Critical roles of the WASP N-terminal domain and Btk in LPS-induced inflammatory response in macrophages

Pneumococcal sialidase promotes bacterial survival by fine-tuning of pneumolysin-mediated membrane disruption

Pneumolysin (Ply) is an indispensable cholesterol-dependent cytolysin for pneumococcal infection. Although Ply-induced disruption of pneumococci-containing endosomal vesicles is a prerequisite for the evasion of endolysosomal bacterial clearance, its potent activity can be a double-edged sword, having a detrimental effect on bacterial survivability by inducing severe endosomal disruption, bactericidal autophagy, and scaffold epithelial cell death. Thus, Ply activity must be maintained at optimal levels. We develop a highly sensitive assay to monitor endosomal disruption using NanoBiT-Nanobody, which shows that the pneumococcal sialidase NanA can fine-tune Ply activity by trimming sialic acid from cell-membrane-bound glycans. In addition, oseltamivir, an influenza A virus sialidase inhibitor, promotes Ply-induced endosomal disruption and cytotoxicity by inhibiting NanA activity in vitro and greater tissue damage and bacterial clearance in vivo. Our findings provide a foundation for innovative therapeutic strategies for severe pneumococcal infections by exploiting the duality of Ply activity.

Nimbolide ameliorates pancreatic inflammation and apoptosis by modulating NF-κB/SIRT1 and apoptosis signaling in acute pancreatitis model

Acute pancreatitis (AP) is a potential gastrointestinal problem most commonly associated with pancreatic inflammation and acinar cells injury. Nimbolide (NB), isolated from the tree Azadirachta indica, possesses antioxidant and anti-inflammatory effects. Here, we aimed to investigate the pancreatic protective effects of NB in ameliorating cerulein-induced pancreatic inflammation and apoptosis in AP model and evaluate the potential mechanism of action. AP was induced in Swiss albino mice by six-hourly intraperitoneal exposures of cerulein (50 µg/kg/hr) and pre-treatment of NB (0.3 and 1 mg/kg) 7 days prior to the cerulein exposure. Various parameters associated with AP in plasma and pancreatic tissues were evaluated. Severity of AP was effectively ameliorated by NB as shown by reducing pancreatic edema, plasma amylase and lipase levels, MPO levels and in cerulein-induced histological damage. Further, the antioxidant effect of NB was associated with a significant inhibition of oxidative-nitrosative stress in Raw 264.7 cells and cerulein-induced AP mice. Moreover, NB suppressed proinflammatory cytokines, iNOS and nitrotyrosine expression. In addition, NB inhibited NF-κB activation and increased SIRT1 expression in cerulein challenged mice. Furthermore, NB also inhibited pancreatic apoptosis by downregulating cleaved caspase 3 and Bax while upregulating Bcl2 expression in cerulein-treated mice. Inhibition of pancreatic inflammation and apoptosis resulted in attenuation of cerulein-induced AP. These results suggest that NB exerts strong anti-pancreatitis effects against cerulein-induced AP by combating inflammatory and apoptosis signaling via SIRT1 activation.

CRISPR/Cas9-mediated deletion of the Wiskott-Aldrich syndrome locus causes actin cytoskeleton disorganization in murine erythroleukemia cells

Wiskott-Aldrich syndrome (WAS) is a recessive X-linked inmmunodeficiency caused by loss-of-function mutations in the gene encoding the WAS protein (WASp). WASp plays an important role in the polymerization of the actin cytoskeleton in hematopoietic cells through activation of the Arp2/3 complex. In a previous study, we found that actin cytoskeleton proteins, including WASp, were silenced in murine erythroleukemia cells defective in differentiation. Here, we designed a CRISPR/Cas9 strategy to delete a 9.5-kb genomic region encompassing the Was gene in the X chromosome of murine erythroleukemia (MEL) cells. We show that Was-deficient MEL cells have a poor organization of the actin cytoskeleton that can be recovered by restoring Was expression. We found that whereas the total amount of actin protein was similar between wild-type and Was knockout MEL cells, the latter exhibited an altered ratio of monomeric G-actin to polymeric F-actin. We also demonstrate that Was overexpression can mediate the activation of Bruton’s tyrosine kinase. Overall, these findings support the role of WASp as a key regulator of F-actin in erythroid cells.

Constitutive activation of WASp in X-linked neutropenia renders neutrophils hyperactive

Congenital neutropenia is characterized by low absolute neutrophil numbers in blood, leading to recurrent bacterial infections, and patients often require life-long granulocyte CSF (G-CSF) support. X-linked neutropenia (XLN) is caused by gain-of-function mutations in the actin regulator Wiskott-Aldrich syndrome protein (WASp). To understand the pathophysiology in XLN and the role of WASp in neutrophils, we here examined XLN patients and 2 XLN mouse models. XLN patients had reduced myelopoiesis and extremely low blood neutrophil number. However, their neutrophils had a hyperactive phenotype and were present in normal numbers in XLN patient saliva. Murine XLN neutrophils were hyperactivated, with increased actin dynamics and migration into tissues. We provide molecular evidence that the hyperactivity of XLN neutrophils is caused by WASp in a constitutively open conformation due to contingent phosphorylation of the critical tyrosine-293 and plasma membrane localization. This renders WASp activity less dependent on regulation by PI3K. Our data show that the amplitude of WASp activity inside a cell could be enhanced by cell-surface receptor signaling even in the context in which WASp is already in an active conformation. Moreover, these data categorize XLN as an atypical congenital neutropenia in which constitutive activation of WASp in tissue neutrophils compensates for reduced myelopoiesis.

Highly selective inhibition of Bruton's tyrosine kinase attenuates skin and brain disease in murine lupus

Background

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease that affects different end organs, including skin and brain. We and others have previously shown the importance of macrophages in the pathogenesis of cutaneous and neuropsychiatric lupus. Additionally, autoantibodies produced by autoreactive B cells are thought to play a role in both the skin and central nervous system pathologies associated with SLE.

Methods

We used a novel inhibitor of Bruton’s tyrosine kinase (BTK), BI-BTK-1, to target both macrophage and B cell function in the MRL-lpr/lpr murine model of SLE, and examined the effect of treatment on skin and brain disease.

Results

We found that treatment with BI-BTK-1 significantly attenuated the lupus associated cutaneous and neuropsychiatric disease phenotypes in MRL/lpr mice. Specifically, BI-BTK-1 treated mice had fewer macroscopic and microscopic skin lesions, reduced cutaneous cellular infiltration, and diminished inflammatory cytokine expression compared to control mice. BTK inhibition also significantly improved cognitive function, and decreased accumulation of T cells, B cells, and macrophages within the central nervous system, specifically the choroid plexus.

Conclusions

Directed therapies may improve the response rate in lupus-driven target organ involvement, and decrease the dangerous side effects associated with global immunosuppression. Overall, our results suggest that inhibition of BTK may be a promising therapeutic option for cutaneous and neuropsychiatric disease associated with SLE.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-017-1500-0) contains supplementary material, which is available to authorized users.

Development and validation of scFv-conjugated affinity silk protein for specific detection of carcinoembryonic antigen

The production costs for monoclonal antibodies (MAbs) utilized in medical diagnostic kits are inevitably high because the MAbs are mostly obtained from hybridoma cell culture. Here, we report the development and validation of a novel affinity silk protein produced by transgenic silkworm technology as a possible alternative diagnostic tool for cancers. We generated a transgenic silkworm expressing a cDNA construct containing fibroin L-chain fused to a single-chain variable fragment (scFv) derived from a MAb against carcinoembryonic antigen (CEA). The transgenic cocoons were dissolved in aqueous lithium bromide solution, applied to 96-well plates, and analysed by enzyme-linked immunosorbent assay. The scFv-conjugated affinity silk protein specifically recognized CEA as well as the parental MAb. The binding activity was retained after several months of storage in coated plates or concentrated solution. Thus, the scFv-conjugated affinity silk protein provides a potentially useful alternative to conventional MAbs in medical diagnostic kits.

Inhibition of BTK protects lungs from trauma-hemorrhagic shock-induced injury in rats

The present study aimed to investigate the role of Bruton's tyrosine kinase (BTK) in the pathogenesis of lung injury induced by trauma‑hemorrhagic shock (THS), and to examine the pulmonary protective effects of BTK inhibition. Male Sprague‑Dawley rats were divided into four groups (n=12/group): i) A Sham group, which received surgery without induced trauma; ii) a THS‑induced injury group; iii) a THS‑induced injury group that also received treatment with the BTK inhibitor LFM‑A13 prior to trauma induction; and iv) a Sham group that was pretreated with LFM‑A13 prior to surgery but did not receive induced trauma. The expression of phosphorylated‑BTK protein in the lungs was measured by immunohistochemistry and western blot analysis. The bronchoalveolar lavage fluid (BALF) protein concentration, total leukocyte and eosinophil numbers, and the expression levels of peripheral blood proinflammatory factors were measured. Morphological alterations in the lungs were detected by hematoxylin and eosin staining. Pulmonary nitric oxide (NO) concentration and inducible NO synthase (iNOS) expression were also assessed. Activities of the nuclear factor (NF)‑κB and mitogen‑activated protein kinase (MAPK) signaling pathways were determined by western blotting or electrophoretic mobility shift assay. BTK was notably activated in lungs of THS rats. BALF protein concentration, total leukocytes and eosinophils, peripheral blood expression levels of tumor necrosis factor‑α, interleukin (IL)‑1β, IL‑6 and monocyte chemotactic protein 1 were significantly upregulated after THS induction, and each exhibited decreased expression upon LFM‑A13 treatment. THS‑induced interstitial hyperplasia, edema and neutrophilic infiltration in lungs were improved by the inhibition of BTK. In addition, THS‑induced NO release, iNOS overexpression, and NF‑κB and MAPK signaling were suppressed by BTK inhibition. Results from the present study demonstrate that BTK may serve a pivotal role in the pathogenesis of THS‑related lung injury, and the inhibition of BTK may significantly alleviate THS‑induced lung damage. These results provide a potential therapeutic application for the treatment of THS‑induced lung injury.

Berberine inhibits inflammatory mediators and attenuates acute pancreatitis through deactivation of JNK signaling pathways

Acute pancreatitis (AP) is a life-threatening disease. Berberine (BBR), a well-known plant alkaloid, is reported to have anti-inflammatory activity in many diseases. However, the effects of BBR on AP have not been clearly elucidated. Therefore, the present study aimed to investigate the effects of BBR on cerulein-induced AP in mice. AP was induced by either cerulein or l-arginine. In the BBR treated group, BBR was administered intraperitoneally 1h before the first cerulein or l-arginine injection. Blood samples were obtained to determine serum amylase and lipase activities and nitric oxide production. The pancreas and lung were rapidly removed for examination of histologic changes, myeloperoxidase (MPO) activity, and real-time reverse transcription-polymerase chain reaction. Furthermore, the regulating mechanisms of BBR were evaluated. Treatment of mice with BBR reduced pancreatic injury and activities of amylase, lipase, and pancreatitis-associated lung injury, as well as inhibited several inflammatory parameters such as the expression of pro-inflammatory cytokines and inducible nitric oxide synthesis (iNOS). Furthermore, BBR administration significantly inhibited c-Jun N-terminal kinase (JNK) activation in the cerulein-induced AP. Deactivation of JNK resulted in amelioration of pancreatitis and the inhibition of inflammatory mediators. These results suggest that BBR exerts anti-inflammatory effects on AP via JNK deactivation on mild and severe acute pancreatitis model, and could be a beneficial target in the management of AP.

Immune regulation of canine tumour and macrophage PD-L1 expression

Expression of programmed cell death receptor ligand 1 (PD-L1) on tumor cells has been associated with immune escape in human and murine cancers, but little is known regarding the immune regulation of PD-L1 expression by tumor cells and tumor-infiltrating macrophages in dogs. Therefore, 14 canine tumor cell lines, as well as primary cultures of canine monocytes and macrophages, were evaluated for constitutive PD-L1 expression and for responsiveness to immune stimuli. We found that PD-L1 was expressed constitutively on all canine tumor cell lines evaluated, although the levels of basal expression were very variable. Significant upregulation of PD-L1 expression by all tumor cell lines was observed following IFN-γ exposure and by exposure to a TLR3 ligand. Canine monocytes and monocyte-derived macrophages did not express PD-L1 constitutively, but did significantly upregulate expression following treatment with IFN-γ. These findings suggest that most canine tumors express PD-L1 constitutively and that both innate and adaptive immune stimuli can further upregulate PD-L1 expression. Therefore the upregulation of PD-L1 expression by tumor cells and by tumor-infiltrating macrophages in response to cytokines such as IFN-γ may represent an important mechanism of tumor-mediated T-cell suppression in dogs as well as in humans.

The Neutrophil Btk Signalosome Regulates Integrin Activation during Sterile Inflammation

Neutrophils are recruited from the blood to sites of sterile inflammation, where they are involved in wound healing but can also cause tissue damage. During sterile inflammation, necrotic cells release pro-inflammatory molecules including formylated peptides. However, the signaling pathway triggered by formylated peptides to integrin activation and leukocyte recruitment is unknown. By using spinning-disk confocal intravital microscopy, we examined the molecular mechanisms of leukocyte recruitment to sites of focal hepatic necrosis in vivo. We demonstrated that the Bruton's tyrosine kinase (Btk) was required for multiple Mac-1 activation events involved in neutrophil recruitment and functions during sterile inflammation triggered by fMLF. The Src family kinase Hck, Wiskott-Aldrich-syndrome protein, and phospholipase Cγ2 were also involved in this pathway required for fMLF-triggered Mac-1 activation and neutrophil recruitment. Thus, we have identified a neutrophil Btk signalosome that is involved in a signaling pathway triggered by formylated peptides leading to the selective activation of Mac-1 and neutrophil recruitment during sterile inflammation.

Anti-WASP intrabodies inhibit inflammatory responses induced by Toll-like receptors 3, 7, and 9, in macrophages

Wiskott-Aldrich syndrome protein (WASP) is an adaptor molecule in immune cells. Recently, we showed that the WASP N-terminal domain interacted with the SH3 domain of Bruton's tyrosine kinase (Btk), and that the complex formed by WASP and Btk was important for TLR2 and TLR4 signaling in macrophages. Several other studies have shown that Btk played important roles in modulating innate immune responses through TLRs in immune cells. Here, we evaluated the significance of the interaction between WASP and Btk in TLR3, TLR7, and TLR9 signaling. We established bone marrow-derived macrophage cell lines from transgenic (Tg) mice that expressed intracellular antibodies (intrabodies) that specifically targeted the WASP N-terminal domain. One intrabody comprised the single-chain variable fragment and the other comprised the light-chain variable region single domain of an anti-WASP N-terminal monoclonal antibody. Both intrabodies inhibited the specific interaction between WASP and Btk, which impaired the expression of TNF-α, IL-6, and IL-1β in response to TLR3, TLR7, or TLR9 stimulation. Furthermore, the intrabodies inhibited the phosphorylation of both nuclear factor (NF)-κB and WASP in response to TLR3, TLR7, or TLR9 stimulation, in the Tg bone marrow-derived macrophages. These results suggested that WASP plays important roles in TLR3, TLR7, and TLR9 signaling by associating with Btk in macrophages.

Tyrosine phosphorylation of WIP releases bound WASP and impairs podosome assembly in macrophages

Podosomes are integrin-containing adhesion structures commonly found in migrating leukocytes of the monocytic lineage. The actin cytoskeletal organisation of podosomes is based on a WASP- and Arp2/3-mediated mechanism. WASP also associates with a second protein, WIP (also known as WIPF1), and they co-localise in podosome cores. Here, we report for the first time that WIP can be phosphorylated on tyrosine residues and that tyrosine phosphorylation of WIP is a trigger for release of WASP from the WIP-WASP complex. Using a knockdown approach together with expression of WIP phosphomimics, we show that in the absence of WIP-WASP binding, cellular WASP is rapidly degraded, leading to disruption of podosomes and a failure of cells to degrade an underlying matrix. In the absence of tyrosine phosphorylation, the WIP-WASP complex remains intact and podosome lifetimes are extended. A screen of candidate kinases and inhibitor-based assays identified Bruton's tyrosine kinase (Btk) as a regulator of WIP tyrosine phosphorylation. We conclude that tyrosine phosphorylation of WIP is a crucial regulator of WASP stability and function as an actin-nucleation-promoting factor.

Establishment of c-myc-immortalized Kupffer cell line from a C57BL/6 mouse strain

We recently demonstrated in several mammalian species, a novel procedure to obtain liver-macrophages (Kupffer cells) in sufficient numbers and purity using a mixed primary culture of hepatocytes. In this study, we applied this method to the C57BL/6 mouse liver and established an immortalized Kupffer cell line from this mouse strain. The hepatocytes from the C57BL/6 adult mouse liver were isolated by a two-step collagenase perfusion method and cultured in T25 culture flasks. Similar to our previous studies, the mouse hepatocytes progressively changed their morphology into a fibroblastic appearance after a few days of culture. After 7-10 days of culture, Kupffer-like cells, which were contaminants in the hepatocyte fraction at the start of the culture, actively proliferated on the mixed fibroblastic cell sheet. At this stage, a retroviral vector containing the human c-myc oncogene and neomycin resistance gene was introduced into the mixed culture. Gentle shaking of the culture flask, followed by the transfer and brief incubation of the culture supernatant, resulted in a quick and selective adhesion of Kupffer cells to a plastic dish surface. After selection with G418 and cloning by limiting dilutions, a clonal cell line (KUP5) was established. KUP5 cells displayed typical macrophage morphology and were stably passaged at 4-5 days intervals for more than 5 months, with a population doubling time of 19 h. KUP5 cells are immunocytochemically positive for mouse macrophage markers, such as Mac-1, F4/80. KUP5 cells exhibited substantial phagocytosis of polystyrene microbeads and the release of inflammatory cytokines upon lipopolysaccharide stimulation. Taken together, KUP5 cells provide a useful means to study the function of Kupffer cells in vitro.

WASPs and WAVEs: from molecular function to physiology in hematopoietic cells

The actin cytoskeleton is critically involved in a variety of cell functions. The Arp2/3 complex mediates branching of filamentous actin. The members of the Wiskott-Aldrich syndrome protein (WASP) family are major regulators of the complex. As such, the family proteins are also involved in numerous aspects of cell biology. In this short review, we first define the expanding WASP family. Next, we compare the domain structure of the members, and explain the known or proposed functions of each domain or region. Finally, we demonstrate the well-characterized roles of the proteins in specific cellular functions.

Tec family kinases in inflammation and disease

Over the last decade, the Tec family of nonreceptor tyrosine kinases (Btk, Tec, Bmx, Itk, and Rlk) have been shown to play a key role in inflammation and bone destruction. Bruton's tyrosine kinase (Btk) has been the most widely studied due to the critical role of this kinase in B-cell development and recent evidence showing that blocking Btk signaling is effective in ameliorating lymphoma progression and experimental arthritis. This review will examine the role of TFK in myeloid cell function and the potential of targeting these kinases as a therapeutic intervention in autoimmune disorders such as rheumatoid arthritis.