Inhibition of NF-kappaB by a TAT-NEMO-binding domain peptide accelerates constitutive apoptosis and abrogates LPS-delayed neutrophil apoptosis

Peptide-Based Inhibitors of the Induced Signaling Protein Interactions: Current State and Prospects

Formation of the transient protein complexes in response to activation of cellular receptors is a common mechanism by which cells respond to external stimuli. This article presents the concept of blocking interactions of signaling proteins by the peptide inhibitors, and describes the progress achieved to date in the development of signaling inhibitors that act by blocking the signal-dependent protein interactions.

Bone Metastasis in Bladder Cancer

Bladder cancer (BCa) is the 10th most common and 13th most deadly malignancy worldwide. About 5% of BCa patients present initially with metastatic disease, with bone being the most diagnosed site for distant metastasis. The overall one-year survival of patients with BCa is 84%, whereas it is only 21% in patients with bone metastasis (BM). Metastasis of BCa cells to bone occurs by epithelial-to-mesenchymal transition, angiogenesis, intravasation, extravasation, and interactions with the bone microenvironment. However, the mechanism of BCa metastasis to the bone is not completely understood; it needs a further preclinical model to completely explain the process. As different imaging mechanisms, PET-CT cannot replace a radionuclide bone scan or an MRI for diagnosing BM. The management of BCa patients with BM includes chemotherapy, immunotherapy, targeted therapy, antibody-drug conjugates, bisphosphonates, denosumab, radioisotopes, and surgery. The objective of these treatments is to inhibit disease progression, improve overall survival, reduce skeletal-related events, relieve pain, and improve the quality of life of patients.

Cell-penetrating peptide-mediated delivery of therapeutic peptides/proteins to manage the diseases involving oxidative stress, inflammatory response and apoptosis

OBJECTIVES

Peptides and proteins represent great potential for modulating various cellular processes including oxidative stress, inflammatory response, apoptosis and consequently the treatment of related diseases. However, their therapeutic effects are limited by their inability to cross cellular barriers. Cell-penetrating peptides (CPPs), which can transport cargoes into the cell, could resolve this issue, as would be discussed in this review.

KEY FINDINGS

CPPs have been successfully exploited in vitro and in vivo for peptide/protein delivery to treat a wide range of diseases involving oxidative stress, inflammatory processes and apoptosis. Their in vivo applications are still limited due to some fundamental issues of CPPs, including nonspecificity, proteolytic instability, potential toxicity and immunogenicity.

SUMMARY

Totally, CPPs could potentially help to manage the diseases involving oxidative stress, inflammatory response and apoptosis by delivering peptides/proteins that could selectively reach proper intracellular targets. More studies to overcome related CPP limitations and confirm the efficacy and safety of this strategy are needed before their clinical usage.

Implications of endotoxins in wound healing: a narrative review

Bacterial toxins are thought to play a role in delayed wound healing in critically colonised and infected wounds. Endotoxins are released from Gram-negative bacteria when they are lysed by host phagocytic cells during an immune response, or by antimicrobial agents, potentially leading to a detrimental effect on the host tissues. Endotoxins can affect all aspects of the wound healing process, leading to delayed healing and contributing to wound chronicity. Release of endotoxins by bacteria can also have serious systemic effects (for example, septic shock) that can lead to high levels of patient mortality. This review summarises the role and implications on wound healing of bacterial endotoxins, describing the impact of endotoxins on the various phases of the wound healing response. There is a paucity of in vivo/clinical evidence linking endotoxins attributed to a wound (via antibiotic treatment) or their release from infecting bacteria with parameters of delayed wound healing. Future work should investigate if this link is apparent and determine the mechanism(s) by which such detrimental effects occur, offering an opportunity to identify possible treatment pathways. This paper describes the phenomenon of antimicrobial-induced endotoxin release and summarises the use of wound dressings to reduce wound bioburden without inducing microbial death and subsequent release of endotoxins, thus limiting their detrimental effects.

Mechanobiology of Bone Metastatic Cancer

PURPOSE OF REVIEW

In this review, we provide an overview of what is currently known about the impacts of mechanical stimuli on metastatic tumor-induced bone disease (TIBD). Further, we focus on the role of the osteocyte, the skeleton's primary mechanosensory cell, which is central to the skeleton's mechanoresponse, sensing and integrating local mechanical stimuli, and then controlling the downstream remodeling balance as appropriate.

RECENT FINDINGS

Exercise and controlled mechanical loading have anabolic effects on bone tissue in models of bone metastasis. They also have anti-tumorigenic properties, in part due to offsetting the vicious cycle of osteolytic bone loss as well as regulating inflammatory signals. The impacts of metastatic cancer on the mechanosensory function of osteocytes remains unclear. Increased mechanical stimuli are a potential method for mitigating TIBD.

NF-κB and neutrophil extracellular traps cooperate to promote breast cancer progression and metastasis

Aberrant NF-κB activation and neutrophil extracellular traps (NETs) are associated with breast cancer progression. How NF-κB and NETs modulate each other in breast cancer development remains unclear. Here, we found that NETs induced by phorbol 12-myristate 13-acetate promote breast cancer cell progression. In turn, cancer cells-derived factors, such as IL-8 and granulocyte colony-stimulating factor, stimulate neutrophils to form NETs. Mechanistically, NETs increased the interaction of NF-κB essential modifier (NEMO) with IκB kinase (IKK)α/β and enhanced NF-κB activation. We then employed a cell-permeable peptide corresponding to the NEMO-binding domain (NBD) of IKKα/β, termed NBD peptide, which disrupts NETs-mediated NEMO interaction with IKKα/β and abolished NF-κB activation in vitro. NBD peptide also reduced IL-8 level and NETs formation, and suppressed primary tumor growth and/or lung metastasis in human breast cancer mouse xenograft models and mouse spontaneous breast cancer model. Blockade of NET formation using a peptidylarginine deiminase 4 (PAD4) pharmacologic inhibitor decreased NF-κB activation and tumor metastasis. Collectively, these data suggest that NF-κB associates with NETs to form a positive loop facilitating breast tumor progression and metastasis, and that selective inhibition of NF-κB and PAD4-dependent NETs provides an effective therapeutic approach for treating breast cancer.

Metabolomic analysis of spontaneous neutrophil apoptosis reveals the potential involvement of glutathione depletion

Spontaneous apoptosis of neutrophils plays a key role in maintaining immune homeostasis and resolving inflammation. However, the mechanism triggering this apoptosis remains obscure. In the present study, we performed a global metabolomics analysis of neutrophils undergoing spontaneous apoptosis by using hydrophilic interaction chromatography ultra-high-performance liquid chromatography-tandem quadrupole/time-of-flight mass spectrometry and found 23 metabolites and 42 related pathways that were altered in these cells. Among them, glutathione, which is known to be involved in apoptosis, was particularly interesting. We found that L-pyroglutamic acid, glutamate, and their glutathione-mediated embolic pathways were all changed. Our findings confirmed the glutathione levels decreased in apoptotic neutrophils. Exogenous glutathione and LPS treatment delayed neutrophil apoptosis and decreased the levels of pro-apoptotic protein caspase-3. γ-glutamylcyclotransferase, 5-oxoprolinase, and ChaC1, which participated in glutathione degradation, were all activated. At the same time, the down-regulation of ATP production suggested the activity of glutathione biosynthesis may be attenuated even if glutamate-cysteine ligase and glutathione synthase, which are two ATP-dependent enzymes participating in glutathione biosynthesis, were enhanced. To our knowledge, this is the first report highlighting a global metabolomics analysis using hydrophilic interaction chromatography ultra-high-performance liquid chromatography-tandem quadrupole/time-of-flight mass spectrometry and the potential involvement of glutathione depletion in spontaneous apoptosis of neutrophils demonstrating that LPS could delay this process.

The adaptor protein c-Cbl-associated protein (CAP) limits pro-inflammatory cytokine expression by inhibiting the NF-κB pathway

C-Cbl-associated protein (CAP), also known as Sorbin and SH3 domain-containing protein 1 (Sorbs1) or ponsin, an adaptor protein of the insulin-signalling pathway, mediates anti-viral and anti-cytotoxic protection in acute viral heart disease. In the present study we describe a novel protective immuno-modulatory function of CAP in inflammation. Among the three members of the Sorbs family of adapter molecules, which include CAP (Sorbs1), ArgBP2 (Sorbs2), and Vinexin (Sorbs3), CAP consistently down-regulated the expression of pro-inflammatory cytokines in mouse fibroblasts, cardiomyocytes, and myeloid-derived leukocytes, after Toll-like receptor (TLR) stimulation. Upon the same TLR stimulation, ArgBP2 partially down-regulated pro-inflammatory cytokine production in mouse fibroblasts and cardiomyocytes, while Vinexin rather promoted their production. Mechanistically, CAP limited pro-inflammatory cytokine expression by suppressing the phosphorylation of Inhibitor of kappa B (IκB) kinase (Iκκ)-α and Iκκ-β and their downstream NF-κB-dependent signalling pathway. Molecular affinity between CAP and Iκκ-α/ Iκκ-β was necessary to block the NF-κB pathway. The CAP-dependent inhibitory mechanism - in vivo exclusively IL-6 inhibition - was confirmed after collecting blood from mice with systemic inflammation induced by lipopolysaccharide (LPS) and in the heart tissue collected from mice infected with the cardiotropic Coxsackievirus B3 (CVB3). Taken together, CAP down-regulates pro-inflammatory cytokines by interfering with the normal function of the NF-κB pathway. The promotion of CAP production could support the development of new strategies aiming to limit excessive and detrimental activation of the immune system.

Cell Type-Specific Roles of NF-κB Linking Inflammation and Thrombosis

The transcription factor NF-κB is a central mediator of inflammation with multiple links to thrombotic processes. In this review, we focus on the role of NF-κB signaling in cell types within the vasculature and the circulation that are involved in thrombo-inflammatory processes. All these cells express NF-κB, which mediates important functions in cellular interactions, cell survival and differentiation, as well as expression of cytokines, chemokines, and coagulation factors. Even platelets, as anucleated cells, contain NF-κB family members and their corresponding signaling molecules, which are involved in platelet activation, as well as secondary feedback circuits. The response of endothelial cells to inflammation and NF-κB activation is characterized by the induction of adhesion molecules promoting binding and transmigration of leukocytes, while simultaneously increasing their thrombogenic potential. Paracrine signaling from endothelial cells activates NF-κB in vascular smooth muscle cells and causes a phenotypic switch to a “synthetic” state associated with a decrease in contractile proteins. Monocytes react to inflammatory situations with enforced expression of tissue factor and after differentiation to macrophages with altered polarization. Neutrophils respond with an extension of their life span—and upon full activation they can expel their DNA thereby forming so-called neutrophil extracellular traps (NETs), which exert antibacterial functions, but also induce a strong coagulatory response. This may cause formation of microthrombi that are important for the immobilization of pathogens, a process designated as immunothrombosis. However, deregulation of the complex cellular links between inflammation and thrombosis by unrestrained NET formation or the loss of the endothelial layer due to mechanical rupture or erosion can result in rapid activation and aggregation of platelets and the manifestation of thrombo-inflammatory diseases. Sepsis is an important example of such a disorder caused by a dysregulated host response to infection finally leading to severe coagulopathies. NF-κB is critically involved in these pathophysiological processes as it induces both inflammatory and thrombotic responses.

Understanding the Bone in Cancer Metastasis

The bone is the third most common site of metastasis for a wide range of solid tumors including lung, breast, prostate, colorectal, thyroid, gynecologic, and melanoma, with 70% of metastatic prostate and breast cancer patients harboring bone metastasis.¹ Unfortunately, once cancer spreads to the bone, it is rarely cured and is associated with a wide range of morbidities including pain, increased risk of fracture, and hypercalcemia. This fact has driven experts in the fields of bone and cancer biology to study the bone, and has revealed that there is a great deal that each can teach the other. The complexity of the bone was first described in 1889 when Stephen Paget proposed that tumor cells have a proclivity for certain organs, where they "seed" into a friendly "soil" and eventually grow into metastatic lesions. Dr. Paget went on to argue that although many study the "seed" it would be paramount to understand the "soil." Since this original work, significant advances have been made not only in understanding the cell-autonomous mechanisms that drive metastasis, but also alterations which drive changes to the "soil" that allow a tumor cell to thrive. Indeed, it is now clear that the "soil" in different metastatic sites is unique, and thus the mechanisms that allow tumor cells to remain in a dormant or growing state are specific to the organ in question. In the bone, our knowledge of the components that contribute to this fertile "soil" continues to expand, but our understanding of how they impact tumor growth in the bone remains in its infancy. Indeed, we now appreciate that the endosteal niche likely contributes to tumor cell dormancy, and that osteoclasts, osteocytes, and adipocytes can impact tumor cell growth. Here, we discuss the bone microenvironment and how it impacts cancer cell seeding, dormancy, and growth. © 2018 American Society for Bone and Mineral Research.

Redox-Sensitive Innate Immune Pathways During Macrophage Activation in Type 1 Diabetes

SIGNIFICANCE

Type 1 diabetes (T1D) is an autoimmune disease resulting in β-cell destruction mediated by islet-infiltrating leukocytes. The role of oxidative stress in human and murine models of T1D is highly significant as these noxious molecules contribute to diabetic complications and β-cell lysis, but their direct impact on dysregulated autoimmune responses is highly understudied. Pro-inflammatory macrophages play a vital role in the initiation and effector phases of T1D by producing free radicals and pro-inflammatory cytokines to facilitate β-cell destruction and to present antigen to autoreactive T cells. Recent Advances: Redox modulation of macrophage functions may play critical roles in autoimmunity. These include enhancing pro-inflammatory innate immune signaling pathways in response to environmental triggers, enforcing an M1 macrophage differentiation program, controlling antigen processing, and altering peptide recognition by oxidative post-translational modification. Therefore, an oxidative environment may act on multiple macrophage functions to orchestrate T1D pathogenesis.

CRITICAL ISSUES

Mechanisms involved in the initiation of T1D remain unclear, making preventive and early therapeutics difficult to develop. Although many of these advances in the redox regulation of macrophages are in their infancy, they provide insight into how oxidative stress aids in the precipitating event of autoimmune activation.

FUTURE DIRECTIONS

Future studies should be aimed at mechanistically determining which redox-regulated macrophage functions are pertinent in T1D pathogenesis, as well as at investigating potential targetable therapeutics to halt and/or dampen innate immune activation in T1D.

Endotoxin promotes neutrophil hierarchical chemotaxis via the p38-membrane receptor pathway

Neutrophils are the most abundant leukocytes in peripheral blood and play critical a role in bacterial infection, tumor immunity and wound repair. Clarifying the process of neutrophil chemotaxis to target sites of immune activity has been a focus of increased interest within the past decade. In bacterial infectious foci, neutrophils migrate toward the bacterial-derived chemoattractant N-formyl-Met-Leu-Phe (fMLP) and ignore other intermediary chemoattractants to arrive at the area of infection. Using an under agarose chemotaxis assay, we observed that the bacterial fMLP-induced neutrophil chemotaxis signal overrode interleukin 8 (IL-8)- and leukotriene B4 (LTB4)-induced chemotaxis signals. Moreover, in the presence of bacterial lipopolysaccharide (LPS), the fMLP-induced hierarchical chemotaxis signal was enhanced. Further studies revealed that LPS increased the membrane expression of the fMLP receptor, formyl peptide receptor 1 (FPR1). However, expression levels of the membrane receptors for IL-8 and LTB4 were decreased by LPS administration. A human Phospho-mitogen-activated protein kinase (MAPK) proteome array showed that the p38 pathway was significantly activated by LPS stimulation. Moreover, p38 was responsible for the altered expression of neutrophil membrane chemoattractant receptors. Inhibition of neutrophil p38 restored LPS-improved hierarchical chemotaxis. Taken together, these data indicate that endotoxin promotes neutrophil hierarchical chemotaxis via the p38-membrane receptor pathway.

Endothelial NF-κB Blockade Abrogates ANCA-Induced GN

ANCA-associated vasculitis (AAV) is a highly inflammatory condition in which ANCA-activated neutrophils interact with the endothelium, resulting in necrotizing vasculitis. We tested the hypothesis that endothelial NF-κB mediates necrotizing crescentic GN (NCGN) and provides a specific treatment target. Reanalysis of kidneys from previously examined murine NCGN disease models revealed NF-κB activation in affected kidneys, mostly as a p50/p65 heterodimer, and increased renal expression of NF-κB-dependent tumor necrosis factor α (TNF-α). NF-κB activation positively correlated with crescent formation, and nuclear phospho-p65 staining showed NF-κB activation within CD31-expressing endothelial cells (ECs) in affected glomeruli. Therefore, we studied the effect of ANCA on NF-κB activation in neutrophil/EC cocultures in vitro ANCA did not activate NF-κB in primed human neutrophils, but ANCA-stimulated primed neutrophils activated NF-κB in ECs, at least in part via TNF-α release. This effect increased endothelial gene transcription and protein production of NF-κB-regulated interleukin-8. Moreover, upregulation of endothelial NF-κB promoted neutrophil adhesion to EC monolayers, an effect that was inhibited by a specific IKKβ inhibitor. In a murine NCGN model, prophylactic application of E-selectin-targeted immunoliposomes packed with p65 siRNA to downregulate endothelial NF-κB significantly reduced urine abnormalities, renal myeloid cell influx, and NCGN. Increased glomerular endothelial phospho-p65 staining in patients with AAV indicated that NF-κB is activated in human NCGN also. We suggest that ANCA-stimulated neutrophils activate endothelial NF-κB, which contributes to NCGN and provides a potential therapeutic target in AAV.

Effects of gene polymorphisms in the endoplasmic reticulum stress pathway on clinical outcomes of chemoradiotherapy in Chinese patients with nasopharyngeal carcinoma

There is considerable inter-individual variabil¬ity in chemoradiotherapy responses in nasopharyngeal carcinoma (NPC) patients receiv¬ing the same or similar treatment protocols. In this study we evaluated the association between the gene polymorphisms in endoplasmic reticulum (ER) stress pathway and chemoradiation responses in Chinese NPC patients. A total of 150 patients with histopathologically conformed NPC and treated with concurrent chemoradiotherapy were enrolled. Genotypes in ER stress pathway genes, including VCP (valosin-containing protein) rs2074549, HSP90B1 rs17034943, CANX (calnexin) rs7566, HSPA5 [heat shock protein family A (Hsp70) member 5] rs430397, CALCR (calcitonin receptor) rs2528521, and XBP1 (X-box binding protein 1) rs2269577 were analyzed by Sequenom MassARRAY system. The short-term effects of primary tumor and lymph node after radiotherapy were assessed based on the Response Evaluation Criteria in Solid Tumors (RECIST) of WHO. And acute radiation-induced toxic reactions were evaluated according to the Radiation Therapy Oncology Group or European Organization for Research and Treatment of Cancer (RTOG/EORTC). The effects of gene polymorphisms on clinical outcomes of chemoradiotherapy were assessed by chi-square test, univariate and multivariate logistic regression analyses. We found that CT and CT+CC genotypes of CANX rs7566 was significantly correlated with primary tumor treatment efficacy at 3 months after chemoradiotherapy and with occurrence of radiation-induced myelosuppression in Chinese NPC patients. CT and CT+CC genotypes of CALCR rs2528521 were significantly correlated with cervical lymph node efficacy at 3 months after chemoradiotherapy. And CC and CT+CC genotypes of VCP rs2074549 were significantly associated with occurrence of myelosuppression. In conclusion, SNPs of VCP rs2074549, CANX rs7566 and CALCR rs2528521 in ER stress pathway genes may serve as predictors for clinical outcomes of chemoradiotherapy in Chinese NPC patients.

Mitochondrial reactive oxygen species are involved in chemoattractant-induced oxidative burst and degranulation of human neutrophils in vitro

Activation of neutrophils is accompanied by the oxidative burst, exocytosis of various granule types (degranulation) and a delay in spontaneous apoptosis. The major source of reactive oxygen species (ROS) in human neutrophils is NADPH oxidase (NOX2), however, other sources of ROS also exist. Although the function of ROS is mainly defensive, they can also play a regulatory role in cell signaling. However, the contribution of various sources of ROS in these processes is not clear. We investigated a possible role of mitochondria-derived ROS (mtROS) in the regulation of neutrophil activation induced by chemoattractant fMLP in vitro. Using the mitochondria-targeted antioxidant SkQ1, we demonstrated that mtROS are implicated in the oxidative burst caused by NOX2 activation as well as in the exocytosis of primary (azurophil) and secondary (specific) granules. Scavenging of mtROS with SkQ1 slightly accelerated spontaneous apoptosis and significantly stimulated apoptosis of fMLP-activated neutrophils. These data indicate that mtROS play a critical role in signal transduction that mediates the major neutrophil functional responses in the process of activation.

Myeloid Deletion of Nemo Causes Osteopetrosis in Mice Owing to Upregulation of Transcriptional Repressors

The transcription factor NF-κB is central to numerous physiologic processes including bone development, and its activation is controlled by IKKγ (also called NEMO), the regulatory subunit of IKK complex. NEMO is X-linked, and mutations in this gene result in Incontinentia Pigmenti in human hemizygous females. In mice, global deficiency causes embryonic lethality. In addition, certain point mutations in the NEMO (IKBKG) human gene manifest skeletal defects implicating NEMO in the regulation of bone homeostasis. To specifically investigate such role, we conditionally deleted Nemo from osteoclast and myeloid progenitors. Morphometric, histologic, and molecular analyses demonstrate that myeloid NEMO deletion causes osteopetrosis in mice. Mechanistically, NEMO deficiency hampered activation of IKK complex in osteoclast precursors, causing arrest of osteoclastogenesis and apoptosis. Interestingly, inhibiting apoptosis by genetic ablation of TNFr1 significantly increased cell survival, but failed to rescue osteoclastogenesis or reverse osteopetrosis. Based on this observation, we analyzed the expression of different regulators of osteoclastogenesis and discovered that NEMO deletion leads to increased RBPJ expression, resulting in a decrease of Blimp1 expression. Consequently, expression of IRF8 and Bcl6 which are targets of Blimp1 and potent osteoclastogenic transcriptional repressors, is increased. Thus, NEMO governs survival and osteoclast differentiation programs through serial regulation of multiple transcription factors.

Use of Cell-Penetrating Peptides in Dendritic Cell-Based Vaccination

Cell-penetrating peptides (CPPs) are short amino acids that have been widely used to deliver macromolecules such as proteins, peptides, DNA, or RNA, to control cellular behavior for therapeutic purposes. CPPs have been used to treat immunological diseases through the delivery of immune modulatory molecules in vivo. Their intracellular delivery efficiency is highly synergistic with the cellular characteristics of the dendritic cells (DCs), which actively uptake foreign antigens. DC-based vaccines are primarily generated by pulsing DCs ex vivo with various immunomodulatory antigens. CPP conjugation to antigens would increase DC uptake as well as antigen processing and presentation on both MHC class II and MHC class I molecules, leading to antigen specific CD4(+) and CD8(+) T cell responses. CPP-antigen based DC vaccination is considered a promising tool for cancer immunotherapy due to the enhanced CTL response. In this review, we discuss the various applications of CPPs in immune modulation and DC vaccination, and highlight the advantages and limitations of the current CPP-based DC vaccination.

Evolution of NADPH Oxidase Inhibitors: Selectivity and Mechanisms for Target Engagement

SIGNIFICANCE

Oxidative stress, an excess of reactive oxygen species (ROS) production versus consumption, may be involved in the pathogenesis of different diseases. The only known enzymes solely dedicated to ROS generation are nicotinamide adenine dinucleotide phosphate (NADPH) oxidases with their catalytic subunits (NOX). After the clinical failure of most antioxidant trials, NOX inhibitors are the most promising therapeutic option for diseases associated with oxidative stress.

RECENT ADVANCES

Historical NADPH oxidase inhibitors, apocynin and diphenylene iodonium, are un-specific and not isoform selective. Novel NOX inhibitors stemming from rational drug discovery approaches, for example, GKT137831, ML171, and VAS2870, show improved specificity for NADPH oxidases and moderate NOX isoform selectivity. Along with NOX2 docking sequence (NOX2ds)-tat, a peptide-based inhibitor, the use of these novel small molecules in animal models has provided preliminary in vivo evidence for a pathophysiological role of specific NOX isoforms.

CRITICAL ISSUES

Here, we discuss whether novel NOX inhibitors enable reliable validation of NOX isoforms' pathological roles and whether this knowledge supports translation into pharmacological applications. Modern NOX inhibitors have increased the evidence for pathophysiological roles of NADPH oxidases. However, in comparison to knockout mouse models, NOX inhibitors have limited isoform selectivity. Thus, their use does not enable clear statements on the involvement of individual NOX isoforms in a given disease.

FUTURE DIRECTIONS

The development of isoform-selective NOX inhibitors and biologicals will enable reliable validation of specific NOX isoforms in disease models other than the mouse. Finally, GKT137831, the first NOX inhibitor in clinical development, is poised to provide proof of principle for the clinical potential of NOX inhibition.

Delayed neutrophil apoptosis mediates intermittent hypoxia-induced progressive heart failure in pressure-overloaded rats

BACKGROUND AND OBJECTIVE

Obstructive sleep apnea (OSA) and heart failure (HF) are common coexisting diseases. Intermittent hypoxia (IH), caused by repeated apnea/hypopnea events, accompanied by increased systemic inflammation, might contribute to the promotion of HF.

METHODS

To assess the hypothesis, rats were exposed to IH or normal air condition 4 weeks on the basis of normal heart function or pre-existing HF, which was induced by pressure overload caused by abdominal aortic constriction surgery performed 12 weeks earlier. Echocardiography was performed before and after IH exposure to evaluate left ventricular (LV) function. Serum concentrations of pro-inflammatory cytokines TNF-α and IL-6 were detected by enzyme-linked immunosorbent assay. Flow cytometric analysis was used to determine the apoptotic rate of polymorphonuclear neutrophils (PMNs).

RESULTS

The echocardiographic study showed a significant decrease in LV fractional shortening (FS) and ejection fraction (EF) as well as an increase in the LV relative wall thickness (RWT) index in HF rats, which was aggravated by further exposure to IH compared with single-handed HF-only and sham-IH and sham-control groups. A reduced PMN apoptotic rate was observed in HF-IH rats compared with HF-only, sham-IH, and sham-control rats. Serum concentrations of TNF-α and IL-6 were also increased in HF-IH rats, accompanied by delayed PMN apoptosis, indicating significant systemic inflammation induced by IH.

CONCLUSION

The results of this study demonstrated that IH aggravates LV remodeling and heart dysfunction in rats with pre-existing HF. Delayed neutrophil apoptosis, which was revealed in HF rats following exposure to IH, contributed to the exacerbation of myocardial damage and progression of heart dysfunction.

Regulation of NF-κB signaling in osteoclasts and myeloid progenitors

The transcription factor nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) is crucial for immune responses and skeletal development. Work in recent years has shown that various members of the NF-κB family are viable targets to regulate activity and survival of bone cells and hence bone metabolism. In this regard, deletion of upstream kinases or distal NF-κB subunits resulted with bone deformities. Thus, it has become increasingly apparent that detailed investigation of NF-κB in bone cells may provide opportunities to design new therapeutic modalities. In this chapter we present modified methodology describing efficient approaches to regulate the NF-κB pathway in vitro and in vivo to assess its function in bone cells and tissues.

Paraquat-induced reactive oxygen species inhibit neutrophil apoptosis via a p38 MAPK/NF-κB-IL-6/TNF-α positive-feedback circuit

Paraquat (PQ), a widely used herbicide and potent reactive oxygen species (ROS) inducer, can injure multiple tissues and organs, especially the lung. However, the underlying mechanism is still poorly understood. According to previous reports, neutrophil aggregation and excessive ROS production might play pivotal pathogenetic roles. In the present study, we found that PQ could prolong neutrophil lifespan and induce ROS generation in a concentration-independent manner. Activated nuclear factor-κB (NF-κB), p38 mitogen-activated kinase (p38 MAPK), and myeloid cell leukemia sequence 1 (Mcl-1) but not Akt signaling pathways were involved in this process, as well as increasing levels of interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and IL-1β. Furthermore, the proinflammatory mediators IL-6 and TNF-α could in turn promote ROS generation, creating a vicious cycle. The existence of such a feedback loop is supported by our finding that neutrophil apoptosis is attenuated by PQ in a concentration-independent manner and could partially explain the clinical dilemma why oxygen therapy will exacerbate PQ induced tissue injury.

NF-κB signaling and bone resorption

The transcription factor NF-κB is a family of proteins involved in signaling pathways essential for normal cellular functions and development. Deletion of various components of this pathway resulted with abnormal skeletal development. Research in the last decade has established that NF-κB signaling mediates RANK ligand-induced osteoclastogenesis. Consistently, it was shown that inhibition of NF-κB was an effective approach to inhibit osteoclast formation and bone resorptive activity. Identification of the molecular machinery underlying NF-κB activation permitted osteoclast-specific deletion of the major components of this pathway. As a result, it was clear that deletion of members of the proximal IKK kinase complex and the distal NF-κB subunits and downstream regulators affected skeletal development. These studies provided several targets of therapeutic intervention in osteolytic diseases. NF-κB activity has been also described as the centerpiece of inflammatory responses and is considered a potent mediator of inflammatory osteolysis. Indeed, inflammatory insults exacerbate physiologic RANKL-induced NF-κB signals leading to exaggerated responses and to inflammatory osteolysis. These superimposed NF-κB activities appear to underlie several bone pathologies. This review will describe the individual roles of NF-κB molecules in bone resorption and inflammatory osteolysis.

A simple and efficient method to detect nuclear factor activation in human neutrophils by flow cytometry

Neutrophils are the most abundant leukocytes in peripheral blood. These cells are the first to appear at sites of inflammation and infection, thus becoming the first line of defense against invading microorganisms. Neutrophils possess important antimicrobial functions such as phagocytosis, release of lytic enzymes, and production of reactive oxygen species. In addition to these important defense functions, neutrophils perform other tasks in response to infection such as production of proinflammatory cytokines and inhibition of apoptosis. Cytokines recruit other leukocytes that help clear the infection, and inhibition of apoptosis allows the neutrophil to live longer at the site of infection. These functions are regulated at the level of transcription. However, because neutrophils are short-lived cells, the study of transcriptionally regulated responses in these cells cannot be performed with conventional reporter gene methods since there are no efficient techniques for neutrophil transfection. Here, we present a simple and efficient method that allows detection and quantification of nuclear factors in isolated and immunolabeled nuclei by flow cytometry. We describe techniques to isolate pure neutrophils from human peripheral blood, stimulate these cells with anti-receptor antibodies, isolate and immunolabel nuclei, and analyze nuclei by flow cytometry. The method has been successfully used to detect NF-κB and Elk-1 nuclear factors in nuclei from neutrophils and other cell types. Thus, this method represents an option for analyzing activation of transcription factors in isolated nuclei from a variety of cell types.

Zebrafish as a model for the study of neutrophil biology

To understand inflammation and immunity, we need to understand the biology of the neutrophil. Whereas these cells can readily be extracted from peripheral blood, their short lifespan makes genetic manipulations impractical. Murine knockout models have been highly informative, and new imaging techniques are allowing neutrophils to be seen during inflammation in vivo for the first time. However, there is a place for a new model of neutrophil biology, which readily permits imaging of individual neutrophils during inflammation in vivo, combined with the ease of genetic and chemical manipulation. The zebrafish has long been the model of choice for the developmental biology community, and the availability of genomic resources and tools for gene manipulation makes this an attractive model. Zebrafish innate immunity shares many features with mammalian systems, including neutrophils with morphological, biochemical, and functional features, also shared with mammalian neutrophils. Transgenic zebrafish with neutrophils specifically labeled with fluorescent proteins have been generated, and this advance has led to the adoption of zebrafish, alongside existing models, by a number of groups around the world. The use of these models has underpinned a number of key advances in the field, including the identification of a tissue gradient of hydrogen peroxide for neutrophil recruitment following tissue injury and direct evidence for reverse migration as a regulatable mechanism of inflammation resolution. In this review, we discuss the importance of zebrafish models in neutrophil biology and describe how the understanding of neutrophil biology has been advanced by the use of these models.

VCP gene variation predicts outcome of advanced non-small-cell lung cancer platinum-based chemotherapy

Valosin-containing protein (VCP), or p97, is a member of the ATP-binding protein family, and is involved in numerous cellular events, such as, protein degradation, membrane fusion, and chaperone activity. VCP has been demonstrated playing a critical role in non-small-cell lung cancer (NSCLC) pathogenesis and progression recently. We investigated the association between VCP polymorphisms and clinical outcome in advanced NSCLC patients undergoing platinum-based chemotherapy. We recruited 663 Chinese advanced NSCLC patients who were treated with platinum-based regimens, and using their clinical data, we assessed the efficacy and side effects of their treatment. Three tag-single nucleotide polymorphisms (SNPs) of VCP were genotyped. SNP rs2074549 showed a significant association with severe neutropenia. Its G/G genotype increased the risk of grade 3 or 4 neutropenia compared with wild-type homozygotes A/A (P = .001, odds ratio = 2.975). Haplotype association analysis revealed that CGA was associated with the increased incidence of severe neutropenia (P = .041, odds ratio = 1.439). However, no significant relationship was found between the presence of VCP polymorphisms and treatment efficacy when objective response, progression-free survival, and overall survival (OS) were evaluated. Our study is the first to provide evidence that VCP polymorphisms are associated with a severe chemotherapy-related adverse outcome in platinum-treated advanced NSCLC patients.

Towards specific NADPH oxidase inhibition by small synthetic peptides

Reactive oxygen species (ROS) production by the phagocyte NADPH oxidase is essential for host defenses against pathogens. ROS are very reactive with biological molecules such as lipids, proteins and DNA, potentially resulting in cell dysfunction and tissue insult. Excessive NADPH oxidase activation and ROS overproduction are believed to participate in disorders such as joint, lung, vascular and intestinal inflammation. NADPH oxidase is a complex enzyme composed of six proteins: gp91phox (renamed NOX2), p22phox, p47phox, p67phox, p40phox and Rac1/2. Inhibitors of this enzyme could be beneficial, by limiting ROS production and inappropriate inflammation. A few small non-peptide inhibitors of NADPH oxidase are currently used to inhibit ROS production, but they lack specificity as they inhibit NADPH oxidase homologues or other unrelated enzymes. Peptide inhibitors that target a specific sequence of NADPH oxidase components could be more specific than small molecules. Here we review peptide-based inhibitors, with particular focus on a molecule derived from gp91phox/NOX2 and p47phox, and discuss their possible use as specific phagocyte NADPH oxidase inhibitors.

Differential effect of CCL2 on constitutive neutrophil apoptosis between normal and asthmatic subjects

In this study, we investigated the effects of CCL2 on constitutive apoptosis of normal and asthmatic neutrophils. CCL2 blocked the constitutive apoptosis of normal neutrophils through CCR2. CCL2 also induced elevation of the cytosolic Ca(2+) concentration but had no effect on normal neutrophil chemotaxis. Constitutive apoptosis, calcium influx, and cell migration of asthmatic neutrophils were not affected by CCL2 stimulation. Supernatant collected from CCL2-treated normal neutrophils inhibited the constitutive apoptosis of normal neutrophils. Anti-apoptotic signaling mediated by CCL2 was found to be associated with the PI3K/Akt/ERK/NF-κB cascade in normal neutrophils. Both the cleavage of procaspase 3 and procaspase 9 and the decrease of in Mcl-1 expression were delayed by CCL2 stimulation. Inhibition of NF-κB blocked constitutive apoptosis of neutrophils from asthmatic patients via inhibition of the cleavage of procaspase 3 and procaspase 9, in contrast to normal neutrophils. NF-κB was involved in CCL2-induced anti-apoptotic signaling in normal neutrophils, whereas NF-κB functioned as a basal pro-apoptotic factor in asthmatic neutrophils. A better understanding of the difference in the regulation of neutrophil apoptosis due to CCL2 between normal individuals and asthmatics will enable elucidation of the role of CC chemokine in neutrophils and a framework for understanding the pathogenesis of asthma.

Inhibition of genotoxic stress induced apoptosis by novel TAT-fused peptides targeting PIDDosome

Genotoxic stress induced apoptosis is mediated by the formation of PIDDosome, which is a caspase-2 activating complex composed of three protein components, PIDD, RAIDD, and caspase-2. Here, synthetic TAT-fused peptides designed by the structure of PIDD and RAIDD, TAT-Y814A and TAT-R147E, respectively, were produced and tested for their ability to inhibit PIDDosome formation in vitro as well as to attenuate genotoxic stress-induced apoptosis in human renal cancer cells. The results show that TAT-Y814A and TAT-R147E have the potential to inhibit formation of the PIDDosome in a dose-dependent manner. Furthermore, both peptides partially inhibit genotoxic stress mediated apoptosis and activation of caspase2 and caspase3 in Caki cells. These results suggest that TAT-Y814A (also TAT-R147E) is a novel inhibitor of genotoxic stress-induced apoptosis that may serve as a prototype for anti-apoptotic drug development.

Backbone rigidity and static presentation of guanidinium groups increases cellular uptake of arginine-rich cell-penetrating peptides

In addition to endocytosis-mediated cellular uptake, hydrophilic cell-penetrating peptides are able to traverse biological membranes in a non-endocytic mode termed transduction, resulting in immediate bioavailability. Here we analysed structural requirements for the non-endocytic uptake mode of arginine-rich cell-penetrating peptides, by a combination of live-cell microscopy, molecular dynamics simulations and analytical ultracentrifugation. We demonstrate that the transduction efficiency of arginine-rich peptides increases with higher peptide structural rigidity. Consequently, cyclic arginine-rich cell-penetrating peptides showed enhanced cellular uptake kinetics relative to their linear and more flexible counterpart. We propose that guanidinium groups are forced into maximally distant positions by cyclization. This orientation increases membrane contacts leading to enhanced cell penetration.

Cell-penetrating peptides can deliver molecular cargoes into living cells, and cross biological membranes by transduction—a non-endocytic mechanism. Here, the transduction efficiency of cyclic arginine-rich peptides is shown to be higher than that of more flexible linear peptides.

Association of polymorphisms in the TLR4 gene with the risk of developing neutropenia in children with leukemia

Infections are a major cause of morbidity and mortality in children with acute lymphoblastic leukemia (ALL). Susceptibility to infections increases as the neutrophil count decreases. Despite identical treatment patients vary considerably in the number of neutropenic episodes. Toll-like receptor 4 (TLR4) has been shown to have a role in inhibiting apoptosis of neutrophils. Therefore, we hypothesized that polymorphisms in the TLR4 gene may influence the number of chemotherapy-induced neutropenic episodes. Eight single-nucleotide polymorphisms (SNPs) of the TLR4 gene were determined in 194 children aged 0-17 years, who were diagnosed with ALL. We compared the genotype distributions of the SNPs with the frequency of neutropenic episodes during treatment with chemotherapeutic regimens. The number of neutropenic episodes varied from 0 to 17, with a median of four neutropenic episodes. Four SNPs in the TLR4 gene (rs10759931, rs11536889, rs1927911 and rs6478317) were associated with an increased risk of developing chemotherapy-induced neutropenia, each sustaining correction for multiple testing. Further studies are required to elucidate whether pediatric patients with ALL with the particular SNPs in the TLR4 gene also experience more infections and would benefit from prophylactic antibiotic treatment, by a reduction of morbidity and mortality due to infections.

The latest developments in synthetic peptides with immunoregulatory activities

In the past few years, many researches have provided us with much data demonstrating the abilities of synthetic peptides to impact immune response in vitro and in vivo. These peptides were designed according to the structure of some important protein molecules which play a key role in immune response, so they act with specific targets. The class I and II MHC-derived peptides inhibit the TCR recognition of antigen peptide-MHC complex. Rationally designed CD80 and CD154-binding peptides block the interaction between cell surface costimulatory molecules on antigen-presenting cells (APCs) and T cells. Some peptides were designed to inhibit the activities of cell signal proteins, including JNK, NF-κB and NFAT. Some peptide antagonists competitively bind to important cytokines and inhibit their activities, such as TNF-α, TGF-β and IL-1β inhibitory peptides. Adhesion molecule ICAM-1 derived peptides block the T cell adhesion and activation. These immunoregulatory peptides showed therapeutic effect in several animal models, including collagen-induced arthritis (CIA), autoimmune cystitis model, murine skin transplant model and cardiac allograft model. These results give us important implications for the development of a novel therapy for immune mediated diseases.

Control of secondary granule release in neutrophils by Ral GTPase

Neutrophil (polymorphonuclear leukocyte; PMN) inflammatory functions, including cell adhesion, diapedesis, and phagocytosis, are dependent on the mobilization and release of various intracellular granules/vesicles. In this study, we found that treating PMN with damnacanthal, a Ras family GTPase inhibitor, resulted in a specific release of secondary granules but not primary or tertiary granules and caused dysregulation of PMN chemotactic transmigration and cell surface protein interactions. Analysis of the activities of Ras members identified Ral GTPase as a key regulator during PMN activation and degranulation. In particular, Ral was active in freshly isolated PMN, whereas chemoattractant stimulation induced a quick deactivation of Ral that correlated with PMN degranulation. Overexpression of a constitutively active Ral (Ral23V) in PMN inhibited chemoattractant-induced secondary granule release. By subcellular fractionation, we found that Ral, which was associated with the plasma membrane under the resting condition, was redistributed to secondary granules after chemoattractant stimulation. Blockage of cell endocytosis appeared to inhibit Ral translocation intracellularly. In conclusion, these results demonstrate that Ral is a critical regulator in PMN that specifically controls secondary granule release during PMN response to chemoattractant stimulation.

Dexamethasone inhibits lipopolysaccharide-induced hydrogen sulphide biosynthesis in intact cells and in an animal model of endotoxic shock

Dexamethasone (1 mg/kg, i.p.) administered either 1 hr before or 1 hr after E. coli lipopolysaccharide (LPS, 4 mg/kg, i.p.) in conscious rats inhibited the subsequent (4 hrs) rise in plasma cytokine (interleukin [IL]-1beta, tumour necrosis factor [TNF]-alpha), nitrate/nitrite (NO(x)), soluble intercellular adhesion molecule-1 (sICAM-1) concentration and lung/liver myeloperoxidase activity indicative of an anti-inflammatory effect. Dexamethasone also reduced the LPS-evoked rise in plasma hydrogen sulphide (H(2)S) concentration, liver H(2)S synthesizing activity and expression of cystathionine gamma lyase (CSE) and inducible nitric oxide synthase (iNOS). Mifepristone (RU-486) inhibited these effects. Dexamethasone (1-10 microM) reduced the LPS-evoked release of IL-1beta, TNF-alpha and L-selectin, decreased expression of CSE and iNOS and diminished nuclear factor kappaB (NF-kappaB)-DNA binding in isolated rat neutrophils. In contrast, NaHS (100 microM) increased L-selectin release from rat neutrophils. Dexamethasone also reduced LPS-induced up-regulation of CSE in foetal liver cells. 6-amino-4-(4-phenoxyphenylethylamino) quinazoline (QNZ, 10 nM), a selective inhibitor of transcription via the NF-kappaB pathway, abolished LPS-induced up-regulation of CSE expression. We propose that inhibition of CSE expression and reduction in formation of the pro-inflammatory component of H(2)S activity contributes to the anti-inflammatory effect of dexamethasone in endotoxic shock. Whether H(2)S plays a part in the anti-inflammatory effect of this steroid in other forms of inflammation such as arthritis or asthma warrants further study.

Abrogation of NF-κB signaling in human neutrophils induces neutrophil survival through sustained p38-MAPK activation

NF-κB, an important transcription factor in the regulation of cellular inflammation, is one of the prime targets for novel anti-inflammatory therapeutics. Nowadays, anti-inflammatory therapies rely mostly on steroids, which among other effects, inhibit NF-κB activity. However, steroids have only limited efficacy in the treatment on neutrophil-driven diseases, such as COPD. Human neutrophils play an important role in the pathogenesis of COPD, and clearance of these cells by apoptosis is an effective pathway for resolution of inflammation. In this study, we tested the hypothesis that modulation of the NF-κB pathway in human neutrophils affects survival. Importantly, the pharmacological NF-κB inhibitor Bay 11-7082 inhibited NF-κB signaling in human neutrophils as expected. However, we found that complete inhibition of NF-κB activity with 10 μM Bay 11-7082 prolonged neutrophil survival significantly, which was not observed with inhibitors for other signaling pathways. Bay 11-7082-induced neutrophil survival was dependent on p38-MAPK kinase activity, as the p38 kinase activity inhibitor SB203580 abrogated this response completely. Bay 11-7082 induced rapid and sustained p38 activation that correlated with inhibited NF-κB signaling and prolonged neutrophil survival. The precise role of NF-κB in regulation of p38-MAPK activation remains to be established. Under these conditions of survival, the stability of Bcl-xL but not Mcl-1 was enhanced. Although inhibition of NF-κB leads to down-regulation of inflammatory genes in many cell types, our results illustrate that interference with basal NF-κB signaling in neutrophils as a drug target should be used with caution.

Defective regulation of CXCR2 facilitates neutrophil release from bone marrow causing spontaneous inflammation in severely NF-kappa B-deficient mice

NF-kappaB is a major regulator of innate and adaptive immunity. Neutrophilic granulocytes (neutrophils) constitutively express RelA/p65 (Rela), c-Rel (Crel), and p50 (Nfkappab1) but not p52 (Nfkappab2) subunits. In this paper, we describe Crel(-/-)Nfkappab1(-/-)Rela(+/-) mice that have the most severe genetic neutrophil NF-kappaB deficiency compatible with life, Rela(-/-) mice being embryonic lethal. Crel(-/-)Nfkappab1(-/-)Rela(+/-) mice developed spontaneous dermal and intestinal inflammation associated with chronic neutrophilia, elevated CXCL1, and G-CSF. The bone marrow contained fewer nucleated cells and was enriched in myeloid progenitor cells. Neutrophilia was preserved when Crel(-/-)Nfkappab1(-/-)Rela(+/-) bone marrow was transferred into wild-type mice, but mixed bone marrow chimeras receiving wild-type and Crel(-/-)Nfkappab1(-/-)Rela(+/-) bone marrow showed normal circulating neutrophil numbers, excluding an intrinsic proliferation advantage. In mixed bone marrow chimeras, Crel(-/-)Nfkappab1(-/-)Rela(+/-) neutrophils were preferentially mobilized from the bone marrow in response to CXCL1 injection, LPS-induced lung inflammation, and thioglycollate-induced peritonitis. Crel(-/-)Nfkappab1(-/-)Rela(+/-) neutrophils expressed higher levels of the CXCL1 receptor CXCR2 both under resting and stimulated conditions and failed to downregulate CXCR2 during inflammation. Treatment with an anti-CXCR2 Ab abolished preferential mobilization of Crel(-/-)Nfkappab1(-/-)Rela(+/-) neutrophils in peritonitis in mixed chimeric mice and neutrophilia in Crel(-/-)Nfkappab1(-/-)Rela(+/-) mice. We conclude that severe NF-kappaB deficiency facilitates neutrophil mobilization, which causes elevated numbers of preactivated neutrophils in blood and tissues, leading to spontaneous inflammation. These neutrophil effects may limit the usefulness of global NF-kappaB inhibitors for the treatment of inflammatory diseases.

Aldosterone abrogates nuclear factor kappaB-mediated tumor necrosis factor alpha production in human neutrophils via the mineralocorticoid receptor

Mineralocorticoid receptor (MR) activation by aldosterone controls salt homeostasis and inflammation in several tissues and cell types. Whether or not a functional MR exists in polymorphonuclear neutrophils is unknown. We investigated the hypothesis that aldosterone modulates inflammatory neutrophil responses via the MR. By flow cytometry, Western blot analysis, and microscopy, we found that neutrophils possess MR. Preincubation with aldosterone (10(-11) to 10(-6) M) dose-dependently inhibited nuclear factor kappaB activation in interleukin (IL)-8- and granulocyte/macrophage colony-stimulating factor-treated neutrophils on fibronectin by IkappaBalpha Western blotting, electrophoretic mobility shift assay, and RT-PCR for IkappaBalpha mRNA. Aldosterone had no effect on tumor necrosis factor alpha- and lipopolysaccharide-mediated nuclear factor kappaB activation or on IL-8- and granulocyte/macrophage colony-stimulating factor-induced extracellular signal-regulated kinase, p38 mitogen-activated protein kinase, or phosphatidylinositol 3-kinase/Akt activation. Spironolactone prevented nuclear factor kappaB inhibition, indicating an MR-specific aldosterone effect. By RT-PCR, we found that neutrophils have 11beta-hydroxysteroid dehydrogenase. Tumor necrosis factor alpha, which is controlled by nuclear factor kappaB, increased in the cell supernatant with IL-8 treatment. Aldosterone completely prevented this effect. RT-PCR showed a strong tumor necrosis factor alpha mRNA increase with IL-8 that was blocked by aldosterone, excluding the possibility that the tumor necrosis factor alpha increase was merely a consequence of secretion. Finally, conditioned medium from IL-8-treated neutrophils increased intercellular adhesion molecule-1 expression on endothelial cells and subsequently the adhesion of IL-8-treated neutrophils to endothelial cells. These effects were reduced when conditioned medium from aldosterone-pretreated neutrophils was used, and spironolactone blocked the aldosterone effect. Our data indicate that a functional MR exists in neutrophils mediating antiinflammatory effects that are at work when neutrophils interact with endothelial cells. These data could be relevant to MR-blockade treatment protocols.

Cationic and tissue-specific protein transduction domains identification, characterization, and therapeutic application

Protein transduction domains (PTDs) are small peptides able to transverse plasma membranes, able to carry proteins, nucleic acid, and viral particles into cells. PTDs can be broadly classified into three types; cationic, hydrophobic, and cell-type specific. The cationic PTDs, comprised of arginines, lysines, and ornithines, and hydrophobic PTDs can efficiently transduce a variety of cell types in culture and in vivo. The tissue-specific transduction domains, identified by screening of peptide display phage libraries for peptides able to confer internalization, have more restricted transduction properties. Here we provide a review of PTDs, focusing on methods for identifying and characterizing both cationic and tissue-specific transduction peptides. In particular, we describe the use of screening peptide phage display libraries to identify tissue-specific transduction peptides.

Inhibiting proinflammatory NF-kappaB signaling using cell-penetrating NEMO binding domain peptides

Nuclear factor kappa B (NF-kappaB) is an inducible transcription factor that regulates the expression of many genes involved in normal immune and inflammatory responses. NF-kappaB activation is normally a rapid and transient response to pro-inflammatory stimuli however dysregulated constitutively active NF-kappaB signaling leads to chronic inflammation and provides a cell survival signal in many types of cancer. NF-kappaB signaling is therefore an important target for the development of novel anti-inflammatory or anti-cancer drugs. We previously identified and characterized a cell-permeable peptide that blocks NF-kappaB signaling by disrupting the critical upstream IkappaB kinase (IKK) complex. We describe in this chapter three separate methods to determine the effects of this NEMO-binding domain (NBD) peptide on pro-inflammatory NF-kappaB signaling in response to tumor necrosis factor (TNF).

The IkappaB kinase complex: master regulator of NF-kappaB signaling

The Nuclear Factor-kappa B (NF-kappaB) family of transcription factors regulates the expression of a wide range of genes critical for immune and inflammatory responses, cell survival, immune development, and cell proliferation. Dysregulated NF-kappaB activity occurs in a number of chronic inflammatory diseases and certain types of cancers making NF-kappaB signaling an attractive target for the development of anti-inflammatory and anti-cancer drugs. A pivotal regulator of all inducible NF-kappaB signaling pathways is the IkappaB kinase (IKK) complex that consists of two kinases (IKKalpha and IKKbeta) and a regulatory subunit named NF-kappaB essential modulator (NEMO). Genetic analysis of the IKK complex has identified two separate pathways named the classical and non-canonical mechanisms that are dependent on either NEMO and IKKbeta (classical) or IKKalpha alone (non-canonical). To better understand the mechanisms that regulate IKK complex activity and to address the differential functions of IKKalpha and IKKbeta we have molecularly dissected the IKKs. We describe here how these studies have identified a unique inhibitor of pro-inflammatory NF-kappaB signaling, an unforeseen role for IKKalpha in the classical NF-kappaB pathway, and a novel functional domain in IKKbeta that is not present in IKKalpha.

Antioxidant therapeutic advances in COPD

Chronic obstructive pulmonary disease (COPD) is associated with a high incidence of morbidity and mortality. Cigarette smoke-induced oxidative stress is intimately associated with the progression and exacerbation of COPD and therefore targeting oxidative stress with antioxidants or boosting the endogenous levels of antioxidants is likely to have beneficial outcome in the treatment of COPD. Among the various antioxidants tried so far, thiol antioxidants and mucolytic agents, such as glutathione, N-acetyl-L-cysteine, N-acystelyn, erdosteine, fudosteine and carbocysteine; Nrf2 activators; and dietary polyphenols (curcumin, resveratrol, and green tea catechins/quercetin) have been reported to increase intracellular thiol status along with induction of GSH biosynthesis. Such an elevation in the thiol status in turn leads to detoxification of free radicals and oxidants as well as inhibition of ongoing inflammatory responses. In addition, specific spin traps, such as alpha-phenyl-N-tert-butyl nitrone, a catalytic antioxidant (ECSOD mimetic), porphyrins (AEOL 10150 and AEOL 10113), and a SOD mimetic M40419 have also been reported to inhibit cigarette smoke-induced inflammatory responses in vivo in the lung. Since a variety of oxidants, free radicals and aldehydes are implicated in the pathogenesis of COPD, it is possible that therapeutic administration of multiple antioxidants and mucolytics will be effective in management of COPD. However, a successful outcome will critically depend upon the choice of antioxidant therapy for a particular clinical phenotype of COPD, whose pathophysiology should be first properly understood. This article will review the various approaches adopted to enhance lung antioxidant levels, antioxidant therapeutic advances and recent past clinical trials of antioxidant compounds in COPD.

A novel method for long term bone marrow culture and genetic modification of murine neutrophils via retroviral transduction

Neutrophils are a critical component of the innate immune response to invading microbial pathogens. However, an excessive and/or prolonged neutrophil response can result in tissue injury that is thought to underlie the pathogenesis of various inflammatory diseases. The development of novel therapeutic strategies for inflammatory diseases depends on an improved understanding of regulation of neutrophil function. However, investigations into neutrophil function have been constrained in part by the difficulty of genetically modifying neutrophils using current techniques. To overcome this, we have developed a novel method for the genetic modification of murine bone marrow derived progenitor cells using retroviral transduction followed by long term bone marrow culture to generate mature neutrophils. These neutrophils are functionally mature as determined by morphology, surface marker (Gr1, CD11b, CD62L and CXCR2) expression, and functional attributes including the ability to generate superoxide, exocytose granule contents, chemotax, and phagocytose and kill bacteria. Further, the in vitro matured neutrophils are capable of migrating to an inflammatory site in vivo. We utilized this system to express the Bcl-2 transgene in mature neutrophils using the retroviral vectors pMIG and pMIT. Bcl-2 overexpression conferred a substantial delay in spontaneous apoptosis of neutrophils as assessed by annexin V and 7-amino-actinomycin D (7AAD) staining. Moreover, Bcl-2 overexpression did not alter granulopoiesis, as assessed by morphology and surface marker expression. This system enables the genetic manipulation of progenitor cells that can be differentiated in vitro to mature neutrophils that are functional in vitro and in vivo.

Cell penetrating peptide inhibitors of nuclear factor-kappa B

The nuclear factor kappa B (NF-kappaB) transcription factors are activated by a range of stimuli including pro-inflammatory cytokines. Active NF-kappaB regulates the expression of genes involved in inflammation and cell survival and aberrant NF-kappaB activity plays pathological roles in certain types of cancer and diseases characterized by chronic inflammation. NF-kappaB signaling is an attractive target for the development of novel anti-inflammatory or anti-cancer drugs and we discuss here how the method of peptide transduction has been used to specifically target NF-kappaB. Peptide transduction relies on the ability of certain small cell-penetrating peptides (CPPs) to enter cells, and a panel of CPP-linked inhibitors (CPP-Is) has been developed to directly inhibit NF-kappaB signaling. Remarkably, several of these NF-kappaB-targeting CPP-Is are effective in vivo and therefore offer exciting potential in the clinical setting.

Pathways regulating lipopolysaccharide-induced neutrophil survival revealed by lentiviral transduction of primary human neutrophils

Human neutrophils express Toll-like receptor 4 (TLR4) at low levels, and the role of this receptor in neutrophil responses to microbial stimuli has been questioned. Genetic manipulation of these cells to enable the study of the role of proteins such as TLR4 in their function is challenging. Here, we show that primary human neutrophils rapidly express novel proteins such as enhanced green fluorescent protein (eGFP) after transduction with lentivirus. Stimulation of transduced neutrophils with lipopolysaccharide (LPS) resulted in increased cell survival, which was inhibited when neutrophils were transduced with a lentivirus encoding a dominant negative (dn) TLR4 protein. LPS-induced survival was also inhibited by lentiviruses encoding dnMyD88 or a truncated TRIF (Toll/interleukin-1R homologous domain-containing adapter protein inducing interferon-beta) molecule, whilst, in contrast, neutrophil survival was enhanced by overexpression of kinase-mutated interleukin-1 receptor-associated kinase 1 (kmIRAK-1), which activated nuclear factor (NF)-kappaB. These studies provide proof of the role of TLR4 in human neutrophil biology, have begun to elucidate TLR-dependent pathways regulating neutrophil survival, and demonstrate that neutrophils can be genetically manipulated to enhance or inhibit survival.

Live-cell analysis of cell penetration ability and toxicity of oligo-arginines

Cell penetrating peptides (CPPs) are useful tools to deliver low-molecular-weight cargoes into cells; however, their mode of uptake is still controversial. The most efficient CPPs belong to the group of arginine-rich peptides, but a systematic assessment of their potential toxicity is lacking. In this study we combined data on the membrane translocation abilities of oligo-arginines in living cells as a function of their chain length, concentration, stability and toxicity. Using confocal microscopy analysis of living cells we evaluated the transduction frequency of the L-isoforms of oligo-arginines and lysines and then monitored their associated toxicity by concomitant addition of propidium iodide. Whereas lysines showed virtually no transduction, the transduction ability of arginines increased with the number of consecutive residues and the peptide concentration, with L-R9 and L-R10 performing overall best. We further compared the L- and D-R9 isomers and found that the D-isoform always showed a higher transduction as compared to the L-counterpart in all cell types. Notably, the transduction difference between D- and L-forms was highly variable between cell types, emphasizing the need for protease-resistant peptides as vectors for drug delivery. Real-time kinetic analysis of the D- and L-isomers applied simultaneously to the cells revealed a much faster transduction for the D-variant. The latter underlies the fact that the isomers do not mix, and penetration of one peptide does not perturb the membrane in a way that gives access to the other peptide. Finally, we performed short- and long-term cell viability and cell cycle progression analyses with the protease-resistant D-R9. Altogether, our results identified concentration windows with low toxicity and high transduction efficiency, resulting in fully bioavailable intracellular peptides.

Mitogen-activated protein kinase assays

Polymorphonuclear neutrophils (PMN) play an essential role in host defense against bacteria and fungi through coordinated responses such as adhesion, migration, phagocytosis, secretion, and activation of the NADPH oxidase. The mitogen-activated protein kinases (MAPKs) and their activation kinase cascades, which transduce signals from the plasma membrane to the cytosol and nucleus, are an integral part of signaling pathways involved in many cellular responses. PMN express several members of the MAPK family that have been shown, mainly through the use of pharmacological inhibitors, to mediate the cellular activities triggered by a variety of extracellular agonists. Methods to determine MAPK activation have been greatly simplified with the availability of antibodies raised to active MAPKs. The recent development of novel inhibitors for the MAPK pathways may further our understanding of their role in neutrophil function.

Strong neuroprotection by inhibition of NF-kappaB after neonatal hypoxia-ischemia involves apoptotic mechanisms but is independent of cytokines

BACKGROUND AND PURPOSE

Interactions between excitotoxic, inflammatory, and apoptotic pathways determine outcome in hypoxic-ischemic brain damage. The transcription factor NF-kappaB has been suggested to enhance brain damage via stimulation of cytokine production. There is also evidence that NF-kappaB activity is required for neuronal survival. We used the NF-kappaB inhibitor NBD, coupled to TAT to facilitate cerebral uptake, to determine the neuroprotective capacity of NF-kappaB inhibition in neonatal hypoxia-ischemia (HI) and to identify its contribution to cerebral inflammation and damage.

METHODS

Brain damage was induced in neonatal rats by unilateral carotid artery occlusion and hypoxia and analyzed immunohistochemically; NF-kappaB activity was analyzed by EMSA. We analyzed cytokine mRNA levels and activation of apoptotic pathways by Western blotting. In vitro effects of TAT-NBD were determined in a neuronal cell line.

RESULTS

Inhibition of cerebral NF-kappaB activity by TAT-NBD had a significant neuroprotective effect; brain damage was reduced by more than 80% with a therapeutic window of at least 6 hours. In contrast to earlier suggestions, the protective effect of TAT-NBD did not involve suppression of early cytokine upregulation after HI. Moreover, NF-kappaB inhibition prevented HI-induced upregulation and nuclear as well as mitochondrial accumulation of p53, prevented mitochondrial cytochrome-c release and activation of caspase-3. Finally, TAT-NBD could directly increase neuronal survival because TAT-NBD was sufficient to inhibit death in a neuronal cell line. A nonactive mutant peptide did not have any effect.

CONCLUSIONS

Inhibition of NF-kappaB has strong neuroprotective effects that involve downregulation of apoptotic molecules but are independent of inhibition of cytokine production.