Signalling mechanisms involved in the induction of inducible nitric oxide synthase by Lactobacillus rhamnosus GG, endotoxin, and lipoteichoic acid

Beyond protein synthesis: the emerging role of arginine in poultry nutrition and host-microbe interactions

Arginine is a functional amino acid essential for various physiological processes in poultry. The dietary essentiality of arginine in poultry stems from the absence of the enzyme carbamoyl phosphate synthase-I. The specific requirement for arginine in poultry varies based on several factors, such as age, dietary factors, and physiological status. Additionally, arginine absorption and utilization are also influenced by the presence of antagonists. However, dietary interventions can mitigate the effect of these factors affecting arginine utilization. In poultry, arginine is utilized by four enzymes, namely, inducible nitric oxide synthase arginase, arginine decarboxylase and arginine: glycine amidinotransferase (AGAT). The intermediates and products of arginine metabolism by these enzymes mediate the different physiological functions of arginine in poultry. The most studied function of arginine in humans, as well as poultry, is its role in immune response. Arginine exerts immunomodulatory functions primarily through the metabolites nitric oxide (NO), ornithine, citrulline, and polyamines, which take part in inflammation or the resolution of inflammation. These properties of arginine and arginine metabolites potentiate its use as a nutraceutical to prevent the incidence of enteric diseases in poultry. Furthermore, arginine is utilized by the poultry gut microbiota, the metabolites of which might have important implications for gut microbial composition, immune regulation, metabolism, and overall host health. This comprehensive review provides insights into the multifaceted roles of arginine and arginine metabolites in poultry nutrition and wellbeing, with particular emphasis on the potential of arginine in immune regulation and microbial homeostasis in poultry.

Subacute Ruminal Acidosis as a Potential Factor that Induces Endometrium Injury in Sheep

The demand for economic benefits has led to an increase in the proportion of high-concentrate (HC) feed in the ruminant diet, resulting in an increased incidence of subacute ruminal acidosis (SARA). During SARA, a high concentration of lipopolysaccharide (LPS) translocated in the rumen induces a systemic inflammatory response. Inflammatory diseases, such as endometritis and mastitis, are often associated with SARA; however, in sheep, the mechanism of the effect of SARA on the endometrium has rarely been reported. Therefore, the aim of this study was to investigate, for the first time, the influence of LPS translocation on endometrial tight junctions (TJs) during SARA in sheep. The results showed that LPS and TNFα levels in the ruminal fluid, serum, and endometrial tissue supernatant during SARA increased, transcription levels of TLR4, NFκB, and TNFα in the endometrium increased, the protein expression level of claudin-1 in the endometrium increased, and the protein expression level of occludin decreased. 17β-estradiol (E₂) inhibits claudin-1 protein expression and promotes occludin expression, and progesterone (P₄) promotes claudin-1 protein expression and inhibits occludin protein expression. E₂ and P₄ regulate claudin-1 and occludin protein expression through their receptor pathways. Here, we found that LPS hindered the regulatory effect of E₂ and P₄ on endometrial TJs by inhibiting their receptor expression. The results of this study indicate that HC feeding can cause SARA-induced LPS translocation in sheep, increase susceptibility to systemic inflammation, induce the endometrial inflammatory response, and cause endometrial epithelial TJ damage directly and/or by obstructing E₂ and P₄ function. LPS translocation caused by SARA has also been suggested to induce an endometrial inflammatory response, resulting in endometrial epithelial barrier damage and physiological dysfunction, which seriously affects ruminant production. Therefore, this study provides new evidence that SARA is a potential factor that induces systemic inflammation in ruminants. It provides theoretical support for research on the prevention of endometritis in ruminants.

Levilactobacillus brevis KU15151 Inhibits Staphylococcus aureus Lipoteichoic Acid-Induced Inflammation in RAW 264.7 Macrophages

Inflammation is a host defense response to harmful agents, such as pathogenic invasion, and is necessary for health. Excessive inflammation may result in the development of inflammatory disorders. Levilactobacillus brevis KU15151 has been reported to exhibit probiotic characteristics and antioxidant activities, but the effect of this strain on inflammatory responses has not been determined. The present study aimed to investigate the anti-inflammatory potential of L. brevis KU15151 in Staphylococcus aureus lipoteichoic acid (aLTA)-induced RAW264.7 macrophages. Treatment with L. brevis KU15151 reduced the production of nitric oxide and prostaglandin E₂ by suppressing the expression of inducible nitric oxide synthase and cyclooxygenase-2. Additionally, the production of proinflammatory cytokines including tumor necrosis factor-α, interleukin (IL)-6, and IL-1β, decreased after treatment with L. brevis KU15151 in aLTA-stimulated RAW 264.7 cells. Furthermore, this strain alleviated the activation of nuclear factor-κB and mitogen-activated protein kinase signaling pathways. Moreover, the generation of reactive oxygen species was downregulated by treatment with L. brevis KU15151. These results demonstrate that L. brevis KU15151 possesses an inhibitory effect against aLTA-mediated inflammation and may be employed as a functional probiotic for preventing inflammatory disorders.

Comparative efficacy and tolerability of probiotics for antibiotic-associated diarrhea: Systematic review with network meta-analysis

Background

Probiotics are commonly used for the prevention of antibiotic-associated diarrhea (AAD). However, the optimum regimen remains controversial.

Objective

The objective of this article is to compare and rank the relative efficacy and tolerability among all available probiotic agents for AAD through a network meta-analysis.

Methods

Eligible studies were identified by searching PubMed, Embase, Medline, Cochrane library and Web of Science for randomized controlled trials (RCTs) that examined the efficacy of probiotic therapy for AAD. A random-effects model was applied within a frequentist framework. Quality of evidence was performed by the GRADE approach. The project was prospectively registered with PROSPERO (CRD 42016050776).

Results

Fifty-one articles (60 comparisons, 9569 participants), including 10 probiotic interventions, were identified. Lactobacillus rhamnosus GG (LGG) had the highest probability of being ranked best both in effectiveness (odds ratio (OR), 95% confidence interval (CI) = 0.28 (0.17, 0.47)) and tolerance (0.44 (0.23, 0.84)) on prevention of AAD. With regard to reducing Clostridium difficile infection rate, Lactobacillus casei (L. casei) was considered better efficacy (0.04 (0.00, 0.77)) and medium tolerance (0.56 (0.19, 1.66)). Strain combination reported no superiority over single strain in either efficacy or tolerability.

Conclusions

LGG is probably the best option to consider when AAD is indicated. L. casei appears to be the most efficacious choice when associated with severe C. difficile-related cases.

Invited review: Role of bacterial endotoxins in the etiopathogenesis of periparturient diseases of transition dairy cows

The dairy industry continues to suffer severe economic losses due to the increased disease incidence cows experience during the transition period. It has long been the classical view that the major contributing factor to the development of these periparturient diseases is the considerable increase in nutritional demands for milk production. This classical view, however, fails to account for the substantial correlation between both metabolic and infectious diseases and the detrimental effects that can occur with the provision of high-energy diets to support these nutritional demands. Currently, increasing evidence implicates bacterial endotoxins in the etiopathology of most periparturient diseases. Bacterial endotoxins are components of the outer cell wall of gram-negative and gram-positive bacteria that are highly immunostimulatory and can trigger proinflammatory immune responses. The ability of endotoxins to translocate from the mucosal tissues, including the gastrointestinal tract, mammary gland, and uterus, into the systemic circulation has been observed. Once they have entered the circulation, endotoxins potentially contribute to disease either directly, through eliciting an inflammatory response, or indirectly through other factors such as the overreaction of the natural protective mechanisms of the host. Although the evidence implicating a role of endotoxins in the pathogenesis of transition diseases continues to grow, our current knowledge of the host response to mucosal endotoxin exposure and pathogenic mechanisms remain largely unknown. Developing our understanding of the connection between endotoxemia and dairy cattle disease holds significant potential for the future development of preventative measures that could benefit the productivity of the dairy industry as well as animal welfare.

Impact of probiotic Lactobacillus plantarum TENSIA in different dairy products on anthropometric and blood biochemical indices of healthy adults

The blood pressure-lowering effect of dairy products holds the potential to decrease the risk of cardiovascular disease (CVD). An open question is if the successful expression of functional properties of the probiotic strain depends on host biomarkers and/or food matrix properties. The probiotic Lactobacillus plantarum strain TENSIA® (DSM 21380) is a novel microorganism with antimicrobial and antihypertensive functional properties. The aim of this study was to characterise the functional properties of the probiotic L. plantarum TENSIA and compare its effects on host anthropometric, clinical, and blood biomarkers when consumed with cheese or yoghurt. This study involved two double-blinded randomised placebo-controlled exploratory trials (ISRCTN15061552 and ISRCTN79645828) of healthy adults over a three-week period. The three-week consumption of probiotic L. plantarum TENSIA in a daily dose of 1×1010 cfu in probiotic cheese or a daily dose of 6×109 cfu in yoghurt with different content of carbohydrates, proteins, and lipids did not significantly change the body mass index (BMI), plasma glucose and lipid levels, or inflammatory markers in the blood. Reduced lowered systolic and diastolic blood pressure values were detected, regardless of food matrix or baseline values for blood pressure and BMI. In conclusion, our study showed that three-week consumption of the probiotic L. plantarum TENSIA either in cheese or yoghurt lowered diastolic and systolic blood pressure regardless of food matrix and baseline values of blood pressure and BMI, confirming the impact of the functional properties of the probiotic strain in decreasing CVD risk.

Screening and Characterization of Lactic Acid Bacteria Strains with Anti-inflammatory Activities through in vitro and Caenorhabditis elegans Model Testing

The present study was conducted to screen candidate probiotic strains for anti-inflammatory activity. Initially, a nitric oxide (NO) assay was used to test selected candidate probiotic strains for anti-inflammatory activity in cultures of the murine macrophage cell line, RAW 264.7. Then, the in vitro probiotic properties of the strains, including bile tolerance, acid resistance, and growth in skim milk media, were investigated. We also performed an in vitro hydrophobicity test and an intestinal adhesion assay using Caenorhabditis elegans as a surrogate in vivo model. From our screening, we obtained 4 probiotic candidate lactic acid bacteria (LAB) strains based on their anti-inflammatory activity in lipopolysaccharide (LPS)-stimulated RAW 264.7 cell cultures and the results of the in vitro and in vivo probiotic property assessments. Molecular characterization using 16S rDNA sequencing analysis identified the 4 LAB strains as Lactobacillus plantarum. The selected L. plantarum strains (CAU1054, CAU1055, CAU1064, and CAU1106) were found to possess desirable in vitro and in vivo probiotic properties, and these strains are good candidates for further investigations in animal models and human clinical studies to elucidate the mechanisms underlying their anti-inflammatory activities.

Probiotics and small bowel mucosa: Molecular aspects of their interactions

Probiotics are described as "friendly bacteria" that could improve the intestine defense by interacting with the resident microflora. There is a large body of evidence suggesting that consumption of functional food containing probiotics exerts positive effects on human health. Several clinical trials have highlighted the efficiency of probiotics in the prevention and treatment of different gastrointestinal disorders including the prevention of antibiotic associated diarrhea, the remission in patients with inflammatory bowel disease, beneficial effects against Helicobacter pylori infection, positive effects in patients affected by allergies and atopic diseases. The clinical benefits of probiotics use are mainly attributed to their antimicrobial substances production and their positive interactions with the enterocytes to reinforce the intestinal epithelial barrier. Moreover, there is evidence suggesting that probiotics stimulate both specific and non-specific host immune responses. Recently, have been published some experiments performed with the DNA microarray technology which provided a global gene screening of the complex bacteria-host interplay. Nevertheless, the molecular mechanisms by which probiotics enhance the intestinal host defense are still not completely elucidated. Here, we review the experiments and clinical studies to date on the complex mechanisms regulating the communication between probiotics and their hosts.

Potential role of probiotic bacteria in the treatment and prevention of localised candidosis

The extensive use of immunosuppressive therapies in recent years has increased the number of patients prone to or actually suffering from localised candidosis. As Candida species gain increasing resistance towards common antifungal drugs, new strategies are needed to prevent and treat infections caused by these pathogens. Probiotic bacteria have been in vogue in the past two decades. More and more dairy products containing such organisms offer promising potential beneficial effects on human health and well-being. Because of the ability of probiotic bacteria to inhibit the growth of pathogens and to modulate human immune responses, these bacteria could provide new possibilities in antifungal therapy. We summarise the recent findings concerning the usefulness of probiotic treatment in localised candidosis, as well as discussing possible risks of probiotic treatment and highlighting the molecular mechanisms that are believed to contribute to probiotic effects.

Effects of Lactobacillus plant arum on genes expression pattern in mice jejunal Peyer's patches

Jejunal Peyer's patches contain specialized epithelial M cells that take up ingested microorganisms from the lumen of the gut by transcytosis. Using DNA-micro array, we analyzed the gene expression patterns of jejunal Peyer's patches in order to gain insight into the molecular mechanism by which Lp6 interacted with the host organism in a gnotobiotic environment v. in the gut normal microflora. The micro array data revealed that, among approximately 14,000 genes, 420 were expressed in Lp6 administration group at twofold or higher levels compared to the control group. These included genes involved in immune response, and cell differentiation, cell-cell signaling, cell adhesion, signal transcription, and transduction. Real-time PCR confirmed the reliability of the analysis. These data indicated that administration of Lactobacillus Lp6 was associated with a complex genetic response in the jejunal Peyer's patches.

Differential regulation of microglial P2X4 and P2X7 ATP receptors following LPS-induced activation

Activation of microglia has been implicated in many neurological conditions including Alzheimer's disease and neuropathic pain. Recent studies provide evidence that P2X ATP receptors on the surface of microglia play a crucial role in initiation of inflammatory cascades. We investigated changes in surface P2X receptors in BV-2 murine microglial cells following their activation by pro-inflammatory bacterial lipopolysaccharides (LPS). mRNA analysis using RT-PCR confirmed the presence of P2X4 and P2X7 as the main P2X subunits. Application of ATP at low (< or =100 microM) and high (> or =1 mM) concentrations, as well as BzATP, activated inward currents in BV-2 cells. Current responses of P2X4 and P2X7 subtypes could be distinguished based on their respective sensitivity to the positive modulator ivermectin and to the antagonist Brilliant Blue G. Treatment of BV-2 cells with LPS leads to a transient increase in ivermectin-sensitive P2X4 currents, while dominant P2X7 currents remain largely unaffected. This increase in P2X4 function was concomitant with higher receptor protein expression, itself related to an upregulation of P2X4 mRNA levels that peaked at 48 h post-LPS treatment. Our data demonstrate that although LPS activation has a minor impact on P2X7 receptors that remain the major ionotropic ATP receptors in microglia, it specifically enhances responses to low ATP concentrations mediated by P2X4 receptors, highlighting the significant contribution of both subtypes to neuroinflammatory mechanisms and pathologies.

Molecular and cellular basis of microflora-host interactions

Mucosal surfaces represent the main sites in which environmental microorganisms and antigens interact with the host. In particular the intestinal mucosal surfaces are in continuous contact with a heterogeneous population of microorganisms of the endogenous flora and are exposed to food and microbes. As a result, the immune system of the host has to discriminate between pathogenic and commensal microorganisms. This article reviews the types of sentinel cells that continuously sense the environment and coordinate immune defenses as well as the mechanisms of the innate and adaptive immune systems that are activated by bacterial and viral molecular patterns leading to inflammatory, allergic, or regulatory immune response with special emphasis on probiotic bacteria.

Endomorphin 1 activates nitric oxide synthase 2 activity and downregulates nitric oxide synthase 2 mRNA expression

Endomorphins 1 and 2 are newly discovered opioid tetrapeptides whose structure is more resistant to enzymatic degradation than that of other opioid peptides. Endomorphins 1 and 2 are considered as endogenous ligands with a high affinity for mu receptors. A number of studies have shown that opioid peptides per se can induce release of nitric oxide from rodent and human immune cells. Endomorphins seemed to be involved in the process of vasodilatation by stimulating release of nitric oxide. In our study we stimulated in vitro J774 macrophages with different concentrations of endomorphin 1 or 2 for measuring nitric oxide release and nitric oxide synthase 2 (NOS 2) mRNA expression. Results showed that 48 h incubation did not enhance nitric oxide release when measured with the Griess method. On the other hand, using real-time amperometric detection of nitric oxide release shortly after challenge with endomorphins, we showed that only 10(-6) M endomorphin 1 was able to stimulate nitric oxide release from a J774 macrophage cell line by activation of NOS 2 isoenzyme. The peak release was 1000-1500 s after stimulation and was in the range of nitric oxide release stimulated with 10 microg/ml lipopolysaccharide. In contrast to this, endomorphin 2 failed to induce nitric oxide release in all tested concentrations. Using a specific inhibitor of nitric oxide synthase 2 (N-(3-[aminomethyl]benzyl)acetamidine, 1400W) we eliminated the stimulatory effect of endomorphin 1 on nitric oxide release. The expression of mRNA for NOS 2 in J774 macrophages, after 30 min incubation with either lipopolysaccharide or 10(-6) M endomorphin 1 was not upregulated. As expected, lipopolysaccharide induced de novo NOS 2 transcription within 4 h. At the same time, in contrast to lipopolysaccharide, mRNA expression of cells treated with endomorphin 1 was downregulated. Since a mu-opioid receptor specific antagonist beta-funaltrexamine hydrochloride inhibited nitric oxide release from endomorphin 1-treated cells, the effect seemed to be mu-opioid receptor mediated.

Chlorophyllin suppresses interleukin-1 beta expression in lipopolysaccharide-activated RAW 264.7 cells

Our previous findings demonstrated that chlorophyllin (CHL) inhibits inducible nitric oxide gene expression in macrophages. In the present study, we show that CHL inhibited IL-1beta production and its mRNA expression in a lipopolysaccharide (LPS)-stimulated murine macrophage cell-line, RAW 264.7. The inhibitory effect of CHL on IL-1beta gene expression was further supported by an in vitro transfection assay using a pIL-1(870 bp)-CAT construct, where CHL inhibited the activation of the IL-1beta promoter. Furthermore, CHL attenuated the activation of NF-kappaB, NF-IL6 and AP-1, which are known to be responsible for IL-1beta gene expression, as determined by an electrophoretic mobility shift assay and an in vitro transfection assay using p(NF-kappaB)3-CAT, p(NF-IL6)3-CAT, and p(AP-1)3-CAT, respectively. However, it was evident that the inhibitory activity of CHL on IL-1beta expression in the LPS-stimulated macrophages was independent of CRE/ATF. The immunoblot experiment demonstrated that CHL also caused a substantial decrease in the phosphorylation of p38 MAP kinase in LPS-stimulated RAW 264.7. These results suggest that CHL inhibits IL-1beta production in macrophages stimulated with LPS at transcriptional level by blocking the phosphorylation of p38 and by suppressing the activation of transcription factors, NF-kappaB, NF-IL6, and AP-1.

Inducible nitric oxide synthase involvement in the mechanism of action of Saccharomyces boulardii in castor oil-induced diarrhoea in rats

The biotherapeutic agent Saccharomyces boulardii has been shown to inhibit castor oil-induced diarrhoea in rats in a dose-response fashion, and one of the suggested mechanisms of action included involvement of the nitric oxide pathway. The present study was designed to address this mechanism of action by firstly measuring the effects of S. boulardii on the inducible nitric oxide synthase (iNOS) isoform activity in vitro. Second, the effects of S. boulardii on the increase in colonic citrulline level associated with castor oil treatment were examined. In vitro, S. boulardii showed a dose-dependent inhibition of iNOS activity with an IC50 of 0.89 mg/ml. In the rat diarrhoea model, the antidiarrhoeal effect of S. boulardii was confirmed using a single oral dose of 12 x 10(10) CFU/kg (viable cells). In this model, castor oil significantly elevated citrulline level from 2526+/-164 to 3501+/-193 nmol/g in the colon. When the rats were treated with the same antidiarrhoeal single dose of S. boulardii, no increase in citrulline level was observed. Moreover, the iNOS inhibitor 1400 W at 10 mg/kg and the inhibitor of iNOS expression dexamethasone at 1 mg/kg, administered subcutaneously, blocked the citrulline production induced by the laxative. Taken together, these findings confirm the involvement of inhibition of the inducible isoform of nitric oxide synthase in the mechanism of action of S. boulardii in diarrhoea.

Probiotic bacteria stimulate virus-specific neutralizing antibodies following a booster polio vaccination

BACKGROUND

Orally ingested probiotic bacteria may modulate the immune response and increase antibody titers against enteric infections by bacteria or viruses. Even though positive effects of probiotics on respiratory tract infections have been reported, overall only few studies have examined effects on virus infections concerning organs other than the gastrointestinal tract.

AIM OF THE STUDY

It was the aim of the study to investigate whether and how probiotics affect the immune response to a standardized enterovirus challenge (polio) and infections not limited to the gastrointestinal tract in healthy adults.

METHODS

In a randomized, controlled and double-blind study 64 volunteers consumed for 5 weeks chemically acidified clotted milk without bacteria or with 10(10)/serving (Lactobacillus rhamnosus ) GG or Lactobacillus acidophilus CRL431 added. In the second week subjects were vaccinated orally against polio 1, 2 and 3. Polio virus neutralizing serum activity, the primary parameter, was determined by the standard neutralization test (WHO) before and three times after vaccination. Polio-specific IgA, IgG and IgM were detected by ELISAs.

RESULTS

Probiotics increased poliovirus neutralizing antibody titers (NT) and affected the formation of poliovirus-specific IgA and IgG in serum. The maximum increase after immunization was about 2, 2.2, or 4-fold higher, respectively, for NT, IgG or, IgA, in volunteers consuming probiotics instead of placebo. No consistent difference was noted between bacterial strains.

CONCLUSIONS

Probiotics induce an immunologic response that may provide enhanced systemic protection of cells from virus infections by increasing production of virus neutralizing antibodies.

The expression of COX2 protein induced by Lactobacillus rhamnosus GG, endotoxin and lipoteichoic acid in T84 epithelial cells

AIMS

Lactobacillus rhamnosus GG (L. rhamnosus GG) possess immunomodulatory effects in the host. In the present study, the effect of L. rhamnosus GG on cyclooxygenase 2 (COX2) expression and its pharmacological control was investigated in human T84 colon epithelial cells.

METHODS AND RESULTS

T84 cells were exposed to freeze-dried L. rhamnosus GG in vitro, and the expression of COX2 was detected by Western blot.

CONCLUSIONS

L. rhamnosus GG induced COX2 expression in a time- and concentration-dependent manner in T84 cells. COX2 expression was inhibited by tyrosine kinase inhibitor genistein (100 micromol l(-1)), p38 mitogen-activated protein kinase (MAP kinase) inhibitor (SB203580; 1 micromol l(-1)) and dexamethasone (10 micromol l(-1)), whereas inhibitors of p42/44 MAP kinase (PD98095; 10 micromol l(-1)), protein kinase C (Ro 31-8220; 1 micromol l(-1)) and transcription factor nuclear factor kappa B (NF-kappaB) [pyrrolidinedithiocarbamate (PDTC) 100 micromol l(-1)] had practically no effect.

SIGNIFICANCE AND IMPACT OF THE STUDY

The results provide novel information on the cellular mechanisms involved in the interaction between L. rhamnosus GG and colon epithelial cells.

Probiotics for mother and child

For the survival of humankind, nothing can be as important as the health of a mother and a child. As the world's population grows to more than 6 billion, it might seem ridiculous to suggest that any real threat exists to the human species. Diseases have long ravaged populations, as have wars, poverty, and malnutrition. Life today is no different with new and emerging diseases such as SARS and Mad Cow Disease leaving a trail of concern around the planet. All that being said, the AIDS crisis is threatening humans like no other. In countries such as Botswana, close to half the population of pregnant women is infected. Of great concern, the disease is now prevalent among women and teenage girls, threatening not only their lives but those of their offspring. Efforts to control this spread are quite abysmal, albeit well intentioned. Likewise, the death of a child every 15 seconds from diarrheal disease is not being addressed with the same vigor as SARS, even though the risk of dying from the latter for most people is similar to being struck by lightning. In the end, it is the economy and politics that dictate health spending. Image and perception are everything. While deaths mount among women and children from AIDS and other infections, the potential to intervene with a low-risk natural concept of probiotics seemed all too distant. As evidence mounts of the attributes of certain probiotic strains to treat diarrhea and reduce the risk of urogenital and other diseases, the developing world has failed to embrace it, support its evaluation and implementation, and take it to where it is needed the most. In this review, the case for and against probiotics for urogenital and intestinal infections is presented based on current literature. The story is far from complete, but the potential for improving the health of the mother and child is significant. United Nations and World Health Organization guidelines have now been developed to vanquish the unproved marketing hype products that have given probiotics a bad name. It is now up to science to deliver the remedies, and to society to make sure that only proven products reach the marketplace and the people in most need.

Effects of antioxidant on NF-κB and iNOS in rats with acute necrotizing pancreatitis

AIM: To observe the influence of antioxidant N-acetylcysteine (NAC) on nuclear factor-kappa B (NF-κB) and inducible nitric oxide synthase (iNOS) in pancreatic tissue of rats with acute necrotizing pancreatitis (ANP).

METHODS: A total of 95 Spraque-Dawley (SD) male rats were randomly divided into control group (group C, n = 25), acute pancreatitis group (group A, n = 35) and NAC intervention group (group N, n = 35). In group A, SD rats were injected twice intraperitoneally with 8 g/L L-arginine (2×1.2 mg/g) in an interval of 1 hour for ANP. In group C, SD rats received the same amount of saline at the same time. In group N, 0.5 mol/L NAC (0.05 mg/g) was administered intraperitoneally 1 hour before the start of L-arginine injection. Animals were killed at 6, 12, 24, 36, and 48 hours after the first L-arginine injection. The concentration of NF-κB and the activity of iNOS in rat's pancreatic tissue of each group were assayed.

RESULTS: The concentration of NF-κB in pancreatic tissue in group N significantly decreased in earlier period than that in group A (10.4±2.3 vs 89.7±6.4, 6.8±3.2 vs 21.5±3.5, 7.9±3.4 vs 32.5±4.5, 5.4±2.7 vs 14.7±5.2, and 5.0±3.7 vs 11.1±2.3, P < 0.05 or P < 0.01). iNOS activity increased in group A, whereas it significantly decreased in group N (15.2± 4.0 vs 24.2±3.8, 28.3±8.0 vs 36.8±6.0, 25.2±3.8 vs 30.5±3.5 , 21.2±3.7 vs 28.7±7.2, and 18.8±5.5 vs 28.2±4.2, P < 0.05 or P < 0.01).

CONCLUSION: Antioxidants may decrease the activity of iNOS through the inhibition of NF-κB activation.

Role of probiotics in the modulation of intestinal infections and inflammation

PURPOSE OF REVIEW

Using microorganisms to influence positively the course of an illness caused by injurious microorganisms is an approach with mounting clinical evidence showing efficacy. Whereas antibiotics will remain an important therapeutic option, there are limitations and problems to their increasing and chronic usage, and probiotics offer a strategy to reduce antibiotic usage. Increasingly, it has become clear that the mechanisms whereby probiotics can impact in intestinal diseases involve a large repertoire of responses. This review summarizes recent findings on how probiotics may effect benefit through interactions with host eukaryotic cells.

RECENT FINDINGS

Limiting the access of microbes associated with the development of disease to host mucosal surfaces and altering the responses of host to microbial insults are potential mechanisms whereby probiotics can influence the pathogenesis of disease. Evidence is accumulating that live, viable probiotic organisms diminish accessibility to intestinal epithelial cell; however, the mucosal exclusion is not through direct blockage of shared epithelial receptors between probiotic microbes and pathogenic organisms. Modulation of mucosal defenses such as innate protective mechanisms, enhanced epithelial cell survival, and immune responses have all been shown to have potential in aiding in these actions. Intestinal epithelial cell adherence influences response and, as such, appears to be necessary but may not be wholly sufficient, because soluble bacterial factors have been reported to effect modulation of immune and nonimmune responses of eukaryotic cells.

SUMMARY

There is a considerable repertoire of responses potentially responsible for the effects of probiotics, and these responses appear to involve a complex interplay between the microbes of the intestinal tract and the cells of the host. Continued work can be expected to further the understanding of the mechanisms involved, and more work is needed to determine the relative clinical importance of each of the phenomena. These studies are expected to help direct the most efficacious use of probiotics for inflammatory conditions arising from the intestinal tract.

Probiotics, antibiotic-associated diarrhoea and Clostridium difficile diarrhoea in humans

Probiotics are living organisms which, when ingested, have a beneficial therapeutic effect. Examples are bacteria, especially Lactobacillus rhamnosus GG, and the yeast Saccharomyces boulardii. Controlled trials indicate a benefit of both of these in the prevention of antibiotic-associated diarrhoea. Other less effective probiotics are Lactinex, Enterococcus faecium and bifidobacteria. In the difficult clinical problem of recurrent Clostridium difficile disease, S. boulardii as an adjunct to antibiotics has shown benefit in controlled trials. There is, however, less convincing evidence for the efficacy of Lactobacillus GG in this disease. Additional controlled trials and safety studies are needed before there can be a widespread endorsement of probiotics for these two conditions.

Beta-adrenergic receptor agonists and antagonists counteract LPS-induced neuronal death in retinal cultures by different mechanisms

Treatment with lipopolysaccharide (LPS) for 72 h was shown to dose-dependently increase nitric oxide production from 6-day-old retinal cultures. Cell death, as determined by lactate dehydrogenase (LDH) release and an increase in neuronal labelling for TUNEL, was elevated concurrently. During treatment there was an increase of both inducible nitric oxide synthase and glial fibrillary acidic protein labelling in glial cells and a reduction in the number of gamma-aminobutyric acid-positive neurones. The NOS inhibitors, N-nitro-L-arginine methyl ester, dexamethasone and indomethacin potently inhibited both nitric oxide stimulation and cell death caused by LPS. In this study, the beta(2)- (ICI-18551), beta(1)- (betaxolol) and mixed beta(1)/beta(2)- (timolol, metipranolol) adrenergic receptor antagonists were all shown to attenuate LPS-induced LDH release from these cultures, but to have no effect on LPS-stimulated nitric oxide production. This effect was mimicked by the calcium channel blocker, nifedipine. Interestingly, the beta-adrenergic receptor agonists, salbutamol, arterenol and isoproterenol were also able to attenuate cell death caused by LPS. Moreover, these compounds also inhibited LPS-stimulated nitric oxide release. These studies suggest that LPS stimulates nitric oxide release from cultured retinal glial cells and that this process leads to neurone death. beta-adrenergic receptor agonists prevent the effects of LPS by inhibiting the stimulation of nitric oxide production. The data also suggest that beta-adrenergic receptor antagonists can attenuate LPS-induced death of neurones, but that these compounds act in a manner that is neurone-dependent, is mimicked by blockade of calcium channels and is independent of the stimulation of nitric oxide release.