Roles of liver innate immune cells in nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) has become the most common liver disease in the United States and other developed countries and is expected to increase in the next few years. Emerging data suggest that some patients with NAFLD may progress to nonalcoholic steatohepatitis (NASH), cirrhosis and even hepatocellular carcinoma. NAFLD can also promote the development and progression of disease in other organ systems, such as the cardiovascular and endocrine (i.e. diabetes) systems. Thus, understanding the pathogenesis of NAFLD is of great clinical importance and is critical for the prevention and treatment of the disease. Although the "two-hit hypothesis" is generally accepted, the exact pathogenesis of NAFLD has not been clearly established. The liver is an important innate immune organ with large numbers of innate immune cells, including Kupffer cells (KCs), natural killer T (NKT) cells and natural killer (NK) cells. Recent data show that an imbalance in liver cytokines may be implicated in the development of fatty liver disease. For example, Th1 cytokine excess may be a common pathogenic mechanism for hepatic insulin resistance and NASH. Innate immune cells in the liver play important roles in the excessive production of hepatic Th1 cytokines in NAFLD. In addition, liver innate immune cells participate in the pathogenesis of NAFLD in other ways. For example, activated KCs can generate reactive oxygen species, which induce liver injury. This review will focus primarily on the possible effect and mechanism of KCs, NKT cells and NK cells in the development of NAFLD.

Calcium phosphate nanoparticles show an effective activation of the innate immune response in vitro and in vivo after functionalization with flagellin

For subunit vaccines,adjuvants play a key role in shaping the magnitude,persistence and form of targeted antigen-specific immune response.Flagellin is a potent immune activator by bridging innate inflammatory responses and adaptive immunity and an adjuvant candidate for clinical application.Calcium phosphate nanoparticles are efficient carriers for different biomolecules like DNA,RNA,peptides and proteins.Flagellin-functionalized calcium phosphate nanoparticles were prepared and their immunostimulatory effect on the innate immune system,i.e.the cytokine production,was studied.They induced the production of the proinflammatory cytokines IL-8 （Caco-2 cells） and IL-1β（bone marrow-derived macrophages; BMDM） in vitro and IL-6 in vivo after intraperitoneal injection in mice.The immunostimulation was more pronounced than with free flagellin.

Nucleotide oligomerization domain 2 contributes to the innate immune response in THCE cells stimulated by Aspergillus fumigatus conidia

AIM: To investigate the expression of nucleotide oligomerization domain 2 (NOD2) in the immortalized human corneal epithelial cell line (THCE), and its role in the innate immune response triggered by inactive Aspergillus fumigatus (Af) conidia. METHODS: The normal THCE cells were investigated as controls. After incubation with inactive Af conidia for 0.5, 2, 4, 6, and 8 hours, THCE cells were harvested, mRNA expression of NOD2 and receptor interacting protein 2 (RIP2) was detected by RT-PCR. Intracellular proteins including NOD2, NF-kappa B and proinflammatory cytokines such as TNF-alpha, IL-8, IL-6 in the cell supernatant were analyzed by ELISA. RESULTS: Our data indicate that NOD2 expressed in the normal THCE cells. After triggered by the inactive Af conidia, the expression of NOD2, RIP2 mRNA and the secretion of NOD2, NF-kappa B, TNF-alpha, IL-8, IL-6 both increased in a time-depended manner, and reached the peak point at 4, 6, 6, 4, 6, 6, 4 hours, respectively. And after pretreated with NOD2 neutralizing antibody, the expression of RIP2, NF-kappa B, TNF-alpha, IL-8 both decreased dramatically at the peak point, while the secretion of IL-6 changed little. CONCLUSION: The results of this study suggest that NOD2 exists and expresses in the THCE cells, and contributes to the innate immune responses triggered by inactive Afconidia by induction of proinflammatory cytokines such as TNF-alpha and IL-8 through the NF-kappa B pathway.

The role of Dectin-1/Raf-1 signal cascade in innate immune of human corneal epithelial cells against Aspergillus fumigatus infection

AIM： To investigate the expression of the v-raf-1murine leukemia viral oncogene homolog 1（Raf-1） and its role in the innate immune response of human corneal epithelial cells（HCECs） infected by Aspergillus fumigatus.METHODS： HCECs were cultured in vitro.They were randomly divided into 4 groups,including control group,Aspergillus fumigatus group,GW5074（an inhibitor of Raf-1） group and Laminarin [an inhibitor of Dendriti-cell-associated C-type lectin 1（Dectin-1）] group.The protein expression level of total Raf-1 and p-Raf-1 was measured by Western blot.The expression of IL-6 and IL-8 m RNA in each group was detected by real-time polymerase chain reaction.RESULTS： In Aspergillus fumigatus group,total Raf-1 protein levels in HCECs remained unchanged at 5,15,30 and 45min after infection,while p-Raf-1 expression was significantly enhanced at 30 min after infection compared with control group.However,the expression of p-Raf-1 was apparently declined after treated with GW5074 or Laminarin compared with Aspergillus fumigatus group.The expression levels of IL-6,IL-8 m RNA were significantly increased after stimulation with fumigatus compared with control group.Pre-treated with GW5074 significantly inhibited Aspergillus fumigatus-induced upregulation of IL-8 and IL-6.CONCLUSION： Aspergillus fumigatus stimulation can elevate the expression of p-Raf-1 in HCECs in vitro.Dectin-1/Raf-1 signal pathway may play a role on regulating the expression of inflammatory cytokines,including IL-6 and IL-8.

Expression patterns and action analysis of genes associated with physiological responses during rat liver regeneration:Innate immune response

AIM： To study the relationship between innate immune response and liver regeneration （LR） at transcriptional level.METHODS： Genes associated with innate immunity response were obtained by collecting the data from databases and retrieving articles, Gene expression changes in rat regenerating liver were detected by rat genome 230 2.0 array.RESULTS： A total of 85 genes were found to be associated with LR. The initially and totally expressed number of genes at the phases of initiation [0.5-4 h after partial hepatectomy （PH）], transition from GO to G1 （4-6 h after PH）, cell proliferation （6-66 h after PH）, cell differentiation and structure-function reconstruction （66-168 h after PH） was 36, 9, 47, 4 and 36, 26, 78, 50, respectively, illustrating that the associated genes were mainly triggered at the initial phase of LR and worked at different phases. According to their expression similarity, these genes were classified into 5 types： 41 up-regulated, 4 predominantly up-regulated, 26 downregulated, 6 predominantly down-regulated, and 8 approximately up/down-regulated genes, respectively. The expression of these genes was up-regulated 350 times and down-regulated 129 times respectively, demonstrating that the expression of most genes was enhanced while the expression of a small number of genes was decreased during LR. Their time relevance was classified into 14 groups, showing that the cellular physiological and biochemical activities dudng LR were staggered. According to the gene expression patterns,they were classified into 28 types, indicating that the cellular physiological and biochemical activities were diverse and complicated during LR. CONCLUSION： Congenital cellular immunity is enhanced mainly in the forepart, prophase and anaphase of LR while congenital molecular immunity is increased dominantly in the forepart and anaphase of LR. A total of 85 genes associated with LR play an important role in innate immunity.

Interplay between hepatitis B virus and the innate immune responses:implications for new therapeutic strategies

Hepatitis B virus(HBV) infection is still a worldwide health problem;however,the current antiviral therapies for chronic hepatitis B are limited in efficacy.The outcome of HBV infection is thought to be the result of complex interactions between the HBV and the host immune system.While the role of the adaptive immune responses in the resolution of HBV infection has been well characterized,the contribution of innate immune mechanisms remains elusive until recent evidence implicates that HBV appears to activate the innate immune response and this response is important for controlling HBV infection.Here,we review our current understanding of innate immune responses to HBV infection and the multifaceted evasion by the virus and discuss the potential strategies to combat chronic HBV infection via induction and restoration of host innate antiviral responses.

Impairment of innate immune responses in cirrhotic patients and treatment by branched-chain amino acids

It has been reported that host defense responses, such as phagocytic function of neutrophils and natural killer (NK) cell activity of lymphocytes, are impaired in cirrhotic patients. This review will concentrate on the impairment of innate immune responses in decompensated cirrhotic patients and the effect of the treatment by branched-chain amino acids (BCAA) on innate immune responses. We already reported that phagocytic function of neutrophils was significantly improved by 3-mo BCAA supplementation. In addition, the changes of NK activity were also significant at 3 mo of supplementation compared with before supplementation. Also, Fisher’s ratios were reported to be significantly increased at 3 mo of BCAA supplementation compared with those before oral supplementation. Therefore, administration of BCAA could reduce the risk of bacterial and viral infection in patients with decompensated cirrhosis by restoring impaired innate immune responses of the host. In addition, it was also revealed that BCAA oral supplementation could reduce the risk of development of hepatocellular carcinoma in cirrhotic patients. The mechanisms of the effects will also be discussed in this review article.

The TAK1-JNK cascade is required for IRF3 function in the innate immune response

Interferon regulatory factor （IRF）3 is critical for the transcriptional induction of chemokines and cytokines during viral or bacterial invasion. The kinases Tank binding kinase （TBK）1 and Ikappa B kinase （IKK）ε can phosphorylate the C-terminal part of IRF3 and play important roles in IRF3 activation. In this study, we show that another kinase, c-Jun-NH2-terminal kinase （JNK）, phosphorylates IRF3 on its N-terminal serine 173 residue, and TAK1 can stimu- late IRF3 phosphorylation via JNK. JNK specific inhibitor SP600125 inhibits the N-terminal phosphorylation with- out affecting the C-terminal phosphorylation. In addition, IRF3-mediated gene expressions on lipopolysaccharide （LPS） or polyinosinic-cytidylic acid （polyI：C） treatment are severely impaired by SP600125, as well as for reporter gene assay of IRF3 activation. Knockdown of TAK1 further confirmed these observations. Interestingly, constitu- tive active IRF3（5D） can be inhibited by SP600125; JNK1 can synergize the action of IRF3（5D）, but not the S173A- IRF3（5D） mutant. More importantly, polyI：C failed to induce the phosphorylation of mutant S173A and SP600125 dramatically abrogated IRF3 phosphorylation and dimerization that was stimulated by polyhC. Thus, this study demonstrates that the TAK1-JNK cascade is required for IRF3 function, in addition to TBK1/IKKε, uncovering a new mechanism for mitogen-activated protein （MAP） kinase to regulate the innate immunity.

Expression of S100B during the innate immune of corneal epithelium against fungi invasion

AIM： To explore the expression of SIOOB in corneal epithelial cells under ,Aspergillus stimulation both in vivo and in vitro. METHODS： Immortalized human corneal epithelial cells （HCECs） were exposed to inactive #lsperg///us fumigatus （A. fumigatus） conidia at 0, 4, 8, 12, 16, and 24h respectively. The corneas of Wistar rats were exposed to active A. fumigatus at 0, 12, 24, 48h and the normal rat corneas were used for normal control. The mRNA level of S100B was evaluated by real time quantitative reverse transcription-polymerase chain reaction （qRT-PCR）. Sl00B protein expression in cornea epithelium was detected by immunohistochemical/immunocytochemical staining （IHC/ICC）. RESULTS： Histopathology revealed a significant inflammatory cell infiltration in fungal keratitis human and rat cornea. Corneal epithelial cells didn＇t express or rarely express S100B at baseline. A. fumigatus significantly induced S100B mRNA expression in cultured corneal epithelial cells in a time depended manner in vitro the mRNA began to rise significantly at 8h in vitro （P〈0.05） and continue to rise as time prolonged （P〈0.01）. in vivo S100B mRNA level was low in the normal corneas. However, it was increased in keratitis corneas from 12h after infection （P〈0.05） and reached to a peak at 24h （P〈0.001）. Immunochemistry revealed an obvious staining in fungal keratitis corneas as well as immortalized HCECs compared to the normal ones respectively, indicating an increased expression of SlOOB protein. CONCLUSION： S100B exists in corneal epithelial cells and is over-expressed under A. fumigatus stimulation. Sl00B may play an important role in the innate immune response of the corneal epithelium during A. fumigatus infection.

Regulation of innate immune responses by rabies virus

Rabies virus(RABV)is an infectious and neurotropic pathogen that causes rabies and infects humans and almost all warm-blooded animals,posing a great threat to people and public safety.It is well known that innate immunity is the critical first line of host defense against viral infection.It monitors the invading pathogens by recognizing the pathogen-associated molecular patterns and danger-associated molecular patterns through pattern-recognition receptors,leading to the production of type I interferons(IFNα/β),inflammatory cytokines,and chemokines,or the activation of autophagy or apoptosis to inhibit virus replication.In the case of RABV,the innate immune response is usually triggered when the skin or muscle is bitten or scratched.However,RABV has evolved many ways to escape or even hijack innate immune response to complete its own replication and eventually invades the central nervous system(CNS).Once RABV reaches the CNS,it cannot be wiped out by the immune system or any drugs.Therefore,a better understanding of the interplay between RABV and innate immu-nity is necessary to develop effective strategies to combat its infection.Here,we review the innate immune responses induced by RABV and illustrate the antagonism mechanisms of RABV to provide new insights for the control of rabies.

The Innate Immune Response in Lateolabrax japonicus Induced by Lipopolysaccharide from Glaciecola polaris Strain ARK149(LMG21854)

Glaciecola polaris strain ARK149, a Gram-negative bacterium from Arctic seas, was used to derive lipopolysaccharide （LPS）, and the effect of the LPS inducing some innate immunity parameters was investigated in Japanese sea bass, Lateolabrax japonicus. The results showed that the LPS could enhance the phagocytosis activity, lysozyme activity, and bacteriolytic activity in L.japonicus, significantly （P〈0.05） at 1, 7, 14, 21, 28, and 35 d after LPS-injection. The indexes of three parameters increased to the peak of value at 28th d post LPS-injection. Moreover, RT-PCR analysis suggested that LPS significantly up-regulated the expression of both IL-8 and hepcidin in several tissues. These data suggest that the LPS extracted from Glaciecola polaris strain ARK149 can induce innate immunity in L. japonicus.

Genetic variants of innate immune receptors and infections after liver transplantation

Infection is the leading cause of complication after liver transplantation, causing morbidity and mortality in the first months after surgery. Allograft rejection is mediated through adaptive immunological responses, and thus immunosuppressive therapy is necessary after transplantation. In this setting, the presence of genetic variants of innate immunity receptors may increase the risk of post-transplant infection, in comparison with patients carrying wild-type alleles. Numerous studies have investigated the role of genetic variants of innate immune receptors and the risk of complication after liver transplantation, but their results are discordant. Tolllike receptors and mannose-binding lectin are arguably the most important studied molecules; however, many other receptors could increase the risk of infection after transplantation. In this article, we review the published studies analyzing the impact of genetic variants in the innate immune system on the development of infectious complications after liver transplantation.

Alterations of autophagic and innate immune responses by the Crohn’s disease-associated ATG16L1 mutation

Crohn’s disease(CD)is driven by the loss of tolerance to intestinal microbiota and excessive production of pro-inflammatory cytokines.These pro-inflammatory cytokines are produced by macrophages and dendritic cells(DCs)upon sensing the intestinal microbiota by the pattern recognition receptors(PRRs).Impaired activation of PRR-mediated signaling pathways is associated with chronic gastrointestinal inflammation,as shown by the fact that loss-of-function mutations in the nucleotide-binding oligomerization domain 2 gene increase the risk of CD development.Autophagy is an intracellular degradation process,during which cytoplasmic nutrients and intracellular pathogens are digested.Given that impaired reaction to intestinal microbiota alters signaling pathways mediated by PRRs,it is likely that dysfunction of the autophagic machinery is involved in the development of CD.Indeed,the loss-of-function mutation T300A in the autophagy related 16 like 1(ATG16L1)protein,a critical regulator of autophagy,increases susceptibility to CD.Recent studies have provided evidence that ATG16L1 is involved not only in autophagy,but also in PRR-mediated signaling pathways.ATG16L1 negatively regulates pro-inflammatory cytokine responses of macrophages and DCs after these cells sense the intestinal microbiota by PRRs.Here,we discuss the molecular mechanisms underlying the development of CD in the T300A ATG16L1 mutation by focusing on PRR-mediated signaling pathways.

Innate immune recognition and modulation in hepatitis D virus infection

Hepatitis D virus(HDV)is a global health threat with more than 15 million humans affected.Current treatment options are largely unsatisfactory leaving chronically infected humans at high risk to develop liver cirrhosis and hepatocellular carcinoma.HDV is the only human satellite virus known.It encodes only two proteins,and requires Hepatitis B virus(HBV)envelope protein expression for productive virion release and spread of the infection.How HDV could evolve and why HBV was selected as a helper virus remains unknown.Since the discovery of Na+-taurocholate co-transporting polypeptide as the essential uptake receptor for HBV and HDV,we are beginning to understand the interactions of HDV and the immune system.While HBV is mostly regarded a stealth virus,that escapes innate immune recognition,HBV-HDV coinfection is characterized by a strong innate immune response.Cytoplasmic RNA sensor melanoma differentiation antigen 5 has been reported to recognize HDV RNA replication and activate innate immunity.Innate immunity,however,seems not to impair HDV replication while it inhibits HBV.In this review,we describe what is known up-to-date about the interplay between HBV as a helper and HDV’s immune evasion strategy and identify where additional research is required.

Oral microbiota and host innate immune response in bisphosphonate-related osteonecrosis of the jaw

Bacterial biofilms have emerged as potential critical triggers in the pathogenesis of bisphosphonate（BP）-related osteonecrosis of the jaw（ONJ） or BRONJ. BRONJ lesions have shown to be heavily colonized by oral bacteria, most of these difficult to cultivate and presents many clinical challenges. The purpose of this study was to characterize the bacterial diversity in BRONJ lesions and to determine host immune response. We examined tissue specimens from three cohorts（n530）; patients with periodontal disease without a history of BP therapy（Control, n510）, patients with periodontal disease having history of BP therapy but without ONJ（BP, n55） and patients with BRONJ（BRONJ, n515）. Denaturing gradient gel electrophoresis of polymerase chain reaction（PCR）-amplified 16 S r RNA gene fragments revealed less bacterial diversity in BRONJ than BP and Control cohorts. Sequence analysis detected six phyla with predominant affiliation to Firmicutes in BRONJ（71.6%）, BP（70.3%） and Control（59.1%）. Significant differences（P,0.05） in genera were observed, between Control/BP, Control/BRONJ and BP/BRONJ cohorts. Enzyme-linked immunosorbent assay（ELISA）results indicated that the levels of myeloperoxidase were significantly lower, whereas interleukin-6 and tumor necrosis factor-alpha levels were moderately elevated in BRONJ patients as compared to Controls. PCR array showed significant changes in BRONJ patients with downregulation of host genes, such as nucleotide-binding oligomerization domain containing protein 2, and cathepsin G, the key modulators for antibacterial response and upregulation of secretory leukocyte protease inhibitor, proteinase 3 and conserved helix–loop–helix ubiquitous kinase. The results suggest that colonization of unique bacterial communities coupled with deficient innate immune response is likely to impact the pathogenesis of ONJ.

Phenoloxidase and Melanization Innate Immune Activities in Green Darner Dragonfly Nymphs (Anax junius)

Insects in the Order Odonata are highly subject to infection by gregarine parasites. However, despite the important ecological roles that insects play in every ecosystem in which they exist, little research has been devoted to the description of insect immunity. Insects rely heavily on the rapid actions of innate immune mechanisms to prevent infection. We characterized the melanization response in the hemolymph of green darner dragonfly (Anax junius) nymphs. Incubation of chymotrypsin-activated hemolymph with L-DOPA resulted in volume- and time-dependent production of dopaquinone via the phenoloxidase (PO) enzyme, with biphasic accumulation of product. The PO activity was temperature-dependent, with a stepwise increase from 20℃ - 35℃ and maximum activity measured at 35℃ - 40℃. The formation of product was also inhibited in a concentration-dependent manner by diethylcarbonate, a specific inhibitor of PO activity, which indicated that the observed activity was due to the presence of PO enzyme. The rate of formation and quantity of melanin was dependent on exposure to different titers of bacteria. This is the first characterization of both PO activity and melanization response in green darner dragonflies.

Cigarette smoking and innate immune responses to influenza infection

Cigarette smoking(CS) suppresses the immune system, and smoking is a well-known major risk factor for respiratory tract infections, including influenza infection. Both smoking cigarettes and passive smoking alter a wide range of immunological functions, including innate and adaptive immune responses. Past reviews on CS and innate immunity have been focused on the effects of CS on structural changes of the lung, as well as the effects on the function of alveolar macrophages, leukocytes, natural killer cells and dendritic cells. The study of innate immunity has developed rapidly in the last decade with the discovery of new receptors for virus recognition and interferon responses. This review aims to give a brief summary of recent findings on the suppressive effects of CS on the innate response to influenza virus, especially as it pertains to suppression of the function of pattern recognition receptors for influ-enza virus.

Innate Immune Response in Human Kidney Transplantation: IRF3 and IRF7 Together with Interferon-Alpha Are Significantly Up-Regulated in Acute Rejection

Background: Ischemia-reperfusion injury of organ transplantation activates several mediators which may link the innate to the adaptive immune response. Down the cascade of TLRs, we selected to study the expression of Interferon Regulatory Factors (IRF)-3 and -7 inside human Kidney Transplanted (KTx) organs and the synthesis of IFNα, the main growth factor induced by them, in KTx aspiration biopsy cultures. Simultaneously, we tested their robustness in diagnosing Acute Rejection (AR). Methods: Fine-needle aspiration biopsies (F-nab) were performed either on day 7 or 14 post-KTx among stable patients or on the day of AR diagnosis. On Fnab cytopreparations, we studied IRF3 and IRF7 by the enzymatic avidin-biotin complex staining, and in a different group of cases we quantified IFNα by ELISA in 48 hours Fnab culture supernatants. Results: AR group showed a significantly up-regulated expression for IRF3 and IRF7, reaching Positive Predictive Values (PPV) of 0.824 and 0.8, respectively, as well as Negative Predictive Values (NPV) above 0.9 for both;IFNα presented a PPV = 1.0 and a NPV = 0.9. A variation in the results was noticed according to different immunosuppressive therapies. Conclusions: Our findings suggest that IRF3 and IRF7, and IFNα which they promote, may be very important players in the early days post-KTx, linking the innate with an adaptive response and triggering acute rejection. These differences were very clear-cut, lending consistency to our speculation. It would be important to scrutinize for other potential effects derived from these IRFs up-regulation which could be of clinical relevance.

Unveiling the dynamic role of innate and adaptive immune cells in COPD pathogenesis induced by cigarette smoke

Chronic obstructive pulmonary disease(COPD)is a multifaceted syndrome characterized by a dysregulated inflammatory cascade within the respiratory system,primarily triggered by exposure to harmful particles and gases,notably from cigarette smoke.This inflammatory response is orchestrated by innate immune cells like macrophages and epithelial cells,which recognize danger signals released from damaged cells.Prolonged inflammation prompts an adaptive immune reaction mediated by dendritic cells,culminating in the formation of lymphoid follicles and involving a complex interplay of T and B cells,as well as cytotoxic activity.Additionally,both viral and bacterial infections exacerbate COPD by further igniting inflammatory pathways,perpetuating the chronic inflammatory state.This comprehensive review encapsulates the intricate interplay between innate and adaptive immunity in COPD,with a particular focus on the role of cigarette smoke in its pathogenesis and potential therapeutic targets.

The role of innate immune cells in post-hepatectomy liver regeneration

The fame of regeneration has been attributed to the liver ever since the era of Greek mythology,in which Prometheus’liver could grow back overnight against the daily predation of Zeus’eagle.Hepatectomy is the very basis of liver surgery including liver transplantation,and post-hepatectomy liver regeneration remains the center of interest for both clinicians and scientists.Novel tools for structural and functional assessment of liver regeneration have been constantly developed and validated,laying the groundwork for clinical management and scientific analysis(1).