Endotoxins and endocrine system

Dietary resistant starch ameliorating lipopolysaccharide-induced inflammation in meat ducks associated with the alteration in gut microbiome and glucagon-like peptide 1 signaling

Background

Consumption of resistant starch (RS) has been associated with various intestinal and systemic health benefits, but knowledge of its effects on intestinal health and inflammatory response in stressed birds is limited. Here, we examined how dietary RS supplementation from 12% raw potato starch (RPS) modulated inflammatory severity induced by lipopolysaccharide (LPS) in meat ducks.

Results

LPS administration at 14, 16, and 18 d (chronic challenge) decreased body weight (BW) and glucagon-like peptide 1 receptor (GLP-1R) level with higher intestinal permeability and inflammation, evident by higher pro-inflammatory cytokine levels. Dietary 12% RPS supplementation enhanced Claudin-1 and GLP-1R expression, along with lower levels of inflammatory factors in both ileum and serum. Microbiome analysis showed that RS treatment shifted microbial structure reflected by enriched the proportion of Firmicutes, Bifidobacterium, Ruminococcus, etc. Dietary RS addition also significantly increased the concentrations of propionate and butyrate during chronic LPS challenge. Furthermore, response to acute challenge, the ducks received 2 mg/kg BW LPS at 14 d had higher concentrations of serum endotoxins and inflammatory cytokines, as well as upregulated transcription of toll like receptor 4 (TLR4) in ileum when compared to control birds. Analogous to GLP-1 agonist liraglutide, dietary RS addition decreased endotoxins and inflammation cytokines, whereas it upregulated the GLP-1 synthesis related genes expression. Meanwhile, dietary RS supplementation suppressed the acute LPS challenge-induced TLR4 transcription.

Conclusions

These data suggest that dietary 12% RPS supplementation could attenuate the LPS-induced inflammation as well as intestinal injury of meat ducks, which might involve in the alteration in gut microbiota, SCFAs production and the signaling pathways of TLR4 and GLP-1/GLP-1R.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40104-022-00735-x.

Cortisol, progesterone, 17α-hydroxyprogesterone, and TSH responses in dogs injected with low-dose lipopolysaccharide

Background

Stress and diseases such as endotoxemia induce cortisol synthesis through a complex biosynthetic pathway involving intermediates (progesterone, and 17α-hydroxyprogesterone (17α-OHP)) and suppression of the hypothalamus-pituitary-thyroid axis.

Objective

To measure plasma concentrations of cortisol, progesterone, 17α-OHP, and thyroid stimulating hormone (TSH) in dogs experimentally injected with intravenous low-dose lipopolysaccharide (LPS). Our hypothesis was that LPS treatment would elicit a significant increase in cortisol and its precursors, and a significant decrease in TSH concentration.

Methods

Hormone measurements were performed on blood samples left over from a previous investigation (2011) on the effect of low-dose LPS on hematological measurands. Five sexually intact female dogs, none in estrous at the time of the study, were administered saline treatment two weeks prior to LPS treatment. LPS was administered intravenously at a dose of 0.1 µg/kg. Blood was collected before (baseline, time -24 hours) and 3-, 6- and 24-hours post-injection. Mixed model analysis for repeated measures was used, with both treatment and time as the repeated factors. Ranked transformation were applied when diagnostic analysis exhibited violation of normality and equal variance assumptions. Post hoc multiple comparisons were performed with Tukey’s adjustment. Statistical significance was defined as p < 0.05.

Results

Significant differences relative to baseline values were detected following both treatments. Compared to baseline, dogs had significantly higher cortisol and 17α-OHP at 3-hours, and significantly lower TSH at 3- and 6-hours following LPS treatment. Dogs had significantly lower TSH at 6- and 24- following saline treatment. Though not statistically significant, the trend in progesterone concentrations was similar to cortisol and 17α-OHP, with an increase at 3-hours post-injection followed by a decrease close to baseline following both LPS and saline. Cortisol and 17α-OHP concentrations were higher after LPS treatment than after saline treatment at 3- and 6-hours post-injection, but differences were not statistically significant, and no significant differences between treatments were detected for any other hormone or timepoint.

Discussion and conclusion

Cortisol and its adrenal precursors are released in the bloodstream following a low dose of LPS, while TSH appears to decrease. Similar changes occurred following saline treatment, suggesting that even routine handling and saline injection in conditioned dogs can elicit alterations in the internal equilibrium with subsequent modification of both hypothalamus-pituitary-adrenal and thyroid axes. Changes to adrenal and thyroid hormone concentrations must be interpreted in light of clinical information. Further studies are needed to elucidate mechanisms of adrenal steroidal hormone synthesis and secretion in response to various stressful stimuli in both neutered and intact animals.

Transcutaneous auricular vagus nerve stimulation protects endotoxemic rat from lipopolysaccharide-induced inflammation

Background. Transcutaneous auricular vagus nerve stimulation (ta-VNS) could evoke parasympathetic activities via activating the brainstem autonomic nuclei, similar to the effects that are produced after vagus nerve stimulation (VNS). VNS modulates immune function through activating the cholinergic anti-inflammatory pathway. Methods. VNS, ta-VNS, or transcutaneous electrical acupoint stimulation (TEAS) on ST36 was performed to modulate the inflammatory response. The concentration of serum proinflammatory cytokines and tissue NF-kappa B p65 (NF-κB p65) were detected in endotoxaemia affected anesthetized rats. Results. Similar to the effect of VNS, ta-VNS suppressed the serum proinflammatory cytokines levels, such as tumour necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), and interleukin-6 (IL-6) as well as NF-kappa B p65 expressions of lung tissues. ST36 stimulation also decreases LPS-induced high TNF-α level and NF-κB signal, but it did not restrain proinflammatory cytokine IL-1β and IL-6. Neither ta-VNS nor ST36 stimulation could suppress LPS-induced TNF-α and NF-κB after vagotomy or with α7nAChR antagonist injection. Conclusions. The present paper demonstrated that ta-VNS could be utilized to suppress LPS-induced inflammatory responses via α7nAChR-mediated cholinergic anti-inflammatory pathway.

Radio-detoxified endotoxin activates natural immunity: A review

It is well demonstrated that serial endotoxin injections produce endotoxin tolerance and elevate the natural immunity/resistance. However, such injections may also have harmful effects such as high fever, hypotension and abortion. For this reason endotoxin (LPS) injections are not suitable to enhance nonspecific resistance in endotoxin-sensitive species like man. Various techniques have been designed (physical, chemical, etc.) for the detoxification of endotoxins while the beneficial effects are maintained. Perhaps one of the best detoxification techniques is the treatment with ionizing radiation. The irradiation of LPS with 60Co (150 kGy) decreased its toxicity in a dose-dependent manner. Such radio-detoxified endotoxin (RD-LPS) preparations show decreased toxicity whereas the beneficial effects were preserved. Irradiation causes marked chemical alterations in LPS, such as a decrease of glucosamine, ketodeoxyoctonic and fatty acids. A single parenteral RD-LPS injection prevents various forms of shock in experimental animals. This preparation has a membrane-stabilizing effect, and thereby it can prevent the membrane-damaging effect of LPS and of some cytostatic agents. Unlike endotoxin, RD-LPS has little hypotensive effects, and the pretreatment with this preparation can prevent practically all the hemodynamic changes induced by LPS. LPS plays an important role in the pathogenesis of intestinal syndrome of radiation disease, which may be prevented by RD-LPS pretreatment up to 70% in rats. RD-LPS retains the adjuvant activity of LPS, and it serves as a good adjuvant for inactivated virus vaccines. RD-LPS can also evoke the regeneration of the immune system in irradiated animals. The decrease of nonspecific resistance in immunodeficient or immunosuppressed patients is the most important cause of opportunistic infections that may lead to sepsis like in endotoxaemia and pneumonia. Organ transplant recipients commonly die of septicaemia. Antilymphocyte serum (ALS) is used in such patients as an immunosuppressant. The augmentation of natural resistance and the induction of endotoxin tolerance are of major significance in such patients. In ALS-treated rats RD-LPS induces also tolerance against the lethal dose of LPS. This demonstrates that in spite of the suppressive effect of ALS on T-lymphocytes the induction of LPS tolerance (the enhancement of natural resistance) remains normal. Facultative pathogenic organisms may flourish and cause disease when specific and nonspecific resistance is impaired. RD-LPS can produce a significant proliferation of lymphoid cells in germ-free animals which are immunodeficient. Many other beneficial effects are preserved by RD-LPS preparations, such as the activation of macrophages and of the reticuloendothelial system and antitumor activity. On the basis of these favorable experimental results, RD-LPS has been tested on 350 surgical patients suffering from gastrointestinal tumors, patients suffering from acquired immunodeficiency syndrome (AIDS) and cancer patients treated with CYSPLATIN. RD-LPS treatment prevented sepsis and activated the bone marrow function in these patients.

Bile acids in physico-chemical host defence

The discovery of the physico-chemical host defence is closely connected with the endotoxin research. It is well known that the toxic effects of endotoxins under experimental conditions can be induced only when they are administered parenterally. However, in naturally occurring entero-endotoxemic diseases (e.g. septic and various shocks, etc.), the endotoxin is absorbed from the intestinal tract. The cause and mode of translocation have been unknown. The generally used experimental shock models differ from natural diseases only in the mode by which endotoxin enters the blood circulation. If the common bile duct of rats was chronically canulated (bile-deprived animals) orally administered endotoxin was absorbed from the intestinal tract into blood circulation and provoked endotoxin shock. This translocation of endotoxins and the consequent shock can be prevented by sodium deoxycholate or natural biles. The bile acids split the endotoxin macromolecule into atoxic fragments. A similar detoxifying detergent action plays a significant role in host defence against infectious agents with outer lipoprotein structure (e.g. so-called 'big' viruses). This defence mechanism of macroorganisms based on the detergent activity of bile acids (end-products of the cholesterol metabolism) is called as physico-chemical defence system. Therefore, bile deficiency and the consequent endotoxemia are important components in the pathogenesis of certain diseases (e.g. sepsis, intestinal syndrome of radiation disease, hepato-renal syndrome, parvovirus infection, herpes, psoriasis, atherosclerosis, etc.). Bile acids may be used for the prevention and/or therapy of the above mentioned clinical conditions.

Endocrine aspects in pathogenesis of mastitis in postpartum dairy cows

In well-managed dairy herds some environmental pathogens including Gram-negative (GN) strains (E. coli and others) have been recognized recently as the predominant causative microbes of mastitis in the peri-parturient period. In early weeks of lactation hyperketonaemia may predispose the high-producing cows for GN mastitis. In GN mastitis cytokines, eicosanoids and oxygen radicals are released, which are responsible for the local and systemic symptoms. Experimental administration of endotoxin induces a complex endocrine cascade. Similar changes in plasma levels of cortisol, insulin, insulin-like growth factor-I and thyroid hormones are seen also in severe cases of GN mastitis. However, leptin is not responsible for the anorexia associated with severe mastitis in ruminants. Mastitis can postpone the resumption of ovarian cyclic activity in dairy cows when its outbreak occurs between days 15 and 28 after calving (at the expected time of first ovulation). In cyclic cows severe cases of GN mastitis can induce premature luteolysis or prolong the follicular phase.

On the significance of the role of cellular stress response reactions in the toxic actions of dioxin

Dioxin is known to cause many toxic effects that vary greatly in different tissues, ages, genders, and species. In this review, an attempt has been made to sort out major signaling pathways involved in the expression of the toxicities of dioxin. The major strategy adopted in analyzing its major signaling pathways is to view the toxic actions of dioxin as the result of the Ah receptor-mediated expression of a major cellular emergency stress response signal. Evidence pointing to the similarities between the symptoms of poisoning by dioxin and those produced by chronic administration of typical stressors, particularly lipopolysaccharides (LPS), bacterial endotoxins, has been assembled and analyzed. The common symptoms are wasting syndrome, atherosclerosis, fatty liver, and thymic atrophy. On the other hand, oxidative stress caused by cytochrome P450 induction is one of the typical stresses of dioxin poisoning, but not LPS poisoning. One of the major means through which dioxin triggers stress responses via "stress-activated kinase pathways" is stimulation of the cellular production of cytokines/autocrines, particularly growth factors. In the case of hepatocytes for instance, transforming growth factor-alpha plays a pivotal role in the dioxin-induced activation of the epidermal growth factor receptor and the extracellular signal-related kinase pathway, which acts as a signal to suppress apoptosis induced by cellular stress. These observations as well as additional experimental data support the idea that one of the major functions of the Ah receptor could be the elicitation of cellular stress response reactions. Another key point in understanding the toxic action of dioxin is that, unlike other cases of stressors, dioxin signaling becomes chronically sustained because of its extreme persistence in the human body, its half-life of 7-10 years, and its selective accumulation in fatty target tissues.

Periparturient endocrine and metabolic changes in healthy cows and in cows affected by mastitis

Transition from pregnancy to lactation in dairy cows involves considerable metabolic adaptation. Additional stress is incurred during infections such as periparturient mastitis. Multiparous Holstein-Friesian cows kept under normal production conditions (n = 15) were used to evaluate changes in circulating metabolite and hormone concentrations from 5 days before to 5 days after calving. Insulin-like growth factor binding protein (IGFBP) profiles were also monitored. Marked time-related changes were observed for plasma thyroid hormone, IGF, cortisol, insulin, beta-hydroxybutyrate (BHB) and non-esterified fatty acid (NEFA) concentrations but not for plasma leptin. A decrease in IGF-II concentration and maximal intensity of the putative IGFBP-1 band occurred at parturition. When compared with the five healthy cows,low IGF-II levels were prolonged to day 2 post-partum in five cows with Escherichia coli-associated mastitis. However, marked decreases in IGFBP-2 band intensity were evident only in two of the four cases examined. Individual total ligand (IGF-I + IGF-II) concentration and IGFBP pattern prepartum were largely regained 5 days post-partum in all cows. Hormone and metabolite concentrations in the two cows with Staphylococcus aureus-associated mastitis were very similar to those in the five healthy cows. Plasma thyroxine (T4) was lower 2 days prepartum in the cows, which later developed Gram-negative mastitis. Multiregression analysis showed that variance in T4 concentration was significantly and independently associated with triiodothyronine (T3) and IGF-I positively and with cortisol negatively (R2 = 0.648). This study confirms the close inter-relationship between the thyroid hormone and IGF axes in cattle and indicates possible effects of Gram-negative mastitis infection on IGF-II metabolism.