4-Phenylbutyric acid regulates CCl4-induced acute hepatic dyslipidemia in a mouse model: A mechanism-based PK/PD study

Endoplasmic Reticulum Stress Induces ROS Production and Activates NLRP3 Inflammasome Via the PERK-CHOP Signaling Pathway in Dry Eye Disease

Purpose

The purpose of this study was to investigate the potential roles of endoplasmic reticulum (ER) stress in the development of dry eye disease (DED).

Methods

Single-cell RNA sequencing (scRNA-seq) data from the Gene Expression Omnibus (GEO) database, derived from corneal tissues of a dry eye mouse model, was processed using the Seurat R program. The results were validated using a scopolamine-induced dry eye mouse model and a hyperosmotic-induced cell model involving primary human corneal epithelial cells (HCECs) and immortalized human corneal epithelial (HCE-2) cells. The HCE-2 cells were treated with 4-phenylbutyric acid (4-PBA) or tunicamycin (TM) to modulate ER stress. TXNIP and PERK knockdown were performed by siRNA transfection. Immunofluorescence, Western blotting, and real-time PCR were used to assess oxidative stress, ER stress, unfolded protein response (UPR) marker proteins, and TXNIP/NLRP3 axis activation.

Results

The analysis of scRNAseq data shows an increase in the ER stress marker GRP78, and the activation of the PERK-CHOP of UPR in DED mouse. These findings were confirmed both in vivo and in vitro. Additionally, HCE-2 cells treated with 4-PBA or TM showed significant effects on the production of reactive oxygen species (ROS) and the activation of the TXNIP/NLRP3-IL1β signaling pathway. Furthermore, siRNA knockdown of PERK or TXNIP, which alleviated the TXNIP/NLRP3-IL1β signaling axis, showed protective effects on HCECs.

Conclusions

This study explores the role of ER stress-induced oxidative stress and NLRP3-IL-1β mediated inflammation in DED, and highlights the therapeutic potential of PERK-CHOP axis and TXNIP in the treatment of DED.

Deoxynivalenol-mediated kidney injury via endoplasmic reticulum stress in mice

OBJECTIVE

Deoxynivalenol (DON) is a common fungal toxin that poses significant health risks to humans and animals. The present study aimed to investigate the adverse effects and molecular mechanisms of DON-induced kidney injury.

METHODS

Male C57BL/6 mice aged 5-6 weeks were used to establish a DON-induced acute kidney injury model. Histological analysis, biochemical assays, molecular techniques, Western blot, RNA sequencing, and transmission electron microscopy were employed to analyze kidney damage, inflammation, oxidative stress, apoptosis, and endoplasmic reticulum (ER) stress.

RESULTS

DON disrupted kidney morphology, induced inflammatory cell infiltration, and triggered inflammatory responses. DON increased MDA content while decreasing antioxidant enzyme activity (SOD and CAT). It also triggered apoptosis, evidenced by elevated levels of caspase-12, cleaved caspase-3, and BAX, and reduced levels of Bcl-2. Transcriptomic analysis identified distinct expression patterns in 1756 genes in DON-exposed mouse kidneys, notably upregulating ER stress-related genes. Further investigation revealed ultrastructural changes in the ER and mitochondrial damage induced by DON, along with increased levels of p-IRE1, p-PERK, and their downstream targets, indicating unfolded protein response (UPR) activation in the kidney. The ER stress inhibitor 4-Phenylbutyric acid (4-PBA) significantly mitigated DON-induced ER stress, oxidative damage, apoptosis, tissue injury, ER expansion, and mitochondrial damage.

CONCLUSION

Our findings highlight the role of ER stress in DON-induced kidney injury and the protective effect of 4-PBA against these adverse effects.

Deoxynivalenol-Induced Spleen Toxicity in Mice: Inflammation, Endoplasmic Reticulum Stress, Macrophage Polarization, and the Dysregulation of LncRNA Expression

The spleen is a primary target of deoxynivalenol (DON) toxicity, but its underlying molecular mechanisms remain unclear. This study investigates the effects of DON on inflammation, splenic macrophage polarization, endoplasmic reticulum (ER) stress, and transcriptome changes (mRNA and lncRNAs) in mouse spleen. We found that DON exposure at doses of 2.5 or 5 mg/kg BW significantly induced inflammation and polarized splenic macrophages towards the M1 phenotype. Additionally, DON activated PERK-eIF2α-ATF4-mediated ER stress and upregulated apoptosis-related proteins (caspase-12, caspase-3). The ER stress inhibitor, 4-Phenylbutyric acid, significantly alleviated DON-induced ER stress, apoptosis, and the M1 polarization of splenic macrophages. Transcriptome analysis identified 1968 differentially expressed (DE) lncRNAs and 2664 DE mRNAs in mouse spleen following DON exposure. Functional enrichment analysis indicated that the upregulated genes were involved in pathways associated with immunity, including Th17 cell differentiation, TNF signaling, and IL-17 signaling, while downregulated mRNAs were linked to cell survival and growth pathways. Furthermore, 370 DE lncRNAs were predicted to target 255 DE target genes associated with immune processes, including the innate immune response, interferon-beta response, cytokine production regulation, leukocyte apoptosis, and NF-κB signaling genes. This study provides new insights into the mechanisms underlying DON toxicity and its effects on the immune system.

Can endoplasmic reticulum stress observed in the PTZ-kindling model seizures be prevented with TUDCA and 4-PBA?

Epilepsy is a chronic neurological disease with recurrent seizures. Increasing evidence suggests that endoplasmic reticulum (ER) stress may play a role in the pathogenesis of epilepsy. We aimed to investigate the effects of Tauroursodeoxycholic acid (TUDCA) and 4-phenyl-butyric acid (4-PBA), which are known to suppress ER stress, on developed seizures in terms of markers of ER stress, oxidative stress, and apoptosis. The pentylenetetrazole (PTZ) kindling model was induced in Wistar albino rats (n = 48) by administering 35 mg/kg PTZ intraperitoneally (I.P.) every other day for 1 month. TUDCA and 4-PBA were administered via I.P. at a dose of 500 mg/kg dose. ER stress, apoptosis, and oxidative stress were determined in the hippocampus tissues of animals in all groups. Immunohistochemistry, qRT-PCR, ELISA, and Western Blot analyzes were performed to determine the efficacy of treatments. Expressions of ATF4, ATF6, p-JNK1/2, Cleaved-Kaspase3, and Caspase12 significantly increased in PTZ-kindled seizures compared to the control group. Increased NOX2 and MDA activity in the seizures were measured. In addition, stereology analyzes showed an increased neuronal loss in the PTZ-kindled group. qRT-PCR examination showed relative mRNA levels of CHOP. Accordingly, TUDCA and 4-PBA treatment suppressed the expressions of ATF4, ATF6, Cleaved-Caspase3, Kaspase12, NOX2, MDA, and CHOP in TUDCA + PTZ and 4-PBA + PTZ groups. ER stress-induced oxidative stress and apoptosis by reducing neuronal loss and degeneration were also preserved in these groups. Our data show molecularly that TUDCA and 4-PBA treatment can suppress the ER stress process in epileptic seizures.

Lipid metabolic disturbance induced by triphenyl phosphate and hydroxy metabolite in HepG2 cells

Triphenyl phosphate (TPHP) has been widely used as flame retardants and been detected with increasing frequency in environment. TPHP can transform into mono-hydroxylated phosphate (OH-TPHP) and diester diphenyl phosphate (DPHP) through biotransformation. So far, information on the cytotoxicity and molecular regulatory mechanisms of TPHP metabolites are still limit. This study investigated the adverse effects of TPHP, OH-TPHP, and DPHP in HepG2 cells in terms of cell proliferation, lactate dehydrogenase release, reactive oxygen species generation, and mitochondrial membrane potential. The transcriptomic changes were measured using RNA sequencing, and bioinformatics characteristics including biological functions, signal pathways and protein-protein interaction were analyzed to explore the potential molecular mechanisms. Results displayed that the order of cytotoxicity was OH-TPHP> TPHP> DPHP. The prioritized biological functions changes induced by TPHP and OH-TPHP were correlated with lipid metabolism. Significant lipid accumulation was observed as confirmed by increased total cholesterol and triglycerides contents, and enhanced oil red O staining. Enrichment of PPARα/γ and down-stream genes suggested the participation of PPARs signal pathway in lipid metabolism disorder. In addition, TPHP and OH-TPHP induced endoplasmic reticulum stress (ERS), which was further confirmed by the ERS inhibitor experiment. In general, TPHP and OH-TPHP had obvious cytotoxic effects in HepG2 cells. PPARs signal pathway and endoplasmic reticulum stress may be involved in the lipid metabolism disorder induced by TPHP and OH-TPHP.

4-Phenylbutyric acid alleviated 3-acetyldeoxynivalenol-induced immune cells response by inhibiting endoplasmic reticulum stress in mouse spleen

3-Acetyldeoxynivalenol (3-Ac-DON), an acetylated derivative of deoxynivalenol (DON), has contaminated grains and grain-based products in general and been harmful to human and animal health. However, the damage effects and regulatory mechanisms to the host immune system have not been well explored. In the present study, our results revealed that 3-Ac-DON significantly decreased spleen index, elevated MPO activity, upregulated mRNA and protein levels of IL-1α, IL-1β, IL-6, IL-17A, TNF-α, M-CSF, G-CSF, CCL2, IFN-β, and IL-10 in the spleen and serum. Interestingly, 4-phenylbutyric acid (4-PBA), an inhibitor of endoplasmic reticulum (ER) stress, largely abolished the above adverse effects. Importantly, 3-Ac-DON enhanced the mRNA abundances of ER stress-related indicators, such as BIP, IRE1A, ATF6, XBP-1, EIF2A, ATF4, and CHOP, which were abolished by 4-PBA, indicating the inhibiting effects of ER stress by 4-PBA in the spleen. Furthermore, 3-Ac-DON reshaped the populations of innate immune cells (neutrophils, macrophages, dendritic cells, natural killer cells) and adaptive immune cells (T lymphocytes, helper T cells, suppressor T cells, and B lymphocytes) in the peripheral blood and spleen lymphocytes. In conclusion, our studies demonstrated that the adverse effects of 3-Ac-DON on immune cells response could be implemented by ER stress and the ameliorative effect of 4-PBA.

Protective effect of Sophora pachycarpa seed extract on carbon tetrachloride-induced toxicity in rats

The aim of the present study was to investigate the protective effect of the Sophora pachycarpa (S. pachycarpa) seed extract against carbon tetrachloride-induced toxicity on body organs, blood, and biochemical factors. In this investigation, 40 male Wistar rats weighing 200–250 g were randomly divided into 5 groups: group I was used as control, group II received carbon tetrachloride (CCl₄) (IP, 1 mL/kg) on day 21, group III and group IV received S. pachycarpa seed extract at doses of 150 mg/kg and 300 mg/kg, respectively for 21 days by oral gavage and CCl₄ on day 21, group V received silymarin (300 mg/kg) for 21 days by oral gavage and CCl₄ on day 21. CCl₄ showed an increase of serum renal and hepatic markers creatinine, urea, blood urea nitrogen (BUN), and uric acid, alkaline phosphatase (ALP), aspartate aminotransferase (AST), and alanine aminotransferase (ALT). Also, it significantly increased MDA level, and decreased CAT, FRAP, GSH, and SOD in the liver and kidney tissues. These changes and also hematological and histopathological alterations were significantly ameliorated by S. pachycarpa seed extract before CCl₄ administration. In conclusion, the data obtained in our investigation confirm the protective effect of S. pachycarpa against acute exposure to CCl₄-induced organ toxicity in rats.

3-Acetyldeoxynivalenol induces cell death through endoplasmic reticulum stress in mouse liver

Ingestion of food or cereal products contaminated by deoxynivalenol (DON) and related derivatives poses a threat to the health of humans and animals. However, the toxicity and underlying mechanisms of 3-acetyldeoxynivalenol (3-Ac-DON), an acetylated form of deoxynivalenol, have not been fully elucidated. In the present study, we showed that 3-Ac-DON caused significant oxidative damage, as shown by elevated aspartate aminotransferase (AST), alanine aminotransferase (ALT), and lactic dehydrogenase (LDH) in serum, increased lipid peroxidation products, such as hydrogen peroxide (H₂O₂) and malondialdehyde (MDA), decreased activities of antioxidant enzymes catalase (CAT) and superoxide dismutase (SOD). In addition, 3-Ac-DON exposure led to elevated infiltrations of immune cell, increased apoptosis and autophagy in the liver. Interestingly, 3-Ac-DON-resulted apoptosis and liver injury were partially reduced by autophagy inhibitors. Further study showed that 3-Ac-DON-treated mice had altered ultrastructural changes of endoplasmic reticulum (ER), as well as enhanced protein levels of p-IRE1α, p-PERK, and downstream targets, indicating activation of unfolded protein response (UPR) in the liver. Importantly, 3-Ac-DON induced ER stress, oxidative damage, cell death, infiltration of immune cells, and increased mRNA levels of inflammatory cytokines were significantly abolished by 4-phenylbutyric acid (4-PBA), an ER stress inhibitor, indicating a critical role of UPR signaling for the cellular damage of the liver in response to 3-Ac-DON exposure. In conclusion, using mice as an animal model, we showed that 3-Ac-DON exposure impaired the function of liver, as shown by oxidative damage, cell death, and infiltration of immune cell, in which ER stress played an important role. Restoration of the ER function might be a preventive strategy to reduce the deleterious effect of 3-Ac-DON on the liver of animals.

The GLP-1 analog liraglutide attenuates acute liver injury in mice

INTRODUCTION AND OBJECTIVES

Acute liver injury is a current health problem with few effective treatments. The present study investigated the hepatoprotective and curative potential of the glucagon-like peptide-1 analog liraglutide against carbon tetrachloride (CCl₄)-induced hepatotoxicity.

MATERIALS AND METHODS

Male Swiss mice were subjected to two protocols. The first protocol (Pretreatment) consisted of intraperitoneal (i.p.) treatment with liraglutide (0.057 and 0.118mgkg^-1) or vehicle (distilled water) once daily for 7 days. On days 6 and 7, the animals were challenged with 2% CCl₄ (5mgkg^-1, i.p.). The second protocol (Late treatment) began with an injection of 5% CCl₄ (5mgkg^-1, i.p.) and subsequent treatment with liraglutide (0.057mgkg^-1) or vehicle (distilled water) for 1 day. In both protocols, 24h after the last administration, blood and bile were collected from anesthetized animals, followed by euthanasia and liver collection. Plasma and bile underwent biochemical analyses, and histological, oxidative stress, and metabolic parameters were evaluated in the liver.

RESULTS

Both liraglutide treatment protocols attenuated hepatotoxicity that was induced by CCl₄, decreasing plasma levels of hepatic enzymes, stimulating the hepatic antioxidant system, and decreasing centrilobular necrosis, hepatic glycogen, and lipid accumulation. CCl₄ tended to reduce bile lipid excretion, but liraglutide did not influence this parameter.

CONCLUSIONS

The present results demonstrated the hepatoprotective and therapeutic effects of liraglutide, which may be attributable to a decrease in liver oxidative stress and the preservation of metabolism. Liraglutide may have potential as a complementary therapy for acute liver injury.

Mechanisms of titanium dioxide nanoparticle-induced oxidative stress and modulation of plasma glucose in mice

Titanium dioxide nanoparticles (TiO₂ NPs) are reported to increase plasma glucose levels in mice at specific doses. The production and accumulation of reactive oxygen species (ROS) is potentially the most important factor underlying the biological toxicity of TiO₂ NPs but the underlying mechanisms are unclear at present. Data from genome-wide analyses showed that TiO₂ NPs induce endoplasmic reticulum (ER) stress and ROS generation, leading to the inference that TiO₂ NP-induced ER stress contributes to enhancement of ROS in mice. Resveratrol (Res) effectively relieved TiO₂ NP-induced ER stress and ROS generation by ameliorating expression of a common set of activated genes for both processes, signifying that ER stress and ROS are closely related. TiO₂ NP-induced ER stress occurred earlier than ROS generation. Upon treatment with 4-phenylbutyric acid to relieve ER stress, plasma glucose levels tended toward normal and TiO₂ NP increased ROS production was inhibited. These results suggest that TiO2 NP-induced ER stress promotes the generation of ROS, in turn, triggering increased plasma glucose levels in mice. In addition, Res that displays the ability to reduce ER stress presents a dietary polyphenol antioxidant that can effectively prevent the toxicological effects of TiO₂ NPs on plasma glucose metabolism.

Methanol extract of Iphiona aucheri ameliorates CCl4 induced hepatic injuries by regulation of genes in rats

We have investigated the protective potential of methanol extract of Iphiona aucheri (IAM) on the expression of endoplasmic reticulum (ER) stress associated genes and inflammatory genes on carbon tetrachloride (CCl4) induced hepatic toxicity in rats. Hepatic damage markers: aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP) and bilirubin were elevated while the content of antioxidants: catalase (CAT), superoxide dismutase (SOD), peroxidase (POD) and reduced glutathione (GSH) were decreased significantly (p < 0.05) in CCl4 treated rats as compared to the control group. The CCl4 intoxication induced a higher expression of glucose-regulated protein 78 kDa (GRP78), X-box-binding protein 1 total (XBP1t), spliced X-box-binding protein 1 (XBP1s), unspliced X-box-binding protein 1 (XBP1u), C/EBP homologous protein (CHOP) and genes involved in inflammation and fibrosis: tumor necrosis factor alpha (TNF-α), transforming growth factor-beta (TGF-β), mothers against DPP homolog 3 (SMAD3), alpha skeletal muscle actin (αSMA) and collagen type I alpha 1 chain (COL1A1). The intoxicated rats showed a low expression of the glutamate-cysteine ligase catalytic subunit (GCLC), protein disulfide isomerase (PDI) and nuclear factor (erythroid-derived 2) like-2 (Nrf2). The administration of IAM to intoxicated rats restored the expression of ER stress, inflammatory, fibrosis and antioxidant genes in a dose dependent manner. Our results indicated that IAM can impede the ER stress and inflammatory genes and it could be a complementary and alternative therapeutic agent for oxidative stress associated disorders.

MFGE8 protects against CCl4 -induced liver injury by reducing apoptosis and promoting proliferation of hepatocytes

Milk fat globule-EGF factor 8 (MFGE8) has been reported to play various roles in acute injury and inflammation response. However, the role of MFGE8 in liver injury is poorly investigated. The present research was designed to clarify the expression and function of MFGE8 in carbon tetrachloride (CCl₄ )-induced liver injury. Using serum cytokine arrays, we selected a promising cytokine MFGE8 as the candidate in the process of hepatitis-fibrosis-hepatocellular carcinoma (HCC) progression, based on the elevated expression in both hepatic fibrosis and HCC models. We validated the increased expression of MFGE8 in liver tissues and serum samples of acute and chronic CCl₄ -induced mice. Immunohistochemistry staining of mouse liver tissues indicated that elevated MFGE8 expression was mainly derived from the injured hepatocytes. In addition, MFGE8 expression in the supernatant of primary hepatocytes was accumulated with prolongation of culture time, and CCl₄ treatment further increased the expression of MFGE8. Moreover, a strong correlation between serum MFGE8 expression and liver transaminase activities suggested that MFGE8 may be a novel candidate in liver injury. Intriguingly, mice pretreated with MFGE8 were protected from CCl₄ -induced liver injury through antiapoptosis role in the early stage and proproliferation role in the late stage. MFGE8 reduced apoptosis by inhibiting the activation of IRE1α/ASK1/JNK pathway and promoted proliferation by phosphorylation of ERK and AKT. Moreover, serum MFGE8 expression was increased in hepatitis patients while decreased in liver cirrhosis patients. All the results suggest MFGE8 as a novel marker and promising therapeutic agent of liver injury.

Lipid-regulating properties of butyric acid and 4-phenylbutyric acid: Molecular mechanisms and therapeutic applications

In the past two decades, significant advances have been made in the etiology of lipid disorders. Concomitantly, the discovery of liporegulatory functions of certain short-chain fatty acids has generated interest in their clinical applications. In particular, butyric acid (BA) and its derivative, 4-phenylbutyric acid (PBA), which afford health benefits against lipid disorders while being generally well tolerated by animals and humans have been assessed clinically. This review examines the evidence from cell, animal and human studies pertaining to the lipid-regulating effects of BA and PBA, their molecular mechanisms and therapeutic potential. Collectively, the evidence supports the view that intakes of BA and PBA benefit lipid homeostasis across biological systems. We reviewed the evidence that BA and PBA downregulate de novo lipogenesis, ameliorate lipotoxicity, slow down atherosclerosis progression, and stimulate fatty acid β-oxidation. Central to their mode of action, BA appears to function as a histone deacetylase (HDAC) inhibitor while PBA acts as a chemical chaperone and/or a HDAC inhibitor. Areas of further inquiry include the effects of BA and PBA on adipogenesis, lipolysis and apolipoprotein metabolism.

Sodium 4-phenylbutyrate treatment protects against renal injury in NZBWF1 mice

Systemic lupus erythematosus (SLE) is an autoimmune disease predominantly affecting women and often leading to lupus nephritis and kidney damage. Endoplasmic reticulum (ER) stress has been implicated in several forms of kidney disease, but whether ER stress contributes to renal injury in SLE is unknown. To investigate this, a small molecule chaperone, sodium 4-phenylbutyrate (4-PBA), was administered to the New Zealand Black x New Zealand White F₁ hybrid (NZBWF1) mouse model of SLE. In a prevention study, treatment with 4-PBA from 20 weeks of age (prior to the development of renal injury) delayed the onset of albuminuria and significantly reduced additional indices of renal injury compared with vehicle-treated NZBWF1 mice at 36 weeks of age, including collagen deposition, tubular casts, renal cell apoptosis, and blood urea nitrogen (BUN) concentration. To test whether ER stress contributes to the progression of renal injury once albuminuria has developed, mice were monitored for the onset of albuminuria (3+ or ≥300 mg/dl by dipstick measurement of 24-h urine sample) and once established, were either killed (onset group), or underwent 4-PBA or vehicle treatment for 4 weeks. Treatment with 4-PBA blocked the worsening of glomerular injury, reduced the number of dilated or cast-filled tubules, and reduced the number of apoptotic cells compared with vehicle-treated mice. BUN and left ventricle to bodyweight ratio (LV:BW) were also reduced by 4-PBA treatment. Renal expression of the endogenous chaperones, protein disulphide isomerase (PDI), and 78 kDa glucose-regulated protein (GRP78, also known as binding Ig protein (BiP)), were increased in 4-PBA-treated mice. Together, these results suggest a therapeutic potential for agents like 4-PBA in combating renal injury in SLE.

New amino acid-Schiff base derived from s-allyl cysteine and methionine alleviates carbon tetrachloride-induced liver dysfunction

In spite of the tremendous stride in modern medicine, conventional drugs used in the hepatotoxic management are mostly inadequate. The present study aims in the synthesis of novel Schiff base compound derived using s-allyl cystiene and methionine. The newly synthesized compound, 2-((2-((2-(allylthio)-1-carboxyethyl)imino)ethylidene)amino)-4-(methylthio)butanoic acid (ACEMB) was characterized using UV-visible spectrophotometer, FTIR, ¹HNMR, and GC-MS. ACEMB showed potent in vitro antioxidant property. Chronic administration of ACEMB prior to CCl₄ intoxication: i) attenuated the leakage of liver injury markers, such as, enzymes (AST, ALT, GGT, ALP and LDH) and biomolecules (bilirubin) into the blood circulation; ii) normalized the concentration of total proteins, albumin and globulin to control level; and iii) protected the liver against dyslipidemia. These effects of ACEMB show the preservation of endoplasmic reticulum function against CCl₄ toxicity in the liver. The protective effect of ACEMB was due to its antioxidant property, which was revealed by reduced oxidative stress (TBARS and HP) and enhanced functions of the endogenous antioxidative system (SOD, catalase, GPx, GST, GSH, vitamin E and C) against CCl₄ intoxication. Also, ACEMB protected the functional activities of the various mitochondrial tricarboxylic acid cycle and oxidative phosphorylation enzymes. The biochemical alterations are in concurrence with the histological observations, wherein ACEMB pretreatment prevented the vacuolation, degeneration of nuclei and necrosis of hepatocytes. In addition, in silico analysis reveals the interaction of ACEMB in the active site of cytochrome P450. ACEMB mediates hepatoprotective effect by substituting itself as an antioxidant and decreasing oxidative stress, thereby diminishing the intracellular organelle dysfunction against CCl₄ toxicity in the liver.