Effects of Simvastatin on RBL-2H3 Cell Degranulation.

Hypercholesterolemia is a major complication of arteriosclerosis. Mast cells in arteriosclerosis plaques induce inflammatory reactions and promote arterial sclerosis. In this study, we evaluated the pharmacological effects of simvastatin (SV)-3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase inhibitors on the degranulation of rat basophilic leukemia (RBL)-2H3 cells, which are commonly used as mast cell models. SV significantly decreased the degranulation induced by three types of stimulation: antigen antibody reaction (Ag-Ab), thapsigargin (Tg) serosal endoplasmic reticulum calcium ATPase (SERCA) inhibitor, and A23187 calcium ionophore. SV had a stronger inhibitory effect on degranulation induced by Ag-Ab stimulation than the other two stimulations. However, SV did not inhibit increase of intracellular Ca2+ concentrations. Mevalonate or geranylgeraniol co-treatment with SV completely prevented the inhibitory effect of SV on the degranulation induced by these stimulations. Immunoblotting results showed that SV inhibited protein kinase C (PKC) delta translocation induced by Ag-Ab but not by Tg or A23187. SV induced a reduction in active Rac1, and actin filament rearrangement. In conclusion, SV inhibits RBL-2H3 cell degranulation by inhibiting downstream signaling pathways, including the sequential degranulation pathway. These inhibitory effects were completely reversed by the addition of geranylgeraniol and might be induced by changes in the translocation of the small guanosine 5'-triphosphatase (GTPase) families Rab and Rho, which are related to vesicular transport PKC delta translocation and actin filament formation, respectively. These changes are caused by the inhibition of HMG-CoA reductase by SV following the synthesis of geranylgeranyl pyrophosphates, which play important roles in the activation of small GTPases, Rab.

Homocysteine causes neuronal leptin resistance and endoplasmic reticulum stress.

Abnormally high serum homocysteine levels have been associated with several disorders, including obesity, cardiovascular diseases or neurological diseases. Leptin is an anti-obesity protein and its action is mainly mediated by the activation of its Ob-R receptor in neuronal cells. The inability of leptin to induce activation of its specific signaling pathways, especially under endoplasmic reticulum stress, leads to the leptin resistance observed in obesity. The present study examined the effect of homocysteine on leptin signaling in SH-SY5Y neuroblastoma cells expressing the leptin receptor Ob-Rb. Phosphorylation of the signal transducer and activator of transcription (STAT3) and leptin-induced STAT3 transcriptional activity were significantly inhibited by homocysteine treatment. These effects may be specific to homocysteine and to the leptin pathway, as other homocysteine-related compounds, namely methionine and cysteine, have weak effect on leptin-induced inhibition of STAT3 phosphorylation, and homocysteine has no impact on IL-6-induced activation of STAT3. The direct effect of homocysteine on leptin-induced Ob-R activation, analyzed by Ob-R BRET biosensor to monitor Ob-R oligomerization and conformational change, suggested that homocysteine treatment does not affect early events of leptin-induced Ob-R activation. Instead, we found that, unlike methionine or cysteine, homocysteine increases the expression of the endoplasmic reticulum (ER) stress response gene, a homocysteine-sensitive ER resident protein. These results suggest that homocysteine may induce neuronal resistance to leptin by suppressing STAT3 phosphorylation downstream of the leptin receptor via ER stress.

[A Case of Postoperative Pulmonary Metastasis of Breast Cancer with Complete Response by Abemaciclib plus Fulvestrant Therapy].

A 66-year-old woman underwent total mastectomy with level Ⅰ and Ⅱ axillary lymph node dissection for right breast cancer in July 2007. The pathology results indicated the presence of T2N0M0 invasive ductal carcinoma(tubule forming type), that was estrogen receptor-positive and human epidermal growth factor 2-negative. She received postoperative adjuvant therapy with oral anastrozole(ANA)for 5 years. Eleven years after surgery, at the age of 77 years, a chest X-ray examination during a routine health checkup identified a mass shadow in the right lung. Further investigation revealed bilateral multiple lung metastases due to breast cancer recurrence. Histological examination of a tissue obtained by computed tomography(CT)-guided lung biopsy confirmed that the histological type and subtype were identical to those found in the initial surgery. Hence, endocrine therapy with ANA plus CDK4/6 inhibitor was started in November 2018. However, the first CDK4/6 inhibitor, palbociclib, caused severe myelosuppression even when the dose was reduced by 2 levels. Therefore in January 2019, the patient was switched to abemaciclib, with the dose reduced by 1 level initially and then reduced by 2 levels from August 2019. In June 2019, new multiple lung metastases appeared, and the patient was switched from ANA to fulvestrant, after which complete response was achieved in 6 months. CT in June 2021 showed no recurrence, and the patient(now 80-year-old)continues to take abemaciclib plus fulvestrant therapy.

[Primary Peritoneal Carcinoma with Long Term Survival-A Case Report].

A 62-year-old woman underwent upper endoscopy in January 2009 to reveal the presence of an extrinsic compression measuring approximately 3 cm in the anterior wall of the gastric antrum. Further examinations suggested that it was caused by peritoneal cancer of an unknown origin; thus, staging laparoscopy was performed in May 2009. Multiple white nodules of varying sizes were found scattered throughout the right upper quadrant of the abdomen and the right abdomen. Based on a biopsy of the greater omentum, the patient was diagnosed with papillary serous adenocarcinoma. As no abnormalities were observed in the uterus and ovary, it was suspected that the patient had primary peritoneal cancer. Hence, in July 2009, the patient underwent resection of the greater omentum, gastric pylorus, gall bladder, and right hemicolon where the tumors were localized, as well as bilateral adnexectomy. Based on intraoperative findings and postoperative histology, the patient was diagnosed with high-grade primary peritoneal serous adenocarcinoma and received paclitaxel and carboplatin therapy. Subsequent follow-up examinations, including positron emission tomography-computed tomography(PET-CT), indicated repeated recurrences in the mesentery, the pelvic floor, and around the remnant stomach. After identifying these recurrences, the patient was treated with platinum-based drugs, experiencing repeated response and cessation cycles. Since September 2019, the patient has received olaparib therapy. PET-CT examination performed in September 2020 indicated that the patient remained in complete remission.

The possible role of biochanin A in ameliorating endoplasmic reticulum stress-induced leptin resistance.

Leptin plays an important role in energy intake and body weight homeostasis. Leptin is secreted mainly from white adipose tissue and circulates in the bloodstream, inhibiting food intake by activating the leptin receptor expressed on hypothalamic neurons. Recent studies have demonstrated leptin resistance as the main factor involved in the development of obesity. We and others have reported that leptin resistance is caused by endoplasmic reticulum (ER) stress due to the accumulation of unfolded protein in the ER. In the present study, we investigated whether isoflavones could affect ER stress and the subsequent development of leptin resistance. We showed that biochanin A, a family of isoflavones, strongly attenuated cell death induced by ER stress in neuronal cells, improved ER stress-induced impairments in leptin signaling, and suppressed ER stress-induced expression of glucose-regulated protein 78. These results suggest that biochanin A may have pharmacological properties that can ameliorate leptin resistance by reducing ER stress.

Histamine- or vascular endothelial growth factor-induced tissue factor expression and gap formation between vascular endothelial cells are synergistically enhanced by lipopolysaccharide, tumor necrosis factor-α, interleukin (IL)-33 or IL-1ß.

The pathogenesis of chronic spontaneous urticaria (CSU), also called chronic idiopathic urticaria, has been considered to be associated with the activation of the extrinsic blood coagulation cascade. However, the trigger for the extrinsic coagulation cascade in patients with CSU remains unclear. We previously reported that histamine and lipopolysaccharide (LPS) synergistically induced the expression of tissue factor (TF), a trigger for the extrinsic coagulation cascade, in human umbilical vein endothelial cells (HUVEC). Because the elevation of tumor necrosis factor (TNF)-α, interleukin (IL)-33, IL-1ß and vascular endothelial growth factor (VEGF) in serum has also been observed in patients with CSU, we examined the effects of LPS, TNF-α, IL-33, IL-1ß, VEGF and histamine on TF expression in HUVEC by reverse transcription polymerase chain reaction and flow cytometry, as well as examining the activity that triggers the extrinsic coagulation cascade and induces intercellular gap formation of HUVEC in the presence of plasma by Actochrome® TF activity assay and impedance sensor, respectively. The expression of TF mRNA and surface protein of TF on HUVEC in response to histamine or VEGF were synergistically enhanced by the treatment with LPS, TNF-α, IL-33 or IL-1ß. Moreover, the activation of the extrinsic coagulation pathway and intercellular gap formation of HUVEC in response to histamine or VEGF were also synergistically increased in the presence of TNF-α and LPS. Thus, TF expression on vascular endothelial cells was strongly enhanced by co-stimulation with CSU-related molecules in blood. Blocking a common pathway of LPS, TNF-α, IL-33 and IL-1ß, and/or that of VEGF and histamine may be an effective therapeutic measure for patients with severe and refractory CSU.

Anticancer effect of nor-wogonin (5, 7, 8-trihydroxyflavone) on human triple-negative breast cancer cells via downregulation of TAK1, NF-κB, and STAT3.

BACKGROUND: Nor-wogonin, a polyhydroxy flavone, has been shown to possess antitumor activity. However, the mechanisms responsible for its antitumor activity are poorly studied. Herein, we investigated the mechanisms of nor-wogonin actions in triple-negative breast cancer (TNBC) cells. METHODS: Effects of nor-wogonin on cell proliferation and viability of four TNBC cell lines (MDA-MB-231, BT-549, HCC70, and HCC1806) and two non-tumorigenic breast cell lines (MCF-10A and AG11132) were assessed by BrdU incorporation assays and trypan blue dye exclusion tests. Cell cycle and apoptosis analyses were carried out by flow cytometry. Protein expression was analyzed by immunoblotting. RESULTS: Nor-wogonin significantly inhibited the growth and decreased the viability of TNBC cells; however, it exhibited no or minimal effects in non-tumorigenic breast cells. Nor-wogonin (40 µM) was a more potent anti-proliferative and cytotoxic agent than wogonin (100 µM) and wogonoside (100 µM), which are structurally related to nor-wogonin. The antitumor effects of nor-wogonin can be attributed to cell cycle arrest via reduction of the expression of cyclin D1, cyclin B1, and CDK1. Furthermore, nor-wogonin induced mitochondrial apoptosis, (as evidenced by the increase in % of cells that are apoptotic), decreases in the mitochondrial membrane potential (ΔΨm), increases in Bax/Bcl-2 ratio, and caspase-3 cleavage. Moreover, nor-wogonin attenuated the expression of the nuclear factor kappa-B and activation of signal transducer and activator of transcription 3 pathways, which can be correlated with suppression of transforming growth factor-ß-activated kinase 1 in TNBC cells. CONCLUSION: These results showed that nor-wogonin might be a potential multi-target agent for TNBC treatment.

Possible involvement of 4-hydroxy-2-nonenal in the pathogenesis of leptin resistance in obesity.

Insensitivity to the antiobesity hormone, leptin, has been suggested to be involved in the pathogenesis of obesity. However, the pathological mechanisms underlying the development of leptin resistance are not well-understood. This study aimed to examine the pathological mechanisms of leptin resistance in obesity. In the present study, we found that 4-hydroxy-2-nonenal (4-HNE), an aldehyde, may be involved in the development of leptin resistance. The SH-SY5Y-Ob-Rb human neuroblastoma cell line, transfected to express the Ob-Rb leptin receptor stably, was treated with 4-HNE, and leptin-induced signal transduction was analyzed. We found that 4-HNE dose- and time-dependently inhibited leptin-induced signal transducer and activator of transcription 3 (STAT3) phosphorylation, a major antiobesity signal of leptin. On the other hand, 4-HNE did not affect tyrosine phosphorylation of broad cellular proteins, suggesting that the inhibitory effect may be selective to leptin signaling. Mechanistically, 4-HNE induced the eukaryotic initiation factor 2α-CCAAT/enhancer-binding protein homologous protein arm of endoplasmic reticulum stress signaling, which may be involved in the pathogenesis of leptin resistance. Overall, these results suggest that 4-HNE may partly affect endoplasmic reticulum stress-induced unfolded protein response signaling and may be involved in the pathogenesis of leptin resistance.

[A Case of Recurrent Breast Cancer with Complete Response to Eribulin Monotherapy after Bevacizumab plus Paclitaxel Combination Therapy].

A 65-year-old woman underwent mastectomy and dissection of a level I axillary lymph node in January 2002 for left breast cancer. The diagnosis was T1N0M0 scirrhous carcinoma that was estrogen receptor-positive, progesterone receptorpositive, and human epidermal growth factor receptor 2-negative. After 3 years 10 months, during which the patient underwent adjuvant therapy with oral aromatase inhibitors, she developed bilateral multiple lung metastases. These were treated with the anticancer agents anthracycline and taxane. Progressive disease(more and larger lung metastases)was diagnosed in April 2013, and bevacizumab plus paclitaxel combination therapy was started. After completion of 4 courses, a lung abscess appeared, which was conjectured to represent rapid tumor necrosis that had become infected. As several tumors remained solid even after the lung abscess improved, the patient received 18 courses of eribulin monotherapy. Computed tomography in April 2016 revealed only patches of linear or cord-like scarring in both lungs, with no metastatic or recurrent foci. In this case, a patient with recurrent breast cancer responded to the sequential administration of bevacizumab plus paclitaxel combination therapy followed by eribulin monotherapy.

Mechanisms of the action of adenine on anti-allergic effects in mast cells.

INTRODUCTION: Mast cells play an important role in allergic responses. METHODS: We herein demonstrated the mechanisms of inhibitory effect of adenine on IgE/antigen-induced degranulation and TNF-α release in mast cells. RESULTS: We found that these effects were dependent on the amino group of adenine because purine only weakly inhibited degranulation. Adenine also inhibited Ca2+ ionophore- and thapsigargin-induced degranulation, however, this inhibitory effect was weaker than that of the antigen. Therefore, the inhibitory effects of adenine on degranulation may be mediated before as well as after the Ca2+ raise under the antigen stimulus. Adenine inhibited antigen-induced Syk and the subsequent induction of AKT and ERK activation under FcϵRI-mediated signal. Adenine also attenuated antigen-induced increase in Ca2+ . Furthermore, adenine inhibited IgE/antigen-induced IKKα/ß activation, which is involved in degranulation. Finally, adenine protected mice against anaphylactic allergic responses in vivo. CONCLUSIONS: The present study revealed a key role of adenine in the attenuation of allergic responses through the inhibition of Syk-mediated signal transduction and IKK-mediated degranulation.

Loss of Stearoyl-CoA Desaturase-1 Activity Induced Leptin Resistance in Neuronal Cells.

The lack of response to leptin's actions in the brain, "leptin resistance," is one of the main causes of the pathogenesis of obesity. However, although high-fat diets affect sensitivity to leptin, the underlying mechanisms of leptin resistance are still an enigma. Here we examined the effect of excess saturated fatty acids (SFAs) on leptin signaling in human neuronal cells. Palmitate, the principle source of SFAs in diet, induced leptin resistance in a human neuroblastoma cell line stably transfected with the Ob-Rb leptin receptor (SH-SY5Y-ObRb). We next investigated the function of stearoyl-CoA desaturase-1 (SCD1), an enzyme which converts SFAs into monounsaturated fatty acids (MUFAs), on leptin-induced signaling. We found that reduction of SCD1 activity, through SCD1 inhibition and knockdown, impairs leptin-induced signal transducer and activator of transcription 3 (STAT3) phosphorylation in human neuronal cells. Our findings suggested that SCD1 plays a key role in the pathophysiology of leptin resistance in neuronal cells associated with obesity.

Endospanin1 affects oppositely body weight regulation and glucose homeostasis by differentially regulating central leptin signaling.

The hypothalamic arcuate nucleus (ARC) is a major integration center for energy and glucose homeostasis that responds to leptin. Resistance to leptin in the ARC is an important component of the development of obesity and type 2 diabetes. Recently, we showed that Endospanin1 (Endo1) is a negative regulator of the leptin receptor (OBR) that interacts with OBR and retains the receptor inside the cell, leading to a decreased activation of the anorectic STAT3 pathway. Endo1 is up-regulated in the ARC of high fat diet (HFD)-fed mice, and its silencing in the ARC of lean and obese mice prevents and reverses the development of obesity. OBJECTIVE: Herein we investigated whether decreased Endo1 expression in the hypothalamic ARC, associated with reduced obesity, could also ameliorate glucose homeostasis accordingly. METHODS: We studied glucose homeostasis in lean or obese mice silenced for Endo1 in the ARC via stereotactic injection of shRNA-expressing lentiviral vectors. RESULTS: We observed that despite being leaner, Endo1-silenced mice showed impaired glucose homeostasis on HFD. Mechanistically, we show that Endo1 interacts with p85, the regulatory subunit of PI3K, and mediates leptin-induced PI3K activation. CONCLUSIONS: Our results thus define Endo1 as an important hypothalamic integrator of leptin signaling, and its silencing differentially regulates the OBR-dependent functions.

Dehydroascorbic acid-induced endoplasmic reticulum stress and leptin resistance in neuronal cells.

Due to its anti-obesity effects, an adipocyte-derived hormone, leptin, has become important for the treatment of obesity. However, most obese subjects are in a state of leptin resistance, and endoplasmic reticulum (ER) stress is suggested to be involved in the pathophysiology of leptin resistance. Dehydroascorbic acid (DHAA), an oxidized form of vitamin C, was found to be increased in diabetes. In the present study, we investigated the possible effects of DHAA on the activation of ER stress and leptin resistance. A human neuroblastoma cell line, stably transfected with the Ob-Rb leptin receptor (SH-SY5Y-ObRb), was treated with DHAA. We found that DHAA upregulated ER stress-related genes such as GRP78, CHOP, and spliced XBP1. Moreover, leptin-induced STAT3 phosphorylation was hindered by DHAA. These results suggested that increases in the levels of DHAA might be harmful to neurons, contributing to defective leptin-responsive signaling.

Inhibition of telomerase causes vulnerability to endoplasmic reticulum stress-induced neuronal cell death.

Endoplasmic reticulum (ER) stress is implicated in several diseases, such as cancer and neurodegenerative diseases. In the present study, we investigated the possible involvement of telomerase in ER stress-induced cell death. ER stress-induced cell death was ameliorated in telomerase reverse transcriptase (TERT) over-expressing MCF7 cells (MCF7-TERT cell). Telomerase specific inhibitor, BIBR1532, reversed the inhibitory effect of TERT on ER stress-induced cell death in MCF7-TERT cells. These findings suggest that BIBR1532 may specifically inhibit telomerase activity, thereby inducing cell death in ER stress-exposed cells. TERT was expressed in the SH-SY5Y neuroblastoma cell line. To analyze the possible involvement of telomerase in ER stress-induced neuronal cell death, we treated SH-SY5Y neuroblastoma cells with BIBR1532 and analyzed ER stress-induced cell death. We found that BIBR1532 significantly enhanced the ER stress-induced neuronal cell death. These findings suggest that inhibition of telomerase activity may enhance vulnerability to neuronal cell death caused by ER stress.

Key role of heat shock protein 90 in leptin-induced STAT3 activation and feeding regulation.

BACKGROUND AND PURPOSE: Leptin, an important regulator of the energy balance, acts on the brain to inhibit feeding. However, the mechanisms involved in leptin signalling have not yet been fully elucidated. Heat shock protein 90 (HSP90) is a molecular chaperone that is involved in regulating cellular homeostasis. In the present study, we investigated the possible involvement of HSP90 in leptin signal transduction. EXPERIMENTAL APPROACH: HEK293 and SH-SY5Y cell lines stably transfected with the Ob-Rb leptin receptor (HEK293 Ob-Rb, SH-SY5Y Ob-Rb) were used in the present study. Phosphorylation of JAK2 and STAT3 was analysed by western blotting. An HSP90 inhibitor was administered i.c.v. into rats and their food intake was analysed. KEY RESULTS: The knock-down of HSP90 in the HEK293 Ob-Rb cell line attenuated leptin-induced JAK2 and STAT3 signalling. Moreover, leptin-induced JAK2/STAT3 phosphorylation was markedly attenuated by the HSP90 inhibitors geldanamycin, radicicol and novobiocin. However, these effects were not mediated through previously known factors, which are known to be involved in the development of leptin resistance, such as suppressor of cytokine signalling 3 or endoplasmic reticulum stress. The infusion of an HSP90 inhibitor into the CNS blunted the anorexigenic actions of leptin in rats (male Wister rat). CONCLUSIONS AND IMPLICATIONS: HSP90 may be a novel factor involved in leptin-mediated signalling that is linked to anorexia.

[Total Gastrectomy for Advanced Gastric Cancer after Coronary Artery Bypass Grafting Using the Right Gastroepiploic Artery: Report of a Case].

An 82-year-old man, who had undergone coronary artery bypass grafting(CABG) with the right gastroepiploic artery( RGEA) 13 years previously, suffered with abdominal pain after meal and tarry stools, and was diagnosed with advanced gastric cancer. Gastroscopy revealed an advanced Borrmann type 4 cancer at the lesser curvature of the gastric body to the pyloric ring. The gastrogram showed poor extension and stenosis at the same part. Abdominal computed tomography showed the tumor reached the subserosal layer and infrapyloric lymph nodes were swollen. Abdominal angiography showed the RGEA graft remained well patent. Total gastrectomy with D2 lymph nodes dissection and arterial reconstruction between the splenic artery and the RGEA graft was performed. He has been well without any sign of cancer recurrence since the operation. Recently, more patients with CABG using RGEA are found to have gastric cancer and require the resection of RGEA for lymph nodes dissection as this case. We consider this procedure one of the options for advanced gastric cancer after coronary bypass grafting using RGEA.

Synthesis of a peptide that can translocate to the endoplasmic reticulum.

The accumulation of unfolded proteins in the endoplasmic reticulum (ER) leads to ER stress, which has been implicated in the development of diseases. In the present study, we synthesized a peptide that entered cells and translocated to the ER. This peptide possessed fluorescein isothiocyanate (FITC), HIV-TAT, mini-αA-crystallin, and KDEL sequences. We demonstrated that this peptide entered cells and translocated to the ER. Time course experiments revealed that this peptide existed in the ER of cos-7 cells for 16 h. Furthermore, we detected the full-length peptide in cells by fluorescent immunostaining followed by SDS-PAGE. The peptide also entered glial and neuronal cells. These results suggest that this peptide has the ability to enter cells and exert chaperone activity at the ER, and provide an insight into the development of new drugs.

Possible involvement of 15-deoxy-Δ(12,14) -prostaglandin J2 in the development of leptin resistance.

Obesity is a worldwide health problem that urgently needs to be solved. Leptin is an anti-obesity hormone that activates satiety signals to the brain. Evidence to suggest that leptin resistance is involved in the development of obesity is increasing; however, the molecular mechanisms involved remain unclear. We herein demonstrated that 15-deoxy-Δ(12,14) -prostaglandin J2 (15d-PGJ2 ) was involved in the development of leptin resistance. A treatment with 15d-PGJ2 inhibited the leptin-induced activation of signal transducer and activator of transcription 3 (STAT3) in neuronal cells (SH-SY5Y-Ob-Rb cells). Furthermore, the intracerebroventricular administration of 15d-PGJ2 reversed the inhibitory effects of leptin on food intake in rats. The peroxisome proliferator-activated receptor gamma (PPAR-γ) antagonist, GW9662, slightly reversed the inhibitory effects of 15d-PGJ2 on the leptin-induced activation of STAT3 in neuronal cells. The PPAR-γ agonist, rosiglitazone, also inhibited leptin-induced STAT3 phosphorylation. Therefore, the inhibitory effects of 15d-PGJ2 may be mediated through PPAR-γ. On the other hand, 15d-PGJ2 -induced leptin resistance may not be mediated by endoplasmic reticulum stress or suppressor of cytokine signaling 3. The results of the present study suggest that 15d-PGJ2 is a novel factor for the development of leptin resistance in obesity. Leptin resistance, an insensitivity to the actions of leptin, is involved in the development of obesity. Here, we found 15-deoxy-Δ(12,14) -prostaglandin J2 (15d-PGJ2 ) may be involved in the development of leptin resistance. The present results suggest that the 15d-PGJ2 may be a novel factor for the development of leptin resistance in obesity. 15d-PGJ2 , 15-Deoxy-Δ(12,14) -prostaglandin J2; STAT3, signal tranducer and activator of transcription 3.

Leptin induced GRP78 expression through the PI3K-mTOR pathway in neuronal cells.

Leptin is a circulating hormone that plays a critical role in regulating energy expenditure and food intake. Evidence to suggest the involvement of endoplasmic reticulum (ER) stress in the development of obesity is increasing. To adapt against ER stress, cells trigger the unfolded protein response (UPR). The 78 kDa glucose-regulated protein (GRP78) is an ER chaperone that protects cells against ER stress by inducing protein folding. In the present study, we hypothesized that leptin may activate UPR and protect against ER stress associated with obesity. SH-SY5Y, a human neuroblastoma cell line stably transfected with the Ob-Rb leptin receptor (SH-SY5Y-ObRb), was treated with leptin. We demonstrated that leptin induced GRP78 expression. We then validated the mechanism responsible for the leptin-induced expression of GRP78. Interestingly, leptin-induced GRP78 expression was not dependent on IRE1-XBP1 pathway. On the other hand, the PI3K inhibitor, LY294002, and mTOR inhibitor, rapamycin, inhibited the leptin-induced expression of GRP78. These results suggested that the leptin-induced expression of GRP78 may be dependent on the PI3K-mTOR pathway. Leptin specifically induced GRP78 because the induction of the ER-apoptotic marker, CHOP, was not detected in leptin-treated cells. Therefore, leptin may upregulate the expression of GRP78, thereby protecting against ER stress associated with obesity.

Therapeutic potential of flurbiprofen against obesity in mice.

Obesity is associated with several diseases including diabetes, nonalcoholic steatohepatitis (NASH), hypertension, cardiovascular disease, and cancer. Therefore, anti-obesity drugs have the potential to prevent these diseases. In the present study, we demonstrated that flurbiprofen, a nonsteroidal anti-inflammatory drug (NSAID), exhibited therapeutic potency against obesity. Mice were fed a high-fat diet (HFD) for 6 months, followed by a normal-chow diet (NCD). The flurbiprofen treatment simultaneously administered. Although body weight was significantly decreased in flurbiprofen-treated mice, growth was not affected. Flurbiprofen also reduced the HFD-induced accumulation of visceral fat. Leptin resistance, which is characterized by insensitivity to the anti-obesity hormone leptin, is known to be involved in the development of obesity. We found that one of the possible mechanisms underlying the anti-obesity effects of flurbiprofen may have been mediated through the attenuation of leptin resistance, because the high circulating levels of leptin in HFD-fed mice were decreased in flurbiprofen-treated mice. Therefore, flurbiprofen may exhibit therapeutic potential against obesity by reducing leptin resistance.