Neurotensin modulation of lipopolysaccharide induced inflammation of gut-liver axis: Evaluation using neurotensin receptor agonist and antagonist

Integration of signal transduction pathways in sensory epithelial enteroendocrine cells

The gastrointestinal (GI) tract plays a crucial role in nutrient absorption, motility, and metabolism, while serving as a barrier against pathogens. The intestinal epithelial layer, particularly enteroendocrine cells (EEC), is pivotal in sensing luminal stimuli due to its strategic position. Although comprising only 1% of the GI epithelium, in total EEC comprises perhaps the largest endocrine organ that couples GI luminal stimuli with release of hormones and neurotransmitters such as serotonin, glucagon-like peptide-1 (GLP-1), and peptide-tyrosine-tyrosine (PYY), which regulate local and systemic physiology. In this review, we use EECs as a model to explore critical intracellular signaling pathways-centering around calcium (Ca²⁺) and cyclic adenosine monophosphate (cAMP). EECs utilize ionotropic and metabotropic receptors to detect luminal stimuli, leading to increased intracellular cytoplasmic Ca²⁺ and altered intracellular cAMP dynamics. Ca²⁺ influx is critical for the exocytosis of signaling molecules. The interplay between Ca²⁺ and cAMP signaling pathways enhances the release of these molecules, affecting both local and systemic responses. We make a point to discuss the conventional and emerging methodologies for measuring Ca²⁺ and cAMP dynamics in EECs, which is a rapidly expanding toolbox, containing genetically encoded indicators and resonance energy transfer techniques. Understanding these signaling cascades is essential for deciphering the complex roles of EECs in GI physiology and their impact on systemic health.

Efficacy of the neurotensin receptor 1 analog PD149163 in modulation of the kidney inflammation: Inhibition of the nuclear factor kappa β signaling pathway and oxidative stress in endotoxemic mice

This study elucidated that the neurotensin receptor 1 agonist PD149163 ameliorated the kidney inflammation in endotoxemic mice inhibiting the nuclear factor kappa β (NF-kβ) pathway and reducing the oxidative stress in a dose-dependent manner. Swiss albino female mice (8 weeks; 25 ± 5 gms) were maintained in six groups (n = 6): Group 1/control, Group 2, Group 3 and Group 4 were exposed to lipopolysaccharide/LPS (1 mg/kg bw; i.p; 5 days) followed by PD149163 treatment with low dose/NTS50 (50 μg/kg BW i.p. 28 days) and high dose/NTS100 (100 μg/kg BW i.p. 28 days) to Group 3 and Group 4 respectively. Group 5 and Group 6 mice were only treated with the agonist, similar low and high doses respectively for the same duration. The results showed LPS-induced significant increase in the plasma levels of the NF-kβ, pro-inflammatory cytokines (TNF-α, IL-6) and a decrease in the anti-inflammatory cytokine IL-10. A significant increase in the pro-oxidant (LPx) and decrease of the anti-oxidants (SOD, CAT) in the kidney tissue was noted. Plasma NTS level was significantly decreased along with a significant increase of the corticosterone. The inflammation was reflected in the kidney histopathology. PD149163 significantly reduced inflammation by down-regulating NF-kβ, TNF-α, IL-6, CORT levels, oxidative stress and alleviated kidney injury. PD149163 enhanced the plasma level of NT. The role of PD149163 in the modulation of inflammation of kidney tissue by its anti-inflammatory and anti-oxidative effects is suggested. Further studies may better confirm the efficacy of the NTS analog for therapeutic intervention in inflammation-related diseases of the kidney.

Probiotics modulation of the endotoxemic effect on the gut and liver of the lipopolysaccharide challenged mice

The multistrain probiotics' efficacy in ameliorating the endotoxemic effect in Lipopolysaccharide (LPS) challenged mice was evaluated with the agonist of anti-inflammatory peptide, neurotensin (NTS), especially targeting the inflammation of the gut and liver. Swiss Albino Mice (Female, 8 weeks old) were maintained in eight groups: Group I as Control, Group II-Group V were exposed to intraperitoneal (i.p.) LPS (1 mg/kg bw) for 5 days. After that, Group III and Group VI were administered probiotics orally (0.6 gm/kg bw/day), Group IV and Group VII with NTS receptor 1 (NTSR1) agonist PD149163 (50 µg/kg bw/day i.p.), and Group V and Group VIII co-administered with probiotics and PD149163 for 28 days. Group II (LPS-exposed) was maintained without any further treatment; mice of all the groups were sacrificed at day 34. In the LPS-exposed mice, endotoxemia was distinct from a significant (P < 0.001) increase of plasma pro-inflammatory cytokines (TNF-α; IL-6), a decrease of anti-inflammatory cytokine (IL-10), oxidative stress, and inflammation of the gut and liver. Increased serum transaminases indicated hepatic inflammation. A decreased population of the bifidobacteria and increased clostridia indicated microbiota dysbiosis. Probiotics when used as an adjunct along with PD149163 have shown better efficacy in inflammation modulation as reflected in the significantly decreased (P < 0.001) inflammatory mediators, oxidative stress, restoration of the beneficial bacterial population, along with a significant reduction in histopathological scores of the gut and the liver than when used alone. This study suggests probiotics could be used as an adjunct in clinical practice along with anti-inflammatory drugs for better therapeutic efficacy.

Prognostic value of neurotensin in experimental terminal ileitis

BackgroundTerminal ileitis (TI) is an inflammatory condition of the distal portion of the ileum.ObjectiveTo investigate the changes and significance of neurotensin (NT) in the course of experimental terminal ileitis (ETI).MethodsA total of 90 Sprague Dawley (SD) rats were randomly divided into the control, model, and suture groups (30 rats in each group). After 2, 4, and 8 weeks of surgery, 10 TI tissues were taken for endoscopic observation in each group. Hematoxylin-eosin (HE) staining was used to detect the pathological changes. The NT levels in serum and terminal ileum mucosa were detected by Enzyme-linked immunosorbent assay (ELISA).ResultsAcute inflammatory changes were observed in the suture and the model groups after 2-week of operation. At 4 weeks, compared to the control group, the inflammatory damage in the model group became heavier, but it was reduced in the suture group. At 8 weeks, the model group showed chronic inflammation. However, there was no obvious inflammatory cell infiltration in both the suture group and control group. NT levels were increased in the suture and model groups at 2 weeks, particularly in the model group, and they were significantly higher in the suture and model groups than those in the control group (P < 0.05). At 4 weeks, the NT levels in the model group continued to rise, while they decreased in the suture group (P < 0.05). After 8 weeks, NT levels in the model group were significantly higher than those in the suture and control groups (P < 0.05). Furthermore, from 2 weeks to 8 weeks, the NT concentration in the model group gradually increased, and the suture group increased for 2 weeks, followed by a downward trend.Conclusions: In the ETI, the changes in NT concentration in serum and TI mucosa were positively correlated with the degree of inflammation.

Neurotensin via Type I Receptor Modulates the Endotoxemia Induced Oxido-Inflammatory Stress on the Sympathetic Adrenomedullary System of Mice Regulating NF-κβ/Nor-Epinephrine Pathway

The present study investigated the role of the neurotensin/NTS in the modulation of the lipopolysaccharide/LPS induced dysfunction of the sympatho-adrenal-medullary system/SAM using both the NTS receptor 1/NTSR1 agonist PD149163/PD and antagonist SR48692 /SR. Forty eight mice were maintained in eight groups; Group I/control, Groups II, III, IV, and VII received LPS for 5 days further Group III/IV/VII received PD low dose/PDL, PD high dose /PDH and SR for 28 days respectively. Group V/VI received similar only PDL and PDH dose respectively whereas Group VIII was exposed to only SR for 28 days. Adrenal tissues histopathology examined through hematoxylin-eosin staining. The plasma levels of pro-inflammatory mediators (NF-kβ, TNF-α, IL-6), IL-10, corticosterone/CORT, nor-epinephrine/NE and NTS were assessed through ELISA. Biochemical detection was adopted to check the level of oxidative stress, assessed by measuring the thiobarbituric acid reactive substance/TBARS, superoxide dismutase/SOD and catalase/CAT in adrenal tissue to determine the therapeutic effect of NTS receptor 1 analogs. Compared with LPS group, PD ameliorated the adrenal medulla histopathology by significantly decreasing pro-inflammatory mediators, CORT and NE as well as enhancing IL-10, normalizing NTS level via down-regulating NF-κβ level. PD inhibited the oxidative stress in SAM system of adrenal by reducing TBARS, while enhancing SOD and CAT activity via regulating the CORT and NE levels. Conversely, SR administration could not normalize the deleterious effect caused by the LPS due to up-regulation of NF-κβ level. Therefore, PD ameliorates the inflammation and oxidative stress of SAM system by inhibiting NF-kβ/NE signaling pathway. Thus, PD could be used as a biological tool in SAM dysfunction for therapeutic evaluation of chronic inflammatory diseases.

Neurotensin receptor agonist PD149163 modulates LPS-induced enterocyte apoptosis by downregulating TNFR pathway and executioner caspase 3 in endotoxemic mice: insights from in vivo and in silico study

This study was designed to evaluate the dose-dependent efficacy of neurotensin receptor-1 (NTSR1) agonist PD149163 in the amelioration of the lipopolysaccharide (LPS)-induced apoptosis in the gastrointestinal tract (GIT) of mice. PD149163 is an analogue of NTS, a GIT tri-decapeptide with anti-inflammatory and anti-oxidative effects. Swiss-albino mice (female/8 weeks/25 ± 2.5 g) were divided into six groups: control; LPS, LPS + PD149163L, and LPS + PD149163H groups were treated with LPS (0.2 μmol/L/kgBW; 5 days), followed by exposure of PD149163 to LPS + PD149163L (10.6 μmol/L/kgBW), and LPS + PD149163H (21.2 μmol/L/kgBW) for 28 days. OnlyPD149163L (10.6 μmol/L/kgBW) and onlyPD149163H (21.2 μmol/L/kgBW) groups were maintained for 28 days. Both the LPS and PD149163 were given intraperitoneally. PD149163 treatment for 4 weeks alleviated the LPS-induced enterocyte apoptosis in a dose-dependent manner. LPS-induced excessive levels of caspase-3, tumour necrosis factor-α, and leptin (biomarkers of LPS-induced apoptosis) in plasma were decreased by PD149163H treatment. Moreover, LPS-induced gut oxidative stress was ameliorated by PD149163H supplementation, as evidenced by the decreased content of malondialdehyde, lipid-hydroperoxide and increased level of superoxide-dismutase, catalase. Furthermore, PD149163H mediated elevation of the plasma anti-apoptotic protein (B-cell leukaemia/lymphoma-2) along with the NTS level contributed to the modulation of LPS-induced enterocyte apoptosis, reflected in histopathology. In vivo results were substantiated with in silico molecular docking analysis that predicted the binding of PD149163-TLR4 complex, suggesting that PD149163 can act as a TLR4 modulator and inhibit the activation of TLR4. The role of PD149163 in ameliorating GIT apoptosis by its anti-apoptotic and antioxidative effects is suggested. Further research may provide significant insights into the therapeutic intervention of PD149163 in apoptosis-related diseases of GIT.

Impact of lifestyle intervention on vitamin D, Adiponectin, Insulin-like growth factor 1 and Proneurotensin in overweight individuals from the Middle East

BACKGROUND

Immigrants from the Middle East (ME) have a higher prevalence of type 2 diabetes (T2D) compared to the native-born Swedish population. In individuals free from T2D, ME immigrants are more insulin resistant and have lower levels of adjusted insulin secretion (Disposition index, DIo) compared to Swedish-born individuals. The ethnic differences are not fully explained by traditional risk factors. This has raised the question as to whether hormonal factors other than insulin are involved, contributing to higher T2D risk in ME immigrants.

AIMS

In ME immigrants at high risk of developing T2D, we aimed to study the effect of a randomized culturally adapted lifestyle intervention on the levels of Vitamin D (25(OH)D), insulin-like growth factor 1 (IGF-1), Pro-neurotensin (Pro-NT) and Adiponectin. Furthermore, we aimed to study if the effect of the intervention was associated to these hormones, or if a direct effect of the intervention remained after accounting for these.

METHODS

In this culturally adapted randomized controlled trial of four months duration, eligible ME immigrants at high risk of developing T2D identified in the MEDIM cohort were invited to participate. The intervention group (N= 35) received a culturally adapted lifestyle intervention program consisting of seven group sessions and cooking classes. The control group (N= 32) were given treatment as usual with oral and written information to improve their lifestyle habits. Using mixed models' linear regression analysis, the changes in the levels of 25(OH)D, IGF-1, Adiponectin and Pro-NT were assessed by comparing the groups and we further studied the effects of the changes on insulin action and secretion.

RESULTS

The adjusted levels of 25(OH)D significantly increased in the intervention group compared to the control group (β for the effect of the intervention on 25(OH)D: 0.061, 95 % CI 0.009-0.113, P = 0.023). The increase in insulin sensitivity index (ISI) observed in the intervention compared to the control group was altered after adjusting for 25(OH)D: 0.129, 95 % CI -0.016-0.274, P = 0.078). IGF-1, Adiponectin and Pro-NT did not significantly influence the change over time concerning insulin secretion.

CONCLUSION

Lifestyle intervention increases the adjusted levels of 25(OH)D. Moreover, the effect of the lifestyle intervention on insulin action and secretion was altered when adjusting for 25(OH)D.

The neurotensin receptor 1 agonist PD149163 alleviates visceral hypersensitivity and colonic hyperpermeability in rat irritable bowel syndrome model

BACKGROUND

An impaired intestinal barrier with the activation of corticotropin-releasing factor (CRF), Toll-like receptor 4 (TLR4), and proinflammatory cytokine signaling, resulting in visceral hypersensitivity, is a crucial aspect of irritable bowel syndrome (IBS). The gut exhibits abundant expression of neurotensin; however, its role in the pathophysiology of IBS remains uncertain. This study aimed to clarify the effects of PD149163, a specific agonist for neurotensin receptor 1 (NTR1), on visceral sensation and gut barrier in rat IBS models.

METHODS

The visceral pain threshold in response to colonic balloon distention was electrophysiologically determined by monitoring abdominal muscle contractions, while colonic permeability was measured by quantifying absorbed Evans blue in colonic tissue in vivo in adult male Sprague-Dawley rats. We employed the rat IBS models, i.e., lipopolysaccharide (LPS)- and CRF-induced visceral hypersensitivity and colonic hyperpermeability, and explored the effects of PD149163.

KEY RESULTS

Intraperitoneal PD149163 (160, 240, 320 μg kg-1) prevented LPS (1 mg kg-1, subcutaneously)-induced visceral hypersensitivity and colonic hyperpermeability dose-dependently. It also prevented the gastrointestinal changes induced by CRF (50 μg kg-1, intraperitoneally). Peripheral atropine, bicuculline (a GABAA receptor antagonist), sulpiride (a dopamine D2 receptor antagonist), astressin2-B (a CRF receptor subtype 2 [CRF2] antagonist), and intracisternal SB-334867 (an orexin 1 receptor antagonist) reversed these effects of PD149163 in the LPS model.

CONCLUSIONS AND INFERENCES

PD149163 demonstrated an improvement in visceral hypersensitivity and colonic hyperpermeability in rat IBS models through the dopamine D2, GABAA, orexin, CRF2, and cholinergic pathways. Activation of NTR1 may modulate these gastrointestinal changes, helping to alleviate IBS symptoms.

Capsaicin Modulates Hepatic and Intestinal Inflammation and Oxidative Stress by Regulating the Colon Microbiota

We aimed to investigate the role of capsaicin (CAP) in modulating lipopolysaccharide (LPS)-induced hepatic and intestinal inflammation, oxidative stress, and its colonic microflora in mice. Thirty healthy male Kunming mice with similar body weights were randomly assigned to three groups: the control group (CON), the LPS group, and the CAP group, with ten mice in each group. The CON and the LPS groups received a daily dose of normal saline, respectively, while the CAP group received an equivalent dose of CAP. On the 28th day of the experiment, the LPS and the CAP groups were intraperitoneally injected with LPS, while the CON group was injected with an equal volume of normal saline. The results lead to the following conclusions. Compared to the LPS group, CAP improved the loss of hepatic lobular structure and significantly increased the duodenal villus length and ratio of villus length to crypt depth. CAP increased hepatic and colon interleukin-10 (IL-10) and decreased IL-6, IL-1β, and tumor necrosis factor (TNF-α) levels. CAP also increased hepatic catalase (CAT), glutathione peroxidase (GSH-Px), and superoxide dismutase (SOD) expression, and decreased malondialdehyde (MDA) levels. CAP significantly increased the relative abundances of Mucispirillum, Helicobacter, Prevotellaceae-UCG-001, Colidextribacter, unclassified-f-Oscillospiraceae, and Odoribacter, some of which were closely related to hepatic and colonic immune and oxidative markers. CAP also decreased the overall content of short-chain fatty acids, except for propionic acid. Overall, CAP can regulate the colon microbiota and exert anti-inflammatory and antioxidant effects. Whether CAP exerts its anti-inflammatory and antioxidant effects by modulating the colonic microflora, mainly Mucispirillum spp. and Helicobacter spp., requires further investigation.

A New Tailored Nanodroplet Carrier of Astaxanthin Can Improve Its Pharmacokinetic Profile and Antioxidant and Anti-Inflammatory Efficacies

Astaxanthin (ATX) is a carotenoid nutraceutical with poor bioavailability due to its high lipophilicity. We tested a new tailored nanodroplet capable of solubilizing ATX in an oil-in-water micro-environment (LDS-ATX) for its capacity to improve the ATX pharmacokinetic profile and therapeutic efficacy. We used liquid chromatography tandem mass spectrometry (LC-MS/MS) to profile the pharmacokinetics of ATX and LDS-ATX, superoxide mutase (SOD) activity to determine their antioxidant capacity, protein carbonylation and lipid peroxidation to compare their basal and lipopolysaccharide (LPS)-induced oxidative damage, and ELISA-based detection of IL-2 and IFN-γ to determine their anti-inflammatory capacity. ATX and LDS-ATX corrected only LPS-induced SOD inhibition and oxidative damage. SOD activity was restored only by LDS-ATX in the liver and brain and by both ATX and LDS-ATX in muscle. While in the liver and muscle, LDS-ATX attenuated oxidative damage to proteins and lipids better than ATX; only oxidative damage to lipids was preferably corrected by LDS-ATX in the brain. IL-2 and IFN-γ pro-inflammatory response was corrected by LDS-ATX and not ATX in the liver and brain, but in muscle, the IL-2 response was not corrected and the IFN-γ response was mitigated by both. These results strongly suggest an organ-dependent improvement of ATX bioavailability and efficacy by the LDS-ATX nanoformulation.

Neurotensin agonist PD149163 modulates lipopolysaccharide induced inflammation and oxidative stress in the female reproductive system of mice

Inflammation-mediated reproductive health problems in females have become an emerging concern. The present investigation was aimed to elucidate the efficacy of the PD149163, agonist of the type I neurotensin receptor, in preventing/ameliorating the lipopolysaccharide (LPS) induced inflammation of the female reproductive system of the mice. Female Swiss Albino Mice (8 weeks old) were maintained in three groups (6/group): Group I as Control, Group II and Group III were exposed to intraperitoneal (i.p) LPS (1 mg/kg bw) for 5 days followed by treatment with PD149163 (100 μg/kg BW i.p.) to Group III (LPS + PD) for 28 days. After termination of the experiment on 29th day, plasma levels of inflammatory cytokines, LH, FSH, estradiol, corticosterone, oxidative stress effects in the ovary and histopathological study of the ovary and uterine horn were done. LPS-induced inflammation of the ovary and uterine horn was ameliorated/prevented by PD149163 as reflected in the reduced histopathological scores, significant elevation of the plasma anti-inflammatory cytokine IL-10 and decrease of the pro inflammatory cytokines TNF-α and IL-6. Significant decrease of lipid peroxide, increase of antioxidant defense enzymes, Superoxide dismutase and Catalase in the ovary indicated reduction of oxidative stress. The plasma levels of the reproduction related hormones and corticosterone were restored. PD149163 acts as an anti-inflammatory and anti-oxidative agent in modulation of inflammation in the female reproductive system (ovary & uterine horn). These findings suggest that the therapeutic potential of the analogs of neurotensin including PD149163 should be explored for the treatment of the female reproductive health issues.

The significance of gut microbiota in the etiology of autoimmune hepatitis: a narrative review

Autoimmune hepatitis (AIH) is a chronic inflammatory disease of the liver that is mediated by autoimmunity and has complex pathogenesis. Its prevalence has increased globally. Since the liver is the first organ to be exposed to harmful substances, such as gut-derived intestinal microbiota and its metabolites, gut health is closely related to liver health, and the "liver-gut axis" allows abnormalities in the gut microbiota to influence the development of liver-related diseases such as AIH. Changes in the composition of the intestinal microbiota and its resultant disruption of the intestinal barrier and microbial transport are involved in multiple ways in the disruption of immune homeostasis and inflammation, thereby influencing the development of AIH. In terms of the mechanisms involved in immune, the gut microbiota or its metabolites, which is decreased in secondary bile acids, short-chain fatty acids (SCFAs), and polyamines, and increased in lipopolysaccharide (LPS), branched-chain amino acids (BCAA), tryptophan metabolite, amino acid, and bile acid, can disrupt immune homeostasis by activating various immune cells and immune-related signaling pathways, resulting in aberrant activation of the immune system. Clarifying this mechanism has significant clinical implications for the treatment of AIH with drugs that target intestinal microbiota and related signaling pathways. Therefore, this narrative review summarizes the progress in exploring the involvement of gut microbiota in the pathogenesis of AIH, with the aim of helping to improve the precise targeting of therapeutic treatments against AIH for the benefit of clinical AIH treatment.