4-Phenylbutyric Acid Attenuates Pancreatic Beta-Cell Injury in Rats with Experimental Severe Acute Pancreatitis

Sustained feeding of a diet high in fat resulted in a decline in the liver's insulin-degrading enzyme levels in association with the induction of oxidative and endoplasmic reticulum stress in adult male rats: Evaluation of 4-phenylbutyric acid

The current study explored the impact of high fat diet (HFD) on hepatic oxidative and endoplasmic reticulum (ER) stress and its insulin degrading enzyme (IDE) content with the injection of 4-phenyl butyric acid (4-PBA) in adult male rats. Following the weaning period, male offspring were distributed among six distinct groups. The corresponding diet was used for 20 weeks, subsequently 4-PBA was administered for three consecutive days. Plasma glucose and insulin levels, HOMA-β (homeostasis model assessment of β-cell), hepatic ER and oxidative stress biomarkers and IDE protein content were assessed. Long-term ingestion of HFD (31 % cow butter) induced oxidative and ER stress in the liver tissue. Accordingly, a rise in the malondialdehyde (MDA) content and catalase enzyme activity and a decrease in the glutathione (GSH) content were detected within the liver of the HFD and HFD + DMSO groups. Consumption of this diet elevated the liver expression of binding immunoglobulin protein (BIP) and C/enhancer-binding protein homologous protein (CHOP) levels while reduced its IDE content. The HOMA-β decreased significantly. The injection of the 4-PBA moderated all the induced changes. Findings from this study indicated that prolonged HFD consumption led to a reduction in plasma insulin levels, likely attributed to pancreatic β cell malfunction, as evidenced by a decline in the HOMA-β index. Also, the HFD appears to have triggered oxidative and ER stress in the liver, along with a decrease in its IDE content.

Differences in glucose homeostasis and islet injury among diverse mice strains post acute pancreatitis

Diverse animal models have been used to study postpancreatitis diabetes mellitus (PPDM) development; however, no study has yet conducted a comparative analysis of the specific differences in glucose homeostasis and islet injury between these models. Therefore, we investigated the differences in pancreatic islet injury and glucose homeostasis among diverse strains in a cerulein-induced acute pancreatitis (AP) model to determine the appropriate animal model for PPDM. BALB/cJ, C57BL/6J, C57BL/6 N, and FVB/NJ mice were administered cerulein to induce AP. Serum amylase levels, pancreatic acinar injury, blood glucose homeostasis, islet function, and islet injury were measured and analyzed. All strains exhibited elevated amylase secretion post pancreatitis, and BALB/cJ, C57BL/6J, and C57BL/6 N mice exhibited sex-related differences. All strains exhibited pancreatic acinar injury post pancreatitis but mostly recovered within 15 days. Overall, glucose homeostasis remained balanced post pancreatitis in all strains compared to that in the control groups, except in FVB/NJ male and female mice, which exhibited an imbalance in glucose homeostasis on day 7 post pancreatitis. All the strains, except BALB/cJ mice, exhibited a decline in Homeostasis model assessment-β(HOMA-β) values post pancreatitis, with significant decrease in C57BL/6J females and FVB/NJ males. Islet size decreased post pancreatitis in all strains, except BALB/cJ mice. Pancreatic islet insulin secretion levels significantly decreased in male FVB/NJ mice post pancreatitis onset and did not recover within 15 days. Therefore, FVB/NJ male mice are a useful model for studying PPDM.

Pancreatic Crosstalk in the Disease Setting: Understanding the Impact of Exocrine Disease on Endocrine Function

The exocrine and endocrine are functionally distinct compartments of the pancreas that have traditionally been studied as separate entities. However, studies of embryonic development, adult physiology, and disease pathogenesis suggest there may be critical communication between exocrine and endocrine cells. In fact, the incidence of the endocrine disease diabetes secondary to exocrine disease/dysfunction ranges from 25% to 80%, depending on the type and severity of the exocrine pathology. Therefore, it is necessary to investigate how exocrine-endocrine "crosstalk" may impact pancreatic function. In this article, we discuss common exocrine diseases, including cystic fibrosis, acute, hereditary, and chronic pancreatitis, and the impact of these exocrine diseases on endocrine function. Additionally, we review how obesity and fatty pancreas influence exocrine function and the impact on cellular communication between the exocrine and endocrine compartments. Interestingly, in all pathologies, there is evidence that signals from the exocrine disease contribute to endocrine dysfunction and the progression to diabetes. Continued research efforts to identify the mechanisms that underlie the crosstalk between various cell types in the pancreas are critical to understanding normal pancreatic physiology as well as disease states. © 2024 American Physiological Society. Compr Physiol 14:5371-5387, 2024.

Role and Mechanism of Endoplasmic Reticulum Stress in Mice Pancreatic Islet Dysfunction After Severe Burns

This study attempted to investigate the role and mechanism of endoplasmic reticulum (ER) stress in the islet dysfunction in mice after severe burns. C57BL/6 mice were randomly divided into the sham group, burn group, and burn+4-phenylbutyric acid (4-PBA) group. Mice were burned with full thickness of 30% total surface area (TBSA), and 4-PBA solution was intraperitoneally injected into mice in burn+4-PBA group. Glucose-stimulated insulin secretion (GSIS), Fasting blood glucose (FBG) and glucose tolerance were detected 24 hours post severe burns. The ER stress-related pathway markers immunoglobulin binding protein (BIP), X-box binding protein 1 (XBP1), phosphorylation-PKR-like ER kinase (p-PERK), phosphorylation-eukaryotic translation initiation factor 2α (p-eIF2α), CHOP, activating transcription factor 6 (ATF6), apoptosis-related protein Cleaved-Caspase 3, and islet cell apoptosis were measured. Mice were characterized with elevated FBG, decreased glucose tolerance and GSIS levels post severe burns. The expression of BIP, XBP1, p-PERK, p-eIF2α, CHOP, ATF6, Cleaved-Caspase 3, and islet cell apoptosis were increased significantly after severe burns. 4-PBA treatment contributed to decreased FBG, improved glucose tolerance, increased GSIS, inhibited islet ER stress, and reduced pancreatic islet cell apoptosis in mice post severe burns. ER stress occurs in islets of severely burned mice, which leads to increased apoptosis of islet cells, thus resulting in islet dysfunction.

A Nano-Liposomal Formulation of Caffeic Acid Phenethyl Ester Modulates Nrf2 and NF-κβ Signaling and Alleviates Experimentally Induced Acute Pancreatitis in a Rat Model

The currently available management strategies for acute pancreatitis are inadequately effective which calls for exploration of new approaches to treat this condition. Caffeic acid phenethyl ester (CAPE) is a major bioactive constituent of honeybee propolis with promising therapeutic and preventive applications. However, its pharmaceutical potential and clinical use are hindered by its poor water solubility and limited plasma stability. In this study, we aimed to prepare, characterize and evaluate a CAPE-loaded nanoliposomal formulation to improve the efficacy of CAPE for the management of acute pancreatitis. The CAPE-loaded nanoliposomes (CAPE-loaded-NL) were prepared by a thin layer evaporation technique and were optimized using three edge activators. CAPE-loaded-NL were characterized for their vesicle size (VS), zeta potential (ZP), encapsulation efficiency (EE), polydispersity index (PDI), crystalline state and morphology. The protective effect of the optimal CAPE-loaded-NL was evaluated in a rat model of acute pancreatitis induced by administering a single intraperitoneal injection of L-ornithine. Oral pretreatment with CAPE-loaded-NL significantly counteracted ornithine-induced elevation in serum activities of pancreatic digestive enzymes and pancreatic levels of malondialdehyde, nuclear factor kappa B (NF-κB) p65, tumor necrosis factor-alpha, nitrite/nitrate, cleaved caspase-3 and myeloperoxidase activity. Moreover, pretreatment with CAPE-loaded-NL significantly reinstated the ornithine-lowered glutathione reductase activity, glutathione, nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase-1 levels and ATP/ADP ratio, and potentiated the Bcl-2/Bax ratio in pancreatic tissue. CAPE-loaded-NL displayed superior antioxidant, anti-inflammatory and anti-apoptotic effects compared to free CAPE oral suspension and achieved a more potent correction of the derangements in serum amylase and pancreatic myeloperoxidase activities. The histological observations were in line with the biochemical findings. Our results suggest that CAPE-loaded-NL provide a promising interventional approach for acute pancreatitis mainly through the enhancement of the exerted antioxidant, anti-inflammatory and anti-apoptotic effects which may be mediated, at least in part, through modulation of Nrf2 and NF-κβ signaling.

Effects of nitroglycerin combined with continuous regional arterial infusion on severe acute pancreatitis, triglyceride, inflammatory factors and prognosis

Background: To evaluate the effects of nitroglycerin combined with continuous regional arterial infusion (CRAI) on severe acute pancreatitis (SAP), triglyceride (TG), inflammatory factors and prognosis.

Methods: SAP patients were randomly divided into control and observation groups (n=169). The control group was treated with intravenous infusion of nitroglycerin once daily for 2 d, while the observation group was treated with nitroglycerin combined with CRAI for 7 d. Their hospitalization time, abdominal pain relief time, abdominal distension relief time and intestinal function recovery time were recorded. The levels of inflammatory factors, and TG were measured. Their liver and kidney functions, hemorheological indices, prognosis, and adverse reactions were evaluated.

Results: The observation group had significantly shorter hospitalization time, abdominal pain relief time, abdominal distension relief time, and intestinal function recovery time than those of the control group (P<0.05). After treatment, the levels of interleukin-6, tumor necrosis factor-alpha, endothelin, thromboxane A2 and TG significantly decreased in contrast with those before treatment in both groups, especially in the observation group (P<0.05). The hemorheological indices were significantly improved after treatment compared with those before treatment in both groups, and the observation group had better indices (P<0.05). The Acute Physiology and Chronic Health Evaluation-II score declined significantly in both groups after treatment, and the observation group had a more obvious decrease (P<0.05). During follow-up, similar incidence rates of adverse reactions were observed for both groups (P>0.05).

Conclusion: Nitroglycerin combined with CRAI is prominently effective for treating SAP, which can facilitate the health recovery and reduce the incidence of microcirculation disturbance-induced adverse events such as organ failure.

Inhibition of Notch activity promotes pancreatic cytokeratin 5-positive cell differentiation to beta cells and improves glucose homeostasis following acute pancreatitis

Some individuals develop prediabetes and/or diabetes following acute pancreatitis (AP). AP-induced beta-cell injury and the limited regenerative capacity of beta cells might account for pancreatic endocrine insufficiency. Previously, we found that only a few pancreatic cytokeratin 5 positive (Krt5⁺) cells differentiated into beta cells in the murine AP model, which was insufficient to maintain glucose homeostasis. Notch signaling determines pancreatic progenitor differentiation in pancreas development. This study aimed to examine whether Notch signaling inhibition could promote pancreatic Krt5⁺ cell differentiation into beta cells and improve glucose homeostasis following AP. Pancreatic tissues from patients with acute necrotizing pancreatitis (ANP) were used to evaluate beta-cell injury, Krt5⁺ cell activation and differentiation, and Notch activity. The murine AP model was induced by cerulein, and the effect of Notch inhibition on Krt5⁺ cell differentiation was evaluated both in vivo and in vitro. The results demonstrated beta-cell loss in ANP patients and AP mice. Krt5⁺ cells were activated in ANP pancreases along with persistently elevated Notch activity, which resulted in the formation of massive duct-like structures. AP mice that received Notch inhibitor showed that impaired glucose tolerance was reversed 7 and 15 days following AP, and increased numbers of newborn small islets due to increased differentiation of Krt5⁺ cells to beta cells to some extent. In addition, Krt5⁺ cells isolated from AP mice showed increased differentiation to beta cells by Notch inhibition. Collectively, these findings suggest that beta-cell loss contributes to pancreatic endocrine insufficiency following AP, and inhibition of Notch activity promotes pancreatic Krt5⁺ cell differentiation to beta cells and improves glucose homeostasis. The findings from this study may shed light on the potential treatment of prediabetes/diabetes following AP.

Early Cytokine-Induced Transient NOX2 Activity Is ER Stress-Dependent and Impacts β-Cell Function and Survival

In type 1 diabetes (T1D) development, proinflammatory cytokines (PIC) released by immune cells lead to increased reactive oxygen species (ROS) production in β-cells. Nonetheless, the temporality of the events triggered and the role of different ROS sources remain unclear. Isolated islets from C57BL/6J wild-type (WT), NOX1 KO and NOX2 KO mice were exposed to a PIC combination. We show that cytokines increase O₂^•− production after 2 h in WT and NOX1 KO but not in NOX2 KO islets. Using transgenic mice constitutively expressing a genetically encoded compartment specific H₂O₂ sensor, we show, for the first time, a transient increase of cytosolic/nuclear H₂O₂ in islet cells between 4 and 5 h during cytokine exposure. The H₂O₂ increase coincides with the intracellular NAD(P)H decrease and is absent in NOX2 KO islets. NOX2 KO confers better glucose tolerance and protects against cytokine-induced islet secretory dysfunction and death. However, NOX2 absence does not counteract the cytokine effects in ER Ca²⁺ depletion, Store-Operated Calcium Entry (SOCE) increase and ER stress. Instead, the activation of ER stress precedes H₂O₂ production. As early NOX2-driven ROS production impacts β-cells’ function and survival during insulitis, NOX2 might be a potential target for designing therapies against early β-cell dysfunction in the context of T1D onset.

4-Phenylbutyric acid, a potent endoplasmic reticulum stress inhibitor, attenuates the severity of collagen-induced arthritis in mice via inhibition of proliferation and inflammatory responses of synovial fibroblasts

4-Phenylbutyric acid (4-PBA) exerts potent pharmacological effects, including anti-inflammatory properties, via inhibition of endoplasmic reticulum (ER) stress. However, it is not known whether 4-PBA attenuates the severity of rheumatoid arthritis. The present study aimed to determine whether the inhibition of ER stress by 4-PBA ameliorated experimentally induced arthritis. The proliferation of synovial fibroblasts (SFs) and expression of matrix metalloproteinases (MMPs) were evaluated in the presence of interleukin (IL)-1β with or without 4-PBA. The effect of 4-PBA on the phosphorylation of Mitogen-activated protein kinase (MAPK) and the activation of Nuclear factor-κB (NF-κB) in IL-1β-stimulated SFs was assessed. In an in vivo study, the effects of 4-PBA were investigated using DBA/1 mice with collagen-induced arthritis (CIA). Clinical, histological, and serological assessments of CIA treated with 4-PBA were performed to determine the therapeutic effect of 4-PBA. In vitro, 4-PBA inhibited the proliferation and expression of IL-1β-stimulated SFs and MMP-1 and MMP-3 through the suppression of both the phosphorylation of MAPKs and NF-κB in IL-1β-stimulated SFs. The 4-PBA treatment markedly attenuated the severity of arthritis in CIA mice. The 4-PBA treatment ameliorated joint swelling and the degree of bone erosion and destruction and decreased the level of inflammatory cytokines and MMP-3 and Cox-2. Furthermore, remarkable improvements in histopathological findings occurred in 4-PBA-treated mice. These findings suggested that 4-PBA could attenuate the severity of arthritis in CIA mice by partially blocking the phosphorylation of MAPKs and the activation of NF-κB in SFs. Thus, through the inhibition of ER stress, 4-PBA may be a potent agent for the treatment of RA.

Single Cell RNA-Seq and Machine Learning Reveal Novel Subpopulations in Low-Grade Inflammatory Monocytes With Unique Regulatory Circuits

Subclinical doses of LPS (SD-LPS) are known to cause low-grade inflammatory activation of monocytes, which could lead to inflammatory diseases including atherosclerosis and metabolic syndrome. Sodium 4-phenylbutyrate is a potential therapeutic compound which can reduce the inflammation caused by SD-LPS. To understand the gene regulatory networks of these processes, we have generated scRNA-seq data from mouse monocytes treated with these compounds and identified 11 novel cell clusters. We have developed a machine learning method to integrate scRNA-seq, ATAC-seq, and binding motifs to characterize gene regulatory networks underlying these cell clusters. Using guided regularized random forest and feature selection, our method achieved high performance and outperformed a traditional enrichment-based method in selecting candidate regulatory genes. Our method is particularly efficient in selecting a few candidate genes to explain observed expression pattern. In particular, among 531 candidate TFs, our method achieves an auROC of 0.961 with only 10 motifs. Finally, we found two novel subpopulations of monocyte cells in response to SD-LPS and we confirmed our analysis using independent flow cytometry experiments. Our results suggest that our new machine learning method can select candidate regulatory genes as potential targets for developing new therapeutics against low grade inflammation.

miR-133b has protective effect on rats with acute lung injury caused by severe acute pancreatitis through targeting sp1 gene

OBJECTIVE

We aimed to investigate the regulatory mechanism of miR-133b and Sp1 in rats with severe acute pancreatitis complicated by acute lung injury.

METHODS

The rats were divided into normal, NC, model, si-Sp1, miR-133b mimic, miR-133b inhibitor, and miR-133b inhibitor + si-Sp1 group and received different treatments.

RESULTS

Compared with normal mice, model mice had a lower miR-133b expression, but higher levels of Sp1 expression, W/D of lung tissue, myeloperoxidase activities, and higher levels of interleukin(IL)-6, tumor necrosis factor (TNF)-α and IL-1β, cell apoptosis rate and Notch-1, and Hes-1, nuclear factor (NF)-κB P65 expressions in lung tissue. Compared with model mice, mice in the si-Sp1 group and the miR-133b mimic group had significantly lower W/D of lung tissue, myeloperoxidase activities, lower levels of IL-6, TNF-α and IL-1β, cell apoptosis rate and Notch-1, Hes-1, and NF-κB P65 expressions in lung tissue. Mice treated by miR-133b inhibitor showed opposite results in all above parameters, which were similar with those in the model group. The negative effects of miR-133b inhibitor could be reversed by the combination use of si-Sp1.

CONCLUSION

Overexpression of miR-133b could inhibit Sp1 expression, thereby improving severe acute pancreatitis in rats and playing a protective role in acute lung injury.

Mechanisms of Post-Pancreatitis Diabetes Mellitus and Cystic Fibrosis-Related Diabetes: A Review of Preclinical Studies

Anatomical proximity and functional correlations between the exocrine and endocrine pancreas warrant reciprocal effects between the two parts. Inflammatory diseases of the exocrine pancreas, such as acute or chronic pancreatitis, or the presence of cystic fibrosis disrupt endocrine function, resulting in diabetes of the exocrine pancreas. Although novel mechanisms are being increasingly identified, the intra- and intercellular pathways regulating exocrine-endocrine interactions are still not fully understood, making the development of new and more effective therapies difficult. Therefore, this review sought to accumulate current knowledge regarding the pathogenesis of diabetes in acute and chronic pancreatitis, as well as cystic fibrosis.

Endoplasmic reticulum stress and pulmonary hypertension

Pulmonary hypertension is a fatal disease of which pulmonary vasculopathy is the main pathological feature resulting in the mean pulmonary arterial pressure higher than 25 mmHg. Moreover, pulmonary hypertension remains a tough problem with unclear molecular mechanisms. There have been dozens of studies about endoplasmic reticulum stress during the onset of pulmonary hypertension in patients, suggesting that endoplasmic reticulum stress may have a critical effect on the pathogenesis of pulmonary hypertension. The review aims to summarize the rationale to elucidate the role of endoplasmic reticulum stress in pulmonary hypertension. Started by reviewing the mechanisms responsible for the unfolded protein response following endoplasmic reticulum stress, the potential link between endoplasmic reticulum stress and pulmonary hypertension were introduced, and the contributions of endoplasmic reticulum stress to different vascular cells, mitochondria, and inflammation were described, and finally the potential therapies of attenuating endoplasmic reticulum stress for pulmonary hypertension were discussed.

Inhibition of endoplasmic reticulum stress by 4-phenylbutyric acid prevents vital organ injury in rat acute pancreatitis

This study was conducted to investigate the effect of 4-phenylbutyric acid (4-PBA) on vital organ injury following sodium taurocholate-induced acute pancreatitis (AP) in rats and the pertinent mechanism. The serum biochemical indicators and key inflammatory cytokines, histopathological damage and apoptosis of vital organs in rat AP, were evaluated in the presence or absence of 4-PBA. Moreover, mRNA and protein levels of endoplasmic reticulum stress (ERS) markers were assessed. 4-PBA significantly attenuated the structural and functional damage of vital organs, including serum pancreatic enzymes, hepatic enzymes, creatinine, and urea. The morphological changes and infiltration of neutrophils and macrophages were reduced as well. These effects were accompanied by decreased serum levels of proinflammatory TNF-α and IL-1β. Furthermore, 4-PBA diminished the expression of ERS markers (glucose-regulated protein 78, CCAAT/enhancer-binding protein homologous protein, protein kinase R-like ER kinase, activated transcription factor 6, and type-1 inositol requiring enzyme) in vital organs of AP rats. 4-PBA also reduced AP-induced apoptosis in lung, liver, and kidney tissues as shown by TUNEL assay. The present study demonstrated that 4-PBA protected pancreas, lung, liver, and kidney from injury in rat AP by regulating ERS and mitigating inflammatory response to restrain cell death and further suggested that 4-PBA may have potential therapeutic implications in the disease. NEW & NOTEWORTHY In this study, we suggest that endoplasmic reticulum stress (ERS) is an important player in the development of acute pancreatitis-induced multiorgan injury, providing additional evidence for the proinflammatory role of ERS. Because 4-phenylbutyric acid has been suggested to inhibit ERS in many pathological conditions, it is possible that this effect can be involved in alleviating inflammatory response and cell death to ameliorate vital organ damage following acute pancreatitis induced by sodium taurocholate in rats.

Magnesium isoglycyrrhizinate alleviates liver injury in obese rats with acute necrotizing pancreatitis

OBJECTIVE

For patients with acute necrotizing pancreatitis (ANP), a high body mass index (BMI) increases the likelihood of acute hepatic injury (AHI). In the current study, we explored whether magnesium isoglycyrrhizinate (MgIg) could alleviate ANP-induced liver injury in obese rats.

METHODS

Sprague-Dawley (SD) rats were selected for the present study, and the ANP model was established by retrograde injection of 5% sodium taurocholate into the biliary-pancreatic duct. Thirty-six SD rats were randomly assigned to six groups: the normal (N), standard rat chow (SRC) normal (SN), SRC ANP (S-ANP), high-fat diet (HFD) normal (H-N), HFD ANP (H-ANP), and MgIg pretreatment HFD ANP (H-ANPT) groups. The rats in the H-ANPT group were treated with MgIg (30 mg/kg) intragastrically for 7 days before the ANP model was established. The rats were sacrificed 12 h after ANP was established, and the blood and pancreatic and liver tissues were collected. Differences in the physiology, pathology and cellular and molecular responses of the rats in each group were examined.

RESULT

Analyses of serum amylase lipase, alanine aminotransferase and aspartate aminotransferase indicated that obesity aggravated ANP-induced hepatic injury and that MgIg improved liver function. The superoxide dismutase, malondialdehyde, M1 macrophage, M2 macrophage, neutrophil, NF-κB, IL-1β and caspase-3 levels in liver tissue showed that MgIg attenuated H-ANP-induced hepatic injury by inhibiting oxidative stress and inflammation.

CONCLUSION

Obesity aggravated ANP-induced liver injury via oxidative stress and inflammatory reactions. MgIg alleviated oxidative stress and decreased the inflammatory reaction, protecting the liver against the AHI induced by ANP in obese rats.

Corrigendum to "4-Phenylbutyric Acid Attenuates Pancreatic Beta-Cell Injury in Rats with Experimental Severe Acute Pancreatitis"

[This corrects the article DOI: 10.1155/2016/4592346.].