Analysis of signal transduction pathways in macrophages using expression vectors with CMV promoters: a cautionary tale

A pilot study to determine the optimal dose of scAAVIL-1ra in a large animal model of post-traumatic osteoarthritis

Gene therapy approaches using adeno-associated viral vectors have been successfully tested in the equine post-traumatic osteoarthritis (PTOA) model. Owing to differences in the levels of transgene expression and adverse tissue reactions observed in published studies, we sought to identify a safe therapeutic dose of scAAVIL-1ra in an inflamed and injured joint that would result in improved functional outcomes without any adverse events. scAAVIL-1ra was delivered intra-articularly over a 100-fold range, and horses were evaluated throughout and at the end of the 10-week study. A dose-related increase in IL-1ra levels with a decrease in PGE2 levels was observed, with the peak IL-1ra concentration being observed 7 days post-treatment in all groups. Perivascular infiltration with mononuclear cells was observed within the synovial membrane of the joint treated with the highest viral dose of 5 × 1012 vg, but this was absent in the lower-dosed joints. The second-highest dose of scAAVeqIL-1ra 5 × 1011 vg demonstrated elevated IL-1ra levels without any cellular response in the synovium. Taken together, the data suggest that the 10-fold lower dose of 5 × 1011vg scAAVIL-1ra would be a safe therapeutic dose in an equine model of PTOA.

Gene therapy approaches for equine osteoarthritis

With an intrinsically low ability for self-repair, articular cartilage injuries often progress to cartilage loss and joint degeneration resulting in osteoarthritis (OA). Osteoarthritis and the associated articular cartilage changes can be debilitating, resulting in lameness and functional disability both in human and equine patients. While articular cartilage damage plays a central role in the pathogenesis of OA, the contribution of other joint tissues to the pathogenesis of OA has increasingly been recognized thus prompting a whole organ approach for therapeutic strategies. Gene therapy methods have generated significant interest in OA therapy in recent years. These utilize viral or non-viral vectors to deliver therapeutic molecules directly into the joint space with the goal of reprogramming the cells' machinery to secrete high levels of the target protein at the site of injection. Several viral vector-based approaches have demonstrated successful gene transfer with persistent therapeutic levels of transgene expression in the equine joint. As an experimental model, horses represent the pathology of human OA more accurately compared to other animal models. The anatomical and biomechanical similarities between equine and human joints also allow for the use of similar imaging and diagnostic methods as used in humans. In addition, horses experience naturally occurring OA and undergo similar therapies as human patients and, therefore, are a clinically relevant patient population. Thus, further studies utilizing this equine model would not only help advance the field of human OA therapy but also benefit the clinical equine patients with naturally occurring joint disease. In this review, we discuss the advancements in gene therapeutic approaches for the treatment of OA with the horse as a relevant patient population as well as an effective and commonly utilized species as a translational model.

Solute Carrier Family 37 Member 2 (SLC37A2) Negatively Regulates Murine Macrophage Inflammation by Controlling Glycolysis

Increased flux of glucose through glycolysis is a hallmark of inflammatory macrophages and is essential for optimal effector functions. Solute carrier (SLC) 37A2 is an endoplasmic reticulum-anchored phosphate-linked glucose-6-phosphate transporter that is highly expressed in macrophages and neutrophils. We demonstrate that SLC37A2 plays a pivotal role in murine macrophage inflammatory activation and cellular metabolic rewiring. Toll-like receptor (TLR) 4 stimulation by lipopolysaccharide (LPS) rapidly increases macrophage SLC37A2 protein expression. SLC37A2 deletion reprograms macrophages to a hyper-glycolytic process and accelerates LPS-induced inflammatory cytokine production, which partially depends on nicotinamide adenine dinucleotide (NAD⁺) biosynthesis. Blockade of glycolysis normalizes the differential expression of pro-inflammatory cytokines between control and SLC37A2 deficient macrophages. Conversely, overexpression of SLC37A2 lowers macrophage glycolysis and significantly reduces LPS-induced pro-inflammatory cytokine expression. In conclusion, our study suggests that SLC37A2 dampens murine macrophage inflammation by down-regulating glycolytic reprogramming as a part of macrophage negative feedback system to curtail acute innate activation.

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LPS treatment rapidly elevates macrophage SLC37A2 protein expression

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SLC37A2 dampens early glycolytic reprogramming in acute macrophage inflammation

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SLC37A2 suppresses macrophage cell-surface and endosomal TLR activation

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SLC37A2 attenuates macrophage cellular ROS production

Gene Therapy for Osteoarthritis: Pharmacokinetics of Intra-Articular Self-Complementary Adeno-Associated Virus Interleukin-1 Receptor Antagonist Delivery in an Equine Model

Toward the treatment of osteoarthritis (OA), the authors have been investigating self-complementary adeno-associated virus (scAAV) for intra-articular delivery of therapeutic gene products. As OA frequently affects weight-bearing joints, pharmacokinetic studies of scAAV gene delivery were performed in the joints of the equine forelimb to identify parameters relevant to clinical translation in humans. Using interleukin-1 receptor antagonist (IL-1Ra) as a secreted therapeutic reporter, scAAV vector plasmids containing codon-optimized cDNA for equine IL-1Ra (eqIL-1Ra) were generated, which produced eqIL-1Ra at levels 30- to 50-fold higher than the native sequence. The most efficient cDNA was packaged in AAV2.5 capsid, and following characterization in vitro, the virus was injected into the carpal and metacarpophalangeal joints of horses over a 100-fold dose range. A putative ceiling dose of 5 × 10¹² viral genomes was identified that elevated the steady-state eqIL-1Ra in the synovial fluids of injected joints by >40-fold over endogenous levels and was sustained for at least 6 months. No adverse effects were seen, and eqIL-1Ra in serum and urine remained at background levels throughout. Using the 5 × 10¹² viral genome dose of scAAV, and green fluorescent protein as a cytologic marker, the local and systemic distribution of vector and transduced cells following intra-articular injection scAAV.GFP were compared in healthy equine joints and in those with late-stage, naturally occurring OA. In both cases, 99.7% of the vector remained within the injected joint. Strikingly, the pathologies characteristic of OA (synovitis, osteophyte formation, and cartilage erosion) were associated with a substantial increase in transgenic expression relative to tissues in healthy joints. This was most notable in regions of articular cartilage with visible damage, where foci of brilliantly fluorescent chondrocytes were observed. Overall, these data suggest that AAV-mediated gene transfer can provide relatively safe, sustained protein drug delivery to joints of human proportions.

Differentiation and cell density upregulate cytochrome c levels in megakaryoblastic cell lines: Implications for analysis of CYCS-associated thrombocytopenia

Mutations in the cytochrome c gene (CYCS) cause autosomal dominant thrombocytopenia by an unknown mechanism. While attempting to generate megakaryoblastic cell lines exogenously expressing cytochrome c variants, we discovered that endogenous cytochrome c expression increased both upon induction of differentiation with the phorbol ester phorbol 12-myristate 13-acetate (PMA), and as cell density increased. A concomitant increase in cytochrome c oxidase subunit II in response to PMA, but not cell higher cell density, suggests upregulation of the mitochondrial respiratory chain may be a specific feature of differentiation. These results highlight the likely importance of cytochrome c in both differentiating and proliferating cells, and illustrate the unsuitability of megakaryoblastic lines for modeling CYCS-associated thrombocytopenia.

Modeling human carcinomas: physiologically relevant 3D models to improve anti-cancer drug development

Anti-cancer drug development is inefficient, mostly due to lack of efficacy in human patients. The high fail rate is partly due to the lack of predictive models or the inadequate use of existing preclinical test systems. However, progress has been made and preclinical models were improved or newly developed, which all account for basic features of solid cancers, three-dimensionality and heterotypic cell interaction. Here we give an overview of available in vivo and in vitro models of cancer, which meet the criteria of being 3D and mirroring human tumor-stroma interactions. We only focus on drug response models without touching models for pharmacokinetic and dynamic, toxicity or delivery aspects.

Induction of murine adenosine A(2A) receptor expression by LPS: analysis of the 5' upstream promoter

Non-activated macrophages express low levels of A(2A)Rs and lipopolysaccharides (LPS) upregulates A(2A)R expression in an NF-κB-dependent manner. The murine A(2A)R gene is encoded by three exons, m1, m2 and m3. Exons m2 and m3 are conserved, while m1 encodes the 5' untranslated UTR. Three m1 variants have been defined, m1A, m1B and m1C, with m1C being farthest from the transcriptional start site. LPS upregulates A(2A)Rs in primary murine peritoneal and bone-marrow-derived macrophages and RAW264.7 cells by selectively splicing m1C to m2, through a promoter located upstream of m1C. We have cloned ∼1.6 kb upstream of m1C into pGL4.16(luc2CP/Hygro) promoterless vector. This construct in RAW 264.7 cells responds to LPS, and adenosine receptor agonists augmented LPS responsiveness. The NF-κB inhibitors BAY-11 and triptolide inhibited LPS-dependent induction. Deletion of a key proximal NF-κB site (402-417) abrogated LPS responsiveness, while deletion of distal NF-κB and C/EBPβ sites did not. Site-directed mutagenesis of CREB (309-320), STAT1 (526-531) and AP2 (566-569) sites had little effect on LPS and adenosine receptor agonist responsiveness; however, mutation of a second STAT1 site (582-588) abrogated this responsiveness. Further analysis of this promoter should provide valuable insights into regulation of A(2A)R expression in macrophages in response to inflammatory stimuli.

Vacuolating cytotoxin A (VacA), a key toxin for Helicobacter pylori pathogenesis

More than 50% of the world's population is infected with Helicobacter pylori (H. pylori). Chronic infection with this Gram-negative pathogen is associated with the development of peptic ulcers and is linked to an increased risk of gastric cancer. H. pylori secretes many proteinaceous factors that are important for initial colonization and subsequent persistence in the host stomach. One of the major protein toxins secreted by H. pylori is the Vacuolating cytotoxin A (VacA). After secretion from the bacteria via a type V autotransport secretion system, the 88 kDa VacA toxin (comprised of the p33 and p55 subunits) binds to host cells and is internalized, causing severe “vacuolation” characterized by the accumulation of large vesicles that possess hallmarks of both late endosomes and early lysosomes. The development of “vacuoles” has been attributed to the formation of VacA anion-selective channels in membranes. Apart from its vacuolating effects, it has recently become clear that VacA also directly affects mitochondrial function. Earlier studies suggested that the p33 subunit, but not the p55 subunit of VacA, could enter mitochondria to modulate organelle function. This raised the possibility that a mechanism separate from pore formation may be responsible for the effects of VacA on mitochondria, as crystallography studies and structural modeling predict that both subunits are required for a physiologically stable pore. It has also been suggested that the mitochondrial effects observed are due to indirect effects on pro-apoptotic proteins and direct effects on mitochondrial morphology-related processes. Other studies have shown that both the p55 and p33 subunits can indeed be efficiently imported into mammalian-derived mitochondria raising the possibility that they could re-assemble to form a pore. Our review summarizes and consolidates the recent advances in VacA toxin research, with focus on the outstanding controversies in the field and the key remaining questions that need to be addressed.

A daphnane diterpenoid isolated from Wikstroemia polyantha induces an inflammatory response and modulates miRNA activity

MicroRNAs (miRNAs) are endogenously expressed single-stranded ∼21–23 nucleotide RNAs that inhibit gene expression post-transcriptionally by binding imperfectly to elements usually within the 3′untranslated region (3′UTR) of mRNAs. Small interfering RNAs (siRNAs) mediate site-specific cleavage by binding with perfect complementarity to RNA. Here, a cell-based miRNA reporter system was developed to screen for compounds from marine and plant extracts that inhibit miRNA or siRNA activity. The daphnane diterpenoid genkwanine M (GENK) isolated from the plant Wikstroemia polyantha induces an early inflammatory response and can moderately inhibit miR-122 activity in the liver Huh-7 cell line. GENK does not alter miR-122 levels nor does it directly inhibit siRNA activity in an in vitro cleavage assay. Finally, we demonstrate that GENK can inhibit HCV infection in Huh-7 cells. In summary, the development of the cell-based miRNA sensor system should prove useful in identifying compounds that affect miRNA/siRNA activity.

Irradiation, cisplatin, and 5-azacytidine upregulate cytomegalovirus promoter in tumors and muscles: implementation of non-invasive fluorescence imaging

Purpose

The cytomegalovirus (CMV) promoter is one of the most commonly used promoters for expression of transgenes in mammalian cells. The aim of our study was to evaluate the role of methylation and upregulation of the CMV promoter by irradiation and the chemotherapeutic agent cisplatin in vivo using non-invasive fluorescence in vivo imaging.

Procedures

Murine fibrosarcoma LPB and mammary carcinoma TS/A cells were stably transfected with plasmids encoding CMV and p21 promoter-driven green fluorescent protein (GFP) gene. Solid TS/A tumors were induced by subcutaneous injection of fluorescent tumor cells, while leg muscles were transiently transfected with plasmid encoding GFP under the control of the CMV promoter. Cells, tumors, and legs were treated either by DNA methylation inhibitor 5-azacytidine, irradiation, or cisplatin. GFP expression was determined using a fluorescence microplate reader in vitro and by non-invasive fluorescence imaging in vivo.

Results

Treatment of cells, tumors, and legs with 5-azacytidine (re)activated the CMV promoter. Furthermore, treatment with irradiation or cisplatin resulted in significant upregulation of GFP expression both in vitro and in vivo.

Conclusions

Observed alterations in the activity of the CMV promoter limit the usefulness of this widely used promoter as a constitutive promoter. On the other hand, inducibility of CMV promoters can be beneficially used in gene therapy when combined with standard cancer treatment, such as radiotherapy and chemotherapy.

A versatile ribosomal protein promoter-based reporter system for selective assessment of RNA stability and post-transcriptional control

Assessment of post-transcriptional control relies on use of transcriptional inhibitors and is masked by copious and cryptic transcriptional induction. We screened several cellular promoters that are constitutively active yet noninducible to external stimuli. The ribosomal protein RPS30 promoter was chosen; its TATA signal and sp1 site location were optimized. The modified promoter (RPS30M) is selective to post-transcriptional effects of AU-rich elements (ARE) in the 3'UTR, while it is not transcriptionally responsive to a wide variety of agents including pro-inflammatory cytokines and RNA-binding proteins. Specific cis-acting elements can be appended to RPS30M by a cloning-free approach to allow coupled transcriptional/post-transcriptional assessment, as demonstrated with NF-kappaB and beta-catenin/wnt signaling experiments. Moreover, efficient tetracycline-regulated RPS30M was created for quantitative assessment of the half-lives of mRNAs containing AREs. The described approach provides enhanced versatility and suitability for selective post-transcriptional assessment with or without transcriptional induction.

Cytomegalovirus promoter up-regulation is the major cause of increased protein levels of unstable reporter proteins after treatment of living cells with proteasome inhibitors

Fluorescent unstable proteins obtained by the fusion of a fluorescent protein coding sequence with specific amino acid sequences that promote its fast degradation have become popular to gauge the activity of the ubiquitin/proteasome system in living cells. The steady-state levels of expression of these unstable proteins is low in agreement with their short half-lives, and they accumulate in the cell upon treatment with proteasome inhibitors. We show here that this accumulation is mainly due to transcriptional up-regulation of the cytomegalovirus promoter by proteasome inhibitors and mediated, at least in part, by AP1 transactivation. These simple facts put under quarantine conclusions reached about the activity of the ubiquitin/proteasome pathway in animal cells in culture or in transgenic mice, where popular cytomegalovirus-driven constructs are used, as transcriptional regulation of the expression of the reporter protein construct and not degradation of the unstable protein by the ubiquitin/proteasome system may contribute significantly to the interpretation of the results observed.

The sequestosome 1/p62 attenuates cytokine gene expression in activated macrophages by inhibiting IFN regulatory factor 8 and TNF receptor-associated factor 6/NF-kappaB activity

Sequestosome 1/p62 (p62) is a scaffold/adaptor protein with multiple functions implicated for neuronal and bone diseases. It carries a ubiquitin binding domain through which it mediates proteasome-dependent proteolysis. In addition, p62 is reported to regulate NF-kappaB activity in some cells. To date, however, the role of p62 in innate immunity has not been fully elucidated. In this study, we report that IFN-gamma plus TLR signaling stimulates late expression of p62 in murine macrophages. Overexpression of p62 inhibited expression of multiple cytokines, IL-12p40, TNF-alpha, IL-1beta, IL-6, and IFN-beta, whereas p62 underexpression by small hairpin RNA markedly elevated their expression, indicating that p62 is a broad negative regulator of cytokine expression in stimulated macrophages. We show that p62 interacts with IFN regulatory factor 8 and Ro52, the transcription factor and ubiquitin E3 ligase that are important for IL-12p40 expression. This interaction, detectable at a late stage in stimulated macrophages, led to increased polyubiquitination and destabilization of IFN regulatory factor 8. We also show that upon macrophage stimulation, p62 binds to TNFR-associated factor 6, another E3 ligase important for NF-kappaB activation, but later this interaction was replaced by the recruitment of the deubiquitinating enzyme, cylindromatosis, an inhibitor of NF-kappaB activity. Recruitment of cylindromatosis coincided with reduced TNFR-associated factor 6 autoubiquitination and lower NF-kappaB activation. Our results indicate that p62 orchestrates orderly regulation of ubiquitin modification processes in macrophages to ensure attenuation of cytokine transcription postactivation. Together, p62 may provide a mechanism by which to control excessive inflammatory responses after macrophage activation.

Lentivirus-mediated bifunctional cell labeling for in vivo melanoma study

Lentiviral vectors (LVs) are capable of labeling a broad spectrum of cell types, achieving stable expression of transgenes. However, for in vivo studies, the duration of marker gene expression has been highly variable. We have developed a series of LVs harboring different promoters for expressing reporter gene in mouse cells. Long-term culture and colony formation of several LV-labeled mouse melanoma cells showed that promoters derived from mammalian house-keeping genes, especially those encoding RNA polymerase II (Pol2) and ferritin (FerH), provided the highest consistency for reporter expression. For in vivo studies, primary B16BL6 mouse melanoma were infected with LVs whose luciferase-green fluorescence protein fusion gene (Luc/GFP) was driven by either Pol2 or FerH promoters. When transplanted into syngeneic C57BL/6 mice, Luc/GFP-labeled B16BL6 mouse melanoma cells can be monitored by bioluminescence imaging in vivo, and GFP-positive cells can be isolated from the tumors by fluorescence-activated cell sorter. Pol2-Luc/GFP labeling, while lower in activity, was more sustainable than FerH-Luc/GFP labeling in B16BL6 over consecutive passages into mice. We conclude that Pol-2-Luc/GFP labeling allows long-term in vivo monitoring and tumor cell isolation in immunocompetent mouse melanoma models.

Application of the dual-luciferase reporter assay to the analysis of promoter activity in Zebrafish embryos

BACKGROUND

The dual-luciferase assay has been widely used in cell lines to determine rapidly but accurately the activity of a given promoter. Although this strategy has proved very useful, it does not allow the promoter and gene function to be analyzed in the context of the whole organism.

RESULTS

Here, we present a rapid and sensitive assay based on the classical dual-luciferase reporter technique which can be used as a new tool to characterize the minimum promoter region of a gene as well as the in vivo response of inducible promoters to different stimuli. We illustrate the usefulness of this system for studying both constitutive (telomerase) and inducible (NF-kappaB-dependent) promoters. The flexibility of this assay is demonstrated by induction of the NF-kappaB-dependent promoters using simultaneous microinjection of different pathogen-associated molecular patterns as well as with the use of morpholino-gene mediated knockdown.

CONCLUSION

This assay has several advantages compared with the classical in vitro (cell lines) and in vivo (transgenic mice) approaches. Among others, the assay allows a rapid and quantitative measurement of the effects of particular genes or drugs in a given promoter in the context of a whole organism and it can also be used in high throughput screening experiments.

Statins can be the potential therapeutic agents for reducing infection evoked cholangiopathy after liver transplantation?

Biliary infection, including bacteria and cytomegalovirus (CMV), can induce inflammatory response and lead to bile duct damage after liver transplantation. This process may involve a major class of pattern recognition receptors-TLRs (Toll-like receptors). Stimulation of these receptors by pathogens (CMV, bacteria, etc.) in bile duct can induce the secretion of a series of cytokines/chemokines mainly via a TLR-2/4-MyD88-dependent pathway. Strategies for prevention and treatment of biliary infection, such as selective digestive decontamination (SDD) and preemptive therapy with gancyclovir and antibiotics are not so satisfactory. Statin, a HMG-CoA reductase inhibitor, have special anti-inflammatory abilities. They can inhibit the expression of TLR-4 and TLR-2, and block the signaling pathways of LPS (TLR-2/4), virus-encoded envelope proteins (TLR-2) and HSP70 (TLR-2/4), This process can lead to a reduction of effector cytokines/chemokines. In addition, statins can suppress the replication of CMV by reducing NF-kappaB binding activity. We hypothesized that statins can be useful for reducing infection evoked cholangiopathy after liver transplantation. We provide reliable evidence supporting the hypothesis and offer proposals for future application.

Maspin augments proteasome inhibitor-induced apoptosis in prostate cancer cells

Proteasome inhibitors are known to induce apoptosis in a variety of cancer cells. On the other hand, maspin, a non-inhibitory serine protease inhibitor, is shown to sensitize cancer cells to therapeutic agents that induce apoptosis. We examined the consequence of maspin expression in prostate cancer cells targeted for treatment with various proteasome inhibitors. We observed that proteasome inhibitors induced apoptosis more effectively in maspin transfected human prostate cancer DU145 cells than in control cells. Interestingly, increased apoptosis in these cells was associated with a significant induction of maspin expression. MG-132, a proteasome inhibitor, induced endogenous and ectopic [cytomegalovirus promoter (CMV)-driven] maspin expression, and maspin siRNA attenuated MG-132-induced apoptosis. Proteasome inhibitor-induced maspin expression was inhibited by actinomycin D (Act D) and cyclohexamide (CHX), and by the inhibitors of p38MAPK, but not ERK1/2 or NF-kappaB. Electrophoretic mobility-shift assay (EMSA) and promoter-reporter activity analyses suggested that p38MAPK activated transcription factor AP-1 is responsible for proteasome inhibitor-induced maspin expression. Taken together, these observations demonstrate that proteasome inhibitors induce maspin expression by activating p38MAPK pathway, and that maspin thus expressed, in turn, augments proteasome inhibitor-induced apoptosis in prostate cancer cells. Our results suggest that gene therapy involving ectopic maspin expression may dramatically improve the efficacy of proteasome inhibitors for the treatment of prostate cancer.