Activation of NF-κB contributes to production of pig-major acute protein and serum amyloid A in pigs experimentally infected with porcine circovirus type 2

Bile acid regulation of xenobiotic nuclear receptors on the expressions of orosomucoids in the liver

The constitutive androstane receptor (CAR) and pregnane X receptor (PXR) are xenobiotic nuclear receptors activated by various xenobiotics, drugs, hormones, and bile acids (BAs). Upon activation, these nuclear receptors play critical roles in regulating systemic energy homeostasis. However, precise mechanisms through which CAR and PXR influence systemic metabolism remain incompletely understood. Here, we investigated the impact of CAR and PXR on the liver-secreted hormone (i.e., hepatokine) expressions in response to BA stress, such as cholic acid (CA) feeding. Our analysis revealed that several BA-activated genes, including the well-known CAR/PXR target, aldo-keto reductase family 1, member B7 (Akr1b7), were commonly increased by CAR- and PXR-agonist treatments. Notably, we identified a gene cluster encoding new BA-regulated hepatokines, orosomucoids (ORMs), as direct transcriptional targets of CAR and PXR. The Orm1 and Orm2 expressions were completely abolished in the absence of both CAR and PXR following CA feeding. In addition, we found that Orm transcriptions are dynamically regulated under various metabolic conditions, proposing a potential contribution of CAR/PXR. In conclusion, our study demonstrated that BA stress activates CAR and PXR, which play a key role in regulating hepatokine expression, including ORMs. This suggests a potential link between hepatic BA signaling, CAR/PXR activity, and systemic metabolic effects.NEW & NOTEWORTHY Hepatic bile acid signaling plays a crucial role in coordinating systemic metabolism between the liver and other peripheral tissues. Our report demonstrates that, under bile acid-enriched conditions, activation of nuclear receptors CAR and PXR stimulate the expression of several putative hepatokines, including the orosomucoid gene family, which may exert regulatory effects in the liver and adipose tissue against metabolic disorders.

Deoxynivalenol Induces Local Inflammation and Lesions in Tissues at Doses Recommended by the EU

The mycotoxin deoxynivalenol (DON) is frequently present in cereals at low levels, resulting in its occurrence in food and feed. DON has been proven to alter the immune response and induce inflammation in all species, with pigs exhibiting heightened sensitivity and exposure. However, no study has yet evaluated the effects of exposure to DON at the recommended levels in pig feed. In two separate trials, piglets were subjected to control feed or feed contaminated with a low level of purified DON (0.83 mg/kg feed in trial 1 and 0.85 mg/kg feed in trial 2) for either three weeks (trial 1) or two weeks (trial 2). Additionally, a group of animals exposed to 2.85 mg/kg feed of DON was included as a positive control in Trial 1. The impact of DON on porcine tissues (intestine, liver, and spleen) was evaluated through histological and qPCR analyses of immune-related genes. Additionally, biochemical analyses and acute-phase proteins were examined in plasma samples. Lesions were identified in the intestine (jejunum and ileum), the liver, and the spleen of pigs receiving diets contaminated with low and high concentrations of DON. The low level of DON also resulted in impaired expression of genes associated with intestinal barrier integrity, intestinal immune responses, and liver function. In conclusion, the results of the two trials demonstrate the impact of DON exposure even at doses below the recommended level of 0.9 mg/kg feed set by the European Union. This suggests that the current recommended level should be reconsidered to ensure the optimal health and well-being of pigs.

Clostridium butyricum Helps to Alleviate Inflammation in Weaned Piglets Challenged With Enterotoxigenic Escherichia coli K88

Background: Whether the probiotic Clostridium butyricum (CB) alleviates enterotoxigenic Escherichia coli (ETEC) K88-induced inflammation by regulating the activation of the toll-like receptor (TLR) signaling pathway is not clear, thus, we carried out this study. A total of 72 piglets (average body weight 7.09 ± 0.2 kg) were randomly divided into three groups of 24 piglets per group. Pigs were either fed a daily diet (NC, negative control), a diet tested every day by 1 × 10⁹ CFU/mL ETEC K88 (PC, positive control), or a basal diet supplemented with 5 × 10⁵ CFU/g CB and challenged with ETEC K88 (PC + CB group).

Results: Our results showed that CB pretreatment attenuated the effect of ETEC K88 by decreasing C-reactive protein (CRP), which resulted in tumor necrosis factor alpha (TNF-α) and interleukin-6 (IL-6) production. Histological examination revealed that CB pretreatment alleviated intestinal villi injury caused by ETEC K88 challenge. Furthermore, CB pretreatment promoted mRNA expression of the negative regulators of TLR signaling, including myeloid differentiation factor (MyD88), toll-interacting protein (Tollip), and B cell CLL/lymphoma 3 (Bcl-3), in the intestines of ETEC K88-challenged piglets. ETEC K88-induced activation of nuclear factor kappa B (NF-κB) and nuclear factor of kappa light polypeptide gene enhancer in B cells inhibitor alpha (IκBα) was attenuated by CB pretreatment.

Conclusion: These findings indicate that CB helps to maintain and strengthen the shape of intestinal villi and limits detrimental inflammatory responses, partly by inhibiting toll-like receptor 2 (TLR-2), toll-like receptor 4 (TLR-4), and toll-like receptor 5 (TLR-5) expression and inhibiting NF-κB p65, and promoting IκBα activation and synergism among its negative regulators.

Herbal extracts as antiviral agents

Phytotherapy, or herbalism, is defined as the usage of plants or herbs as medication to treat or prevent diseases in human and animals. The usage is gaining more attention among medical practitioners as well as large-scale livestock producers. A number of reports have shown the positive effects of herbal extracts as an antiviral agent used in animal feed or as a prophylaxis and remedy. Besides being a cheaper and safer alternative, the use of herbs may reduce the incidence of drug resistance and may modulate the immune system in preventing viral-related diseases. In this chapter, the antiviral effects of several herbs and their extracts against viruses in terms of the mechanism of action in targeting viral replication steps, the effects in the host and the application in animals will be discussed. The information given may aid in improving the health and increase the production of animals.

Porcine Circovirus Type 2 Induces Single Immunoglobulin Interleukin-1 Related Receptor (SIGIRR) Downregulation to Promote Interleukin-1β Upregulation in Porcine Alveolar Macrophage

Multisystemic inflammation in pigs affected by porcine circovirus type 2 (PCV2) indicates the disordered expression of inflammatory cytokines. However, the PCV2-induced expression profile of inflammation cytokines and its regulating mechanism remain poorly understood. In this study, inflammatory cytokines and receptors in porcine alveolar macrophages (PAMs) after PCV2 infection were profiled in vitro by an RT² Profiler^TM PCR array assay. The regulatory mechanism of interleukin-1β (IL-1β) expression was investigated. Results showed that 49 of 84 inflammation cytokines and receptors were differentially expressed (p < 0.05, absolute fold change ≥2) in PAMs at different stages post-PCV2 infection. Moreover, the overexpression of single-immunoglobulin interleukin-1 related receptor (SIGIRR) or the blocking of NF-κB activation by its inhibitor markedly decreased IL-1β secretion. This finding suggested that PCV2-induced overexpression of IL-1β was associated with the downregulation of SIGIRR and the activation of NF-κB. Furthermore, the excessive activity of NF-κB in SIGIRR-knockout PAMs cell line, indicating that SIGIRR negatively regulated IL-1β production by inhibiting the activation of NF-κB. Overall, PCV2-induced downregulation of SIGIRR induction of NF-κB activation is a critical process in enhancing IL-1β production in PAMs. This study may provide insights into the underlying inflammatory response that occurs in pigs following PCV2 infection.

High mobility group box-1 mediates hippocampal inflammation and contributes to cognitive deficits in high-fat high-fructose diet-induced obese rats

High-fat high-sugar diet-induced obesity can lead to hippocampal inflammation and cognitive deficits, but the detailed underlying mechanism is still not clear. We aim to investigate the role of HMGB1 in hippocampal inflammatory responses and cognitive impairment in high-fat high-fructose diet (HFHFD)-induced obesity. Rats were fed with a normal control diet or an HFHFD diet for 14 weeks. In the last 6 weeks on the diets, the rats were treated with control, or an HMGB1 inhibitor glycyrrhizin, or an anti-HMGB1 neutralizing monoclonal antibody (mAb). Obesity was induced in the HFHFD-fed rats, which had higher body weight, epididymal white adipose tissue (EWAT) weight and caloric efficiency, and lower brain/body weight ratio, glucose tolerance and insulin sensitivity than the ones on normal diets. In the HFHFD-induced obese rats, the HMGB1 levels in plasma and hippocampus were increased, and the nucleus-to-cytoplasm translocation of HMGB1 was promoted. The hippocampal inflammatory responses were enhanced in the HFHFD-induced obesity, including the activation of TLR4 and NF-κB, the production of IL-1β, TNF-α and IL-6, as well as the activation of microglia and astrocytes. In addition, the hippocampal cell apoptosis and cognitive impairment were observed in the HFHFD-fed rats. The treatment with glycyrrhizin or HMGB1 mAb successfully decreased the HMGB1 levels in plasma and hippocampus, and prevented the HMGB1 translocation from the nucleus to cytoplasm. Inhibiting HMGB1 by glycyrrhizin or HMGB1 mAb suppressed the hippocampal inflammatory, alleviated the apoptosis and ameliorated the cognitive impairment in HFHFD-fed rats. These findings indicate that HMGB1 mediates the hippocampal inflammation and contributes to the cognitive deficits in HFHFD-induced obesity. Therefore, inhibition of HMGB1 may have beneficial effect in protecting against hippocampal inflammation and cognitive deficits in dietary obesity.

Cytokines and serum amyloid A in the pathogenesis of hepatitis C virus infection

Expression of the acute phase protein serum amyloid A (SAA) is dependent on the release of the pro-inflammatory cytokines IL-1, IL-6 and TNF-α during infection and inflammation. Hepatitis C virus (HCV) upregulates SAA-inducing cytokines. In line with this, a segment of chronically infected individuals display increased circulating levels of SAA. SAA has even been proposed to be a potential biomarker to evaluate treatment efficiency and the course of disease. SAA possesses antiviral activity against HCV via direct interaction with the viral particle, but might also divert infectivity through its function as an apolipoprotein. On the other hand, SAA shares inflammatory and angiogenic activity with chemotactic cytokines by activating the G protein-coupled receptor, formyl peptide receptor 2. These latter properties might promote chronic inflammation and hepatic injury. Indeed, up to 80 % of infected individuals develop chronic disease because they cannot completely clear the infection, due to diversion of the immune response. In this review, we summarize the interconnection between SAA and cytokines in the context of HCV infection and highlight the dual role SAA could play in this disease. Nevertheless, more research is needed to establish whether the balance between those opposing activities can be tilted in favor of the host defense.

Porcine circovirus type 2 increases interleukin-1beta and interleukin-10 production via the MyD88-NF-kappa B signaling pathway in porcine alveolar macrophages in vitro

Porcine alveolar macrophages (PAMs) represent the first line of defense in the porcine lung after infection with porcine circovirus type 2 (PCV2) via the respiratory tract. However, PCV2 infection impairs the microbicidal capability of PAMs and alters cytokine production and/or secretion. At present, the reason for the imbalance of cytokines has not been fully elucidated, and the regulatory mechanisms involved are unclear. In this study, we investigated the expression levels and regulation of interleukin-1beta (IL-1β) and IL-10 in PAMs following incubation with PCV2 in vitro. Levels of IL-1β and IL-10 increased in PAM supernatants, and the distribution of nuclear factor kappa B (NF-κB) p65staining in nucleus, expression of MyD88 and p-IκB in cytoplasm, and DNA-binding activity of NF-κB increased after incubation with PCV2, while p65 expression in PAM cytoplasm decreased. However, when PAMs were co-incubated with PCV2 and small interfering RNA targeting MyD88, those effects were reversed. Additionally, mRNA expression levels of Toll-like receptors (TLR)-2, -3, -4, -7, -8, and -9 increased when PAMs were incubated with PCV2. These results show that PCV2 induces increased IL-1β and IL-10 production in PAMs, and these changes in expression are related to the TLR-MyD88-NF-κB signaling pathway.

Antiviral and Immunoregulatory Role Against PCV2 in Vivo of Chinese Herbal Medicinal Ingredients

Introduction

The aim of the research was to investigate the antiviral and immunoregulatory effects of saikosaponin A, saikosaponin D, Panax notoginseng saponins, notoginsenoside R1, and anemoside B4 saponins commonly found in Chinese herbal medicines.

Material and Methods

control mice were challenged intramuscularly (im) with 0.2 mL of porcine circovirus 2 (PCV2) solution containing 10⁷ TCID₅₀ of the virus/mL. Mice of high-, middle-, and low-dose saponin groups were initially challenged im with 0.2 mL of PCV2 solution and three days later treated intraperitoneally (ip) with one of five saponins at one of three doses (10, 5, or 1 mg/kg b.w.). In the drug control group, mice were dosed ip with 10 mg/kg b.w. of a given saponin, and mice in a blank control group were administered the same volume of normal saline.

Results

The results revealed that the saponins could reduce the incidence and severity of PCV2-induced immunopathological damage, e.g. body temperature elevation, weight loss, anaemia, and internal organ swelling. In addition, it was seen that the saponins could affect the immunoglobulin levels and protein absorption.

Conclusion

The data suggested that the saponins might effectively regulate immune responses.

RIG-1 and MDA-5 signaling pathways contribute to IFN-β production and viral replication in porcine circovirus virus type 2-infected PK-15 cells in vitro

Type I Interferons (IFNs) is known for its antiviral activity; however, it is surprising that in vitro treatment of IFN-α and IFN-γ enhanced the replication of porcine circovirus type 2 (PCV2), indicating a complex relationship between interferon and PCV2. To date, it remains poorly understood how the interferon is produced during PCV2 infection and whether the interferon induced by PCV2 itself can promote viral replication. In this study, PCV2 induced the up-regulation of IFN-β in PK-15 cells, while treatment of PCV2-infected cells with the interferon regulatory factor-3 (IRF3) inhibitor, BX795, decreased the expression of IFN-β, whereas treatment with the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) inhibitor, BAY11-7082, did not. These findings indicate that PCV2 can induce IFN-β production via the IRF3-mediated rather than the NF-κB-mediated signal pathway. Moreover, PCV2 increased the protein expression levels of phosphorylation-IRF3 (p-IRF3), mitochondria antiviral-signaling protein (MAVS), retinoic acid-inducible gene I (RIG-1) and melanoma differentiation-associated protein 5 (MDA-5), and the knockdown of RIG-1 and MDA-5 decreased the expression level of IFN-β in PK-15 cells. Therefore, PCV2 induces IFN-β production via the RIG-1/MDA-5/MAVS/IRF signaling pathway. Furthermore, the PCV2 load and PCV2 infectivity decreased after knockdown of RIG-1 and MDA-5, indicating that RIG-1 and MDA-5 signaling pathways contribute to PCV2 replication. In conclusion, PCV2 induces the production of IFN-β via the RIG-1 and MDA-5 signaling pathways, and the IFN-β produced during PCV2 infection facilitates viral replication. These results will help us further understand the pathogenic mechanisms of PCV2.

Porcine circovirus type 2 activates PI3K/Akt and p38 MAPK pathways to promote interleukin-10 production in macrophages via Cap interaction of gC1qR

Porcine circovirus type 2 (PCV2) infection caused PCV2-associated diseases (PCVAD) is one of the major emerging immunosuppression diseases in pig industry. In this study, we investigated how PCV2 inoculation increases interleukin (IL)-10 expression in porcine alveolar macrophages (PAMs). PCV2 inoculation significantly upregulated IL-10 expression compared with PCV1. Upon initial PCV2 inoculation, PI3K/Akt cooperated with NF-κB pathways to promote IL-10 transcription via p50, CREB and Ap1 transcription factors, whereas inhibition of PI3K/Akt activation blocked Ap1 and CREB binding to the il10 promoter, and decreased the binding level of NF-κB1 p50 with il10 promoter, leading to great reduction in early IL-10 transcription. In the later phase of inoculation, PCV2 further activated p38 MAPK and ERK pathways to enhance IL-10 production by promoting Sp1 binding to the il10 promoter. For PCV2-induced IL-10 production in macrophages, PCV2 capsid protein Cap, but not the replicase Rep or ORF3, was the critical component. Cap activated PI3K/Akt, p38 MAPK, and ERK signaling pathways to enhance IL-10 expression. In the whole process, gC1qR mediated PCV2-induced PI3K/Akt and p38 MAPK activation to enhance IL-10 induction by interaction with Cap. Depletion of gC1qR blocked PI3K/Akt and p38 MAPK activation, resulting in significant decrease in IL-10 production in PCV2-inoculated cells. Thus, gC1qR might be a critical functional receptor for PCV2-induced IL-10 production. Taken together, these data demonstrated that Cap protein binding with host gC1qR induction of PI3K/Akt and p38 MAPK signalings activation is a critical process in enhancing PCV2-induced IL-10 production in porcine alveolar macrophages.

Matrine displayed antiviral activity in porcine alveolar macrophages co-infected by porcine reproductive and respiratory syndrome virus and porcine circovirus type 2

The co-infection of porcine reproductive respiratory syndrome virus (PRRSV) and porcine circovirus type 2 (PCV2) is quite common in clinical settings and no effective treatment to the co-infection is available. In this study, we established the porcine alveolar macrophages (PAM) cells model co-infected with PRRSV/PCV2 with modification in vitro, and investigated the antiviral activity of Matrine on this cell model and further evaluated the effect of Matrine on virus-induced TLR3,4/NF-κB/TNF-α pathway. The results demonstrated PAM cells inoculated with PRRSV followed by PCV2 2 h later enhanced PRRSV and PCV2 replications. Matrine treatment suppressed both PRRSV and PCV2 infection at 12 h post infection. Furthermore, PRRSV/PCV2 co- infection induced IκBα degradation and phosphorylation as well as the translocation of NF-κB from the cytoplasm to the nucleus indicating that PRRSV/PCV2 co-infection induced NF-κB activation. Matrine treatment significantly down-regulated the expression of TLR3, TLR4 and TNF-α although it, to some extent, suppressed p-IκBα expression, suggesting that TLR3,4/NF-κB/TNF-α pathway play an important role of Matrine in combating PRRSV/PCV2 co-infection. It is concluded that Matrine possesses activity against PRRSV/PCV2 co-infection in vitro and suppression of the TLR3,4/NF-κB/TNF-α pathway as an important underlying molecular mechanism. These findings warrant Matrine to be further explored for its antiviral activity in clinical settings.

Activation of the TLR/MyD88/NF-κB signal pathway contributes to changes in IL-4 and IL-12 production in piglet lymphocytes infected with porcine circovirus type 2 in vitro

Porcine circovirus type 2 (PCV2) causes immunosuppression in pigs. One causative factor is an imbalance in cytokine levels in the blood and lymphoid tissues. Many studies have reported changes in cytokine production, but the regulatory mechanisms involved have not yet been elucidated. In this study, we investigated alteration and regulation of IL-4 and IL-12 production in lymphocytes following incubation with PCV2 in vitro. The levels of IL-4 decreased and levels of IL-12 increased in lymphocyte supernatants, and the DNA-binding activity of NF-κB and the expression of p65 in the nucleus and p-IκB in the cytoplasm of lymphocytes increased after incubation with PCV2. However, these effects were reversed when lymphocytes were coincubated with PCV2 and the NF-κB inhibitor BAY11-7082. In addition, the expression of MyD88 protein increased and the expression of mRNA for the toll-like receptors (TLRs) TLR2, TLR3, TLR4 and TLR9 was upregulated when lymphocytes were incubated with PCV2. However, no change was seen in TLR7 and TLR8 mRNA expression. In conclusion, this study showed that PCV2 induced a decrease in IL-4 and an increase in IL-12 production in lymphocytes, and these changes were regulated by the TLR-MyD88-NF-κB signal pathway.