Ex vivo gene editing and cell therapy for hereditary tyrosinemia type 1.

BACKGROUND: We previously demonstrated the successful use of in vivo CRISPR gene editing to delete 4-hydroxyphenylpyruvate dioxygenase (HPD) to rescue mice deficient in fumarylacetoacetate hydrolase (FAH), a disorder known as hereditary tyrosinemia type 1 (HT1). The aim of this study was to develop an ex vivo gene-editing protocol and apply it as a cell therapy for HT1. METHODS: We isolated hepatocytes from wild-type (C57BL/6J) and Fah-/- mice and then used an optimized electroporation protocol to deliver Hpd-targeting CRISPR-Cas9 ribonucleoproteins into hepatocytes. Next, hepatocytes were transiently incubated in cytokine recovery media formulated to block apoptosis, followed by splenic injection into recipient Fah-/- mice. RESULTS: We observed robust engraftment and expansion of transplanted gene-edited hepatocytes from wild-type donors in the livers of recipient mice when transient incubation with our cytokine recovery media was used after electroporation and negligible engraftment without the media (mean: 46.8% and 0.83%, respectively; p=0.0025). Thus, the cytokine recovery medium was critical to our electroporation protocol. When hepatocytes from Fah-/- mice were used as donors for transplantation, we observed 35% and 28% engraftment for Hpd-Cas9 ribonucleoproteins and Cas9 mRNA, respectively. Tyrosine, phenylalanine, and biochemical markers of liver injury normalized in both Hpd-targeting Cas9 ribonucleoprotein and mRNA groups independent of induced inhibition of Hpd through nitisinone, indicating correction of disease indicators in Fah-/- mice. CONCLUSIONS: The successful liver cell therapy for HT1 validates our protocol and, despite the known growth advantage of HT1, showcases ex vivo gene editing using electroporation in combination with liver cell therapy to cure a disease model. These advancements underscore the potential impacts of electroporation combined with transplantation as a cell therapy.

Treatment of Obesity Through Glial Cell-Derived Neurotrophic Factor Lipid Nanoparticle Delivery in Mice.

BACKGROUND AND AIMS: The overexpression of glial cell-derived neurotrophic factor (GDNF) in the liver and adipose tissues offers strong protection against high-fat diet (HFD)-induced obesity in mice. We hypothesize that sustainably enhancing GDNF expression in the liver may provide a therapeutic effect that can prevent the progression of HFD-induced obesity in mice. METHODS: Expression lentivector encoding mouse GDNF (GDNF(pDNA) or empty vector (pDNA, control) were encapsulated in lipid nanoparticles (LNPs) using the thin-film hydration method. Mice were fed with regular diet (RD) or HFD for 20 weeks prior to injection and the GDNF and control vector-loaded LNPs were administered by intravenous (IV) injection to mice once weekly for 5 weeks. Changes in body weight were monitored and mice tissues were collected and imaged for fluorescence using an IVIS in vivo imaging system. Post-treatment abdominal fat weight, colon length, and spleen weight were obtained. GDNF protein levels in the liver and serum were quantified by enzyme-linked immunosorbent assay, while liver AKT serine/threonine kinase and AMP-activated protein kinase phosphorylation levels were evaluated by Western blotting. RESULTS: IV-injected GDNF(pDNA)-loaded LNPs targeted the liver and remained in there for up to 15 days postinjection. A single injection of GDNF(pDNA)-loaded LNPs significantly increased GDNF expression for 7 days and consequently increased the levels of phosphorylated AKT serine/threonine kinase and AMP-activated protein kinase. Once weekly injections of GDNF(pDNA)-loaded LNPs for 5 weeks slowed increase in body weight, reduced abdominal fat, and modulated the gut microbiota toward a healthier composition in HFD-fed mice. CONCLUSION: GDNF(pDNA)-loaded LNPs could potentially be developed as a therapeutic strategy to reverse weight gain in obese patients.

Targeting PKC alleviates iron overload in diabetes and hemochromatosis.

Diabetes is one of the most prevalent chronic diseases worldwide. Iron overload increases the incidence of diabetes and aggravates diabetic complications that cause mortality. Reciprocally, diabetes potentially promotes body iron loading, but the mechanism remains not well understood. In this study, we demonstrated systemic iron excess and the upregulation of iron exporter ferroportin (Fpn) in the enterocytes and macrophages of multiple diabetic mouse models. Increased Fpn expression and iron efflux was also seen in the enterocytes of type 2 diabetic human patients. We further showed that protein kinase C (PKC), which is activated in hyperglycemia, was responsible for the sustained membrane expression of Fpn in physiological and in diabetic settings. For the first time, we identified that PKCs were novel binding proteins and positive regulators of Fpn. Mechanistically, hyperactive PKC promoted exocytotic membrane insertion while inhibited the endocytic trafficking of Fpn in the resting state. PKC also protected Fpn from internalization and degradation by its ligand hepcidin dependent on decreased ubiquitination and increased phosphorylation of Fpn. Importantly, the loss-of-function and pharmacological inhibition of PKC alleviated systemic iron overload in diabetes and hemochromatosis. Our study thus highlights PKC as a novel target in the control of systemic iron homeostasis.

Microbiome differences related to metformin intolerance among Black individuals with diabetes, a pilot cross-sectional study.

Aims: Metformin is the broadly accepted the first-line medication for diabetes. Its use, however, is limited by gastrointestinal side effects present in approximately 25% of patients. This study aimed to better understand the interplay between metformin intolerance and gut microbiota among Black individuals with diabetes. Methods: We performed a cross-sectional study among 29 Black individuals living with diabetes with or without metformin intolerance. Participants with mean age 59±11, 58% female, were stratified into three groups: 1)intolerant: metformin intolerance in the past, not on metformin; 2)partially intolerant: mild to moderate gastrointestinal symptoms, currently taking metformin 3)tolerant: using metformin without symptoms. We collected and analyzed rectal swabs and analyzed microbiota composition using V3-V4 regions of the 16s rRNA. Results: Metformin intolerant subjects trended towards having greatest alpha diversity, followed by tolerant and partially tolerant (Intolerant:4.9; Tolerant:4.2; Partially tolerant:3.9). Mean difference in alpha diversity for intolerant versus partially tolerant was 1.0 (95% CI-0.1,2.1) and intolerant versus tolerant were 0.7 (95% CI -0.4,1.8). Conclusion: This was the first study to evaluate the role of microbiota and metformin intolerance among Black individuals. We report on differences in alpha diversity as well as microbiota composition.

Differences in hepatocellular iron metabolism underlie sexual dimorphism in hepatocyte ferroptosis.

Males show higher incidence and severity than females in hepatic injury and many liver diseases, but the mechanisms are not well understood. Ferroptosis, an iron-mediated lipid peroxidation-dependent death, plays an important role in the pathogenesis of liver diseases. We determined whether hepatocyte ferroptosis displays gender difference, accounting for sexual dimorphism in liver diseases. Compared to female hepatocytes, male hepatocytes were much more vulnerable to ferroptosis by iron and pharmacological inducers including RSL3 and iFSP1. Male but not female hepatocytes exhibited significant increases in mitochondrial Fe2+ and mitochondrial ROS (mtROS) contents. Female hepatocytes showed a lower expression of iron importer transferrin receptor 1 (TfR1) and mitochondrial iron importer mitoferrin 1 (Mfrn1), but a higher expression of iron storage protein ferritin heavy chain 1 (FTH1). It is well known that TfR1 expression is positively correlated with ferroptosis. Herein, we showed that silencing FTH1 enhanced while knockdown of Mfrn1 decreased ferroptosis in HepG2 cells. Removing female hormones by ovariectomy (OVX) did not dampen but rather enhanced hepatocyte resistance to ferroptosis. Mechanistically, OVX potentiated the decrease in TfR1 and increase in FTH1 expression. OVX also increased FSP1 expression in ERK-dependent manner. Elevation in FSP1 suppressed mitochondrial Fe2+ accumulation and mtROS production, constituting a novel mechanism of FSP1-mediated inhibition of ferroptosis. In conclusion, differences in hepatocellular iron handling between male and female account, at least in part, for sexual dimorphism in induced ferroptosis of the hepatocytes.

Differences in Hepatocellular Iron Metabolism Underlie Sexual Dimorphism in Hepatocyte Ferroptosis.

Males show higher incidence and severity than females in hepatic injury and many liver diseases, but the mechanisms are not well understood. Ferroptosis, an iron-mediated lipid peroxidation-dependent death, plays an important role in the pathogenesis of liver diseases. We determined whether hepatocyte ferroptosis displays gender difference, accounting for sexual dimorphism in liver diseases. Compared to female hepatocytes, male hepatocytes were much more vulnerable to ferroptosis by iron and pharmacological inducers including RSL3 and iFSP1. Male but not female hepatocytes exhibited significant increases in mitochondrial Fe 2+ and mitochondrial ROS (mtROS) contents. Female hepatocytes showed a lower expression of iron importer transferrin receptor 1 (TfR1) and mitochondrial iron importer mitoferrin 1 (Mfrn1), but a higher expression of iron storage protein ferritin heavy chain 1 (FTH1). It is well known that TfR1 expression is positively correlated with ferroptosis. Herein, we showed that silencing FTH1 enhanced while knockdown of Mfrn1 decreased ferroptosis in HepG2 cells. Removing female hormones by ovariectomy (OVX) did not dampen but rather enhanced hepatocyte resistance to ferroptosis. Mechanistically, OVX potentiated the decrease in TfR1 and increase in FTH1 expression. OVX also increased FSP1 expression in ERK-dependent manner. Elevation in FSP1 suppressed mitochondrial Fe 2+ accumulation and mtROS production, constituting a novel mechanism of FSP1-mediated inhibition of ferroptosis. In conclusion, differences in hepatocellular iron handling between male and female account, at least in part, for sexual dimorphism in induced ferroptosis of the hepatocytes.

Defective neurite elongation and branching in Nibp/Trappc9 deficient zebrafish and mice.

Loss of function in transport protein particles (TRAPP) links a new set of emerging genetic disorders called "TRAPPopathies". One such disorder is NIBP syndrome, characterized by microcephaly and intellectual disability, and caused by mutations of NIBP/TRAPPC9, a crucial and unique member of TRAPPII. To investigate the neural cellular/molecular mechanisms underlying microcephaly, we developed Nibp/Trappc9-deficient animal models using different techniques, including morpholino knockdown and CRISPR/Cas mutation in zebrafish and Cre/LoxP-mediated gene targeting in mice. Nibp/Trappc9 deficiency impaired the stability of the TRAPPII complex at actin filaments and microtubules of neurites and growth cones. This deficiency also impaired elongation and branching of neuronal dendrites and axons, without significant effects on neurite initiation or neural cell number/types in embryonic and adult brains. The positive correlation of TRAPPII stability and neurite elongation/branching suggests a potential role for TRAPPII in regulating neurite morphology. These results provide novel genetic/molecular evidence to define patients with a type of non-syndromic autosomal recessive intellectual disability and highlight the importance of developing therapeutic approaches targeting the TRAPPII complex to cure TRAPPopathies.

Inhibition of protein kinase C-α and activation of ezrin by Lactobacillus acidophilus restore Na+/H+ exchange activity and fluid absorption in db/db mice.

Gastrointestinal (GI) complications, including diarrhea, constipation, and gastroparesis, are common in patients with diabetes. Dysregulation of the Na+/H+ exchanger NHE3 in the intestine is linked to diarrhea and constipation, and recent studies showed that NHE3 expression is reduced in type 1 diabetes and metformin causes diarrhea in the db/db mouse model of type 2 diabetes (T2D) via inhibition of NHE3. In this study, we investigated whether NHE3 expression is altered in type 2 diabetic intestine and the underlying mechanism that dysregulates NHE3. NHE3 expression in the brush border membrane (BBM) of the intestine of diabetic mice and humans was decreased. Protein kinase C (PKC) activation is associated with pathologies of diabetes, and immunofluorescence (IF) analysis revealed increased BBM PKCα abundance. Inhibition of PKCα increased NHE3 BBM abundance and NHE3-mediated intestinal fluid absorption in db/db mice. Previous studies have shown that Lactobacillus acidophilus (LA) stimulates intestinal ion transporters. LA increased NHE3 BBM expression and mitigated metformin-mediated inhibition of NHE3 in vitro and in vivo. To understand the underlying mechanism of LA-mediated stimulation of NHE3, we used Caco-2bbe cells overexpressing PKCα that mimic the elevated state of PKCα in T2D. LA diminished PKCα BBM expression, increased phosphorylation of ezrin, and the interaction of NHE3 with NHE regulatory factor 2 (NHERF2). In addition, inhibition of PKCι blocked phosphorylation of ezrin and activation of NHE3 by LA. These findings demonstrate that NHE3 is downregulated in T2D, and LA restores NHE3 expression via regulation of PKCα, PKCι, and ezrin.NEW & NOTEWORTHY We used mouse models of type 2 diabetes (T2D) and human patient-derived samples to show that Na+/H+ exchanger 3 (NHE3) expression is decreased in T2D. We show that protein kinase C-α (PKCα) is activated in diabetes and inhibition of PKCα increased NHE3 expression and mitigates diarrhea. We show that Lactobacillus acidophilus (LA) stimulates NHE3 via inhibition of PKCα and phosphorylation of ezrin.

Role of stimulator of interferon genes (STING) in the enteric nervous system in health and disease.

Stimulator of Interferon Genes (STING) is a crucial protein that controls the immune system's reaction to bacterial and viral infections. As a pattern-recognition receptor, STING is found in immune cells as well as in neurons and glia in the enteric nervous system (ENS). Recent studies have linked STING to the pathogenesis of several neurological disorders like multiple sclerosis (MS), Alzheimer's disease (AD), and gastrointestinal disorders, including irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD), which are characterized by chronic inflammation and dysregulation of the enteric nervous system (ENS) in the digestive tract. STING plays a crucial role in the pathway that induces the production of interferon in response to viral infection in the central nervous system (CNS). A new study by Dharshika et al. in the current issue of Neurogastroenterology and Motility has demonstrated distinct roles for STING in enteric neurons and glia, namely activation of STING leads to IFN-ß production in enteric neurons but not in glia and reducing STING activation in enteric glia does not modulate the severity of Dextran sulfate sodium (DSS) colitis or subsequent loss of enteric neurons. Rather, the role of STING in enteric glia is related to enhancing autophagy. STING can influence gastrointestinal motility and barrier function and therefore be involved in the pathophysiology of IBS and IBD. This mini review highlights the current knowledge of STING in the pathophysiology of CNS and gastrointestinal diseases as well as these newly uncovered roles STING in enteric neurons and glia.

SARS-CoV-2 Induces Epithelial-Enteric Neuronal Crosstalk Stimulating VIP Release.

BACKGROUND: Diarrhea is present in up to 30-50% of patients with COVID-19. The mechanism of SARS-CoV-2-induced diarrhea remains unclear. We hypothesized that enterocyte-enteric neuron interactions were important in SARS-CoV-2-induced diarrhea. SARS-CoV-2 induces endoplasmic reticulum (ER) stress in enterocytes causing the release of damage associated molecular patterns (DAMPs). The DAMPs then stimulate the release of enteric neurotransmitters that disrupt gut electrolyte homeostasis. METHODS: Primary mouse enteric neurons (EN) were exposed to a conditioned medium from ACE2-expressing Caco-2 colonic epithelial cells infected with SARS-CoV-2 or treated with tunicamycin (ER stress inducer). Vasoactive intestinal peptides (VIP) expression and secretion by EN were assessed by RT-PCR and ELISA, respectively. Membrane expression of NHE3 was determined by surface biotinylation. RESULTS: SARS-CoV-2 infection led to increased expression of BiP/GRP78, a marker and key regulator for ER stress in Caco-2 cells. Infected cells secreted the DAMP protein, heat shock protein 70 (HSP70), into the culture media, as revealed by proteomic and Western analyses. The expression of VIP mRNA in EN was up-regulated after treatment with a conditioned medium of SARS-CoV-2-infected Caco-2 cells. CD91, a receptor for HSP70, is abundantly expressed in the cultured mouse EN. Tunicamycin, an inducer of ER stress, also induced the release of HSP70 and Xbp1s, mimicking SARS-CoV-2 infection. Co-treatment of Caco-2 with tunicamycin (apical) and VIP (basolateral) induced a synergistic decrease in membrane expression of Na+/H+ exchanger (NHE3), an important transporter that mediates intestinal Na+/fluid absorption. CONCLUSIONS: Our findings demonstrate that SARS-CoV-2 enterocyte infection leads to ER stress and the release of DAMPs that up-regulates the expression and release of VIP by EN. VIP in turn inhibits fluid absorption through the downregulation of brush-border membrane expression of NHE3 in enterocytes. These data highlight the role of epithelial-enteric neuronal crosstalk in COVID-19-related diarrhea.

Aryl hydrocarbon receptor activation affects nitrergic neuronal survival and delays intestinal motility in mice.

Despite progress describing the effects of persistent organic pollutants (POPs) on the central nervous system, the effect of POPs on enteric nervous system (ENS) function remains underexplored. We studied the effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a POP, and a potent aryl hydrocarbon receptor (AHR) ligand, on the ENS and intestinal motility in mice. C57Bl/6J mice treated with TCDD (2.4 µg/kg body weight) for 8 weeks (once per week) exhibited significant delay in intestinal motility as shown by reduced stool frequency, prolonged intestinal transit time, and a persistence of dye in the jejunum compared to control mice with maximal dye retention in the ileum. TCDD significantly increased Cyp1a1 expression, an AHR target gene, and reduced the total number of neurons and affected nitrergic neurons in cells isolated from WT mice, but not Ahr-/- mice. In immortalized fetal enteric neuronal cells, TCDD-induced nuclear translocation of AHR as well as increased Cyp1a1 expression. AHR activation did not affect neuronal proliferation. However, AHR activation resulted in enteric neuronal toxicity, specifically, nitrergic neurons. Our results demonstrate that TCDD adversely affects nitrergic neurons and thereby contributes to delayed intestinal motility. These findings suggest that AHR signaling in the ENS may play a role in modulating TCDD-induced gastrointestinal pathophysiology.

SIRT3 activation promotes enteric neurons survival and differentiation.

Enteric neuron degeneration has been observed during aging, and in individuals with metabolic dysfunction including obesity and diabetes. Honokiol, a naturally occurring compound, is an activator of Sirtuin-3 (SIRT3) that has antioxidant activity. Its role in modulating enteric neuron-specific neurodegeneration is unknown. We studied the effects of honokiol and its fluorinated analog, hexafluoro-honokiol, on enteric neuronal differentiation and survival. We used a previously established model of mouse primary enteric neuronal cells and an enteric neuronal cell line treated with palmitate (PA) and lipopolysaccharide (LPS) to induce mitochondrial dysfunction and enteric neuronal cell death. The effect of honokiol and hexafluoro-honokiol was assessed on neuronal phenotype, fiber density, differentiation, and pyroptosis. Honokiol and hexafluoro-honokiol significantly increased neuronal networks and fiber density in enteric neurons and increased levels of neuronal nitric oxide synthase and Choline acetyltransferase mRNA. Hexafluoro-honokiol and honokiol also significantly increased SIRT3 mRNA levels and suppressed palmitate and LPS-induced neuronal pyroptosis. SIRT3 knock-down prevented the hexafluoro-honokiol mediated suppression of mitochondrial superoxide release. Our data supports a neuroprotective effect of honokiol and its derivative and these could be used as prophylactic or therapeutic agents for treating enteric neurodegeneration and associated motility disorders.

Glial cell derived neurotrophic factor prevents western diet and palmitate-induced hepatocyte oxidative damage and death through SIRT3.

Nonalcoholic fatty liver disease (NAFLD) is associated with increased oxidative stress that leads to hepatocyte and mitochondrial damage. In this study we investigated the mechanisms involved in the induction of oxidative stress and impairment of mitochondrial quality control and mitophagy in hepatocytes by the saturated fatty acid palmitate and Western diet feeding in mice and if their harmful effects could be reversed by the neurotrophic factor glial cell derived neurotrophic factor (GDNF). Western diet (WD)-feeding increased hepatic lipid peroxidation in control mice and, in vitro palmitate induced oxidative stress and impaired the mitophagic clearance of damaged mitochondria in hepatocytes. This was accompanied by reductions in hepatocyte sirtuin 3 (SIRT3) deacetylase activity, gene expression and protein levels as well as in superoxide dismutase enzyme activity. These reductions were reversed in the liver of Western diet fed GDNF transgenic mice and in hepatocytes exposed to palmitate in the presence of GDNF. We demonstrate an important role for Western diet and palmitate in inducing oxidative stress and impairing mitophagy in hepatocytes and an ability of GDNF to prevent this. These findings suggest that GDNF or its agonists may be a potential therapy for the prevention or treatment of NAFLD.

Integrated regulation of stress responses, autophagy and survival by altered intracellular iron stores.

Iron is a mineral essential for blood production and a variety of critical cellular functions. Altered iron metabolism has been increasingly observed in many diseases and disorders, but a comprehensive and mechanistic understanding of the cellular impact of impaired iron metabolism is still lacking. We examined the effects of iron overload or iron deficiency on cellular stress responses and autophagy which collectively regulate cell homeostasis and survival. Acute iron loading led to increased mitochondrial ROS (mtROS) production and damage, lipid peroxidation, impaired autophagic flux, and ferroptosis. Iron-induced mtROS overproduction is the mechanism of increased lipid peroxidation, impaired autophagy, and the induction of ferroptosis. Iron excess-induced ferroptosis was cell-type dependent and regulated by activating transcription factor 4 (ATF4). Upregulation of ATF4 mitigated iron-induced autophagic dysfunction and ferroptosis, whereas silencing of ATF4 expression impaired autophagy and resulted in increased mtROS production and ferroptosis. Employing autophagy-deficient hepatocytes and different autophagy inhibitors, we further showed that autophagic impairment sensitized cells to iron-induced ferroptosis. In contrast, iron deficiency activated the endoplasmic reticulum (ER) stress response, decreased autophagy, and induced apoptosis. Decreased autophagy associated with iron deficiency was due to ER stress, as reduction of ER stress by 4-phenylbutyric acid (4-PBA) improved autophagic flux. The mechanism of decreased autophagy in iron deficiency is a disruption in lysosomal biogenesis due to impaired posttranslational maturation of lysosomal membrane proteins. In conclusion, iron excess and iron deficiency cause different forms of cell stress and death in part through the common mechanism of impaired autophagic function.

Relationship between dysphagia, lower esophageal sphincter relaxation, and esophagogastric junction distensibility.

BACKGROUND: It is debated whether high-resolution manometric (HRM) integrated relaxation pressure (IRP) or functional lumen imaging probe (FLIP) distensibility index (DI) is the superior measure of esophagogastric junction (EGJ) opening. We examined the relationship between the DI and IRP and assessed correlations with dysphagia symptoms in patients with achalasia and EGJ outflow obstruction (EGJOO). METHODS: Patients with achalasia and those with barium tablet retention at the EGJ were grouped as follows: Group 1:Achalasia (IRP ≥ 15 mmHg + complete absence of normal peristalsis); Group 2: Manometric +FLIP EGJOO (IRP ≥ 15 mmHg with some intact peristalsis + DI ≤ 2.8 mm2 /mmHg); Group 3: Abnormal DI only (DI ≤ 2.8 mm2 /mmHg + IRP <15 mmHg); and Group 4: Normal IRP and DI (IRP ≥ 15 mmHg + DI > 2.8 mm2 /mmHg). Correlation between the DI, baseline lower esophageal sphincter pressure (BLESP), IRP, and dysphagia (Eckardt score) was assessed. Multivariable analysis was used to assess variables associated with dysphagia score ≥2. KEY RESULTS: A total of 79 patients were included: Group 1 (n = 31), Group 2 (n = 33), Group 3 (n = 14), and Group 4 (n = 1). DI did not correlate with BLESP or IRP in the whole sample or subgroups. DI was the only variable associated with dysphagia score ≥2 (p = 0.006). DI < 1.25 mm2 /mmHg had sensitivity of 87% and specificity of 52% (p = 0.0003) for dysphagia score ≥2. CONCLUSIONS & INFERENCES: DI does not correlate with HRM EGJ measurements and is the metric with the strongest effect on dysphagia severity. The various biological elements that may cause restrictive EGJ function should be the subject of future studies.

Nrf2 attenuates hyperglycemia-induced nNOS impairment in adult mouse primary enteric neuronal crest cells and normalizes stomach function.

Enteric neuronal cells play a vital role in gut motility in humans and experimental rodent models. Patients with diabetes are more vulnerable to gastrointestinal dysfunction due to enteric neuronal degeneration. In this study, we examined the mechanistic role and regulation of nuclear factor-erythroid 2-related factor 2 (Nrf2) in hyperglycemia-induced enteric neuronal cell apoptosis in vitro by using adult mouse primary enteric neuronal crest cells (pENCs). Our data show that hyperglycemia (HG) or inhibition of Nrf2 induces apoptosis by elevating proinflammatory cytokines, reactive oxygen species (ROS) and suppresses neuronal nitric oxide synthase (nNOS-α) via PI3K/Nrf2-mediated signaling. Conversely, treating pENCs with cinnamaldehyde (CNM), a naturally occurring Nrf2 activator, prevented HG-induced apoptosis. These novel data reveal a negative feedback mechanism for GSK-3 activation. To further demonstrate that loss of Nrf2 leads to inflammation, oxidative stress, and reduces nNOS-mediated gastric function, we have used streptozotocin (STZ)-induced diabetic and Nrf2 null female mice. In vivo activation of Nrf2 with CNM (50 mg/kg, 3 days a week, ip) attenuated impaired nitrergic relaxation and delayed gastric emptying (GE) in conventional type 1 diabetic but not in Nrf2 null female mice. Supplementation of CNM normalized diabetes-induced altered gastric antrum protein expression of 1) p-AKT/p-p38MAPK/p-GSK-3ß, 2) BH4 (cofactor of nNOS) biosynthesis enzyme GCH-1, 3) nNOSα, 4) TLR4, NF-κB, and 5) inflammatory cytokines (TNF-α, IL-1ß, IL-6). We conclude that activation of Nrf2 prevents hyperglycemia-induced apoptosis in pENCs and restores nitrergic-mediated gastric motility and GE in STZ-induced diabetes female mice.NEW & NOTEWORTHY Primary neuronal cell crust (pENCs) in the intestine habitats nNOS and Nrf2, which was suppressed in diabetic gastroparesis. Activation of Nrf2 restored nNOS by suppressing inflammatory markers in pENCs cells. Inhibition of Nrf2 reveals a negative feedback mechanism for the activation of GSK-3. Activation of Nrf2 alleviates STZ-induced delayed gastric emptying and nitrergic relaxation in female mice. Activation of Nrf2 restored impaired gastric BH4 biosynthesis enzyme GCH-1, nNOSα expression thus regulating nitric oxide levels.

Enteric Nervous System in Neonatal Necrotizing Enterocolitis.

BACKGROUND: The pathophysiology of necrotizing enterocolitis (NEC) is not clear, but increasing information suggests that the risk and severity of NEC may be influenced by abnormalities in the enteric nervous system (ENS). OBJECTIVE: The purpose of this review was to scope and examine the research related to ENS-associated abnormalities that have either been identified in NEC or have been noted in other inflammatory bowel disorders (IBDs) with histopathological abnormalities similar to NEC. The aim was to summarize the research findings, identify research gaps in existing literature, and disseminate them to key knowledge end-users to collaborate and address the same in future studies. METHODS: Articles that met the objectives of the study were identified through an extensive literature search in the databases PubMed, EMBASE, and Scopus. RESULTS: The sources identified through the literature search revealed that: (1) ENS may be involved in NEC development and post-NEC complications, (2) NEC development is associated with changes in the ENS, and (3) NEC-associated changes could be modulated by the ENS. CONCLUSION: The findings from this review identify the enteric nervous as a target in the development and progression of NEC. Thus, factors that can protect the ENS can potentially prevent and treat NEC and post-NEC complications. This review serves to summarize the existing literature and highlights a need for further research on the involvement of ENS in NEC.

Utilizing functional lumen imaging probe in directing treatment for post-fundoplication dysphagia.

BACKGROUND: Esophagogastric junction obstruction (EGJO) post-fundoplication (PF) is difficult to identify with currently available tests. We aimed to assess the diagnostic accuracy of EGJ opening on functional lumen imaging probe (FLIP) and dilation outcome in FLIP-detected EGJO in PF dysphagia. METHODS: We prospectively collected data on PF patients referred to Esophageal Clinic over 18 months. EGJO diagnosis was made by (a) endoscopist's description of a narrow EGJ/wrap area, (b) appearance of wrap obstruction or contrast/tablet retention on esophagram, or (c) EGJ-distensibility index (DI) < 2.8 mm2/mmHg on real-time FLIP. In patients with EGJO and dysphagia, EGJ dilation was performed to 20 mm, 30 mm, or 35 mm in a stepwise fashion. Outcome was assessed as % dysphagia improvement during phone call or on brief esophageal dysphagia questionnaire (BEDQ) score. RESULTS: Twenty-six patients were included, of whom 17 (65%) had a low EGJ-DI. No patients had a hiatal hernia greater than 3 cm. Dysphagia was the primary symptom in 17/26 (65%). In 85% (κ = 0.677) of cases, EGJ assessment (tight vs. open) was congruent between the combination of endoscopy (n = 26) and esophagram (n = 21) vs. EGJ-DI (n = 26) on FLIP. Follow-up data were available in 11 patients who had dilation based on a low EGJ-DI (4 with 20 mm balloon and 7 with ≥ 30 mm balloon). Overall, the mean % improvement in dysphagia was 60% (95% CI 37.7-82.3%, p = 0.0001). Nine out of 11 patients, including 6 out of 7 undergoing pneumatic dilation, had improvement ≥ 50% in dysphagia (mean % improvement 72.2%; 95% CI 56.1-88.4%, p = 0.0001). CONCLUSIONS AND INFERENCES: Functional lumen imaging probe is an accurate modality for evaluating for EGJ obstruction PF. FLIP may be used to select patients who may benefit from larger diameter dilation.

Inhibition of GSK-3ß restores delayed gastric emptying in obesity-induced diabetic female mice.

Diabetic gastroparesis (DG) is a clinical syndrome characterized by delayed gastric emptying (DGE). Loss of nuclear factor erythroid 2-related factor 2 (Nrf2) is associated with reduced neuronal nitric oxide synthase-α (nNOSα)-mediated gastric motility and DGE. Previous studies have shown that nuclear exclusion and inactivation of Nrf2 is partly regulated by glycogen synthase kinase 3ß (GSK-3ß). In the current study, the molecular signaling of GSK-3ß-mediated Nrf2 activation and its mechanistic role on DG were investigated in high-fat diet (HFD)-induced obese/Type 2 diabetes (T2D) female mice. Adult female C57BL/6J mice were fed with HFD or normal diet (ND) with or without GSK-3ß inhibitor (SB 216763, 10 mg/kg body wt ip) start from the 14th wk and continued feeding mice for an additional 3-wk time period. Our results show that treatment with GSK-3ß inhibitor SB attenuated DGE in obese/T2D mice. Treatment with SB restored impaired gastric 1) Nrf2 and phase II antioxidant enzymes through PI3K/ERK/AKT-mediated pathway, 2) tetrahydrobiopterin (BH4, cofactor of nNOS) biosynthesis enzyme dihydrofolate reductase, and 3) nNOSα dimerization in obese/T2 diabetic female mice. SB treatment normalized caspase 3 activity and downstream GSK-3ß signaling in the gastric tissues of the obese/T2 diabetic female mice. In addition, GSK-3ß inhibitor restored impaired nitrergic relaxation in hyperglycemic conditions. Finally, SB treatment reduced GSK3 marker, pTau in adult primary enteric neuronal cells. These findings emphasize the importance of GSK-3ß on regulating gastric Nrf2 and nitrergic mediated gastric emptying in obese/diabetic rodents.NEW & NOTEWORTHY Inhibition of glycogen synthase kinase 3ß (GSK-3ß) with SB 216763 attenuates delayed gastric emptying through gastric nuclear factor erythroid 2-related factor 2 (Nrf2)-phase II enzymes in high-fat diet-fed female mice. SB 216763 restored impaired gastric PI3K/AKT/ ß-catenin/caspase 3 expression. Inhibition of GSK-3ß normalized gastric dihydrofolate reductase, neuronal nitric oxide synthase-α expression, dimerization and nitrergic relaxation. SB 216763 normalized both serum estrogen and nitrate levels in female obese/Type 2 diabetes mice. SB 216763 reduced downstream signaling of GSK-3ß in enteric neuronal cells in vitro.

Caspase-11-mediated enteric neuronal pyroptosis underlies Western diet-induced colonic dysmotility.

Enteric neuronal degeneration, as seen in inflammatory bowel disease, obesity, and diabetes, can lead to gastrointestinal dysmotility. Pyroptosis is a novel form of programmed cell death but little is known about its role in enteric neuronal degeneration. We observed higher levels of cleaved caspase-1, a marker of pyroptosis, in myenteric ganglia of overweight and obese human subjects compared with normal-weight subjects. Western diet-fed (WD-fed) mice exhibited increased myenteric neuronal pyroptosis, delayed colonic transit, and impaired electric field stimulation-induced colonic relaxation responses. WD increased TLR4 expression and cleaved caspase-1 in myenteric nitrergic neurons. Overactivation of nitrergic neuronal NF-κB signaling resulted in increased pyroptosis and delayed colonic motility. In caspase-11-deficient mice, WD did not induce nitrergic myenteric neuronal pyroptosis and colonic dysmotility. To understand the contributions of saturated fatty acids and bacterial products to the steps leading to enteric neurodegeneration, we performed in vitro experiments using mouse enteric neurons. Palmitate and lipopolysaccharide (LPS) increased nitrergic, but not cholinergic, enteric neuronal pyroptosis. LPS gained entry to the cytosol in the presence of palmitate, activating caspase-11 and gasdermin D, leading to pyroptosis. These results support a role of the caspase-11-mediated pyroptotic pathway in WD-induced myenteric nitrergic neuronal degeneration and colonic dysmotility, providing important therapeutic targets for enteric neuropathy.