Endoplasmic Reticulum Stress-related Apoptosis Research Articles

Honokiol Attenuates Torsion/Detorsion-induced Testicular Injury in Rat Testis by Way of Suppressing Endoplasmic Reticulum Stress-related Apoptosis

To investigate the protective effect of honokiol, a phytochemical used in traditional medicine, on testicular injury after torsion/detorsion (T/D) in a rat model. Testicular torsion is a medical emergency that can cause impairment of semen quality and permanent testicular atrophy or loss. Male Wistar rats were randomized to each time point of each group (n = 6/time point/group). After 2 hours of torsion, the testes were counter-rotated to the natural position. The rats in each group underwent a sham operation, T/D, or T/D with honokiol treatment (5 mg/kg and 10 mg/kg intraperitoneally, immediately before detorsion). Bilateral orchiectomy was performed at 6 and 24 hours and 3 months after detorsion. The testes were examined histologically. Apoptosis and endoplasmic reticulum stress were detected by Western blot. Histologic examination revealed that testicular T/D induced acute injury after 6 and 24 hours, and spermatogenesis was decreased at 3 months of follow-up. At 24 hours after T/D, increases were found in the activation of apoptosis-related molecules [poly (ADP-ribose) polymerase and caspases 3 and 7], and the expression levels of endoplasmic reticulum stress-associated molecules (phosphorylated-eukaryotic translation initiation factor 2 subunit α and CCAAT/enhancer-binding protein homologous protein). These increases were significantly reversed with honokiol treatment. Furthermore, honokiol effectively reversed the inhibition of spermatogenesis in testes treated with T/D for 3 months. The results of our study have shown that the endoplasmic reticulum stress-related apoptotic pathway is involved in testicular injury after testicular T/D. It remains to be determined whether alterations in this pathway would have a protective affect against reperfusion damage.

Protective effect of telmisartan on endoplasmic reticulum stress-related kidney cells apoptosis in diabetic rats

To investigate the effect of angiotensin receptor blocker ( ARB ) telmisartan on endoplasmic reticulum stress -related kidney cells apoptosis in diabetic rats.31 male SD rats were divided into 3 groups:normal control group,diabetic group,and telmisartan treated diabetic group.After 12 weeks' experiment,weight,24 h urinary albumin excretion,blood glucose,serum insulin,and serum creatinine were determined.Renal cell apoptosis was examined by using TUNEL; Renal cell endoplasmic reticulum stress signaling pathway molecules glucose regulated protien 78 ( GRP78 ),caspase12,and CHOP were detected with immunohistochemistry and realtime PCR.24 h urine protein and serum creatinine in diabetic group were significantly higher than those in the control group; while body weight and plasma insulin were significantly lower than those in the control group( P＜0.05 ) ;Compared with diabetic group,24 h urinary protein and serum creatinine were decreased significantly in telmisartan treated diabetic group( P＜0.05 ).The apoptosis index of telmisartan treated group was significantly lower than that of diabetic group( P＜0.05 ).Endoplasmic reticulum stress signaling pathway molecules GRP78,caspase12,CHOP protein and mRNA expression in diabetic group were significantly higher than those in control group( P＜0.05 ),as well as in telmisartan treated group( P＜0.05 ).Endoplasmic reticulum stress took part in kidney cell apoptosis of the diabetic rat.Telmisartan possessed a protective effect on endoplasmic reticulum stress-related renal cells apoptosis. Key words: Diabetic nephropathy ; Endoplasmic reticulum stress; Apoptosis; Telmisartan

Endoplasmic Reticulum Stress Implicated in the Development of Renal Fibrosis

Endoplasmic reticulum (ER) stress-associated apoptosis plays a role in organ remodeling after insult. The effect of ER stress on renal tubular damage and fibrosis remains controversial. This study aims to investigate whether ER stress is involved in tubular destruction and interstitial fibrosis in vivo. Renal cell apoptosis was proven by terminal deoxynucleotidyl transferase dUTP nick end-labeling (TUNEL) stain and poly-ADP ribose polymerase expression in the unilateral ureteral obstruction (UUO) kidney. ER stress was evoked and confirmed by the upregulation of glucose-regulated protein 78 (GRP78) and the common Lys-Asp-Glu-Leu (KDEL) motif of ER retention proteins after UUO. ER stress-associated proapoptotic signals, including B-cell chronic lymphocytic leukemia (CLL)/lymphoma 2-associated × protein (BAX) expression, caspase-12 and c-Jun N-terminal kinase (JNK) phosphorylation, were activated in the UUO kidney. Prolonged ER stress attenuated both unsplicing and splicing X-box binding protein 1 (XBP-1) protein expression, but continued to activate inositol-requiring 1α (IRE1α)-JNK phosphorylation, protein kinase RNA-like endoplasmic reticulum kinase (PERK), eukaryotic translation initiation factor 2α subunit (eIF2α), activating transcription factor (ATF)-4, CCAAT/enhancer binding protein (C/EBP) homologous protein (CHOP) and cleavage activating transcription factor 6 (cATF6)-CHOP signals, which induce ER stress-related apoptosis but attenuate adaptive unfolded protein responses in UUO kidneys. However, renal apoptosis and fibrosis were attenuated in candesartan-treated UUO kidney. Candesartan was associated with maintenance of XBP-1 expression and attenuated ATF4, cATF6 and CHOP protein expression. Taken together, results show that overwhelming ER stress leads to renal cell apoptosis and subsequent fibrosis; and candesartan, at least in part, restores renal integrity by blocking ER stress-related apoptosis. Reducing ER stress may present a way to attenuate renal fibrosis.

Effect of neurotrophin-4 on endoplasmic reticulum stress-related neuronal apoptosis in diabetic and high glucose exposed rat retinas

The purpose of this study was to investigate the effect of NT-4 on the endoplasmic reticulum (ER) stress-related apoptosis of retinal neurons of isolated retinas. The retinas were isolated from normal and diabetic rats, and the normal retinas were exposed to high glucose (HG). Our results showed that the number of TUNEL-positive, and PERK- and CHOP-positive cells was significantly higher in diabetic and HG exposed retinas than in normal retinas. In diabetic and HG exposed retinas supplemented with NT-4, the number of TUNEL-positive, and PERK- and CHOP-positive cells was significantly lower than in retinas without NT-4. The neuroprotective effect of NT-4 on retinas cultured under diabetic stress was correlated with the suppression in the expression of PERK and CHOP, ER stress-related factors.

Induction of apoptosis by the BRAFV600E kinase inhibitor PLX4032 in BRAFV600E melanoma cells through regulation of endoplasmic reticulum stress-related genes.

8518 Background: In a previous study, we showed that the pan-RAF inhibitor sorafenib induces upregulation of endoplasmic reticulum (ER) stress-related genes and apoptosis in melanoma cells in vitro. Methods: In this study, we posed the question whether PLX4032, which selectively inhibits the BRAFV600E kinase and demonstrated potent antitumor activity in melanoma patients with the BRAFV600E mutation, induces ER stress-mediated apoptosis in metastatic melanoma cells harboring a BRAFV600E mutation. Results: The BRAFV600E kinase inhibitor PLX4032 inhibited growth, induced apoptosis and upregulated the ER stress-related genes p8, CHOP, ATF4, ATF3 and TRB3 exclusively in BRAFV600E mutated melanoma cell lines. Furthermore, electron microscopy showed morphological features of ER stress, in particular significant swelling of the ER lumen of BRAFV600E melanoma cells treated with PLX4032 compared with BRAFV600E melanoma cells treated with vehicle. siRNA inhibition of p8 reduced melanoma cell apoptosis induced by PLX4032, overexpression of p8 enforced melanoma cell apoptosis induced by PLX4032. Furthermore, classical ER stress inducers such as thapsigargin and tunicamycin potently inhibited growth, induced apoptosis and suppressed invasive tumor growth of melanoma cells. Moreover, both thapsigargin and tunicamycin upregulated p8 and CHOP and induced apoptosis in PLX4032-resistant melanoma cells. Conclusions: These data suggest that the BRAFV600E kinase inhibitor PLX4032 induces apoptosis in BRAFV600E melanoma cells through upregulation of ER stress-related genes, and that melanoma cells which acquired resistance to PLX4032 may be sensitive to agents which induce ER stress-mediated apoptosis through a different mechanism.

Salubrinal, an eIF2α dephosphorylation inhibitor, enhances cisplatin-induced oxidative stress and nephrotoxicity in a mouse model

Although cisplatin attacks various tumors with remarkable efficacy, its clinical usage has been limited by its side effects, particularly nephrotoxicity. Salubrinal, a selective eukaryotic translation initiation factor 2 subunit α (eIF2α) dephosphorylation inhibitor, has been found to protect cells from endoplasmic reticulum (ER)-stress-induced cytotoxicity. In this study, we hypothesized that salubrinal would protect against cisplatin-induced nephrotoxicity in a mouse model. Cisplatin treatment significantly increased serum blood urea nitrogen and creatinine levels, renal kidney injury marker (kim-1) mRNA expression, renal cell apoptosis, and renal histopathological changes in mice. Unexpectedly, administration of salubrinal significantly enhanced the cisplatin-induced nephrotoxicity in mice. Salubrinal by itself did not induce alterations in the function or histomorphology of mouse kidneys. Salubrinal significantly enhanced the phosphorylation of eIF2α, the protein expression of activating transcription factor 4 and CCAAT/enhancer binding protein homologous protein, and the cleavage of caspases 12, 9, and 3 in the kidneys of cisplatin-treated mice. Moreover, salubrinal enhanced the cisplatin-induced oxidative stress in the kidneys. The antioxidant N-acetylcysteine significantly reversed the increased renal lipid peroxidation, activated renal caspase cascade, and increased blood BUN and creatinine in cisplatin-alone- or cisplatin plus salubrinal-treated mice. These findings suggest that salubrinal aggravates cisplatin-induced nephrotoxicity through the enhancement of oxidative stress and ER stress-related cell apoptosis.

Cardiotoxin III‐induced apoptosis is mediated by Ca2+‐dependent caspase‐12 activation in K562 cells

Cardiotoxin III (CTX III), a basic polypeptide with 60 amino acid residues isolated from Naja naja atra venom, has been reported to have anticancer activity. When K562 cells were treated with CTX III, cytosolic calcium concentration was rapidly and persistently increased. This CTX III-induced cell death was partially reversed by pretreatment with BAPTA/AM (20 microM), a chelator of intracellular Ca2+. Moreover, CTX III-induced apoptotic signals, such as caspase-12 and c-Jun N-terminal kinase (JNK) activation, were induced in a time-dependent manner and inhibited by BAPTA/AM. In contrast, the neutral protease micro-calpain, a key enzyme in endoplasmic reticulum (ER) stress-related apoptosis via caspase-12 activation, was unchanged during apoptosis. Taken together, our findings suggest CTX III-induced apoptosis is triggered by Ca2+ influx, then activated caspase-12 and JNK through micro-calpain-independent cascade, and consequently caused apoptosis.

A preliminary study on the econazole induced endoplasmic reticulum related apoptosis in HL-60 leukemic cells

Objective: To investigate the anti-leukemic function of econazole (Ec), an azole anti-fungal drug. Methods: We compared efficacy of econazole to induce apoptosis in HL-60 cells with two other known endoplasmic reticulum (ER) stress inducer thapsigargin (Tg) and tunicamycin (Tu). Results: Cells treated with Ec showed typical morphology of apoptosis following 24 h incubation, parallel to the morphological changes, the expression of molecular chaperone GRP 78 was up-regulated in all cases and the caspase 12, an ER resident caspase was activated. Conclusion: Ec induced ER stress related apoptosis in HL-60 cells; the underlying mechanisms are protein synthesis inhibition through elF2a phosphorylation and caspase 12 activation.

Betaine decreases hyperhomocysteinemia, endoplasmic reticulum stress, and liver injury in alcohol-fed mice

Background & Aims: Alcohol-induced hyperhomocysteinemia has been reported in rats and humans. Hyperhomocysteinemia has been associated with endoplasmic reticulum (ER) stress leading to the activation of ER-dependent apoptosis or up-regulation of lipid synthesis. This novel ER stress mechanism of alcoholic liver injury was studied in the model of intragastric alcohol-fed mice. Methods: Effects of alcohol on gene expression were analyzed using cDNA microarrays, RT-PCR, and Western blots over a period of 6 weeks. Liver injury was examined by histologic staining and TUNEL. Results: We observed fatty liver, increased hepatic necroinflammation and apoptosis, and hyperhomocysteinemia. Of 1176 toxicology-related genes, glucose-regulated proteins (GRP-78 and -94), growth arrest/DNAdamage-inducible protein 153 (CHOP/GADD153), and caspase-12 indicative of an ER stress response were among the alcohol-responsive genes. Sterol regulatory element binding protein (SREBP-1) and HMG-CoA reductase also were enhanced with alcohol administration. RT-PCR and selective Western blots confirmed the alcohol-induced expression of ER stress-related apoptosis and lipid synthesis genes. Addition of 0.5% and maximal 1.5% betaine to the alcohol diet reduced the elevated level of plasma homocysteine by 54% and more than 80% accompanied by a decrease in hepatic lipids and ER stress response. Betaine did not attenuate the ethanol-induced increase in tumor necrosis factor α or CD14 mRNA. Conclusions: The results strongly suggest that alcohol may modulate both apoptotic and fat synthetic gene expression through homocysteine-induced ER stress in chronic alcoholic mouse liver and that correction of hyperhomocysteinemia by betaine or other approaches may be useful to prevent alcoholic liver disease.