Potencies of vitamin D analogs, 1α‐hydroxyvitamin D3, 1α‐hydroxyvitamin D2 and 25‐hydroxyvitamin D3, in lowering cholesterol in hypercholesterolemic mice in vivo

Vitamin D₃ and the synthetic vitamin D analogs, 1α‐hydroxyvitamin D₃ [1α(OH)D₃], 1α‐hydroxyvitamin D₂ [1α(OH)D₂] and 25‐hydroxyvitamin D₃ [25(OH)D₃] were appraised for their vitamin D receptor (VDR) associated‐potencies as cholesterol lowering agents in mice in vivo. These precursors are activated in vivo: 1α(OH)D₃ and 1α(OH)D₂ are transformed by liver CYP2R1 and CYP27A1 to active VDR ligands, 1α,25‐dihydroxyvitamin D₃ [1,25(OH)₂D₃] and 1α,25‐dihydroxyvitamin D₂ [1,25(OH)₂D₂]_, respectively. 1α(OH)D₂ may also be activated by CYP24A1 to 1α,24‐dihydroxyvitamin D₂ [1,24(OH)₂D₂], another active VDR ligand. 25(OH)D₃, the metabolite formed via CYP2R1 and or CYP27A1 in liver from vitamin D₃, is activated by CYP27B1 in the kidney to 1,25(OH)₂D₃. In C57BL/6 mice fed the high fat/high cholesterol Western diet for 3 weeks, vitamin D analogs were administered every other day intraperitoneally during the last week of the diet. The rank order for cholesterol lowering, achieved via mouse liver small heterodimer partner (Shp) inhibition and increased cholesterol 7α‐hydroxylase (Cyp7a1) expression, was: 1.75 nmol/kg 1α(OH)D₃ > 1248 nmol/kg 25(OH)D₃ (dose ratio of 0.0014) > > 1625 nmol/kg vitamin D₃. Except for 1.21 nmol/kg 1α(OH)D₂ that failed to lower liver and plasma cholesterol contents, a significant negative correlation was observed between the liver concentration of 1,25(OH)₂D₃ formed from the precursors and liver cholesterol levels. The composite results show that vitamin D analogs 1α(OH)D₃ and 25(OH)D₃ exhibit cholesterol lowering properties upon activation to 1,25(OH)₂D₃: 1α(OH)D₃ is rapidly activated by liver enzymes and 25(OH)D₃ is slowly activated by renal Cyp27b1 in mouse.     

Validation of a new yeast‐based reporter assay consisting of human estrogen receptors α/β and coactivator SRC‐1: Application for detection of estrogenic activity in environmental samples

Endocrine disruptors are exogenous substances that act like hormones in the endocrine system and disrupt the physiologic function of endogenous hormones. In the present study, we established reporter yeast strains (Saccharomyces cerevisiae) expressing human estrogen receptors, ERα or ERβ. These strains contain a reporter plasmid carrying an estrogen responsive element (ERE) upstream of the β‐galactosidase gene, and a plasmid expressing a steroid receptor coactivator, SRC‐1e. Using these reporter strains, we demonstrated dose‐dependent estrogenic activities of different categories of ligands, a natural hormone, 17β‐estradiol (E2); a synthetic drug, diethylstilbestrol (DES); phytoestrogens, genistein, daizein and emodin; and an environmental endocrine disrupter, bisphenol A. EC₅₀ values of E2 for ERα and ERβ are 5.31 × 10^?10 and 5.85 × 10^?10 M, respectively. We also demonstrated that these yeasts were applicable for measuring estrogenic activities of environmental water samples. Most downstream sites of a river showed similar activity in both ERα and ERβ assays. These yeast strains are useful and convenient for detecting and comparing the estrogenic ligand activities of environmental samples in response to ERα and ERβ. © 2009 Wiley Periodicals, Inc. Environ Toxicol, 2009.     

Comparative effects of 1α‐hydroxyvitamin D3 and 1,25‐dihydroxyvitamin D3 on transporters and enzymes in fxr(+/+) and fxr(‐/‐) mice

Previous studies have shown that 1α,25‐dihydroxyvitamin D₃ [1,25(OH)₂D₃] treatment in mice resulted in induction of intestinal and renal Cyp24a1 and Trpv6 expression, increased hepatic Cyp7a1 expression and activity, as well as higher renal Mdr1/P‐gp expression. The present study compared the equimolar efficacies of 1α‐hydroxyvitamin D₃ [1α(OH)D₃] (6 nmol/kg i.p. q2d × 4), a lipophilic precursor with a longer plasma half‐life that is converted to 1,25(OH)₂D₃, and 1,25(OH)₂D₃ on vitamin D receptor (VDR) target genes. To clarify whether changes in VDR genes was due to VDR and not secondary, farnesoid X receptor (FXR)‐directed effects, namely, lower Cyp7a1 expression in rat liver due to increased bile acid absorption, wildtype [fxr(+/+)] and FXR knockout [fxr(‐/‐)] mice were used to distinguish between VDR and FXR effects. With the exception that hepatic Sult2a1 mRNA was increased equally well by 1α(OH)D₃ and 1,25(OH)₂D₃, 1α(OH)D₃ treatment led to higher increases in hepatic Cyp7a1, renal Cyp24a1, VDR, Mdr1 and Mrp4, and intestinal Cyp24a1 and Trpv6 mRNA expression in both fxr(+/+) and fxr(‐/‐) mice compared to 1,25(OH)₂D₃ treatment. A similar induction in protein expression and microsomal activity of hepatic Cyp7a1 and renal P‐gp and Mrp4 protein expression was noted for both compounds. A higher intestinal induction of Trpv6 was observed, resulting in greater hypercalcemic effect following 1α(OH)D₃ treatment. The higher activity of 1α(OH)D₃ was explained by its rapid conversion to 1,25(OH)₂D₃ in tissue sites, furnishing higher plasma and tissue 1,25(OH)₂D₃ levels compared to following 1,25(OH)₂D₃‐treatment. In conclusion, 1α(OH)D₃ exerts a greater effect on VDR gene induction than equimolar doses of 1,25(OH)₂D₃ in mice. Copyright © 2013 John Wiley & Sons, Ltd.     

Estrogen and ERα enhanced β‐catenin degradation and suppressed its downstream target genes to block the metastatic function of HA22T hepatocellular carcinoma cells via modulating GSK‐3β and β‐TrCP expression

In our previous experiments, we found β‐catenin was highly expressed in the tumor area with high invasive ability and poor prognosis. In this study, we have examined the mechanism by which ERα regulates β‐catenin expression as well as the metastasis ability of hepatocellular cancer HA22T cells. To identify whether the anticancer effect of estrogen and ERα is mediated through suppression of β‐catenin expression, we co‐transfected pCMV‐β‐catenin and ERα into HA22T cells, and determined the cell motility by wound healing, invasion, and migration assays. Results showed that estrogen and/or ERα inhibited β‐catenin gene expression and repressed HA22T cell motility demonstrated that similar data was observed in cells expressing the ERα stable clone. Moreover, we examined the protein‐protein interaction between ERα and β‐catenin by immunostain, co‐immunoprecipitation, and Western blotting. E2 enhanced the binding of ERα with β‐catenin and then triggered β‐catenin to bind with E3 ligase (βTrCP) to promote β‐catenin degradation. Finally by employing systematic ChIP studies, we showed ERα can interact directly with the β‐catenin promoter region following E2 treatment. All our results reveal that estrogen and ERα blocked metastatic function of HA22T cells by modulating GSK3β and βTrCP expression and further enhanced β‐catenin degradation and suppressed its downstream target genes. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 519–529, 2017.     

Agonist function of the recombinant α4β3δ GABAA receptor is dependent on the human and rat variants of the α4‐subunit

1. It is known that the α₄‐subunit is likely to occur in the brain predominantly in α₄β₃δ receptors at extrasynaptic sites. Recent studies have revealed that the α₁‐, α₄‐, γ₂‐ and δ‐subunits may colocalize extrasynaptically in dentate granule cells of the hippocampus. In the present study, we characterized a series of recombinant GABA_A receptors containing human (H) and rat (R) α₁/α₄‐, β₂/β₃‐ and γ_2S/δ‐subunits in Xenopus oocytes using the two‐electrode voltage‐clamp technique. 2. Both Hα₁β₃δ and Hα₄β₃γ_2S receptors were sensitive to activation by GABA and pentobarbital. Contrary to earlier findings that the α₄β₃δ combination was more sensitive to agonist action than the α₄β₃γ_2S receptor, we observed extremely small GABA‐ and pentobarbital‐activated currents at the wild‐type Hα₄β₃δ receptor. However, GABA and pentobarbital activated the wild‐type Rα₄β₃δ receptor with high potency (EC₅₀ = 0.5 ± 0.7 and 294 ± 5 μmol/L, respectively). 3. Substituting the Hα₄ subunit with Rα₄ conferred a significant increase in activation on the GABA and pentobarbital site in terms of reduced EC₅₀ and increased I_max. When the Hα₄ subunit was combined with the Rβ₃ and Rδ subunit in a heteropentameric form, the amplitude of GABA‐ and pentobarbital‐activated currents increased significantly compared with the wild‐type Hα₄β₃δ receptor. 4. Thus, the results indicate that the Rα₄β₃δ, Hα₁β₃δ and Hα₄β₃γ_2S combinations may contribute to functions of extrasynaptic GABA_A receptors. The presence of the Rα₄ subunit at recombinant GABA_A receptors containing the δ‐subunit is a strong determinant of agonist action. The recombinant Hα₄β₃δ receptor is a less sensitive subunit composition in terms of agonist activation.     

二烯丙基二硫诱导人胃癌细胞G_2/M期阻滞中p-CDK1、cyclin B1和p21~(WAF1)蛋白的表达

二烯丙基二硫(diallyl disulfide, DADS)是大蒜中提取的一种低分子量的脂溶性成分,也是大蒜中的主要有效成分,对结肠癌、乳腺癌、肝癌、肺癌、膀胱癌、前列腺癌和白血病等多种肿瘤均有明显的抑制作用.本实验室以前研究表明[1],DADS对人类白血病细胞HL60有诱导分化作用,对体外[2]和体内[3]的人胃癌MGC803细胞均有生长抑制作用、G2/M期阻滞作用.对体内的人胃癌细胞有诱导分化作用[3],对体外的人胃癌细胞有诱导凋亡作用[4].     

Specific α7 nicotinic acetylcholine receptor agonist ameliorates isoproterenol‐induced cardiac remodelling in mice through TGF‐β1/Smad3 pathway

It is well‐accepted that inflammation plays an important role in the development of cardiac remodelling and that therapeutic approaches targeting inflammation can inhibit cardiac remodelling. Although a large amount of evidence indicates that activation of α7 nicotinic acetylcholine receptor (α7nAChR) causes an anti‐inflammatory effect, the role of α7nAChR in cardiac remodelling and the underlying mechanism have not been established. To investigate the effect of the specific α7nAChR agonist, PNU282987, on cardiac remodelling induced by isoproterenol (ISO 60 mg/kg per day) in mice, the cardiomyocyte cross‐sectional area (CSA) and collagen volume fraction were evaluated by hematoxylin and eosin (HE) and Masson staining, respectively. Cardiac function and ventricular wall thickness were measured by echocardiography. The protein expressions of collagen I, matrix metalloproteinase 9 (MMP‐9), transforming growth factor β1 (TGF‐β1), and Smad3 were analyzed by Western blot. ISO‐induced cardiac hypertrophy, characterized by an increase in the heart weight/body weight ratio, CSA and ventricular wall thickness. Moreover, cardiac fibrosis indices, such as collagen volume fraction, MMP‐9 and collagen I protein expression, were also increased by ISO. PNU282987 not only attenuated cardiac hypertrophy but also decreased the cardiac fibrosis induced by ISO. Furthermore, PNU282987 suppressed TGF‐β1 protein expression and the phosphorylation of Smad3 induced by ISO. In conclusion, PNU282987 ameliorated the cardiac remodelling induced by ISO, which may be related to the TGF‐β1/Smad3 pathway. These data imply that the α7nAChR may represent a novel therapeutic target for cardiac remodelling in many cardiovascular diseases.     

NF‐κB/p53‐activated inflammatory response involves in diquat‐induced mitochondrial dysfunction and apoptosis

Inflammation generated by environmental toxicants including pesticides could be one of the factors underlying neuronal cell damage in neurodegenerative diseases. In this study, we investigated the mechanisms by which inflammatory responses contribute to apoptosis in PC12 cells treated with diquat. We found that diquat induced apoptosis, as demonstrated by the activation of caspases and nuclear condensation, inhibition of mitochondrial complex I activity, and decreased ATP level in PC12 cells. Diquat also reduced the dopamine level, indicating that cell death induced by diquat is due to cytotoxicity of dopaminergic neuronal components in these cells. Exposure of PC12 cells to diquat led to the production of reactive oxygen species (ROS), and the antioxidant N‐acetyl‐cystein attenuated the cytotoxicity of caspase‐3 pathways. These results demonstrate that diquat‐induced apoptosis is involved in mitochondrial dysfunction through production of ROS. Furthermore, diquat increased expression of cyclooxygenase‐2 (COX‐2) and tumor necrosis factor‐α (TNF‐α) via inflammatory stimulation. Diquat induced nuclear accumulation of NF‐κB and p53 proteins. Importantly, an inhibitor of NF‐κB nuclear translocation blocked the increase of p53. Both NF‐κB and p53 inhibitors also blocked the diquat‐induced inflammatory response. Pretreatment of cells with meloxicam, a COX‐2 inhibitor, also blocked apoptosis and mitochondrial dysfunction. These results represent a unique molecular characterization of diquat‐induced cytotoxicity in PC12 cells. Our results demonstrate that diquat induces cell damage in part through inflammatory responses via NF‐κB‐mediated p53 signaling. This suggests the potential to generate mitochondrial damage via inflammatory responses and inflammatory stimulation‐related neurodegenerative disease.     

Synthesis of 5,5,6,6‐D4‐L‐lysine‐aflatoxin Bl for use as a mass spectrometric internal standard

Human exposure to the hepatocarcinogenic mycotoxin aflatoxin B_l results in modification of serum albumin lysine ε‐amino residues to form lysine‐aflatoxin adducts. A perdeuterated reference standard is now required to quantitatively measure this adduct in epidemiologic studies of liver cancer using isotopic dilution mass spectrometry. A convenient method for the preparation of D4‐L ‐lysine‐AFB_l using commercially available 5,5,6,6‐D4‐l ‐lysine is demonstrated for the first time. The application of two standard α‐amino protection methods is also reported that simplifies the production of natural isotopic abundance lysine‐AFB_l over the currently used method employing N_α‐acetyl‐l ‐lysine. t‐Boc‐N_α‐lysine was used to prepare lysine‐AFB_l; however, a preferred method for directing reaction of AFB_l‐dialdehyde to the ε‐amino group of 5,5,6,6‐D4‐l ‐lysine utilized cupric ions that were spontaneously removed during the reverse phase HPLC purification of D4‐lysine‐AFB_l using 1% HOAc. This strategy eliminates the need to otherwise synthesize and purify t‐Boc‐N_α‐ or N_α‐acetyl‐5,5,6,6‐D4‐lysine and then TFA or enzymatically deprotect overnight to obtain the target compound. Copyright © 2004 John Wiley & Sons, Ltd.     

MiR‐21‐3p modulates lipopolysaccharide‐induced inflammation and apoptosis via targeting TGS4 in retinal pigment epithelial cells

Age‐related macular degeneration (AMD) is a major reason of blindness in the elderly. MicroRNAs are implicated in various pathological processes, including inflammation and apoptosis. In this study, we aim to investigate the biological functions of miR‐21‐3p in inflammation and apoptosis caused by lipopolysaccharide (LPS) in human retinal pigment epithelial (ARPE‐19) cells. The miR‐21‐3p inhibitor and mimic were transfected into ARPE‐19 cells for 48 hours, followed by exposed to LPS (10 μg/mL) for 24 hours. The mRNA and protein expression of IL‐6 and MCP‐1 were measured using real‐time PCR (RT‐PCR) and enzyme‐linked immunosorbent assays. Cell viability, apoptosis, caspase 3 activity, cleaved caspase‐3 and cleaved‐PARP protein levels were detected to evaluate the effects of miR‐21‐3p on apoptosis. Additionally, the target relationship between miR‐21‐3p and regulator of G‐protein signalling 4 (RGS4) was verified by dual luciferase reporter assay. RT‐PCR analysis demonstrated that LPS induced miR‐21‐3p expression. Inhibition of miR‐21‐3p reduced the mRNA and protein levels of IL‐6 and MCP‐1. Apoptosis, caspase‐3 activity, and cleaved‐caspase 3 and cleaved PARP protein levels were repressed by the miR‐21‐3p inhibitor. However, overexpression of miR‐21‐3p showed the opposite results. Furthermore, we identified that miR‐21‐3p directly targeted the 3′ untranslated region of RGS4. MiR‐21‐3p negatively regulated the expression of RGS4 both in mRNA and protein levels. Silencing RGS4 reduced the anti‐inflammatory and anti‐apoptotic effects of miR‐21‐3p inhibitor. Our results revealed that miR‐21‐3p inhibition targeted RGS4 to attenuate inflammatory responses and apoptosis caused by LPS in ARPE‐19 cells.     

Synthesis of [18F]3‐[1‐(3‐fluoropropyl)‐(S)‐pyrrolidin‐2‐ylmethoxy]pyridine ([18F]NicFP): a potential α4β2 nicotinic acetylcholine receptor radioligand for PET

Nicotinic acetylcholine receptors are widely distributed throughout the human brain and are believed to play a role in several neurological and psychiatric disorders. In order to identify an effective PET radioligand for in vivo assessment of the α4β2 subtype of nicotinic receptor, we synthesized [¹⁸F]3‐[1‐(3‐fluoropropyl)‐(S)‐pyrrolidin‐2‐ylmethoxy]pyridine (NicFP). The in vitro K_D of NicFP was determined to be 1.1 nM, and the log P value obtained by HPLC analysis of the unlabelled standard was found to be 2.2. The radiosynthesis of [¹⁸F]NicFP was carried out by a nucleophilic substitution reaction of anhydrous [¹⁸F]fluoride and the corresponding mesylate precursor. After purification by HPLC, the radiochemical yield was determined to be 11.3±2.1% and the specific activity was 0.47±0.18 Ci/μmol (EOS, n = 3). The time of synthesis and purification was 99±2 min. The final product was prepared as a sterile saline solution suitable for in vivo use. Copyright © 2003 John Wiley & Sons, Ltd.     

Cobalt oxide nanoparticles induced oxidative stress linked to activation of TNF‐α/caspase‐8/p38‐MAPK signaling in human leukemia cells

The purpose of this study was to determine the intracellular signaling transduction pathways involved in oxidative stress induced by nanoparticles in cancer cells. Activation of reactive oxygen species (ROS) has some therapeutic benefits in arresting the growth of cancer cells. Cobalt oxide nanoparticles (CoO NPs) are an interesting compound for oxidative cancer therapy. Our results showed that CoO NPs elicited a significant (P <0.05) amount of ROS in cancer cells. Co‐treatment with N‐aceyltine cystine (an inhibitor of ROS) had a protective role in cancer cell death induced by CoO NPs. In cultured cells, the elevated level of tumor necrosis factor‐alpha (TNF‐α) was noted after CoO NPs treatment. This TNF‐α persuaded activation of caspase‐8 followed by phosphorylation of p38 mitogen‐activated protein kinase and induced cell death. This study showed that CoO NPs induced oxidative stress and activated the signaling pathway of TNF‐α‐Caspase‐8‐p38‐Caspase‐3 to cancer cells. Copyright © 2015 John Wiley & Sons, Ltd.     

Blueberry (Vaccinium ashei Reade) extract ameliorates ovarian damage induced by subchronic cadmium exposure in mice: Potential δ‐ALA‐D involvement

Females are born with a finite number of oocyte‐containing follicles and ovary damage results in reduced fertility. Cadmium accumulates in the reproductive system, damaging it, and the cigarette smoke is a potential exposure route. Natural therapies are relevant to health benefits and disease prevention. This study verified the effect of cadmium exposure on the ovaries of mice and the blueberry extract as a potential therapy. Blueberry therapy was effective in restoring reactive species levels and δ‐aminolevulinate dehydratase activity, and partially improved the viability of cadmium‐disrupted follicles. This therapy was not able to restore the 17 β‐hydroxysteroid dehydrogenase activity. Extract HPLC evaluation indicated the presence of quercetin, quercitrin, isoquercetin, and ascorbic acid. Ascorbic acid was the major substance and its concentration was 620.24 µg/mL. Thus, cadmium accumulates in the ovaries of mice after subchronic exposure, inducing cellular damage, and the blueberry extract possesses antioxidant properties that could protect, at least in part, the ovarian tissue from cadmium toxicity. © 2015 Wiley Periodicals, Inc. Environ Toxicol 32: 188–196, 2017.     

Peroxisome proliferator‐activated receptor‐γ coactivator‐1α in muscle links metabolism to inflammation

1. In higher eukaryotes, metabolism and immunity are tightly coupled. However, whereas in evolutionary terms a compromised immune response due to undernourishment has been the predominant problem, the inflammatory response to obesity and other lifestyle‐associated diseases has increased in relevance in Western societies in the past 100 years. 2. Traditionally, fat tissue has been considered as the major source of pro‐inflammatory secreted factors in these pathologies. However, in recent years the contribution of other tissues to disease‐causing chronic inflammation has been increasingly appreciated. 3. Peroxisome proliferator‐activated receptor‐γ coactivator‐1α (PGC‐1α) is one of the key regulatory factors in active skeletal muscle. Aberrant expression of PGC‐1α in inactive muscle fibres could be linked to a sedentary lifestyle, persistent systemic inflammation and a higher risk for many chronic diseases. Accordingly, modulation of PGC‐1α activity in skeletal muscle may have a broad range of therapeutic effects. Here, recent advances in the understanding of the role of muscle PGC‐1α in health and disease are reviewed.     

Glucose suppresses IL‐1β‐induced MMP‐1 expression through the FAK,MEK, ERK,and AP‐1 signaling pathways

Osteoarthritis (OA) commonly affects the synovial joint and is characterized by degradation of articular cartilage. Increased matrix metalloproteinase (MMP) activity plays a major role in this degradation. Dextrose (D‐glucose) prolotherapy has shown promising activity in the treatment of different musculoskeletal disorders, including OA. However, little is known about the role of glucose on MMP inhibition in OA therapy. We found that stimulating chondrocytes with the proinflammatory cytokine interleukin‐1β (IL‐1β) increased the expression of MMP‐1, MMP‐3, and MMP‐13. Glucose reduced this increase in MMP‐1 expression, but had no effect upon MMP‐3 or MMP‐13 expression. Analyses using a focal adhesion kinase (FAK) inhibitor, MEK inhibitors (U0126 and PD98059), an ERK inhibitor, AP‐1 inhibitors (curcumin and tanshinone), or siRNAs demonstrated that the FAK, MEK, ERK, and AP‐1 pathways mediate IL‐1β‐induced increases in MMP‐1 expression. Glucose antagonized IL‐1β‐promoted phosphorylation of FAK, MEK, ERK, and c‐Jun. Thus, glucose decreased IL‐1β‐induced MMP‐1 expression through the FAK, MEK, ERK, and AP‐1 signaling cascades. These findings may provide a better understanding of the mechanisms of prolotherapy on inhibiting MMP expression.     

Radiosynthesis of the α4β2 nicotinic acetylcholine receptor ligand: 5‐((1‐[11C]‐methyl‐2‐(S)‐pyrrolidinyl)methoxy)‐2‐chloro‐3‐((E)‐2‐(2‐fluoropyridin‐4‐yl)vinyl)pyridine

5‐((1‐[¹¹C]‐methyl‐2‐(S)‐pyrrolidinyl)methoxy)‐2‐chloro‐3‐((E)‐2‐(2‐fluoropyridin‐4‐yl)‐vinyl)pyridine ([¹¹C]‐FPVC) was synthesized from [¹¹C]‐methyl iodide and the corresponding normethyl precursor. The average time of synthesis, purification, and formulation was 42 min with an average non‐decay‐corrected radiochemical yield of 19%. The average specific radioactivity was 359 GBq/µmol (9691 mCi/µmole) at end of synthesis (EOS). Copyright © 2006 John Wiley & Sons, Ltd.     

Protective effects of β‐sheet breaker α/β‐hybrid peptide against amyloid β‐induced neuronal apoptosis in vitro

Alzheimer's disease is most common neurodegenerative disorder and is characterized by increased production of soluble amyloid‐β oligomers, the main toxic species predominantly formed from aggregation of monomeric amyloid‐β (Aβ). Increased production of Aβ invokes a cascade of oxidative damages to neurons and eventually leads to neuronal death. This study was aimed to investigate the neuroprotective effects of a β‐sheet breaker α/β‐hybrid peptide (BSBHp) and the underlying mechanisms against Aβ₄₀‐induced neurotoxicity in human neuroblastoma SH‐SY5Y cells. Cells were pretreated with the peptide Aβ₄₀ to induce neurotoxicity. Assays for cell viability, cell membrane damage, cellular apoptosis, generation of reactive oxygen species (ROS), intracellular free Ca²⁺, and key apoptotic protein levels were performed in vitro. Our results showed that pretreatment with BSBHp significantly attenuates Aβ₄₀‐induced toxicity by retaining cell viability, suppressing generation of ROS, Ca²⁺ levels, and effectively protects neuronal apoptosis by suppressing pro‐apoptotic protein Bax and up‐regulating antiapoptotic protein Bcl‐2. These results suggest that α/β‐hybrid peptide has neuroprotective effects against Aβ₄₀‐induced oxidative stress, which might be a potential therapeutic agent for treating or preventing neurodegenerative diseases.