CARD9 gene silencing with siRNA protects rats against severe acute pancreatitis: CARD9-dependent NF-κB and P38MAPKs pathway

Leucine-rich repeat kinase 2 promotes the development of experimental severe acute pancreatitis

Translocation of gut bacteria into the pancreas promotes the development of severe acute pancreatitis (SAP). Recent clinical studies have also highlighted the association between fungal infections and SAP. The sensing of gut bacteria by pattern recognition receptors promotes the development of SAP via the production of proinflammatory cytokines; however, the mechanism by which gut fungi mediate SAP remains largely unknown. Leucine-rich repeat kinase 2 (LRRK2) is a multifunctional protein that regulates innate immunity against fungi via Dectin-1 activation. Here, we investigated the role of LRRK2 in SAP development and observed that administration of LRRK2 inhibitors attenuated SAP development. The degree of SAP was greater in Lrrk2 transgenic (Tg) mice than in control mice and was accompanied by an increased production of nuclear factor-kappaB-dependent proinflammatory cytokines. Ablation of the fungal mycobiome by anti-fungal drugs inhibited SAP development in Lrrk2 Tg mice, whereas the degree of SAP was comparable in Lrrk2 Tg mice with or without gut sterilization by a broad range of antibiotics. Pancreatic mononuclear cells from Lrrk2 Tg mice produced large amounts of IL-6 and TNF-α upon stimulation with Dectin-1 ligands, and inhibition of the Dectin-1 pathway by a spleen tyrosine kinase inhibitor protected Lrrk2 Tg mice from SAP. These data indicate that LRRK2 activation is involved in the development of SAP through proinflammatory cytokine responses upon fungal exposure.

Macrophage CARD9 mediates cardiac injury following myocardial infarction through regulation of lipocalin 2 expression

Immune cell infiltration in response to myocyte death regulates extracellular matrix remodeling and scar formation after myocardial infarction (MI). Caspase-recruitment domain family member 9 (CARD9) acts as an adapter that mediates the transduction of pro-inflammatory signaling cascades in innate immunity; however, its role in cardiac injury and repair post-MI remains unclear. We found that Card9 was one of the most upregulated Card genes in the ischemic myocardium of mice. CARD9 expression increased considerably 1 day post-MI and declined by day 7 post-MI. Moreover, CARD9 was mainly expressed in F4/80-positive macrophages. Card9 knockout (KO) led to left ventricular function improvement and infarct scar size reduction in mice 28 days post-MI. Additionally, Card9 KO suppressed cardiomyocyte apoptosis in the border region and attenuated matrix metalloproteinase (MMP) expression. RNA sequencing revealed that Card9 KO significantly suppressed lipocalin 2 (Lcn2) expression post-MI. Both LCN2 and the receptor solute carrier family 22 member 17 (SL22A17) were detected in macrophages. Subsequently, we demonstrated that Card9 overexpression increased LCN2 expression, while Card9 KO inhibited necrotic cell-induced LCN2 upregulation in macrophages, likely through NF-κB. Lcn2 KO showed beneficial effects post-MI, and recombinant LCN2 diminished the protective effects of Card9 KO in vivo. Lcn2 KO reduced MMP9 post-MI, and Lcn2 overexpression increased Mmp9 expression in macrophages. Slc22a17 knockdown in macrophages reduced MMP9 release with recombinant LCN2 treatment. In conclusion, our results demonstrate that macrophage CARD9 mediates the deterioration of cardiac function and adverse remodeling post-MI via LCN2.

Mesenchymal stem cells regulate M1 polarization of peritoneal macrophages through the CARD9-NF-κB signaling pathway in severe acute pancreatitis

BACKGROUND

Macrophages release large numbers of proinflammatory cytokines that trigger inflammatory cascade reactions, which promote the rapid development of severe acute pancreatitis (SAP) from local to systemic inflammation. The ability of mesenchymal stem cells (MSCs) to suppress inflammation is related to inhibition of M1 polarization of macrophages. Our previous studies revealed that caspase recruitment domain protein 9 (CARD9) was involved in SAP inflammation and activation of the CARD9-NF-κB signaling pathway plays an important proinflammatory role in SAP. At present, there is no effective treatment to control the inflammatory response in SAP. Therefore, the aim of the present study was to determine whether MSCs regulate the polarization of macrophages through the CARD9-NF-κB signaling pathway in SAP.

METHODS

Short hairpin RNA interference technology and coculture in vitro were used to assess the activation status of the CARD9-NF-κB signal pathway in macrophages. Furthermore, flow cytometry was used to determine the polarization state of macrophages.

RESULTS

The results showed MSCs inhibited CARD9 expression in vivo and in vitro (P < .05), alleviated inflammation induced by proinflammatory cytokines, and inhibited the phosphorylation of NF-κB in macrophages both in vivo and in vitro. Meanwhile, MSCs downregulated the CARD9-NF-κB signal pathway and inhibited M1 polarization of macrophages.

CONCLUSION

In conclusion, MSCs regulate M1 polarization of peritoneal macrophages through the CARD9-NF-κB signaling pathway in SAP and transplantation of MSCs presents an effective treatment option for SAP.

CARD9 Signaling, Inflammation, and Diseases

Caspase-recruitment domain 9 (CARD9) protein is expressed in many cells especially in immune cells, and is critically involved in the function of the innate and adaptive immune systems through extensive interactions between CARD9 and other signaling molecules including NF-κB and MAPK. CARD9-mediated signaling plays a central role in regulating inflammatory responses and oxidative stress through the productions of important cytokines and chemokines. Abnormalities of CARD9 and CARD9 signaling or CARD9 mutations or polymorphism are associated with a variety of pathological conditions including infections, inflammation, and autoimmune disorders. This review focuses on the function of CARD9 and CARD9-mediated signaling pathways, as well as interactions with other important signaling molecules in different cell types and the relations to specific disease conditions including inflammatory diseases, infections, tumorigenesis, and cardiovascular pathologies.

Role of CARD9 in inflammatory signal pathway of peritoneal macrophages in severe acute pancreatitis

Previous studies revealed that caspase recruitment domain protein 9 (CARD9) was involved in severe acute pancreatitis (SAP) inflammation and that interfering with its expression in vivo could inhibit inflammation. However, the specific mechanism is unknown. This study aimed to discover the related signal pathways of CARD9 in macrophages. SiRNA interference technology was used in vivo and in vitro to detect CARD9‐related signal pathways in peritoneal macrophages. Furthermore, Toll‐like receptor 4 (TLR4) and membrane‐associated C‐type lectin‐1 (Dectin‐1) pathways in macrophages were activated specially to looking for the upstream signal path of CARD9. Results showed up‐regulation of CARD9 expression in peritoneal macrophages of SAP rats (P < .05). CARD9 siRNA alleviated inflammatory cytokines, and inhibited the phosphorylation of NF‐κB and p38MAPK in peritoneal macrophages in vivo or in vitro. Meanwhile, CARD9 siRNA reduced the concentration of CARD9 and Bcl10 in peritoneal macrophages, and TLR4 and Dectin‐1 took part in CARD9 signal pathways in macrophages. In conclusion, there is an inflammation signal pathway comprised of TLR4/Dectin‐1‐CARD9‐NF‐κB/p38MAPK activated in macrophages in SAP. Blockade of CARD9 expression in macrophages can effectively alleviate SAP inflammation.

The adaptor protein CARD9, from fungal immunity to tumorigenesis

The adaptor protein CARD9 is in charge of mediating signals from PRRs of myeloid cells to downstream transcription factor NF-κB. CARD9 plays an indispensable role in innate immunity. Both mice and humans with CARD9 deficiency show increased susceptibility to fungal and bacterial infections. CARD9 signaling not only activates but also shapes adaptive immune responses. The role of this molecule in tumor progression is increasingly being revealed. Our early study found that CARD9 is associated with the development of colon cancer and functions as a regulator of antitumor immunity. In this review, we focus on the upstream and downstream signaling pathways of CARD9, then we summarize the immunological recognition and responses induced by CARD9 signaling. Furthermore, we review the function of CARD9 in multiple aspects of host immunity, ranging from fungal immunity to tumorigenesis.

Silencing ICAM-1 reduces the adhesion of vascular endothelial cells in mice with immunologic contact urticaria

OBJECTIVE

Immunologic contact urticaria (ICU) is an immediate response of wheal caused by various contactants in vulnerable individuals, with undefined pathogenesis.

METHODS

In the present study, we aim to explore the effects of intercellular cell adhesion molecule-1 (ICAM-1) gene silencing by RNA inference (RNAi) on vascular endothelial cells (VECs) adhesion molecule expression and cell-cell adhesion in ICU mice. Sixty BALB/c mice were selected, among which 48 mice were used for establishment of ICU models. VECs from normal and ICU mice were grouped into different groups. Expressions of ICAM-1, eosinophilic cationic protein (ECP), total immunologlobulin E (tIgE), L-selectin (CD62L), integrin, alpha L (CD11a) in tissues and cells were evaluate by RT-qPCR and western blotting. Cell proliferation was evaluated by MTT assay and EdU staining and cell adhesive function by cell-cell adhesion assay.

RESULTS

Compared with normal mice, ICU mice had increased expressions of ICAM-1, ECP, tIgE, CD62L, and CD11a.ICAM-1 gene silencing decreased expressions of ECP, tIgE, CD62L, and CD11a, enhanced cell proliferation, and more activity in cell adhesion.

CONCLUSION

These findings indicate that RNAi-mediated gene silencing of ICAM-1 may decrease VECs adhesion expression and reduce cell-cell adhesion in mice with ICU.

The Role of CARD9 in Metabolic Diseases

Caspase recruitment domain containing protein 9 (CARD9) is an adaptor protein that plays a critical role in pattern recognition receptors (PRRs)-mediated activation of NF-?B and mitogen-activated protein kinase (MAPK). This elicits initiation of the pro-inflammatory cytokines and leads to inflammatory responses, which has been recognized as a critical contributor to chronic inflammation. Current researches demonstrate that CARD9 is strongly associated with metabolic diseases, such as obesity, insulin resistance, atherosclerosis and so on. In this review, we summarize CARD9 signaling pathway and the role of CARD9 in metabolic diseases.

Physiological and Pathological Functions of CARD9 Signaling in the Innate Immune System

Caspase recruitment domain protein 9 (CARD9) forms essential signaling complexes in the innate immune system that integrate cues from C-type lectin receptors and specific intracellular pattern recognition receptors. These CARD9-mediated signals are pivotal for host defense against fungi, and they mediate immunity against certain bacteria, viruses and parasites. Furthermore, CARD9-regulated pathways are involved in sterile inflammatory responses critical for immune homeostasis and can control pro- and antitumor immunity in cancer microenvironments. Consequently, multiple genetic alterations of human CARD9 are connected to primary immunodeficiencies or prevalent inflammatory disorders in patients. This review will summarize our current understanding of CARD9 signaling in the innate immune system, its physiological and pathological functions and their implications for human immune-mediated diseases.

Inflammatory stimuli promote oxidative stress in pancreatic acinar cells via Toll-like receptor 4/nuclear factor-κB pathway

The Toll‑like receptor 4/nuclear factor‑κB (TLR4/NF‑κB) pathway is vital to the pathogenesis of acute pancreatitis (AP). The aim of the present study was to identify the mechanism of the activation of the TLR4/NF‑κB signaling pathway in the viability of primary pancreatic cells. The cells were stimulated with lipopolysaccharide (LPS) for the activation of NF‑κB signaling. Next, the reactive oxygen species (ROS) level was evaluated by detecting the concentration of malondialdehyde and glutathione peroxidase. Cell viability was measured by Cell Counting Kit‑8 and MTT assays, while the percentage of apoptosis was detected by flow cytometry. Quantitative polymerase chain reaction was used to detect TLR4, B‑cell lymphoma 2 (Bcl2), Bcl2‑associated X protein (Bax) and phorbol‑12‑myristate‑13‑acetate‑induced protein 1 (PMAIP1) expression levels. Western blot assay was also conducted to detect TLR4 protein expression, while the activity of NF‑κB signaling was measured by determining the p65 and phosphorylated p65 protein levels. In addition, the effect of TLR4 overexpression or treatment with TLR4 antagonists in the presence of LPS stimulation was investigated. The results revealed that ROS levels were increased and cell viability was decreased in LPS‑stimulated pancreatic acinar cells. TLR4, Bax and PMAIP1 levels were increased, Bcl2 expression was decreased and NF‑κB signaling was activated in LPS‑stimulated pancreatic acinar cells. Furthermore, pancreatic cells with TLR4 overexpression exhibited increased ROS level and decreased viability. Finally, the effect caused by LPS stimulation was partially reversed by treatment of pancreatic acinar cells with TLR4 antagonists. In conclusion, the current study investigated a novel regulatory mechanism of the TLR4/NF‑κB pathway in LPS‑stimulated pancreatic cells, which may contribute to pancreatitis. The damage of these cells due to increased ROS levels was observed to occur through activation of the TLR4/NF‑κB pathway.

Effects of RNA interference-mediated E-selectin gene silencing on cell adhesion molecule expression and cell-cell adhesion in vascular endothelial cells in mice with immunologic contact urticaria

Contact urticaria is recognized as the wheal and flare reaction at a site from direct contact with a chemical or protein agent. Ongoing studies have proposed that gene silencing may have a promising future in finding optimal treatment of a variety of disease; hence, the aim of the study was to investigate the effect of RNA interference-mediated E-selectin ( SELE) gene silencing on cell adhesion molecule expression and on cell-cell adhesion in vascular endothelial cells (VECs) in a mouse model of immunologic contact urticaria (ICU). Following the successful establishment of mouse models of ICU induced by antidinitrophenol immunoglobulin E (IgE) combining 2,4-dinitrofluorobenzene challenge, enzyme-linked immunosorbent assay and immunohistochemistry were used to measure the levels of IgE, interleukin 4 (IL-4), interferon-γ (IFN-γ), and histamine as well as the positive expression rate of SELE, respectively. The siRNA- SELE vector was constructed and transfection efficiency was estimated prior to performing quantitative reverse-transcription polymerase chain reaction and Western blot assay to determine the relative expression of SELE, eosinophil cationic protein (ECP), intercellular adhesion molecule 1 (ICAM-1), L-selectin (CD62L), and the alpha chain of leukocyte function-associated antigen-1 (CD11a). Adhesion assay was then performed to assess the cell adhesion ability in VECs. Elevated levels of IgE, IL-4, IFN-γ, and histamine and increased positive expression rate of SELE were indicative of successful establishment of mouse models of ICU. Furthermore, the relative expression levels of SELE, ECP, ICAM-1, CD62L, and CD11a were highest in the OE- SELE group. Besides, cell adhesion ability of VECs was notably promoted. Collectively, the current study define the potential role of SELE silencing as an inhibitor to ICU development by inhibiting cell adhesion ability of VECs.

The essential function of CARD9 in diet-induced inflammation and metabolic disorders in mice

Inflammation and metabolic disorder are common pathophysiological conditions, which play a vital role in the development of obesity and type 2 diabetes. The purpose of this study was to explore the effects of caspase recruitment domain (CARD) 9 in the high fat diet (HFD)‐treated mice and attempt to find a molecular therapeutic target for obesity development and treatment. Sixteen male CARD9^−/− and corresponding male WT mice were fed with normal diet or high fat diet, respectively, for 12 weeks. Glucose tolerance, insulin resistance, oxygen consumption and heat production of the mice were detected. The CARD9/MAPK pathway‐related gene and protein were determined in insulin‐responsive organs using Western blotting and quantitative PCR. The results showed that HFD‐induced insulin resistance and impairment of glucose tolerance were more severe in WT mice than that in the CARD9^−/− mice. CARD9 absence significantly modified O₂ consumption, CO₂ production and heat production. CARD9^−/− mice displayed the lower expression of p38 MAPK, JNK and ERK when compared to the WT mice in both HFD‐ and ND‐treated groups. HFD induced the increase of p38 MAPK, JNK and ERK in WT mice but not in the CARD9^−/− mice. The results indicated that CARD9 absence could be a vital protective factor in diet‐induced obesity via the CARD9/MAPK pathway, which may provide new insights into the development of gene knockout to improving diet‐induced obesity and metabolism disorder.

Molecular and physiological roles of the adaptor protein CARD9 in immunity

CARD9 is a caspase recruitment domain-containing signaling protein that plays a critical role in innate and adaptive immunity. It has been widely demonstrated that CARD9 adaptor allows pattern recognition receptors to induce NF-κB and MAPK activation, which initiates a “downstream” inflammation cytokine cascade and provides effective protection against microbial invasion, especially fungal infection. Here our aim is to update existing paradigms and summarize the most recent findings on the CARD9 signaling pathway, revealing significant mechanistic insights into the pathogenesis of CARD9 deficiency. We also discuss the effect of CARD9 genetic mutations on the in vivo immune response, and highlight clinical advances in non-infection inflammation.

Therapeutic effect and potential mechanism of pioglitazone in rats with severe acute pancreatitis

Caspase recruitment domain-containing protein 9 (Card9) is located upstream of the nuclear factor kappa B (NF-κB) and p38 mitogen-activated protein kinase (MAPK) inflammatory pathways. This study investigated the therapeutic effect and potential mechanism of pioglitazone in rats with severe acute pancreatitis (SAP). SAP was induced by a retrograde infusion of 5.0% sodium taurocholate into the biliopancreatic duct of Sprague Dawley rats (n=54), which were then treated with pioglitazone. Blood and pancreatic tissues were harvested at 3, 6, and 12 h after SAP induction. Pancreatic pathological damage was evaluated by hematoxylin and eosin staining. Serum amylase, serum pro-inflammatory cytokines, and pancreatic myeloperoxidase (MPO) activities were determined by enzyme-linked immunosorbent assay. The expression of Card9 mRNA and protein in pancreatic tissues was detected by real-time polymerase chain reaction and western blotting. Pioglitazone had a therapeutic effect in treating rats with SAP by decreasing the level of amylase activity, ameliorating pancreatic histological damage, decreasing serum pro-inflammatory cytokine levels and tissue MPO activity, and downregulating the expression of NF-κB, p38MAPK, and Card9 mRNAs and proteins (P<0.05). The present study demonstrated that the inhibition of Card9 expression could reduce the severity of SAP. Card9 has a role in the pathogenic mechanism of SAP.

Adenovirus-mediated artificial miRNA targetting fibrinogen-like protein 2 attenuates the severity of acute pancreatitis in mice

Severe acute pancreatitis (SAP) remains to be challenging for its unpredictable inflammatory progression from acute pancreatitis to SAP. Apoptosis is an important pathology of SAP. Fibrinogen-like protein 2 (FGL2) has been reported to be involved in apoptosis. The present study aimed to explore the therapeutic effect of an adenovirus-mediated artificial miRNA targetting FGL2 (Ad-FGL2-miRNA) in taurocholate-induced murine pancreatitis models. Sodium taurocholate was retrogradely injected into the biliopancreatic ducts of the C57/BL mice to induce SAP. FGL2 expression was measured with reverse transcription-PCR, Western blotting, and immunohistochemical staining. ELISA was used to detect the activity of amylase and the concentrations of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β). In addition, the mRNA levels of TNF-α and IL-1β were also detected. Finally, apoptosis was assessed by terminal deoxynucleotidyl transferase mediated dUTP-biotin nick-end labeling (TUNEL) method and Western blotting. Ad-FGL2-miRNA significantly suppressed FGL2 expression and alleviated pancreatic injury. Also, Ad-FGL2-miRNA markedly inhibited a post-SAP increase in the activation of TNF-α and IL-1β. Finally, pretreatment with Ad-FGL2-miRNA ameliorated apoptosis at the early stage of SAP by modulating cleaved caspase-3 and therefore played a protective role. These results indicated that FGL2 might be a promising target for attenuating the severity of SAP and adenovirus-mediated artificial miRNAs targetting FGL2 represented a potential therapeutic approach for the treatment of SAP.

Immunology of pancreatitis and environmental factors

PURPOSE OF REVIEW

This report reviews recent aspects of pancreatitis immunology and environmental factors that link to development and progression of disease.

RECENT FINDINGS

Limited human and animal model studies have recently attempted to understand immune mechanisms that lead to the pathogenesis of acute and chronic pancreatitis. Based on these studies innate immune responses emerge as critical elements in disease pathogenesis and severity of inflammation. The immune basis for environmental factors such as smoking, which are highly associated with disease progression highlight novel cross talk mechanisms between immune and nonimmune pancreatic cells such as the pancreatic stellate cells.

SUMMARY

Better understanding of immune responses and signaling pathways are emerging as important contributors in pancreatitis development and progression. Such mechanisms are likely to offer future targetable therapies that can either halt or reverse disease progression.

Picroside II Shows Protective Functions for Severe Acute Pancreatitis in Rats by Preventing NF-κB-Dependent Autophagy

Picroside II, from the herb Picrorhiza scrophulariiflora Pennell, has antioxidant and anti-inflammatory activities. However, its function on severe acute pancreatitis (SAP) and molecular mechanism remains unknown. The effects of picroside II on the SAP induced by cerulean were investigated. SAP rats were treated with picroside II (25 mg/kg). The severity of SAP was evaluated by using biochemical and histological analyses. Pancreatic cancer cell PANC-1 was transfected with ptfLC3 (an indicator of autophagic activity), pcDNA3.1-NF-κB (nuclear factor kappa B), and pTZU6+1-NF-κB-shRNA and then treated with picroside II. Relative molecules related with NF-κB-dependent autophagy were detected by using Western blot. Autophagic activities were observed by phase-contrast and fluorescent microscopes. Acetylated LC3 was detected by immunoprecipitation. The results showed that picroside II treatment reduced the level of ALT, AST, NF-κB, IL-1β, IL-6, TNF-α, and SIRT1 (NAD⁺-dependent deacetylase) and increased the level of SOD and GSH. The autophagic activity was reduced when NF-κB was silenced, and the levels of TNF-α and SIRT1 were reduced. In contrast, the overexpression of NF-κB increased autophagic activity and the level of TNF-α, which activated SIRT1. SIRT1 deacetylated LC3 and increased autophagic activities. Picroside II ameliorates SAP by improving antioxidant and anti-inflammtory activities of SAP models via NF-κB-dependent autophagy.