve as a novel cardioprotective agent for DC.

Nerve growth factor protects the ischemic heart via attenuation of the endoplasmic reticulum stress induced apoptosis by activation of phosphatidylinositol 3-kinase

BACKGROUND

Increased expression of nerve growth factor (NGF) has been found in the myocardium suffered from ischemia and reperfusion (I/R). The pro-survival activity of NGF on ischemic heart has been supposed to be mediated by phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) signaling pathway. Endoplasmic reticulum (ER) stress, which is activated initially as a defensive response to eliminate the accumulated unfolded proteins, has shown a critical involvement in the ischemia induced myocardial apoptosis. This study was aimed to investigate whether NGF induced heart protection against I/R injury includes a mechanism of attenuation of ER stress-induced myocardial apoptosis by activation of PI3K/Akt pathway.

METHODS

Isolated adult rat hearts were perfused with a Langendörff perfusion system. Hearts in the Sham group were subjected to 225 min of continuous Krebs-Henseleit buffer (KHB) perfusion without ischemia. Hearts in I/R group were perfused with KHB for a 75-min of equilibration period followed by 30 min of global ischemia and 120 min of KHB reperfusion. Hearts in the NGF group accepted 45 min of euilibration perfusion and 30 min of NGF pretreatment (with a final concentration of 100 ng/ml in the KHB) before 30 min of global ischemia and 120 min of reperfusion. Hearts in K252a and LY294002 groups were pretreated with either a TrkA inhibitor, K252a or a phosphatidyl inositol 3-kinase inhibitor, LY294002 for 30 min before NGF (100 ng/ml) administration. Cardiac hemodynamics were measured from the beginning of the perfusion. Cardiac enzymes and cardiac troponin I (cTnI) were assayed before ischemia and at the end of reperfusion. Myocardial apoptosis rate was measured by TUNEL staining, and expression of glucose-related protein 78 (GRP78), CCAAT/enhancer-binding protein homologous protein (CHOP), caspase-12, total- and phospho-(Ser473)-Akt were assessed by Western blot analyses.

RESULTS

NGF pretreatment significantly improved the recovery of post-ischemia cardiac hemodynamics. Reduced creatine kinase-MB (CK-MB), lactate dehydrogenase (LDH) activity and cTnI levels, as well as decreased myocardial apoptosis ratio were observed in the NGF group. The improvement of NGF on recovery of cardiac function and alleviation of myocardial injury were completely abolished by K252a or LY294002. GRP78, caspase-12 and CHOP were highly expressed in ischemic myocardium, while NGF significantly inhibited the overexpression of these proteins which were involved in ER stress-induced myocardial apoptosis. NGF pretreatment also induced phosphorylation of Akt. When the activation of PI3K/Akt pathway is blocked by LY294002, the NGF induced suppression of the apoptosis-related proteins expression was reversed.

CONCLUSIONS

NGF pretreatment may protect the ischemic heart via inhibition of the ER stress-induced apoptosis; this pro-survival effect is mediated by PI3K/Akt pathway.

Glucose deprivation induces reticulum stress by the PERK pathway and caspase-7- and calpain-mediated caspase-12 activation

Glucose is the main energy source in brain and it is critical for correct brain functioning. Type 1 diabetic patients might suffer from severe hypoglycemia if exceeding insulin administration, which can lead to acute brain injury if not opportunely corrected. The mechanisms leading to hypoglycemic brain damage are not completely understood and the role of endoplasmic reticulum (ER) stress has not been studied. ER stress resulting from the accumulation of unfolded or misfolded proteins in the ER is counteracted by the unfolded protein response (UPR). When the UPR is sustained, apoptotic death might take place. We have examined UPR activation during glucose deprivation (GD) in hippocampal cultured neurons and its role in the induction of apoptosis. Activation of the PERK pathway of the UPR was observed, as increased phosphorylation of eIF2α and elevated levels of the transcription factor ATF4, occurred 30 min after GD and the levels of the chaperone protein, GRP78 and the transcription factor CHOP, increased after 2 h of GD. In addition, we observed an early activation of caspase-7 and 12 during GD, while caspase-3 activity increased only transiently during glucose reintroduction. Inhibition of caspase-3/7 and the calcium-dependent protease, calpain, significantly decreased caspase-12 activity. The ER stress inhibitor, salubrinal prevented neuronal death and caspase-12 activity. Results suggest that the PERK pathway of the UPR is involved in GD-induced apoptotic neuronal death through the activation of caspase-12, rather than the mitochondrial-dependent caspase pathway. In addition, we show that calpain and caspase-7 are soon activated after GD and mediate caspase-12 activation and neuronal death.

Evaluation of the toxic activity of anorectic diethylpropion in Chinese hamster ovary cells

Diethylpropion has been available in the market for treating obesity for over 50 years. Refined studies are lacking to fully elucidate its action spectrum. The aim of our study was to evaluate possible toxic effects of anorectic diethylpropion in Chinese hamster ovary (CHO) cells. Comet assay (detects breaks in the DNA strand), micronucleus test (detects clastogenic/aneugenic damage), and cell survival test (detects cytotoxic damage) were used to evaluate the toxic effects. In comet assay, we found that the damage scores with diethylpropion treatments at the concentrations of 20 and 40 μg/mL were more significant ( p < 0.05) than that of the negative control. When assessing the possible aneugenic and/or clastogenic damage caused by the drug in CHO cells, we found no difference ( p > 0.05) in the values of micronucleated cells when comparing different diethylpropion treatments and the negative control. Regarding the cell viability, for all the diethylpropion concentrations tested, higher values ( p < 0.05) of apoptosis were found compared with those of the negative control. In relation to the number of necrotic cells, no difference ( p > 0.05) was noted between the means of the three concentrations of diethylpropion evaluated and the negative control. In the experimental conditions, we conclude that diethylpropion has weak genotoxic and cytotoxic activities.

Modulation of the Akt pathway reveals a novel link with PERK/eIF2α, which is relevant during hypoxia

The unfolded protein response (UPR) and the Akt signaling pathway share several regulatory functions and have the capacity to determine cell outcome under specific conditions. However, both pathways have largely been studied independently. Here, we asked whether the Akt pathway regulates the UPR. To this end, we used a series of chemical compounds that modulate PI3K/Akt pathway and monitored the activity of the three UPR branches: PERK, IRE1 and ATF6. The antiproliferative and antiviral drug Akt-IV strongly and persistently activated all three branches of the UPR. We present evidence that activation of PERK/eIF2α requires Akt and that PERK is a direct Akt target. Chemical activation of this novel Akt/PERK pathway by Akt-IV leads to cell death, which was largely dependent on the presence of PERK and IRE1. Finally, we show that hypoxia-induced activation of eIF2α requires Akt, providing a physiologically relevant condition for the interaction between Akt and the PERK branch of the UPR. These data suggest the UPR and the Akt pathway signal to one another as a means of controlling cell fate.

Immune sculpting of norepinephrine on MHC-I, B7-1, IDO and B7-H1 expression and regulation of proliferation and invasion in pancreatic carcinoma cells

BACKGROUND

The sympathetic neurotransmitter Norepinephrine (NE) contributes to tumorigenesis and cancer progression. This study aims to investigate the role of NE in modulating the immune phenotype and allowing pancreatic carcinoma (PC) cells to escape the immune response.

METHODS

Varied concentrations of NE and interferon-gamma (IFN-γ) were administrated to MIA PaCa-2 and BxPC-3 cell lines for 48 hours. Proliferation and invasion were then investigated using an MTT assay and a membrane invasion culture system respectively. MHC-I, B7-1, IDO and B7-H1 expression were measured using real-time quantitative RT-PCR, western blotting and immunocytochemistry. The synergistic and time-dependent effects of NE/IFN-γ were also investigated. Adrenergic antagonists were used to identify the relevant target receptor of NE.

RESULTS

The results showed that NE had dose-dependent and time-dependent effects on cell biological processes as well as on the expression of MHC-I, B7-1, IDO and B7-H1. These effects occurred mainly via the β(2)-adrenergic receptor. Long-term NE treatment was able to antagonize some of the effects of IFN-γ (after 2 weeks of treatment), but NE and IFN-γ had significant synergistic stimulatory effects on IDO and B7-H1 expression. The residual effects on biological activities lasted for 2 weeks, while the immunophenotypic changes decreased at early time points after treatment.

CONCLUSIONS

NE plays important roles in modulating PC cell biological activities and affecting MHC-I, B7-1, IDO and B7-H1 expression in vitro, mainly via the β2-adrenergic receptor (β2-AR) in a time- and dose-dependent fashion. Only at extended treatment durations could NE affect PC cell progression and immune evasion.

bFGF inhibits ER stress induced by ischemic oxidative injury via activation of the PI3K/Akt and ERK1/2 pathways

Extensive research has focused on finding effective strategies to prevent or improve recovery from brain ischemia and reperfusion (I/R) injury. The basic fibroblast growth factor (bFGF) has been shown to have therapeutic potential in some central nervous system (CNS) disorders, including ischemic injury. In this study, we demonstrate that bFGF administration can improve locomotor activity and inhibit the ER stress induced in the CA1 region of the hippocampus in a mouse model of I/R injury. In vitro, bFGF exerts a protective effect by inhibiting the ER stress response proteins CHOP, XBP-1, ATF-6 and caspase-12 that are induced by H(2)O(2) treatment. Both of these in vivo and in vitro effects are related to the activation of two downstream signaling pathways, PI3K/Akt and ERK1/2. Inhibition of the PI3K/Akt and ERK1/2 pathways by specific inhibitors, LY294002 and U0126, respectively, partially reduce the protective effect of bFGF. Taken together, our results indicate that the neuroprotective role of bFGF involves the suppression of ER stress in the ischemic oxidative damage models and oxidative stress-induced PC12 cell injury, and these effects is underlying the activation of the PI3K/Akt and ERK1/2 signal pathway.

α1-adrenergic drugs exhibit affinity to a thapsigargin-sensitive binding site and interfere with the intracellular Ca2+ homeostasis in human erythroleukemia cells

Even though the erythroleukemia cell lines K562 and HEL do not express α1-adrenoceptors, some α1-adrenergic drugs influence both survival and differentiation of these cell lines. Since Ca2+ is closely related to cellular homeostasis, we examined the capacity of α1-adrenergic drugs to modulate the intracellular Ca2+ content in K562 cells. Because of morphological alterations of mitochondria following α1-adrenergic agonist treatment, we also scrutinized mitochondrial functions. In order to visualize the non-adrenoceptor binding site(s) of α1-adrenergic drugs in erythroleukemia cells, we evaluated the application of the fluorescent α1-adrenergic antagonist BODIPY® FL-Prazosin. We discovered that the α1-adrenergic agonists naphazoline, oxymetazoline and also the α1-adrenergic antagonist benoxathian are able to raise the intracellular Ca2+-content in K562 cells. Furthermore, we demonstrate that naphazoline treatment induces ROS-formation as well as an increase in Δψm in K562 cells. Using BODIPY® FL-Prazosin we were able to visualize the non-adrenoceptor binding site(s) of α1-adrenergic drugs in erythroleukemia cells. Interestingly, the SERCA-inhibitor thapsigargin appears to interfere with the binding of BODIPY® FL-Prazosin. Our data suggest that the effects of α1-adrenergic drugs on erythroleukemia cells are mediated by a thapsigargin sensitive binding site, which controls the fate of erythroleukemia cells towards differentiation, senescence and cell death through modulation of intracellular Ca2+.

ALS genetic modifiers that increase survival of SOD1 mice and are suitable for therapeutic development

Amyotrophic lateral sclerosis (ALS) is a frequently fatal motor neuron disease without any cure. To find molecular therapeutic targets, several studies crossed transgenic ALS murine models with animals transgenic for some ALS target genes. We aimed to revise the new discoveries and new works in this field. We selected the 10 most promising genes, according to their capability when down-regulated or up-regulated in ALS animal models, for increasing life span and mitigating disease progression: XBP-1, NogoA and NogoB, dynein, heavy and medium neurofilament, NOX1 and NOX2, MLC-mIGF-1, NSE-VEGF, and MMP-9. Interestingly, some crucial modifier genes have been described as being involved in common pathways, the most significant of which are inflammation and cytoskeletal activities. The endoplasmic reticulum also seems to play an important role in ALS pathogenesis, as it is involved in different selected gene pathways. In addition, these genes have evident links to each other, introducing the hypothesis of a single unknown, common pathway involving all of these identified genes and others to be discovered.

Calpain and caspase processing of caspase-12 contribute to the ER stress-induced cell death pathway in differentiated PC12 cells

Neuronal cell death after traumatic brain injury, Alzheimer's disease and ischemic stroke may in part be mediated through endoplasmic reticulum (ER) stress and unfolded protein response (UPR). UPR results in induction of molecular chaperone GRP78 and the ER-resident caspase-12, whose activation has been proposed to be mediated by calpain and caspase processing, although their relative contribution remains unclear. In this study we induced ER stress with thapsigargin (TG), and determined the activation profile of calpain-2, caspase-3, caspase-7, and caspase-12 by analyses of protein levels, corresponding substrates and breakdown products (BDP). Specific calpain and caspase activity was assessed by analysis of αII-spectrin BDP of 145 kDa (SBDP145), BDP of 150 kDa (SBDP150) and BDP of 120 kDa (SBDP120). Decrease in pro-calpain-2 protein and increased SBDP145 levels by 3 h after TG treatment indicated early calpain activity. Active caspase-7 (p20) increase occurred after 8 h, followed by concomitant up-regulation of active caspase-3 and SBDP120 after 24 h. In vitro digestion experiments supported that SBDP120 was exclusively generated by active caspase-3 and validated that kinectin and co-chaperone p23 were calpain and caspase-7 substrates, respectively. Pro-caspase-12 protein processing by the specific action of calpain and caspase-3/7 was observed in a time-dependent manner. N-terminal pro-domain processing of pro-caspase-12 by calpain generated a 38 kDa fragment, while caspase-3/7 generated a 35 kDa fragment. Antibody developed specifically against the caspase-3/7 C-terminal cleavage site D(341) detected the presence of large subunit (p20) containing 23 kDa fragment that increased after 24 h of TG treatment. Significant caspase-12 enzyme activity was only detected after 24 h of TG treatment and was completely inhibited by caspase 3/7 inhibitor DEVD-fmk and partially by calpain inhibitor SNJ-1945. ER-stress-induced cell death pathway in TG-treated PC12 cells was characterized by up-regulation of GRP-78 and processing and activation of caspase-12 by the orchestrated proteolytic activity of calpain-2 and caspase-3/7.

Cyclic stretch-induced apoptosis in rat annulus fibrosus cells is mediated in part by endoplasmic reticulum stress through nitric oxide production

Various mechanical stresses in vivo induce disc cell apoptosis and intervertebral disc (IVD) degeneration, but the underlying molecular mechanism is not fully known. The aim of this study was to investigate the role of endoplasmic reticulum stress in cyclic stretch-induced apoptosis of rat annulus fibrosus (AF) cells. Flexercell Tension Plus system was used to apply cyclic stretch to rat annulus fibrosus cells at a frequency of 0.5 Hz with 20% elongation for 12, 24, 36, or 48 h. Apoptosis was detected by flow cytometry, and nuclei morphologic changes were visualized by Hoechst 33258 staining and caspase-8, 9 activity assays. The expression of the markers of endoplasmic reticulum stress including CHOP, GRP78, and caspase-12 were determined by RT-PCR and Western blot. Mitochondrial membrane potential change was observed by JC-1 staining in situ. In addition, the levels of the nitric oxide (NO) were determined with the Griess reaction and fluorescence staining. The results indicated that cyclic stretch at a frequency of 0.5 Hz with 20% elongation-induced apoptosis in rat AF cells. Prolonged exposure of the unphysiologically cyclic stretch to AF cells caused NO overproduction, up-regulation of endoplasmic reticulum stress markers including CHOP, GRP78, and caspase-12, depolarization of mitochondria and activation of caspase-9. However, cyclic stretch at this level had no effect on caspase-8 activity. In addition, specific inhibitor of caspase-12 (Z-ATAD-FMK) and caspase-9 (Z-LEHD-FMK) partly suppressed cyclic stretch-induced AF cell apoptosis and the anti-apoptotic effects of the caspase inhibitors were additive. Our data suggest that endoplasmic reticulum stress, likely mediated by NO, contributes to the AF cell apoptosis induced by cyclic stretch in addition to the mitochondrial pathway. These findings could be helpful to understand the mechanism of disc cell apoptosis, the root cause of IVD degeneration.

Matrix metalloproteinase-3 is increased and participates in neuronal apoptotic signaling downstream of caspase-12 during endoplasmic reticulum stress

Although endoplasmic reticulum (ER) stress-induced apoptosis has been associated with pathogenesis of neurodegenerative diseases, the cellular components involved have not been well delineated. The present study shows that matrix metalloproteinase (MMP)-3 plays a role in the ER stress-induced apoptosis. ER stress induced by brefeldin A (BFA) or tunicamycin (TM) increases gene expression of MMP-3, selectively among various MMP subtypes, and the active form of MMP-3 (actMMP-3) in the brain-derived CATH.a cells. Pharmacological inhibition of enzyme activity, small interference RNA-mediated gene knockdown, and gene knock-out of MMP-3 all provide protection against ER stress. MMP-3 acts downstream of caspase-12, because both pharmacological inhibition and gene knockdown of caspase-12 attenuate the actMMP-3 increase, but inhibition and knock-out of MMP-3 do not alter caspase-12. Furthermore, independently of the increase in the protein level, the catalytic activity of MMP-3 enzyme can be increased via lowering of its endogenous inhibitor protein TIMP-1. Caspase-12 causes liberation of MMP-3 enzyme activity by degrading TIMP-1 that is already bound to actMMP-3. TIMP-1 is decreased in response to ER stress, and TIMP-1 overexpression leads to cell protection and a decrease in MMP-3 activity. Taken together, actMMP-3 protein level and catalytic activity are increased following caspase-12 activation during ER stress, and this in turn plays a role in the downstream apoptotic signaling in neuronal cells. MMP-3 and TIMP-1 may therefore serve as cellular targets for therapy against neurodegenerative diseases.

X-box binding protein 1 regulates brain natriuretic peptide through a novel AP1/CRE-like element in cardiomyocytes

The unfolded protein response (UPR) is triggered to assist protein folding when endoplasmic reticulum (ER) function is impaired. Recent studies demonstrated that ER stress can also induce cell-specific genes. In this study, we examined whether X-box binding protein 1 (XBP1), a major UPR-linked transcriptional factor, regulates the expression of brain natriuretic peptide (BNP) in cardiomyocytes. In samples from failing human hearts, extensive splicing of XBP1 was observed along with increased expression of glucose-regulated protein of 78 kDa (GRP78), a target of spliced XBP1 (sXBP1), suggesting that the UPR was induced in heart failure in humans. Interestingly, quantitative real-time PCR revealed a positive correlation between cardiac expression of GRP78 and BNP, leading us to test the hypothesis that sXBP1 regulates BNP as well as GRP78 in cardiomyocytes. A pharmacological ER stressor caused a dose-dependent increase in the expression of sXBP1 and BNP by cultured cardiomyocytes. Short interfering RNA targeting XBP1 suppressed the induction of BNP expression by a pharmacological ER stressor or norepinephrine, which was rescued by the adenovirus-mediated overexpression of sXBP1. The promoter assay with overexpression of sXBP1 or norepinephrine showed that the proximal AP1/CRE-like element in the promoter region of BNP was critical for transcriptional regulation of BNP by sXBP1. Direct binding of sXBP1 to this element was confirmed by the chromatin immunoprecipitation assay. These findings suggest that ER stress observed in failing hearts regulates cardiac BNP expression through a novel promoter region of the AP1/CRE-like element.

Effects of insulin-like growth factor-1 (IGF-1) receptor signaling on rates of apoptosis in retina of dopamine beta hydroxylase (Dbh-/-) knockout mice

We have investigated whether insulin-like growth factor-1 (IGF-1) receptor signaling alters rates of apoptosis in dopamine beta-hydroxylase (Dbh(-/-)) knockout mice. Retinal lysates from Dbh(-/-) and their heterozygote littermates (Dbh(+/-)) were used to examine the role of norepinephrine in the regulation of IGF-1 receptor signaling and apoptosis in the retina. Western blot analysis was done for protein levels of total and phosphorylated IGF-1 receptor, insulin receptor substrate-1 (IRS-1), insulin receptor substrate-2 (IRS-2), and Akt. A caspase 3 ELISA and dopamine ELISA were done on retinal lysates. To verify which regions of the retina were undergoing apoptosis, TUNEL labeling was performed. No changes in dopamine were noted between the KO and heterozygote mice. IGF-1 receptor phosphorylation was significantly decreased in Dbh(-/-) mice as compared to their heterozygote littermates (P<0.05 vs. heterozygous mice). IRS-1 protein phosphorylation was significantly decreased in KO mice (P<0.05 vs. heterozygous mice), while no significant changes were noted in IRS-2 protein phosphorylation. Akt protein phosphorylation was also reduced in the KO mice, likely leading to increased cleaved caspase 3 levels. The increase in apoptosis in the Dbh(-/-) mice occurred predominantly in the inner retina. Our results suggest that IGF-1 receptor signaling is reduced in the retina of mice with dysfunctional adrenergic receptor signaling. The data also indicate that IGF-1 receptor signaling occurs primarily through IRS-1, rather than IRS-2. The reduction in Akt phosphorylation, likely through reduced IGF-1 receptor signaling, could explain the increase in cleaved caspase 3, leading to apoptosis. These results suggest that alterations in adrenergic receptor signaling modulate IGF-1 receptor signaling, which can regulate apoptosis in the retina.

Implications of endoplasmic reticulum stress, the unfolded protein response and apoptosis for molecular cancer therapy. Part I: targeting p53, Mdm2, GADD153/CHOP, GRP78/BiP and heat shock proteins

BACKGROUND

In eukaryotes, endoplasmic reticulum stress (ERS) and the unfolded protein response (UPR) are coordinately regulated to maintain steady-state levels and activities of various cellular proteins to ensure cell survival.

OBJECTIVE

This review (Part I of II) focuses on specific ERS and UPR signalling regulators, their expression in the cancer phenotype and apoptosis, and proposes how their implication in these processes can be rationalised into proteasome inhibition, apoptosis induction and the development of more efficacious targeted molecular cancer therapies.

METHOD

In this review, we contextualise many ERS and UPR client proteins that are deregulated or mutated in cancers and show links between ERS and the UPR, their implication in oncogenic transformation, tumour progression and escape from immune surveillance, apoptosis inhibition, angiogenesis, metastasis, acquired drug resistance and poor cancer prognosis.

CONCLUSION

Evasion of programmed cell death or apoptosis is a hallmark of cancer that enables tumour cells to proliferate uncontrollably. Successful eradication of cancer cells through targeting ERS- and UPR-associated proteins to induce apoptosis is currently being pursued as a central tenet of anticancer drug discovery.

Gastrointestinal growth factors and hormones have divergent effects on Akt activation

Akt is a central regulator of apoptosis, cell growth and survival. Growth factors and some G-protein-coupled receptors (GPCR) regulate Akt. Whereas growth-factor activation of Akt has been extensively studied, the regulation of Akt by GPCR's, especially gastrointestinal hormones/neurotransmitters, remains unclear. To address this area, in this study the effects of GI growth factors and hormones/neurotransmitters were investigated in rat pancreatic acinar cells which are high responsive to these agents. Pancreatic acini expressed Akt and 5 of 7 known pancreatic growth-factors stimulate Akt phosphorylation (T308, S473) and translocation. These effects are mediated by p85 phosphorylation and activation of PI3K. GI hormones increasing intracellular cAMP had similar effects. However, GI-hormones/neurotransmitters [CCK, bombesin, carbachol] activating phospholipase C (PLC) inhibited basal and growth-factor-stimulated Akt activation. Detailed studies with CCK, which has both physiological and pathophysiological effects on pancreatic acinar cells at different concentrations, demonstrated CCK has a biphasic effect: at low concentrations (pM) stimulating Akt by a Src-dependent mechanism and at higher concentrations (nM) inhibited basal and stimulated Akt translocation, phosphorylation and activation, by de-phosphorylating p85 resulting in decreasing PI3K activity. This effect required activation of both limbs of the PLC-pathway and a protein tyrosine phosphatase, but was not mediated by p44/42 MAPK, Src or activation of a serine phosphatase. Akt inhibition by CCK was also found in vivo and in Panc-1 cancer cells where it inhibited serum-mediated rescue from apoptosis. These results demonstrate that GI growth factors as well as gastrointestinal hormones/neurotransmitters with different cellular basis of action can all regulate Akt phosphorylation in pancreatic acinar cells. This regulation is complex with phospholipase C agents such as CCK, because both stimulatory and inhibitory effects can be seen, which are mediated by different mechanisms.

The molecular mechanism of endoplasmic reticulum stress-induced apoptosis in PC-12 neuronal cells: the protective effect of insulin-like growth factor I

Endoplasmic reticulum (ER) stress has been implicated in several neurodegenerative diseases. Although CCAAT/enhancer-binding protein homologous protein (CHOP) has been shown to play a critical role in ER stress, the precise apoptosis cascade downstream of CHOP is unknown. In this report, we investigated the mechanism of ER stress-mediated apoptosis as well as the action of IGF-I in PC-12 neuronal cells. Our results demonstrated that tribbles-related protein 3 (TRB3), which is a target gene of CHOP, was responsible for tunicamycin (an ER stress inducer)-induced apoptosis. TRB3 could promote dephosphorylation of Akt in PC-12 cells. IGF-I inhibited ER stress-induced apoptosis by restoring the phosphorylation level of Akt. Both wortmannin (a phosphatidylinositide 3-kinase inhibitor) and SB 212090 (a p38 MAPK inhibitor) suppressed the protective effect of IGF-I on ER stress-induced apoptosis. Interestingly, IGF-I attenuated ER stress-mediated expression of TRB3 but not CHOP. This action of IGF-I was abolished by SB 212090 but not by wortmannin. Immunoprecipitation analysis revealed that IGF-I promoted the phosphorylation of CHOP by activating p38 MAPK, probably leading to a decrease in the transcriptional activity of CHOP. The dephosphorylation of Akt resulted in increased expression of a proapoptotic protein, p53 up-regulated modulator of apoptosis (PUMA), in a forkhead box O3a-dependent manner. Knockdown of PUMA by short hairpin RNA attenuated ER stress-mediated apoptosis. Thus, our current study indicates that both TRB3 and PUMA are critical molecules in ER stress-induced apoptosis. IGF-I effectively protects PC-12 neuronal cells against ER stress-induced apoptosis through the phosphatidylinositide 3-kinase/Akt and p38 MAPK pathways.

Chemical induction of the unfolded protein response in the liver increases glucose production and is activated during insulin-induced hypoglycaemia in rats

AIMS/HYPOTHESIS

Endoplasmic reticulum (ER) stress and the unfolded protein response (UPR) can regulate insulin secretion, insulin action and in vitro hepatocyte glucose release. The aims of this study were to determine whether chemical agents that induce ER stress regulate glucose production in vivo and to identify a physiological setting in which this may be important.

METHODS

A pancreatic clamp test was performed in anaesthetised rats, and insulin and glucagon were replaced at basal levels. [6,6-(2)H(2)]Glucose was infused in the absence (CON, n = 10) or presence of ER stress-inducing agents, namely, tunicamycin (Tun, n = 10) or thapsigargin (Thap, n = 10).

RESULTS

Arterial insulin, glucagon, corticosterone and NEFA concentrations were constant throughout experiments and not different among groups. After 1 h, the glucose concentration was significantly increased in Tun and Thap rats (1.5 +/- 0.2 and 2.1 +/- 0.3 mmol/l, respectively; mean +/- SD), but did not change in CON rats. Glucose production increased (p < 0.05) by 11.0 +/- 1.6 and 13.2 +/- 2.2 micromol kg(-1) min(-1) in Tun and Thap rats, respectively, but did not change in CON rats. When glucose was infused in a fourth group (HYPER) to match the increase in glucose observed in the Tun and Thap rats, glucose production decreased by approximately 22 micromol kg(-1) min(-1). Liver phosphorylase activity was increased and glycogen decreased in the Tun and Thap groups compared with the CON and HYPER groups. Given that glucose deprivation induces ER stress in cells, we hypothesised that hypoglycaemia, a condition that elicits increased glucose production, would activate the UPR in the liver. Three hour hyperinsulinaemic (5 mU kg(-1) min(-1)) -euglycaemic (EUG, approximately 7.2 mmol/l, n = 6) or -hypoglycaemic (HYPO, approximately 2.8 mmol/l, n = 6) clamps were performed in conscious rats. Several biochemical markers of the UPR were significantly increased in the liver, but not in kidney or pancreas, in HYPO vs EUG rats.

CONCLUSIONS/INTERPRETATION

Based on our findings that the chemical induction of the UPR increased glucose production and that prolonged hypoglycaemia activated the UPR in the liver, we propose that the UPR in the liver may contribute to the regulation of glucose production during prolonged hypoglycaemia.

Darbepoetin alfa exerts a cardioprotective effect in autoimmune cardiomyopathy via reduction of ER stress and activation of the PI3K/Akt and STAT3 pathways

Dilated human cardiomyopathy is associated with suppression of the prosurvival phosphatidylinositol-3-kinase (PI3K)/Akt and STAT3 pathways. The present study was carried out to determine if restoration of the PI3K/Akt and STAT3 activity by darbepoetin alfa improved cardiac function or reduced cardiomyocyte apoptosis in rabbit autoimmune cardiomyopathy induced by a peptide corresponding to the second extracellular loop of the ss(1)-adrenergic receptor (ss(1)-EC(II)). We found that ss(1)-EC(II) immunization produced progressive LV dilation, systolic dysfunction and myocyte apoptosis as measured by TUNEL, single-stranded DNA antibody, and active caspase-3. These changes were associated with activation of p38 mitogen-activated protein kinase (MAPK), endoplasmic reticulum stress markers (GRP78 and CHOP), and increased cleavage of procaspase-12, as well as decreased phosphorylation of Akt and STAT3, and decreased Bcl2/Bax ratio. As expected, darbepoetin alfa treatment increased phosphorylation of Akt and STAT3. It also increased the myocardial expression of erythropoietin receptor which was reduced in the failing myocardium, and improved cardiac function in the ss(1)-EC(II)-immunized animals. The latter was associated with reductions of myocyte apoptosis and cleaved caspase-3, as well as reversal of increased phosphorylation of p38-MAPK, increased ER stress, and decline in Bcl2/Bax ratio. The anti-apoptotic effects of darbepoetin alfa via Akt and STAT activation were also demonstrated in cultured cardiomyocytes treated with the anti-ss(1)-EC(II) antibody. These effects of darbepoetin alfa in vitro were prevented by LY294002 and STAT3 peptide inhibitor. Thus, we conclude that darbepoetin alfa improves cardiac function and prevents progression of dilated cardiomyopathy probably by activating the PI3K/Akt and STAT3 pathways and reducing ER stress.

Pharmacogenomics and end-organ susceptibility to injury in the perioperative period

Genomic medicine has provided new mechanistic understanding for many complex diseases over the last 5-10 years. More recently genomic approaches have been applied to the perioperative paradigm, facilitating identification of patients at high risk for adverse events, as well as those who will respond better/worse to specific pharmacologic therapies. The consistent biological theme emerging is that while inflammation is important in healing from surgical trauma, patients who are too robustly proinflammatory appear to be at higher risk for adverse perioperative events. Precise predictors of each adverse event are being elucidated so that corrective therapeutics can be instituted to improve outcomes in high-risk patients. While the field of perioperative genomics could be considered in its infancy, such approaches are the wave of the future.

Nerve growth factor blocks thapsigargin-induced apoptosis at the level of the mitochondrion via regulation of Bim

This study examined how the neurotrophin, nerve growth factor (NGF), protects PC12 cells against endoplasmic reticulum (ER) stress-induced apoptosis. ER stress was induced using thapsigargin (TG) that inhibits the sarcoplasmic/ER Ca2+-ATPase pump (SERCA) and depletes ER Ca2+ stores. NGF pre-treatment inhibited translocation of Bax to the mitochondria, loss of mitochondrial transmembrane potential, cytochrome c release, activation of caspases (-3, -7 and -9) and apoptosis induction by TG. Notably, TG also caused a marked induction of BimEL mRNA and protein, and knockdown of Bim with siRNA protected cells against TG-induced apoptosis. NGF delayed the induction and increased the phosphorylation of BimEL. NGF-mediated protection was dependent on phosphatidylinositol-3 kinase (PI3K) signalling since all above apoptotic events, including expression and phosphorylation status of BimEL protein, could be reverted by the PI3K inhibitor LY294002. In contrast, NGF had no effect on the TG-mediated induction of the unfolded protein response (increased expression of Grp78, GADD34, splicing of XBP1 mRNA) or ER stress-associated pro-apoptotic responses (induction of C/EBP homologous protein [CHOP], induction and processing of caspase-12). These data indicate that NGF-mediated protection against ER stress-induced apoptosis occurs at the level of the mitochondria by regulating induction and activation of Bim and mitochondrial translocation of Bax.

Epoxyeicosatrienoic acids induce growth inhibition and calpain/caspase-12 dependent apoptosis in PDGF cultured 3T6 fibroblast

Previous studies have demonstrated that arachidonic acid (AA) metabolites released by the cyclooxygenase pathway is involved in serum-induced 3T6 fibroblast cycle progression and proliferation. However, these results also suggest that other AA cascade pathways might be involved. Recently, we also described the role of hydroxyeicosatetraenoic acids, which are produced by cytochrome P450 monooxygenases (CYP), in 3T6 fibroblast growth. AA can be also metabolized by the epoxygenase activity of CYP-producing epoxyeicosatrienoic acids (EETs). Finally, the cytosolic epoxide hydrolases catalyze the hydration of the EETs, transforming them into dihydroxyeicosatetraenoic acids (DHETEs). In this work, we have studied the role of the EETs/DHETEs on 3T6 fibroblasts growth. Our results show that PDGF stimulates 3T6 fibroblast proliferation and [3H]thymidine incorporation, while the addition of 5,6-EET, 8,9-EET, 11,12-EET or 14,15-EET (0.1-1 microM) inhibit these processes. Furthermore, 5,6-DHETE and 11,12-DHETE (0.1-1 microM) also inhibit cell proliferation and DNA synthesis. Interestingly, this growth inhibition was correlated with an induction of apoptosis. Thus, we observed that in the presence of PDGF, EETs or DHETEs (0.1-1 microM) induce phosphatidylserine externalization (as measured by annexin V-binding) and DNA fragmentation (as quantified using a TUNEL assay). Our results show that calpain, as well as caspase-12 and caspase-3, are involved in these events. Therefore, EETs and DHETEs have anti-proliferative and pro-apoptotic effects on PDGF-stimulated 3T6 fibroblasts.

Adoptive passive transfer of rabbit beta1-adrenoceptor peptide immune cardiomyopathy into the Rag2-/- mouse: participation of the ER stress

Auto-antibodies against the beta(1)-adrenoceptors are present in 30-40% of patients with dilated cardiomyopathy. Recently, a synthetic peptide corresponding to a sequence of the second extracellular loop of the human beta(1)-adrenoceptor (beta(1)-EC(II)) has been shown to produce endoplasmic reticulum (ER) stress, myocyte apoptosis and cardiomyopathy in immunized rabbits. To study the direct cardiac effects of anti-beta(1)-EC(II) antibody in intact animals and if they are mediated via beta(1)-adrenoceptor stimulation, we administered IgG purified from beta(1)-EC(II)-immunized rabbits to recombination activating gene 2 knock-out (Rag2(-/-)) mice every 2 weeks with and without metoprolol treatment. Serial echocardiography and cardiac catheterization showed that beta(1)-EC(II) IgG reduced cardiac systolic function after 3 months. This was associated with increase in heart weight, myocyte apoptosis, activation of caspase-3, -9 and -12, and increased ER stress as evidenced by upregulation of GRP78 and CHOP and cleavage of ATF6. The Rag2(-/-) mice also exhibited increased phosphorylation of CaMKII and p38 MAPK. Metoprolol administration, which attenuated the phosphorylation of CaMKII and p38 MAPK, reduced the ER stress, caspase activation and cell death. Finally, we employed the small-interfering RNA technology to reduce caspase-12 in cultured rat cardiomyocytes. This reduced not only the increase of cleaved caspase-12 but also of the number of myocyte apoptosis produced by beta(1)-EC(II) IgG. Thus, we conclude that ER stress plays an important role in cell death and cardiac dysfunction in beta(1)-EC(II) IgG cardiomyopathy, and the effects of beta(1)-EC(II) IgG are mediated via the beta(1)-adrenergic receptor.

Cardiomyocyte apoptosis in autoimmune cardiomyopathy: mediated via endoplasmic reticulum stress and exaggerated by norepinephrine

Evidence suggests that the autoimmune cardiomyopathy produced by a peptide corresponding to the sequence of the second extracellular loop of the beta(1)-adrenergic receptor (beta(1)-EC(II)) is mediated via a biologically active anti-beta(1)-EC(II) antibody, but the mechanism linking the antibody to myocyte apoptosis and cardiac dysfunction has not been well elucidated. Since the beta(1)-EC(II) autoantibody is a partial beta(1)-agonist, we speculate that the cardiomyopathy is produced by the beta(1)-receptor-mediated stimulation of the CaMKII-p38 MAPK-ATF6 signaling pathway and endoplasmic reticulum (ER) stress, and that excess norepinephrine (NE) exaggerates the cardiomyopathy. Rabbits were randomized to receive beta(1)-EC(II) immunization, sham immunization, NE pellet, or beta(1)-EC(II) immunization plus NE pellet for 6 mo. Heart function was measured by echocardiography and catheterization. Myocyte apoptosis was determined by terminal deoxytransferase-mediated dUTP nick-end labeling and caspase-3 activity, whereas CaMKII, MAPK family (JNK, p38, ERK), and ER stress signals (ATF6, GRP78, CHOP, caspase-12) were measured by Western blot, immunohistochemistry, and kinase activity assay. beta(1)-EC(II) immunization produced progressive LV dilation, systolic dysfunction, and myocyte apoptosis. These changes were associated with activation of GRP78 and CHOP and increased cleavage of caspase-12, as well as increased CaMKII activity, increased phosphorylation of p38 MAPK, and nucleus translocation of cleaved ATF6. NE pellet produced additive effects. In addition, KN-93 and SB 203580 abolished the induction of ER stress and cell apoptosis produced by the beta(1)-EC(II) antibody in cultured neonatal cardiomyocytes. Thus ER stress occurs in autoimmune cardiomyopathy induced by beta(1)-EC(II) peptide, and this is enhanced by increased NE and caused by activation of the beta(1)-adrenergic receptor-coupled CaMKII, p38 MAPK, and ATF6 pathway.