Inhibition of JNK and activation of the AMPK-Nrf2 axis by corosolic acid suppress osteolysis and oxidative stress

Effects of Oltipraz on the Glycolipid Metabolism and the Nrf2/HO-1 Pathway in Type 2 Diabetic Mice

Purpose

Oltipraz has various applications, including for treating cancer, liver fibrosis, and cirrhosis. However, its role in regulating metabolic processes, inflammation, oxidative stress, and insulin resistance in STZ-induced T2DM remains unclear. Hence, a comprehensive understanding of how oltipraz ameliorates diabetes, particularly inflammation and oxidative stress, is imperative.

Methods

The negative control (NC), T2DM model (T2DM), and T2DM models treated with oltipraz (OLTI) and metformin (MET) were constructed. The RNA sequencing (RNA-Seq) was performed on the pancreatic tissues. H&E staining was conducted on the liver and pancreatic tissues. The intraperitoneal glucose tolerance test (IPGTT), blood glucose and lipids, inflammatory factors, and oxidative stress indexes were measured. qPCR and Western blotting examined the nuclear factor erythroid-derived 2-like 2 (Nrf2)/ hemoglobin-1 (HO-1) signaling pathway, cell apoptosis-related genes, and Reg3g levels. Immunofluorescence (IF) analysis of the pancreas was performed to measure insulin secretion.

Results

A total of 256 DEGs were identified in OLTI_vs_T2DM, and they were mainly enriched in circadian rhythm, cAMP, AMPK, insulin, and MAPK signaling pathways. Moreover, Reg3g exhibits reduced expression in T2DM_vs_NC, and elevated expression in OLTI_vs_T2DM, yet remains unchanged in MET_vs_T2DM. OLTI reduced fasting blood glucose and alleviated T2DM-induced weight loss. It improved blood glucose and insulin resistance, decreased blood lipid metabolism, reduced inflammation and oxidative stress through the Nrf2/HO-1 signaling pathway, mitigated pancreatic and liver tissue injury, and enhanced pancreatic β-cell insulin secretion. OLTI exhibited anti-apoptosis effects in T2DM. Moreover, OLTI exhibits superior antioxidant activity than metformin.

Conclusion

In summary, OLTI improves blood glucose and insulin resistance, decreases blood lipid metabolism, reduces inflammation and apoptosis, suppresses oxidative stress through the Nrf2/HO-1 signaling pathway, mitigates pancreatic and liver tissue injury, and enhances pancreatic β-cell insulin secretion, thereby mitigating T2DM symptoms. Moreover, Reg3g could be an important target for OLTI treatment of T2DM.

A triterpenoid (corosolic acid) ameliorated AOM-mediated aberrant crypt foci in rats: modulation of Bax/PCNA, antioxidant and inflammatory mechanisms

Corosolic acid (CA) is a well-known natural pentacyclic triterpene found in numerous therapeutic plants that can exhibit many bioactivities including anti-inflammatory and anti-tumor actions. The current investigation explores the chemoprotective roles of CA against azoxymethane (AOM)-induced colonic aberrant crypt foci (ACF) in rats. Thirty Sprague Dawley rats were grouped in 5 cages; Group A, normal control rats inoculated subcutaneously (sc) with two doses of normal saline and fed orally on 10% tween 20; Groups B-E received two doses (sc) of azoxymethane in two weeks and treated with either 10% tween 20 (group B) or two intraperitoneal injections of 35 mg/kg 5-fluorouracil each week for one month (group C), while group D and E treated with 30 and 60 mg/kg, respectively, for 2 months. The toxicity results showed lack of any behavioral abnormalities or mortality in rats ingested with up-to 500 mg/kg of CA. The present AOM induction caused a significant initiation of ACF characterized by an increased number, larger in size, and well-matured tissue clusters in cancer controls. AOM inoculation created a bizarrely elongated nucleus, and strained cells, and significantly lowered the submucosal glands in colon tissues of cancer controls compared to 5-FU or CA-treated rats. CA treatment led to significant suppression of ACF incidence, which could be mediated by its modulatory effects on the immunohistochemical proteins (pro-apoptotic (Bax) and reduced PCNA protein expressions in colon tissues). Moreover, CA-treated rats had improved oxidative stress-mediated cytotoxicity indicated by increased endogenous antioxidants (SOD and CAT) and reduced lipid peroxidation indicators (MDA). In addition, CA ingestion (30 and 60 mg/kg) suppressed the inflammatory cascades, indicated by decreased serum TNF-α and IL-6 cytokines and increased anti-inflammatory (IL-10) cytokines consequently preventing further tumor development. CA treatment maintained liver and kidney functions in rats exposed to AOM cytotoxicity. CA could be a viable alternative for the treatment of oxidative-related human disorders including ACF.

Corosolic acid attenuates platelet-derived growth factor signaling in macrophages and smooth muscle cells of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a progressive and life-threatening disease that is characterized by vascular remodeling of the pulmonary artery. Pulmonary vascular remodeling is primarily caused by the excessive proliferation and migration of pulmonary arterial smooth muscle cells (PASMCs), which are facilitated by perivascular inflammatory cells including macrophages. Corosolic acid (CRA) is a natural pentacyclic triterpenoid that exerts anti-inflammatory effects. In the present study, the effects of CRA on the viability of macrophages were examined using monocrotaline (MCT)-induced PAH rats and human monocyte-derived macrophages. Although we previously reported that CRA inhibited signal transducer and activator of transcription 3 (STAT3) signaling and ameliorated pulmonary vascular remodeling in PAH, the inhibitory mechanism remains unclear. Therefore, the underlying mechanisms were investigated using PASMCs from idiopathic PAH (IPAH) patients. In MCT-PAH rats, CRA inhibited the accumulation of macrophages around remodeled pulmonary arteries. CRA reduced the viability of human monocyte-derived macrophages. In IPAH-PASMCs, CRA attenuated cell proliferation and migration facilitated by platelet-derived growth factor (PDGF)-BB released from macrophages and PASMCs. CRA also downregulated the expression of PDGF receptor β and its signaling pathways, STAT3 and nuclear factor-κB (NF-κB). In addition, CRA attenuated the phosphorylation of PDGF receptor β and STAT3 following the PDGF-BB simulation. The expression and phosphorylation levels of PDGF receptor β after the PDGF-BB stimulation were reduced by the small interfering RNA knockdown of NF-κB, but not STAT3, in IPAH-PASMCs. In conclusion, CRA attenuated the PDGF-PDGF receptor β-STAT3 and PDGF-PDGF receptor β-NF-κB signaling axis in macrophages and PASMCs, and thus, ameliorated pulmonary vascular remodeling in PAH.

Corosolic acid enhances oxidative stress-induced apoptosis and senescence in pancreatic cancer cells by inhibiting the JAK2/STAT3 pathway

BACKGROUND

Pancreatic cancer (PC) is a fatal human malignancy with a poor prognosis. Corosolic acid (CRA) is a triterpenoid, has been reported to have inhibitory effects on tumor growth. However, the role of CRA on PC has not been explored. Here, we aimed to uncover the molecular mechanisms of CRA in PC progression.

METHODS

Cell viability, lactate dehydrogenase (LDH) release, cell apoptosis and senescence were detected by cell counting kit-8 (CCK-8), LDH, flow cytometry and senescence associated-β-galactosidase (SA-β-gal) assay. Levels of relevant proteins and oxidative stress (OS) markers were evaluated by Western blot and enzyme-linked immunosorbent assay (ELISA). A xenograft tumor model was established to explore the in vivo effects of CRA on PC.

RESULTS

We found that CRA inhibited PC cell viability and promoted LDH release in a dose-dependent manner, but had no significant effect on human normal pancreatic ductal epithelial cells HPDE6C7. CRA increased OS-induced cell apoptosis and senescence in HAPC and SW1990 cells. And CRA decreased the levels of anti-apoptotic protein Bcl-2, and elevated the expression of pro-apoptotic protein Bax and senescence-associated proteins P21 and P53. Besides, CRA decreased tumor growth in xenograft models. Furthermore, CRA inactivated the Janus kinase-2 (JAK2)/Signal Transducer and Activator of Transcription 3 (STAT3) signaling pathway in HAPC and SW1990 cells. Functional experiments demonstrated that activation of the JAK2/STAT3 pathway by the JAK2 activator coumermycin A1 (C-A1) or the STAT3 activator colivelin (col) reduced the contribution effect of OS, apoptosis and senescence by CRA.

CONCLUSION

Taken together, our findings indicated that CRA exerted anti-cancer effects in PC by inhibiting the JAK2/STAT3 pathway.

Map4k4 is up-regulated and modulates granulosa cell injury and oxidative stress in polycystic ovary syndrome via activating JNK/c-JUN pathway: An experimental study

The regulatory mechanism on granulosa cells (GCs) oxidative injury is becoming increasingly important in polycystic ovary syndrome (PCOS) studies. Serine/threonine kinase mitogen-activated protein 4 kinase 4 (Map4k4) is linked with oxidative injury and possibly associated with premature ovarian failure and ovarian dysgenesis. Herein, we investigated the function and mechanism of Map4k4 in a PCOS rat model. A microarray from GEO database identified Map4k4 was up-regulated in the ovarian of PCOS rats, and functional enrichments suggested that oxidative stress-associated changes are involved. We verified the raised Map4k4 expression in an established PCOS rat model and also in the isolated PCOS-GCs, which were consistent with the microarray data. Map4k4 knockdown in vivo contributed to regular estrous cycle, restrained steroid concentrations and ovarian injury in PCOS rats. Both Map4k4 silencing in vivo and in vitro attenuated the PCOS-related GC oxidative stress and apoptosis. Mechanically, Map4k4 activated the JNK/c-JUN signaling pathway. Importantly, a JNK agonist restored the suppressive effects of Map4k4 silencing on PCOS-induced granulosa cell injury and oxidative stress. Besides, Map4k4 may be a target gene of miR-185-5p. In conclusion, Map4k4, a potential target of miR-185-5p, is up-regulated and induces ovarian GC oxidative injury by activating JNK/c-JUN pathway in PCOS. The Map4k4/JNK/c-JUN mechanism may provide a new idea on the treatment of PCOS.

Structural characterization and anti-osteoporosis effects of polysaccharide purified from Eucommia ulmoides Oliver cortex based on its modulation on bone metabolism

EuOCP3, with a molecular weight of 38.1 kDa, is an acidic polysaccharide purified from Eucommia ulmoides Oliver cortex. Herein, we determined that the main backbone of EuOCP3 was predominantly composed of →4)-α-GalpA-(1 → 4)-α-GalpA-(1→, →4)-α-GalpA-(1 → 5)-α-Araf-(1→, →4)-α-GalpA-(1 → 2)-α-Rhap-(1→, and →4)-α-GalpA-(1 → 5)-α-Araf-(1 → 2)-α-Rhap-(1 → repeating blocks, which were connected by →2,3,5)-α-Araf-(1→. The side chains, substituted at C-2 and C-5 of →2,3,5)-α-Araf-(1→, contained T-β-Araf→ and T-β-Araf → 4)-α-GalpA-(1 → residues. In dexamethasone (Dex)-induced osteoporosis (OP) mice, EuOCP3 treatment restored cortical bone thickness, increased mineralized bone area, enhanced the number of osteoblasts, and decreased the number of osteoclasts on the surface of cortical bone. Combining analysis of gut microflora, serum metabolite profiles, and biological detection results, we demonstrated that EuOCP3 regulated the abundance of specific species within the gut microflora, such as g_Dorea and g_Prevotella, and ameliorated oxidative stress. In turn, enhancement of osteogenic function and restoration of bone metabolism via the extracellular signal-regulated kinase (ERK)/c-Jun N-terminal kinase (JNK)/nuclear factor erythroid-2 related factor 2 (Nrf2) signaling pathway was indicated. The current findings contribute to understanding the potential of EuOCP3 in anti-OP treatment.

High fructose-induced skeletal muscle insulin resistance could be alleviated by berberine via AMPD1 and ADSL

AMP-activated protein kinase (AMPK) is a master regulator of energy homeostasis that is activated in response to an elevated intracellular AMP/ATP ratio. Although many studies have shown berberine is an AMPK activator widely used in metabolic syndrome, how to properly control AMPK activity remains obscure. Our present study aimed to examine the protective effect of berberine against fructose-induced insulin resistance in rats and L6 cells, as well as its potential activation mechanism on AMPK. The results showed that berberine effectively reversed body weight gain, Lee's index, dyslipidemia and insulin intolerance. Moreover, berberine alleviated inflammatory response, antioxidant capacity and promoted glucose uptake in vivo and in vitro. The beneficial effect was associated with upregulation of both Nrf2 and AKT/GLUT4 pathways, which were regulated by AMPK. Notably, berberine could increase the level of AMP and the ratio of AMP/ATP, then further activate AMPK. Mechanistic experiments revealed that berberine suppressed the expression of adenosine monophosphate deaminase 1 (AMPD1) and promoted the expression of adenylosuccinate synthetase (ADSL). Taken together, berberine exerted excellent therapeutic effect on insulin resistance. And its mode of action may be related to the AMP-AMPK pathway by regulating AMPD1 and ADSL.

LncRNA MHRT Prevents Angiotensin II-Induced Myocardial Oxidative Stress and NLRP3 Inflammasome via Nrf2 Activation

The development of angiotensin II (Ang II)-induced cardiomyopathies is reportedly mediated via oxidative stress and inflammation. Nuclear factor erythroid 2-related factor (Nrf2) is an important regulator of cellular antioxidant defense, and reactive oxygen species (ROS) can activate the NLRP3 inflammasome. MHRT is a newly discovered lncRNA exhibiting cardioprotective effects, demonstrated by inhibiting myocardial hypertrophy via Brg1 and myocardial apoptosis via Nrf2 upregulation. However, the underlying mechanism of MHRT remains unclear. We explored the potential protective effects of MHRT against Ang II-induced myocardial oxidative stress and NLRP3-mediated inflammation by targeting Nrf2. Chronic Ang II administration induced NLRP3 inflammasome activation (increased NLRP3, caspase-1 and interleukin-1β expression), oxidative stress (increased 3-nitrotyrosine and 4-hydroxy-2-nonenal), cardiac dysfunction and decreased MHRT and Nrf2 expression. Lentivirus-mediated MHRT overexpression inhibited Ang II (100 nM)-induced oxidative stress and NLRP3 inflammasome activation in AC16 human cardiomyocyte cells. Mechanistically, MHRT overexpression upregulated the expression and function of Nrf2, as determined by the increased transcription of downstream genes HO-1 and CAT, subsequently decreasing intracellular ROS accumulation and inhibiting the expression of thioredoxin-interacting protein (NLRP3 activator) and its direct binding to NLRP3. Accordingly, MHRT could protect against Ang II-induced myocardial injury by decreasing oxidative stress and NLRP3 inflammasome activation via Nrf2 activation.

Corosolic acid ameliorates vascular remodeling in pulmonary arterial hypertension via the downregulation of STAT3 signaling

Pulmonary arterial hypertension (PAH) is a progressive and fatal disease that is characterized by vascular remodeling of the pulmonary artery. PAH remodeling is primarily caused by the excessive proliferation of pulmonary arterial smooth muscle cells (PASMCs). Therefore, an inhibitory mechanism is expected as a target for the treatment of PAH. Corosolic acid (CRA) is a pentacyclic triterpenoid extracted from the leaves of Banaba (Lagerstroemia speciosa) that exerts anti-diabetic, anti-inflammatory, and anti-tumor effects. In the present study, the effects of CRA on PAH remodeling were examined using PASMCs from idiopathic pulmonary arterial hypertension (IPAH) patients and monocrotaline (MCT)-induced pulmonary hypertensive (PH) rats. CRA inhibited the excessive proliferation of IPAH-PASMCs in a concentration-dependent manner (IC₅₀ = 14.1 μM). It also reduced the migration of IPAH-PASMCs. The CRA treatment downregulated the expression of signal transducer and activator of transcription 3 (STAT3) in IPAH-PASMCs. In MCT-PH rats, the administration of CRA (1 mg/kg/day) attenuated increases in right ventricular systolic pressure, pulmonary vascular remodeling, and right ventricular hypertrophy. CRA also decreased the expression of STAT3 in pulmonary arterial smooth muscles from MCT-PH rats. In conclusion, the anti-proliferative and anti-migratory effects of CRA in PASMCs ameliorated PAH remodeling by downregulating STAT3 signaling pathways.

Hyperoside Ameliorates Renal Tubular Oxidative Damage and Calcium Oxalate Deposition in Rats through AMPK/Nrf2 Signaling Axis

Background

Nephrolithiasis is a common disease that seriously affects the health and life quality of patients. Despite the reported effect of hyperoside (Hyp) against nephrolithiasis, the specific mechanism has not been clarified. Therefore, this study is aimed at investigating the effect and potential mechanism of Hyp on renal injury and calcium oxalate (CaOx) crystal deposition.

Methods

Rat and cell models of renal calculi were constructed by ethylene glycol (EG) and CaOx induction, respectively. The renal histopathological damage, CaOx crystal deposition, and renal function damage of rats were assessed by HE staining, Pizzolato staining, and biochemical detection of blood and urine parameters. MTT and crystal-cell adhesion assays were utilized to determine the activity of HK-2 cells and crystal adhesion ability, biochemical detection and enzyme-linked immunosorbent assay (ELISA) to measure the levels of oxidative stress-related substances and inflammatory factors, and western blot to test the expression levels of proteins related to the AMPK/Nrf2 signaling pathway.

Results

Briefly speaking, Hyp could improve the renal histopathological injury and impaired renal function, reduce the deposition of CaOx crystals in the renal tissue of rats with renal calculi, and decrease the adhesion of crystals to CaOx-treated HK-2 cells. Besides, Hyp also significantly inhibited oxidative stress response. Furthermore, Hyp was associated with the downregulation of malondialdehyde, lactate dehydrogenase, and reactive oxygen species and upregulation of superoxide dismutase activity. Additionally, Hyp treatment also suppressed inflammatory response and had a correlation with declined levels of interleukin (IL)-1β, IL-6, IL-8, and tumor necrosis factor. Further exploration of mechanism manifested that Hyp might play a protective role through promoting AMPK phosphorylation and nuclear translation of Nrf2 to activate the AMPK/Nrf2 signaling pathway.

Conclusion

Hyp can improve renal pathological and functional damage, decrease CaOx crystal deposition, and inhibit oxidative stress and inflammatory response. Such effects may be achieved by activating the AMPK/Nrf2 signaling pathway.

How zoledronic acid improves osteoporosis by acting on osteoclasts

Osteoporosis is called a silent disease, because it is difficult to detect until comprehensive examinations for osteoporosis are performed or osteoporotic fractures occur. Zoledronic acid is currently the first-line anti-osteoporotic drug, with good efficacy and treatment compliance. A major advantage of zoledronic acid is that intravenous zoledronic acid often guarantees a therapeutic effect for up to 1 year after infusion. The reasons why zoledronic acid is effective in improving osteoporosis are that it can inhibit osteoclast differentiation and induce osteoclast apoptosis, thus suppressing bone resorption and increasing bone density. The story between zoledronic acid and osteoclasts has been written long time ago. Both the canonical receptor activator of the receptor activator of nuclear factor-κB ligand (RANKL) pathway and the non-canonical Wnt pathway are the main pathways by which zoledronic acid inhibits osteoclast differentiation. Farnesyl pyrophosphate synthase (FPPS), reactive oxygen species (ROS), and ferroptosis that was first proposed in 2012, are all considered to be closely associated with zoledronic acid-induced osteoclast apoptosis. Here, we provide a brief review of the recent progress on the study of zoledronic acid and osteoclasts, and hope to elaborate how zoledronic acid improves osteoporosis by acting on osteoclasts.

23-Hydroxyursolic acid from Viburnum lutescens inhibits osteoclast differentiation in vitro and lipopolysaccharide-induced bone loss in vivo by suppressing c-Fos and NF-κB signalling

Bone homeostasis is maintained by a combination of osteoclast-mediated bone resorption and osteoblast-mediated bone formation. Excessive osteoclast activity is linked to several bone-related disorders, including osteoporosis and rheumatoid arthritis. Pharmacological therapy might have a number of adverse effects. Therefore, the development of natural anti-osteoclastogenic drugs with greater efficacy and fewer adverse effects is desirable. In this study, the anti-osteoclastogenic effects of 23-hydroxyursolic acid (HUA), a triterpene isolated from Viburnum lutescens, were investigated in vitro and in vivo. HUA significantly inhibited receptor activator of nuclear factor kappa-B ligand (RANKL)-induced mature osteoclast differentiation by reducing the number of tartrate-resistant acid phosphatase (TRAP)-positive osteoclasts and F-actin ring formation. It also inhibited the expression of osteoclast-specific marker genes such OSCAR, MMP-9, TRAP, DC-STAMP, and CtsK, as well as transcription factors, c-Fos and nuclear factor of activated T cells cytoplasmic 1 (NFATc1) in response to RANKL. Mice orally administered with HUA (25 and 50 mg/kg) exhibited significant protection against bone loss and osteoclast formation induced by lipopolysaccharide (LPS). HUA suppressed RANKL-induced nuclear factor kappa B (NF-κB) activation and phosphorylation of JNK and ERK mitogen-activated protein kinases (MAPKs). These results suggest that HUA attenuates osteoclast formation in vitro and in vivo by suppressing the RANKL-mediated AP1, NF-κB, and NFATc1 pathways. Therefore, HUA may be a lead compound for the prevention or treatment of osteolytic bone disorders.

Fucoidan-loaded nanofibrous scaffolds promote annulus fibrosus repair by ameliorating the inflammatory and oxidative microenvironments in degenerative intervertebral discs

Tissue engineering holds potential in the treatment of intervertebral disc degeneration (IDD). However, implantation of tissue engineered constructs may cause foreign body reaction and aggravate the inflammatory and oxidative microenvironment of the degenerative intervertebral disc (IVD). In order to ameliorate the adverse microenvironment of IDD, in this study, we prepared a biocompatible poly (ether carbonate urethane) urea (PECUU) nanofibrous scaffold loaded with fucoidan, a natural marine bioactive polysaccharide which has great anti-inflammatory and antioxidative functions. Compared with pure PECUU scaffold, the fucoidan-loaded PECUU nanofibrous scaffold (F-PECUU) decreased the gene and protein expression related to inflammation and the oxidative stress in the lipopolysaccharide (LPS) induced annulus fibrosus cells (AFCs) significantly (p<0.05). Especially, gene expression of Ill 6 and Ptgs2 was decreased by more than 50% in F-PECUU with 3.0 wt% fucoidan (HF-PECUU). Moreover, the gene and protein expression related to the degradation of extracellular matrix (ECM) were reduced in a fucoidan concentration-dependent manner significantly, with increased almost 3 times gene expression of Col1a2 and Acan in HF-PECUU. Further, in a 'box' defect model, HF-PECUU decreased the expression of COX-2 and deposited more ECM between scaffold layers when compared with pure PECUU. The disc height and nucleus pulposus hydration of repaired IVD reached up to 75% and 85% of those in the sham group. In addition, F-PECUU helped to maintain an integrate tissue structure with a similar compression modulus to that in sham group. Taken together, the F-PECUU nanofibrous scaffolds showed promising potential to promote AF repair in IDD treatment by ameliorating the harsh degenerative microenvironment. STATEMENT OF SIGNIFICANCE: Annulus fibrosus (AF) tissue engineering holds potential in the treatment of intervertebral disc degeneration (IDD), but is restricted by the inflammatory and oxidative microenvironment of degenerative disc. This study developed a biocompatible polyurethane scaffold (F-PECUU) loaded with fucoidan, a marine bioactive polysaccharide, for ameliorating IDD microenvironment and promoting disc regeneration. F-PECUU alleviated the inflammation and oxidative stress caused by lipopolysaccharide and prevented extracellular matrix (ECM) degradation in AF cells. In vivo, it promoted ECM deposition to maintain the height, water content and mechanical property of disc. This work has shown the potential of marine polysaccharides-containing functional scaffolds in IDD treatment by ameliorating the harsh microenvironment accompanied with disc degeneration.

Cancer Chemopreventive Role of Dietary Terpenoids by Modulating Keap1-Nrf2-ARE Signaling System—A Comprehensive Update

ROS, RNS, and carcinogenic metabolites generate excessive oxidative stress, which changes the basal cellular status and leads to epigenetic modification, genomic instability, and initiation of cancer. Epigenetic modification may inhibit tumor-suppressor genes and activate oncogenes, enabling cells to have cancer promoting properties. The nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor that in humans is encoded by the NFE2L2 gene, and is activated in response to cellular stress. It can regulate redox homoeostasis by expressing several cytoprotective enzymes, including NADPH quinine oxidoreductase, heme oxygenase-1, UDP-glucuronosyltransferase, glutathione peroxidase, glutathione-S-transferase, etc. There is accumulating evidence supporting the idea that dietary nutraceuticals derived from commonly used fruits, vegetables, and spices have the ability to produce cancer chemopreventive activity by inducing Nrf2-mediated detoxifying enzymes. In this review, we discuss the importance of these nutraceuticals in cancer chemoprevention and summarize the role of dietary terpenoids in this respect. This approach was taken to accumulate the mechanistic function of these terpenoids to develop a comprehensive understanding of their direct and indirect roles in modulating the Keap1-Nrf2-ARE signaling system.

Canagliflozin Improves Liver Function in Rats by Upregulating Asparagine Synthetase

INTRODUCTION

Canagliflozin (CANA) is a sodium-glucose cotransporter 2 inhibitor that was recently approved for treating diabetes. However, its effects on liver function are not well understood. The function of asparagine synthetase (ASNS) has been studied in several cancers but not in liver injury. Therefore, we investigated the connection between CANA and ASNS in alleviating damage (i.e., their hepatoprotective effect) in a rat liver injury model.

METHODS

The rat model of liver injury was established using carbon tetrachloride treatment. Rats with liver injury were administered CANA orally for 8 weeks daily. After week 8, peripheral blood was collected to measure serum alanine aminotransferase, aspartate aminotransferase, and lactate dehydrogenase levels. Liver histopathology was examined using hematoxylin and eosin staining to determine the degree of liver injury. Protein expression in the rat livers was examined using Western blotting.

RESULTS

CANA treatment decreased serum alanine aminotransferase, aspartate aminotransferase, and lactate dehydrogenase levels compared with those of the untreated group, demonstrating diminished liver injury. Mechanistically, CANA treatment activated AMP-activated protein kinase (AMPK), leading to increased nuclear translocation of nuclear factor erythroid 2-related factor 2 (Nrf2) and activating transcription factor 4 (ATF4), which upregulated ASNS expression in liver-injured rats.

CONCLUSION

CANA significantly alleviated liver injury by activating the AMPK/Nrf2/ATF4 axis and upregulating ASNS expression, indicating its potential for treating patients with type 2 diabetes mellitus with impaired liver function.

Effect of Oxidative Stress on Bone Remodeling in Periprosthetic Osteolysis

The success of implant performance and arthroplasty is based on several factors, including oxidative stress-induced osteolysis. Oxidative stress is a key factor of the inflammatory response. Implant biomaterials can release wear particles which may elicit adverse reactions in patients, such as local inflammatory response leading to tissue damage, which eventually results in loosening of the implant. Wear debris undergo phagocytosis by macrophages, inducing a low-grade chronic inflammation and reactive oxygen species (ROS) production. In addition, ROS can also be directly produced by prosthetic biomaterial oxidation. Overall, ROS amplify the inflammatory response and stimulate both RANKL-induced osteoclastogenesis and osteoblast apoptosis, resulting in bone resorption, leading to periprosthetic osteolysis. Therefore, a growing understanding of the mechanism of oxidative stress-induced periprosthetic osteolysis and anti-oxidant strategies of implant design as well as the addition of anti-oxidant agents will help to improve implants’ performances and therapeutic approaches.

Retinal oxidative stress activates the NRF2/ARE pathway: An early endogenous protective response to ocular hypertension

Oxidative stress contributes to degeneration of retinal ganglion cells and their axons in glaucoma, a leading cause of irreversible blindness worldwide, through sensitivity to intraocular pressure (IOP). Here, we investigated early elevations in reactive oxygen species (ROS) and a role for the NRF2-KEAP1-ARE endogenous antioxidant response pathway using microbead occlusion to elevate IOP in mice. ROS levels peaked in the retina at 1- and 2-wks following IOP elevation and remained elevated out to 5-wks. Phosphorylation of NRF2 and antioxidant gene transcription and protein levels increased concomitantly at 2-wks after IOP elevation, along with phosphorylation of PI3K and AKT. Inhibiting PI3K or AKT signaling prevented NRF2 phosphorylation and reduced transcription of antioxidant-regulated genes. Ocular hypertensive mice lacking Nrf2 had elevated ROS and a diminished increase in antioxidant gene expression. They also exhibited earlier axon degeneration and loss of visual function. In conclusion, the NRF2-KEAP1-ARE pathway is endogenously activated early in ocular hypertension due to phosphorylation of NRF2 by the PI3K/AKT pathway and serves to slow the onset of axon degeneration and vision loss in glaucoma. These data suggest that exogenous activation of this pathway might further slow glaucomatous neurodegeneration.

Corosolic acid ameliorates cardiac hypertrophy via regulating autophagy

Aim: In this work, we explored the role of corosolic acid (CRA) during pressure overload-induced cardiac hypertrophy. Methods and results: Cardiac hypertrophy was induced in mice by aortic banding. Four weeks post-surgery, CRA-treated mice developed blunted cardiac hypertrophy, fibrosis, and dysfunction, and showed increased LC3 II and p-AMPK expression. In line with the in vivo studies, CRA also inhibited the hypertrophic response induced by PE stimulation accompanying with increased LC3 II and p-AMPK expression. It was also found that CRA blunted cardiomyocyte hypertrophy and promoted autophagy in Angiotensin II (Ang II)-treated H9c2 cells. Moreover, to further verify whether CRA inhibits cardiac hypertrophy by the activation of autophagy, blockade of autophagy was achieved by CQ (an inhibitor of the fusion between autophagosomes and lysosomes) or 3-MA (an inhibitor of autophagosome formation). It was found that autophagy inhibition counteracts the protective effect of CRA on cardiac hypertrophy. Interestingly, AMPK knockdown with AMPKα2 siRNA-counteracted LC3 II expression increase and the hypertrophic response inhibition caused by CRA in PE-treated H9c2 cells. Conclusion: These results suggest that CRA may protect against cardiac hypertrophy through regulating AMPK-dependent autophagy.

Puerarin Exerts Protective Effects on Wear Particle-Induced Inflammatory Osteolysis

Wear particle-stimulated inflammatory bone destruction and the consequent aseptic loosening remain major postoperative problems for artificial joints. Studies have indicated that puerarin promotes osteogenesis and alleviates lipopolysaccharide-induced osteoclastogenesis in vitro. However, the underlying molecular mechanism by which puerarin interacts with receptor activator of nuclear factor kappa-B ligand (RANKL)-mediated osteoclast formation in vitro and wear particle-stimulated osteolysis in vivo has not been reported. In this work, the protective effects exerted by puerarin on titanium particle-stimulated bone destruction in vivo and on RANKL-induced osteoclast activation in osteoclastic precursor cells in vitro were investigated. As expected, puerarin significantly inhibited wear particle-mediated bone resorption and proinflammatory cytokine productions in a calvarial resorption model. Additionally, puerarin inhibited RANKL-induced osteoclast activation, bone resorption ability, and F-actin ring formation in vitro as puerarin concentration increased. Furthermore, mechanistic investigation indicated that reduced RANKL-stimulated MEK/ERK/NFATc1 signaling cascades might regulate the protective effect of puerarin. Conclusively, these results indicate that puerarin, a type of polyphenol, might serve as a protective agent to prevent osteoclast-related osteolytic diseases.