Characterization of growth inhibition of oral bacteria by sophorolipid using a microplate-format assay

Sophorolipid (SL) is a class of glycolipid biosurfactant produced by yeast and has potent antimicrobial activity against many microorganisms. In this paper, a microplate-based method was developed to characterize the growth inhibition by SL on five representative species of caries-causing oral bacteria. Bacterial growth on microplate in the absence and presence of varying concentrations of SL was continuously monitored by recording the absorbance at 600nm of the cultures using a microplate reader. The results showed that SL completely inhibited the growth of the Lactobacilli at ≥1mg/ml and the Streptococci at much lower concentrations of ≥50μg/ml. More importantly, we further defined the mechanism of antimicrobial activity of SL by analyzing the pattern of the cell growth curves. SL at sublethal concentrations (<1mg/ml) is bactericidal towards the Lactobacilli; it lengthens the apparent cell-doubling time (T_d) and decreases the final cell density (as indicated by A_600nm) in a concentration-dependent manner. Against the oral Streptococci, on the other hand, SL at sublethal concentrations (<50μg/ml) is bacteriostatic; it delays the onset of cell growth in a concentration-dependent fashion, but once the cell growth is commenced there is no noticeable adverse effect on T_d and the final A_600nm. Scanning electron microscopic (SEM) study of L. acidophilus grown in sublethal concentration of SL reveals extensive structural damage to the cells. S. mutans grown in sublethal level of SL did not show morphological damage to the cells, but numerous protruding structures could be seen on the cell surface. At the respective lethal levels of SL, L. acidophilus cells were lysed (at 1mg/ml SL) and the cell surface structure of S. mutans (at 130μg/ml SL) was extensively deformed. In summary, this paper presents the first report on a detailed analysis of the effects of SL on Lactobacilli and Streptococci important to oral health and hygiene.

Pregnenolone co-treatment partially restores steroidogenesis, but does not prevent growth inhibition and increased atresia in mouse ovarian antral follicles treated with mono-hydroxy methoxychlor

Mono-hydroxy methoxychlor (mono-OH MXC) is a metabolite of the pesticide, methoxychlor (MXC). Although MXC is known to decrease antral follicle numbers, and increase follicle death in rodents, not much is known about the ovarian effects of mono-OH MXC. Previous studies indicate that mono-OH MXC inhibits mouse antral follicle growth, increases follicle death, and inhibits steroidogenesis in vitro. Further, previous studies indicate that CYP11A1 expression and production of progesterone (P4) may be the early targets of mono-OH MXC in the steroidogenic pathway. Thus, this study tested whether supplementing pregnenolone, the precursor of progesterone and the substrate for HSD3B, would prevent decreased steroidogenesis, inhibited follicle growth, and increased follicle atresia in mono-OH MXC-treated follicles. Mouse antral follicles were exposed to vehicle (dimethylsulfoxide), mono-OH MXC (10 μg/mL), pregnenolone (1 μg/mL), or mono-OH MXC and pregnenolone together for 96 h. Levels of P4, androstenedione (A), testosterone (T), estrone (E1), and 17β-estradiol (E2) in media were determined, and follicles were processed for histological evaluation of atresia. Pregnenolone treatment alone stimulated production of all steroid hormones except E2. Mono-OH MXC-treated follicles had decreased sex steroids, but when given pregnenolone, produced levels of P4, A, T, and E1 that were comparable to those in vehicle-treated follicles. Pregnenolone treatment did not prevent growth inhibition and increased atresia in mono-OH MXC-treated follicles. Collectively, these data support the idea that the most upstream effect of mono-OH MXC on steroidogenesis is by reducing the availability of pregnenolone, and that adding pregnenolone may not be sufficient to prevent inhibited follicle growth and survival.

Inhibition of AKT enhances mitotic cell apoptosis induced by arsenic trioxide

Accumulated evidence has revealed a tight link between arsenic trioxide (ATO)-induced apoptosis and mitotic arrest in cancer cells. AKT, a serine/threonine kinase frequently over-activated in diverse tumors, plays critical roles in stimulating cell cycle progression, abrogating cell cycle checkpoints, suppressing apoptosis, and regulating mitotic spindle assembly. Inhibition of AKT may therefore enhance ATO cytotoxicity and thus its clinical utility. We show that AKT was activated by ATO in HeLa-S3 cells. Inhibition of AKT by inhibitors of the phosphatidyl inositol 3-kinase/AKT pathway significantly enhanced cell sensitivity to ATO by elevating mitotic cell apoptosis. Ectopic expression of the constitutively active AKT1 had no effect on ATO-induced spindle abnormalities but reduced kinetochore localization of BUBR1 and MAD2 and accelerated mitosis exit, prevented mitotic cell apoptosis, and enhanced the formation of micro- or multi-nuclei in ATO-treated cells. These results indicate that AKT1 activation may prevent apoptosis of ATO-arrested mitotic cells by attenuating the function of the spindle checkpoint and therefore allowing the formation of micro- or multi-nuclei in surviving daughter cells. In addition, AKT1 activation upregulated the expression of aurora kinase B (AURKB) and survivin, and depletion of AURKB or survivin reversed the resistance of AKT1-activated cells to ATO-induced apoptosis. Thus, AKT1 activation suppresses ATO-induced mitotic cell apoptosis, despite the presence of numerous spindle abnormalities, probably by upregulating AURKB and survivin and attenuating spindle checkpoint function. Inhibition of AKT therefore effectively sensitizes cancer cells to ATO by enhancing mitotic cell apoptosis.

Induction of Indoleamine 2,3-Dioxygenase in Vascular Smooth Muscle Cells by Interferon-γ Contributes to Medial Immunoprivilege

Atherosclerosis and graft arteriosclerosis are characterized by leukocytic infiltration of the vessel wall that spares the media. The mechanism(s) for medial immunoprivilege is unknown. In a chimeric humanized mouse model of allograft rejection, medial immunoprivilege was associated with expression of IDO by vascular smooth muscle cells (VSMCs) of rejecting human coronary artery grafts. Inhibition of IDO by 1-methyl-tryptophan (1-MT) increased medial infiltration by allogeneic T cells and increased VSMC loss. IFN-gamma-induced IDO expression and activity in cultured human VSMCs was considerably greater than in endothelial cells (ECs) or T cells. IFN-gamma-treated VSMCs, but not untreated VSMCs nor ECs with or without IFN-gamma pretreatment, inhibited memory Th cell alloresponses across a semipermeable membrane in vitro. This effect was reversed by 1-MT treatment or tryptophan supplementation and replicated by the absence of tryptophan, but not by addition of tryptophan metabolites. However, IFN-gamma-treated VSMCs did not activate allogeneic memory Th cells, even after addition of 1-MT or tryptophan. Our work extends the concept of medial immunoprivilege to include immune regulation, establishes the compartmentalization of immune responses within the vessel wall due to distinct microenvironments, and demonstrates a duality of stimulatory EC signals versus inhibitory VSMC signals to artery-infiltrating T cells that may contribute to the chronicity of arteriosclerotic diseases.

Cutting edge: opposite effects of IL-1 and IL-2 on the regulation of IL-17+ T cell pool IL-1 subverts IL-2-mediated suppression

In this report, we show that IL-17(+)CD4(+) and IL-17(+)CD8(+) T cells are largely found in lung and digestive mucosa compartments in normal mice. Endogenous and exogenous IL-1 dramatically contribute to IL-17(+) T cell differentiation mediated by TGFbeta and IL-6. IL-1 is capable of stimulating IL-17(+) T cell differentiation in the absence of IL-6. Furthermore, although IL-2 reduces IL-17(+) T cell differentiation, IL-1 completely disables this effect. Mechanistically, IL-1 and IL-2 play opposite roles in regulating the expression of several molecules regulating Th17 cell differentiation, including the orphan nuclear receptor ROR gamma t, the IL-1 receptor, and the IL-23 receptor. IL-1 subverts the effects of IL-2 on the expression of these gene transcripts. Altogether, our work demonstrates that IL-6 is important but not indispensable for IL-17(+) T cell differentiation and that IL-1 plays a predominant role in promoting IL-17(+) T cell induction. Thus, the IL-17(+) T cell pool may be controlled by the local cytokine profile in the microenvironment.

Cleavage of growth differentiation factor 15 (GDF15) by membrane type 1-matrix metalloproteinase abrogates GDF15-mediated suppression of tumor cell growth

Growth differentiation factor 15 (GDF15), a transforming growth factor (TGF)-beta superfamily member, has been cloned from a placenta cDNA library as a gene product that has promoted activation of pro-matrix metalloproteinase (MMP)2 mediated by membrane type (MT)1-MMP. Expression of MT1-MMP in HEK293T cells caused cleavage of the GDF15 mature form at N(252)-M(253) to produce a 6-kDa C-terminal fragment. Treatment of MCF7 cells with GDF15 induced activation of p53 and enhanced expression of p21, which was abrogated by MT1-MMP expression. GDF15 mRNA synthesis was also shown to be induced by treatment of cells with GDF15. Treatment of MCF7 cells with GDF15 caused suppression of cell proliferation. However, proliferation of MCF7 cells transfected with the MT1-MMP gene was not affected by GDF15 treatment, but was suppressed in the presence of the MMP inhibitor BB94. HT1080 cells transfected with the GDF15 gene, which endogenously express MT1-MMP, synthesize a high-level GDF15 precursor form and a low-level mature form, and treatment of cells with BB94 enhanced production of the GDF15 mature form. Consistent with GDF15 production, HT1080 cells transfected with the GDF15 gene proliferated almost equally with control cells, and addition of BB94 effectively suppressed growth of HT1080 cells transfected with the GDF15 gene concomitant with the accumulation of the GDF15 mature form, but not control cells. These results suggest that MT1-MMP contributes to tumor cell proliferation through the cleavage of GDF15, which down-regulates cell proliferation by inducing activation of p53 and p21 synthesis.

Sesamin, a lignan of sesame, down-regulates cyclin D1 protein expression in human tumor cells

Sesamin is a major lignan constituent of sesame and possesses multiple functions such as antihypertensive, cholesterol-lowering, lipid-lowering and anticancer activities. Several groups have previously reported that sesamin induces growth inhibition in human cancer cells. However, the nature of this growth inhibitory mechanism remains unknown. The authors here report that sesamin induces growth arrest at the G1 phase in cell cycle progression in the human breast cancer cell line MCF-7. Furthermore, sesamin dephosphorylates tumor-suppressor retinoblastoma protein (RB). It is also shown that inhibition of MCF-7 cell proliferation by sesamin is correlated with down-regulated cyclin D1 protein expression, a proto-oncogene that is overexpressed in many human cancer cells. It was found that sesamin-induced down-regulation of cyclin D1 was inhibited by proteasome inhibitors, suggesting that sesamin suppresses cyclin D1 protein expression by promoting proteasome degradation of cyclin D1 protein. Sesamin down-regulates cyclin D1 protein expression in various kinds of human tumor cells, including lung cancer, transformed renal cells, immortalized keratinocyte, melanoma and osteosarcoma. Furthermore, depletion of cyclin D1 protein using small interfering RNA rendered MCF-7 cells insensitive to the growth inhibitory effects of sesamin, implicating that cyclin D1 is at least partially related to the antiproliferative effects of sesamin. Taken together, these results suggest that the ability of sesamin to down-regulate cyclin D1 protein expression through the activation of proteasome degradation could be one of the mechanisms of the antiproliferative activity of this agent.

Regeneration-based therapies for spinal cord injuries

Although it has been long believed that the damaged central nervous system does not regenerate upon injury, there is an emerging hope for regeneration-based therapy of the damaged central nervous system (CNS) due to the progress of developmental biology and regenerative medicine including stem cell biology. In this review, we have summarized recent studies aimed at the development of regeneration-based therapeutic approaches for spinal cord injuries, including therapy with anti-inflammatory cytokines, transplantation of neural stem/precursor cells and induction of axonal regeneration.

Sensory afferents regenerated into dorsal columns after spinal cord injury remain in a chronic pathophysiological state

Axon regeneration after experimental spinal cord injury (SCI) can be promoted by combinatorial treatments that increase the intrinsic growth capacity of the damaged neurons and reduce environmental factors that inhibit axon growth. A prior peripheral nerve conditioning lesion is a well-established means of increasing the intrinsic growth state of sensory neurons whose axons project within the dorsal columns of the spinal cord. Combining such a prior peripheral nerve conditioning lesion with the infusion of antibodies that neutralize the growth inhibitory effects of the NG2 chondroitin sulfate proteoglycan promotes sensory axon growth through the glial scar and into the white matter of the dorsal columns. The physiological properties of these regenerated axons, particularly in the chronic SCI phase, have not been established. Here we examined the functional status of regenerated sensory afferents in the dorsal columns after SCI. Six months post-injury, we located and electrically mapped functional sensory axons that had regenerated beyond the injury site. The regenerated axons had reduced conduction velocity, decreased frequency-following ability, and increasing latency to repetitive stimuli. Many of the axons that had regenerated into the dorsal columns rostral to the injury site were chronically demyelinated. These results demonstrate that regenerated sensory axons remain in a chronic pathophysiological state and emphasize the need to restore normal conduction properties to regenerated axons after spinal cord injury.

Down-Regulation of the SWI/SNF Chromatin Remodeling Activity by TCR Signaling Is Required for Proper Thymocyte Maturation

The process of thymocyte development requires an exquisite regulation of many genes via transcription factors and chromatin remodeling activities. Even though the SWI/SNF chromatin remodeling complex has been thought to play important roles during thymocyte development, its known function is very limited. In this study, we show that the SWI/SNF chromatin remodeling activity is finely regulated during thymocyte maturation process, especially during thymocyte selections. We found that TCR signaling directly down-regulates mBRG1 and SWI3-related gene, the core components of murine SWI/SNF complex, during thymocyte maturation. Constitutive expression of SWI3-related gene in developing thymocytes attenuated the down-regulation of the SWI/SNF complex and resulted in a change in the expression of genes such as linker for activation of T cells and casitas B lineage lymphoma, which affected the TCR-mediated intracellular signaling pathway. The defects in TCR signaling resulted in the disruption of both positive and negative selections in specific TCR transgenic mice systems. Our results state, for the first time, that the chromatin remodeling activity needs to be finely controlled for proper thymocyte selection and maturation processes.

Glucocorticoid receptor overexpression exerts an antisurvival effect on human small cell lung cancer cells

Small cell lung cancer (SCLC) is an aggressive tumour with an abysmal prognosis. These cancers are characteristically resistant to glucocorticoid (Gc) action, owing to impaired expression of the glucocorticoid receptor (GR). We identified reduced GR expression in human SCLC cell lines, compared to a non-SCLC cell line. The SCLC cells also showed no Gc inhibition of proliferation, in contrast to non-SCLC cells. Retroviral overexpression of GR resulted in significantly increased cell death, which was partially blocked by the GR antagonist, RU486. Indeed, in cells sorted for GR expression, there was rapid, near complete loss of live cells by 72 h, in contrast to control cells that proliferated as expected. Flow cytometry using Annexin V revealed that cell death was by apoptosis. In addition, confocal analysis of fixed cells showed that cells overexpressing GR displayed a significant increase in fragmenting apoptotic nuclei. Microarray studies showed that transgenic GR expression upregulated the proapoptotic genes, BAD and BAX. We have, therefore, identified a profound apoptotic effect of GR in SCLC cells, which may explain the low levels of endogenous GR in SCLC cells. Understanding how GR overexpression leads to apoptotic cell death in SCLC cells may uncover new therapeutic strategies.

Role of the basic helix-loop-helix protein ITF2 in the hormonal regulation of Sertoli cell differentiation

Sertoli cells are a post-mitotic terminally differentiated cell population that forms the seminiferous tubules in the adult testis and provides the microenvironment and structural support for developing germ cells. During pubertal development, Sertoli cells are responsive to follicle-stimulating hormone (FSH) to promote the expression of differentiated gene products. The basic helix-loop-helix (bHLH) and inhibitors of differentiation (Id) transcription factors are involved in the differentiation of a variety of cell lineages during development. Both bHLH and Id transcription factors have been identified in Sertoli cells. A yeast two-hybrid screen was conducted using a rat Sertoli cell cDNA library to identify bHLH dimerization partners for the Id1 transcription factor. The ubiquitous bHLH protein ITF2 (i.e., E2-2) was identified as one of the interacting partners. The current study investigates the expression and function of ITF2 in Sertoli cells. ITF2 was found to be ubiquitously expressed in all testicular cell types including germ cells, peritubular myoid cells, and Sertoli cells. Stimulation of cultured Sertoli cells with FSH or dibutryl cAMP resulted in a transient decrease in expression of ITF2 mRNA levels followed by a rise in expression with FSH treatment. ITF2 expression was at its highest in mid-pubertal 20-day-old rat Sertoli cells. ITF2 was found to directly bind to negative acting Id HLH proteins and positive acting bHLH proteins such as scleraxis. Transient overexpression of ITF2 protein in cultured Sertoli cells stimulated transferrin promoter activity, which is a marker of Sertoli cell differentiation. Co-transfections of ITF2 and Id proteins sequestered the inhibitory effects of the Id family of proteins. Observations suggest ITF2 can enhance FSH actions through suppressing the inhibitory actions of the Id family of proteins and increasing the actions of stimulatory bHLH proteins (i.e., scleraxis) in Sertoli cells.

Expression and effect of inhibition of the ubiquitin-conjugating enzyme E2C on esophageal adenocarcinoma

Ubiquitin-dependent proteolysis of cyclins plays a critical role in cell cycle progression and tumorigenesis. We examined the expression of ubiquitin-conjugating enzyme E2C (UBE2C) during progression from Barrett's metaplasia to esophageal adenocarcinoma (EA) and the effects of targeting this enzyme on EA-derived cell lines. Using oligonucleotide microarrays UBE2C expression was elevated in 73% (11 of 15) of EAs relative to Barrett's metaplasia. Tissue microarray showed elevated UBE2C in 70% (7 of 10) of dysplastic samples and in 87% (58 of 67) of tumors relative to metaplastic samples. Transfection of dominant-negative UBE2C into Seg-1 cells decreased proliferation (P = .04) and increased mitotic arrest compared to vector controls (63.5% vs 6.8%; P < .001). Transfection of UBE2C small interfering RNA also caused inhibiton of cell proliferation and distortion of the cell cycle, with maximal increase of G(2) cells (155% of mock cells) at 72 hours and of S-phase cells (308% of mock cells) at 24 hours. Treatment of Seg-1 cells with the proteasome inhibitor MG-262 (1 nM-1 microM) showed decreased proliferation (P = .02). EA-derived cells expressing UBE2C are sensitive to treatment with MG-262 and to silencing of UBE2C, suggesting that patients with EAs overexpressing UBE2C may benefit from agents targeting this ubiquitin-conjugating enzyme.

Myostatin inhibition slows muscle atrophy in rodent models of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is an incurable neurodegenerative disease leading to motor neuron cell death, but recent studies suggest that non-neuronal cells may contribute to the pathological mechanisms involved. Myostatin is a negative regulator of muscle growth whose function can be inhibited using neutralizing antibodies. In this study, we used transgenic mouse and rat models of ALS to test whether treatment with anti-myostatin antibody slows muscle atrophy, motor neuron loss, or disease onset and progression. Significant increases in muscle mass and strength were observed in myostatin-antibody-treated SOD1(G93A) mice and rats prior to disease onset and during early-stage disease. By late stage disease, only diaphragm muscle remained significantly different in treated animals in comparison to untreated controls. Myostatin inhibition did not delay disease onset nor extend survival in either the SOD1(G93A) mouse or rat. Together, these results indicate that inhibition of myostatin does not protect against the onset and progression of motor neuron degenerative disease. However, the preservation of skeletal muscle during early-stage disease and improved diaphragm morphology and function maintained through late stage disease suggest that anti-myostatin therapy may promote some improved muscle function in ALS.

Targeting myelin to optimize plasticity of spared spinal axons

Functional re-innervation of target neurons following neurological damage such as spinal cord injury is an essential requirement of potential therapies. There are at least two avenues by which this can be achieved: (a) through the regeneration of injured axons and (b) through promoting plasticity of those spared by the initial insult. There are several reasons why the latter approach may be more feasible, not the least of which are the inhibitory character of the glial scar, the often long distances over which injured axons must regrow, and the fact that spared axons are often already in the vicinity of denervated targets. The challenge is to unveil the well-recognized intrinsic plasticity of spared axons in a way that avoids complications, such as pain or autonomic dysfunction. One approach that we as well as others have taken is to target growth-suppressing signaling pathways initiated in spared axons by myelin-derived proteins. This article reviews models used for the study of spinal axon plasticity and describes the anatomical and behavioral effects of interfering with myelinderived proteins, their receptors, and components of their intracellular signaling cascades.

The cytokine interleukin-6 is sufficient but not necessary to mimic the peripheral conditioning lesion effect on axonal growth

Lesioning the peripheral branch of a dorsal root ganglion (DRG) neuron before injury of the central branch of the same neuron enables spontaneous regeneration of these spinal axons. This effect is cAMP and transcription dependent. Here, we show that the cytokine interleukin-6 (IL-6) is upregulated in DRG neurons after either a conditioning lesion or treatment with dibutyryl-cAMP. In culture, IL-6 allows neurons to grow in the presence of inhibitors of regeneration present in myelin. Importantly, intrathecal delivery of IL-6 to DRG neurons blocks inhibition by myelin both in vitro and in vivo, effectively mimicking the conditioning lesion. Blocking IL-6 signaling has no effect on the ability of cAMP to overcome myelin inhibitors. Consistent with this, IL-6-deficient mice respond to a conditioning lesion as effectively as wild-type mice. We conclude that IL-6 can mimic both the cAMP effect and the conditioning lesion effect but is not an essential component of either response.

Knockdown of MBP-1 in human prostate cancer cells delays cell cycle progression

We have previously shown that MBP-1 acts as a general transcriptional repressor, and forced expression of MBP-1 exerts an anti-proliferative effect on a number of human cancer cells. In this report, we have investigated the role of endogenous MBP-1 in cell growth regulation. For this, we generated human prostate cancer cells (PC3) stably transfected with short hairpin RNA targeting MBP-1. We have observed retarded growth and longer doubling time of MBP-1 knockdown PC3 cells as compared with control mock-transfected PC3 cells. Fluorescence-activated cell sorter analysis suggested that PC3 cells expressing MBP-1-specific small interfering RNA accumulated during G2/M phase of the cell cycle. Further analysis suggested that depletion of MBP-1 was associated with reduction of cyclin A and cyclin B1 expression when compared with that of the control cells. A delayed induction of cyclin A and B1 expression was observed in MBP-1-depleted PC3 cells (PC3-4.2) upon serum stimulation, although the level of expression was much lower than that of control PC3 cells. Supplementation of MBP-1 in PC3-4.2 cells restored cyclin A and cyclin B1 expression. Together, these results suggest that knockdown of MBP-1 in prostate cancer cells perturbs cell proliferation by inhibiting cyclin A and cyclin B1 expression.

Intrathecally infused antibodies against Nogo-A penetrate the CNS and downregulate the endogenous neurite growth inhibitor Nogo-A

Neutralizing antibodies against the neurite growth inhibitory protein Nogo-A are known to induce regeneration, enhance compensatory growth, and enhance functional recovery. In intact adult rats and monkeys or spinal cord injured adult rats, antibodies reached the entire spinal cord and brain through the CSF circulation from intraventricular or intrathecal infusion sites. In the tissue, anti-Nogo antibodies were found inside Nogo-A expressing oligodendrocytes and neurons. Intracellularly, anti-Nogo-A antibodies were colocalized with endogenous Nogo-A in large organels, some of which containing the lysosomal marker cathepsin-D. This suggests antibody-induced internalization of cell surface Nogo-A. Total Nogo-A tissue levels in spinal cord were decreased in intact adult rats following 7 days of antibody infusion. This mechanism was confirmed in vitro; cultured oligodendrocytes and neurons had lower Nogo-A contents in the presence of anti-Nogo-A antibodies. These results demonstrate that antibodies against a CNS cell surface protein reach their antigen through the CSF and can induce its downregulation.

RGMa inhibition promotes axonal growth and recovery after spinal cord injury

Repulsive guidance molecule (RGM) is a protein implicated in both axonal guidance and neural tube closure. We report RGMa as a potent inhibitor of axon regeneration in the adult central nervous system (CNS). RGMa inhibits mammalian CNS neurite outgrowth by a mechanism dependent on the activation of the RhoA–Rho kinase pathway. RGMa expression is observed in oligodendrocytes, myelinated fibers, and neurons of the adult rat spinal cord and is induced around the injury site after spinal cord injury. We developed an antibody to RGMa that efficiently blocks the effect of RGMa in vitro. Intrathecal administration of the antibody to rats with thoracic spinal cord hemisection results in significant axonal growth of the corticospinal tract and improves functional recovery. Thus, RGMa plays an important role in limiting axonal regeneration after CNS injury and the RGMa antibody offers a possible therapeutic agent in clinical conditions characterized by a failure of CNS regeneration.

Actions of neurotrophic factors and their signaling pathways in neuronal survival and axonal regeneration

Adult axons in the mammalian central nervous system do not elicit spontaneous regeneration after injury, although many affected neurons have survived the neurotrauma. However, axonal regeneration does occur under certain conditions. These conditions include: (a) modification of regrowth environment, such as supply of peripheral nerve bridges and transplantation of Schwann cells or olfactory ensheathing glia to the injury site; (b) application of neurotrophic factors at the cell soma and axon tips; (c) blockade of growth-inhibitory molecules such as Nogo-A, myelin-associated glycoprotein, and oligodendrocyte-myelin glycoprotein; (d) prevention of chondroitin-sulfate-proteoglycans-related scar tissue formation at the injury site using chondroitinase ABC; and (e) elevation of intrinsic growth potential of injured neurons via increasing intracellular cyclic adenosine monophosphate level. A large body of evidence suggests that these conditions achieve enhanced neuronal survival and axonal regeneration through sometimes overlapping and sometimes distinct signal transduction mechanisms, depending on the targeted neuronal populations and intervention circumstances. This article reviews the available information on signal transduction pathways underlying neurotrophic-factor-mediated neuronal survival and neurite outgrowth/axonal regeneration. Better understanding of signaling transduction is important in helping us develop practical therapeutic approaches for encouraging neuronal survival and axonal regeneration after traumatic injury in clinical context.

BMP-signaling regulates the generation of hair-cells

Bone morphogenetic proteins (BMPs) are diffusible molecules involved in a variety of cellular interactions during development. Bmp4 expression accompanies the development of the ear sensory organs during patterning and specification of sensory cell fates, yet there is no understanding of the role of BMP4 in this process. The present work was aimed at exploring the effects of BMP-signaling on the development of hair-cells. For this purpose, we studied gene expression, cell proliferation and cell death in isolated chick otic vesicles that were grown in vitro in the presence of recombinant BMP4 or the BMP-inhibitor Noggin. Cath1 was used as a marker for hair-cell specification. BMP4 reduced the number of Cath1-cells and, conversely, Noggin increased the size of the sensory patches and the number of Cath1-positive cells. The effect of BMP4 was irreversible and occurred before hair-cell specification. Lfng and Fgf10 were expressed in the prosensory domain before Cath1, and their expression was expanded by Noggin. At these stages, modifications of BMP activity did not respecify non-sensory epithelium of the otic vesicle. The expression of Bmp4 at sensory patches was suppressed by BMP4 and induced by Noggin suggesting an autoregulatory loop. Analysis of BrdU incorporation during 6 and 18 h indicated that the effects of BMP4 were due to its ability to reduce the number of actively proliferating progenitors and inhibit cell fate specification. BMP4 induced cell death within the prosensory domain of the otic vesicle, along with the expression of Msx1, but not Msx2. On the contrary, BMP-inhibition with Noggin favored hair-cell specification without changes in the overall cell proliferation. We propose that about the stage of terminal division, the balance between BMP and BMP-inhibitory signals regulates survival and specification of hair-cell precursors, the final number of sensory hair-cells being limited by excess levels of BMPs. The final size of sensory patches would hence depend on the balance between BMP4 and opposing signals.

Axonal regeneration in adult CNS neurons ? signaling molecules and pathways

Failure of severed adult CNS axons to regenerate could be attributed to both a reduced intrinsic capacity to grow and an heightened susceptibility to inhibitory factors of the CNS extracellular environment. A particularly interesting and useful paradigm for investigating CNS axonal regeneration is its enhancement at the CNS branch of dorsal root ganglion (DRG) neurons after conditional lesioning of their peripheral branch. Recent reports have implicated the involvement of two well-known signaling pathways utilizing separate transcription factors; the Cyclic AMP (cAMP) response element binding protein (CREB) and signal transducer and activator of transcription 3 (STAT3), in conditional lesioning. The former appears to be the pathway activated by neurotrophic factors and Bcl-2, while the latter is responsible for the neurogenic effect of cytokines [such as the leukemia inhibitory factor (LIF) and interleukin-6 (IL-6) elevated at lesion sites]. Recent findings also augmented earlier notions that modulations of the activity of another class of cellular signaling intermediate, the conventional protein kinase C (PKC), could result in a contrasting growth response by CNS neurons to myelin-associated inhibitors. We discuss these signaling pathways and mechanisms, in conjunction with other recent reports of regeneration enhancement and also within the context of what is known about aiding regeneration of injured CNS axons.

Expression of mTert in primary murine cells links the growth-promoting effects of telomerase to transforming growth factor-β signaling

Here, we show that ectopic expression of the catalytic subunit of mouse telomerase (mTert) confers a growth advantage to primary murine embryonic fibroblasts (MEFs), which have very long telomeres, as well as facilitates their spontaneous immortalization and increases their colony-forming capacity upon activation of oncogenes. We demonstrate that these telomere length-independent growth-promoting effects of mTert overexpression require catalytically active mTert, as well as the formation of mTert/Terc complexes. The gene expression profile of mTert-overexpressing MEFs indicates that telomerase enhances growth in these cells through the repression of growth-inhibiting genes of the transforming growth factor-beta (TGF-beta) signaling network. We functionally validate this result by showing that mTert abrogates the growth-inhibitory effect of TGF-beta in MEFs, thus demonstrating that telomerase increments the proliferative potential of primary mouse embryonic fibroblasts by targeting the TGF-beta pathway.

MKP1/CL100 controls tumor growth and sensitivity to cisplatin in non-small-cell lung cancer

Non-small-cell lung cancer (NSCLC) represents the most frequent and therapy-refractive sub-class of lung cancer. Improving apoptosis induction in NSCLC represents a logical way forward in treating this tumor. Cisplatin, a commonly used therapeutic agent in NSCLC, induces activation of N-terminal-c-Jun kinase (JNK) that, in turn, mediates induction of apoptosis. In analysing surgical tissue samples of NSCLC, we found that expression of MKP1/CL100, a negative regulator of JNK, showed a strong nuclear staining for tumor cells, whereas, in normal bronchial epithelia, MKP1 was localized in the cytoplasm as well as in nuclei. In the NSCLC-derived cell lines H-460 and H-23, we found that MKP1 was constitutively expressed. Expressing a small-interfering RNA (siRNA) vector for MKP1 in H-460 cells resulted in a more efficient activation by cisplatin of JNK and p38 than in the parental cells, and this correlated with a 10-fold increase in sensitivity to cisplatin. A similar response was also observed in H-460 and H-23 cells when treated with the MKP1 expression inhibitor RO-31-8220. Moreover, expression of a siRNA-MKP2, an MKP1-related phosphatase, had no effect on H-460 cell viability response to cisplatin. Tumors induced by H-460 cells expressing MKP1 siRNA grew slower in nu(-)/nu(-) mice and showed more susceptibility to cisplatin than parental cells, and resulted in an impaired growth of the tumor in mice. On the other hand, overexpression of MKP1 in the H-1299 NSCLC-derived cell line resulted in further resistance to cisplatin. Overall, the results showed that inhibition of MKP1 expression contributes to a slow down in cell growth in mice and an increase of cisplatin-induced cell death in NSCLC. As such, MKP1 can be an attractive target in sensitizing cells to cisplatin to increase the effectiveness of the drug in treating NSCLC.

Glial cell line-derived neurotrophic factor (GDNF) family ligands reduce the sensitivity of neuroblastoma cells to pharmacologically induced cell death, growth arrest and differentiation

The glial cell line-derived neurotrophic factor (GDNF) family of ligands play essential roles in promoting normal neural crest differentiation during embryogenesis, and, may have a therapeutic role in malignancies of neural crest origin, such as neuroblastoma. However, we report here that GDNF and neurturin blocked the growth inhibitory and neuritogenic effects of all-trans-retinoic acid in neuroblastoma cells in vitro. GDNF caused neuroblastoma cells to proliferate in the presence of a range of cytotoxic chemotherapeutic agents at low concentrations. Thus, our findings suggest a role for GDNF signaling in promoting resistance to differentiation or cytotoxic therapy of neuroblastoma, and, preclude their use in this neural crest tumor.

C2GnT-M is downregulated in colorectal cancer and its re-expression causes growth inhibition of colon cancer cells

Changes in carbohydrates on the cell surface are associated with tumor malignancy. The mucin-type core 2 beta-1,6-N-acetylglucosaminyltransferase (C2GnT-M) is highly expressed in the gastrointestinal tract and catalyses the formation of core 2, core 4, and blood group I branches on O-glycans. In the present study, we evaluated the role of C2GnT-M in colorectal cancer. C2GnT-M downexpression was observed in 73.6% of the primary tumors from colorectal cancer patients (39 of 53) analysed by cancer profiling array. Consistently, the majority of colon cancer cell lines and primary colon tumors expressed lower levels of C2GnT-M than did normal colon tissues by RT-PCR. HCT116 cells stably transfected with C2GnT-M inhibited expression of the core 1 structure, Galbeta1,3GalNAcalpha1-Ser/Thr, on the cell surface. Moreover, C2GnT-M expression suppressed cell adhesion, motility, and invasion as well as colony formation ability. The growth of C2GnT-M-transfected HCT116 and SW480 cells was dramatically suppressed, and the cell death induced by C2GnT-M was demonstrated by an increase in the annexin V-positive cells. Interestingly, C2GnT-M inhibited cell adhesion to collagen IV and fibronectin, and decreased tyrosine phosphorylation of paxillin, indicating that the changes in cancer behavior may be partly mediated by integrin-signaling pathways. Tumor growth in vivo was also significantly suppressed by C2GnT-M in the xenografts of nude mice. These results demonstrate that C2GnT-M is frequently downregulated in colorectal cancer and suppresses colon cancer cell growth.

A novel role of p38 alpha MAPK in mitotic progression independent of its kinase activity

Activation of p38alpha MAPK triggers G2/M checkpoint, thus inhibiting cell proliferation. In this study we found that depletion of p38alpha by RNAi also inhibited cell proliferation and caused mitotic arrest. However, treatment with selective small molecule p38 kinase inhibitors had no effect on cell cycle progression, even though the p38 kinase was completely inhibited, revealing p38alpha functions that are independent of its kinase activity. Indeed, ectopic expression of a kinase negative p38alpha rescued the lethality caused by RNAi-depletion of the endogenous p38alpha, thus providing further evidence for a kinase-independent function of p38alpha. In addition, we showed that overexpression of the wild type or kinase-negative p38alpha also strongly inhibited cell proliferation, similarly as RNAi depletion of p38alpha. Together the results demonstrate that, in addition to its kinase-dependent functions, such as in activation of G2/M checkpoint, p38alpha also has an essential, kinase-independent function.

Interaction of fibroblast growth factor and C-natriuretic peptide signaling in regulation of chondrocyte proliferation and extracellular matrix homeostasis

Overexpression of C-natriuretic peptide (CNP) in cartilage partially rescues achondroplasia in the mouse. Here, we studied the interaction of fibroblast growth factor (FGF) and CNP signaling in chondrocytes. CNP antagonized FGF2-induced growth arrest of rat chondrosarcoma (RCS) chondrocytes by inhibition of the Erk mitogen activated protein kinase pathway. This effect of CNP was protein kinase G-dependent and was mimicked by the cGMP analog pCPT-cGMP. FGF2-mediated activation of both MEK and Raf-1 but not Ras or FRS2 was abolished by CNP demonstrating that CNP blocks the Erk pathway at the level of Raf-1. CNP also counteracted the FGF2-mediated degradation of RCS extracellular matrix. CNP partially antagonized FGF2-induced expression, release and activation of several matrix-remodeling molecules including matrix metalloproteinase 2 (MMP2), MMP3, MMP9, MMP10 and MMP13. In addition, CNP compensated for FGF2-mediated matrix loss by upregulation of matrix production independent of its interference with FGF signaling. We conclude that CNP utilizes both direct and indirect ways to counteract the effects of FGF signaling in a chondrocyte environment.

TGF-beta inhibits Fas-mediated apoptosis of a follicular dendritic cell line by down-regulating the expression of Fas and caspase-8: counteracting role of TGF-beta on TNF sensitization of Fas-mediated apoptosis

Follicular dendritic cells (FDC) constitute the framework of germinal center (GC) in secondary lymphoid follicles, and the integrity of FDC networks is critically affected by cytokines present in the GC. We have previously shown that TNF promotes Fas-mediated apoptosis of HK cells, an established FDC-like cell line, by up-regulating Fas expression. However, in the developing GC, FDC death is not a hallmark of GC despite the presence of TNF and FasL. In this study, we report that TGF-beta inhibits Fas-mediated apoptosis of HK cells by down-regulating the expression of surface Fas and caspase-8. The inhibitory effect of TGF-beta can be observed when HK cells were simultaneously treated with TNF and TGF-beta, indicating that TGF-beta counteracts the effect of TNF in sensitizing cells to Fas-mediated apoptosis. Furthermore, the deprivation of TGF-beta by injecting neutralizing TGF-beta Abs to the SRBC-immunized mice resulted in the sporadic appearance of FDC undergoing apoptosis in the lymphoid follicles, suggesting that TGF-beta functions as a naturally occurring inhibitor that rescues FDCs which are predisposed to apoptosis. Our study documents a novel function of TGF-beta in the maintenance of FDC networks.

TGF-beta 1 uses distinct mechanisms to inhibit IFN-gamma expression in CD4+ T cells at priming and at recall: differential involvement of Stat4 and T-bet

TGF-beta1 plays a critical role in restraining pathogenic Th1 autoimmune responses in vivo, but the mechanisms that mediate TGF-beta1's suppressive effects on CD4(+) T cell expression of IFN-gamma expression remain incompletely understood. To evaluate mechanisms by which TGF-beta1 inhibits IFN-gamma expression in CD4(+) T cells, we primed naive wild-type murine BALB/c CD4(+) T cells in vitro under Th1 development conditions in the presence or the absence of added TGF-beta1. We found that the presence of TGF-beta1 during priming of CD4(+) T cells suppressed both IFN-gamma expression during priming as well as the development of Th1 effector cells expressing IFN-gamma at a recall stimulation. TGF-beta1 inhibited the development of IFN-gamma-expressing cells in a dose-dependent fashion and in the absence of APC, indicating that TGF-beta1 can inhibit Th1 development by acting directly on the CD4(+) T cell. During priming, TGF-beta1 strongly inhibited the expression of both T-bet (T box expressed in T cells) and Stat4. We evaluated the importance of these two molecules in the suppression of IFN-gamma expression at the two phases of Th1 responses. Enforced expression of T-bet by retrovirus prevented TGF-beta1's inhibition of Th1 development, but did not prevent TGF-beta1's inhibition of IFN-gamma expression at priming. Conversely, enforced expression of Stat4 partly prevented TGF-beta1's inhibition of IFN-gamma expression during priming, but did not prevent TGF-beta1's inhibition of Th1 development. These data show that TGF-beta1 uses distinct mechanisms to inhibit IFN-gamma expression in CD4(+) T cells at priming and at recall.

Inhibition of granulocyte-macrophage colony-stimulating factor signaling and microglial proliferation by anti-CD45RO: role of Hck tyrosine kinase and phosphatidylinositol 3-kinase/Akt

Increasing evidence suggests that CD45, a transmembrane protein tyrosine phosphatase, is an important modulator of macrophage activation. Microglia, resident brain macrophages, express CD45 and proliferate under pathologic conditions. In this study, we examined the role of CD45 in modulating GM-CSF-induced proliferation and signal transduction in primary human microglial cultures. Soluble, but not immobilized anti-CD45RO induced tyrosine phosphatase activity and inhibited GM-CSF-induced microglial proliferation. Microglial proliferation was also inhibited by PP2 (Src inhibitor), LY294002 (PI3K inhibitor), and U0126 (MEK inhibitor). GM-CSF induced phosphorylation of Jak2, Stat5, Hck (the myeloid-restricted Src kinase), Akt, Stat3, and Erk MAPKs in microglia. Of these, anti-CD45RO inhibited phosphorylation of Hck and Akt, and PP2 inhibited phosphorylation of Hck and Akt. In a macrophage cell line stably overexpressing wild-type or kinase-inactive Hck, GM-CSF increased proliferation of the control (empty vector) and wild-type but not kinase-inactive cells, and this was inhibited by anti-CD45RO. Together, these results demonstrate that, in macrophages, Hck tyrosine kinase is activated by GM-CSF, and that Hck plays a pivotal role in cell proliferation and survival by activating the PI3K/Akt pathway. Ab-mediated activation of macrophage and microglial CD45 tyrosine phosphatase may have therapeutic implications for CNS inflammatory diseases.

Smad7 induces tumorigenicity by blocking TGF-beta-induced growth inhibition and apoptosis

Smad proteins play a key role in the intracellular signaling of the transforming growth factor beta (TGF-beta) superfamily of extracellular polypeptides that initiate signaling to regulate a wide variety of biological processes. The inhibitory Smad, Smad7, has been shown to function as intracellular antagonists of TGF-beta family signaling and is upregulated in several cancers. To determine the effect of Smad7-mediated blockade of TGF-beta signaling, we have stably expressed Smad7 in a TGF-beta-sensitive, well-differentiated, and non-tumorigenic cell line, FET, that was derived from human colon adenocarcinoma. Smad7 inhibits TGF-beta-induced transcriptional responses by blocking complex formation between Smad 2/3 and Smad4. While Smad7 has no effect on TGF-beta-induced activation of p38 MAPK and ERK, it blocks the phosphorylation of Akt by TGF-beta and enhances TGF-beta-induced phosphorylation of c-Jun. FET cells expressing Smad7 show anchorage-independent growth and enhance tumorigenicity in athymic nude mice. Smad7 blocks TGF-beta-induced growth inhibition by preventing TGF-beta-induced G1 arrest. Smad7 inhibits TGF-beta-mediated downregulation of c-Myc, CDK4, and Cyclin D1, and suppresses the expression of p21(Cip1). As a result, Smad7 inhibits TGF-beta-mediated downregulation of Rb phosphorylation. Furthermore, Smad7 inhibits the apoptosis of these cells. Together, Smad7 may increase the tumorigenicity of FET cells by blocking TGF-beta-induced growth inhibition and by inhibiting apoptosis. Thus, this study provides a mechanism by which a portion of human colorectal tumors may become refractory to tumor-suppressive actions of TGF-beta that might result in increased tumorigenicity.

Targeting Neurite Growth Inhibitors to Induce CNS Regeneration

Prominent among the several endogenous inhibitors known to limit recovery and plasticity after CNS injury are Nogo (neurite outgrowth inhibitor) and MAG (myelin associated glycoprotein). The effects of these inhibitors on axonal regeneration can be reduced by administration of specific antagonists, some of which are commercially available for experimental investigation. There are three aspects of therapeutic manipulations: targeting the inhibitory proteins, antagonizing the known receptor, and inhibiting the intracellular signal transduction of these inhibitory molecules. Infusion of an antibody against Nogo improves behavioral deficits and enhances corticospinal tract regeneration in animals after stroke and spinal cord injury (SCI). Similarly, peripheral injection of a mouse monoclonal antibody directed against MAG results in dramatic preferential motor reinnervation in mice after transection of the femoral nerve, indicating that interference with the repellant function of MAG facilitates reinnervation of correct pathways by motor neurons. Further, antagonism of the Nogo receptor by the peptide NEP 1-40 (Nogo extracellular peptide residues 1-40) can promote axonal regeneration in rats after SCI. Blockade of signal transduction also can be effective. The p75 neurotrophin receptor probably represents the signaling part of the receptor complex for neurite growth inhibitors. There is evidence in vitro that the inhibitory actions of MAG and myelin are blocked if neurons are primed with a variety of neurotrophins. Thus, there are several therapeutic approaches to overcome the actions of endogenous neurite growth inhibitors so as to promote CNS regeneration.

Exercise reverses ethanol inhibition of neural stem cell proliferation

Neural stem cells in the adult brain may contribute to learning and neural plasticity, to stress-induced neuropathologic changes, to mood and affective disorders, and to other complex brain functions. Learning, an enriched environment, and exercise (as modeled by running) all increase neural stem cell proliferation in the hippocampus and improve performance on learning tests, whereas acute ethanol consumption decreases neural stem cell proliferation in the hippocampus. To explore the interaction of exercise and ethanol consumption (two behaviors important for mental health), C57BL/6 mice were given access to ethanol, a running wheel, or both, and neural stem cell proliferation was investigated in the hippocampal dentate gyrus, corpus callosum, and forebrain subventricular zone of these mice. Mice given access to ethanol consumed large amounts of ethanol, and mice given access to a running wheel ran long distances, with the combined groups' behavior being comparable to that of the ethanol access alone group and of the running wheel access alone group. Neural stem cell proliferation was assessed by treating mice with bromodeoxyuridine (12 days, 300 mg/kg/day, i.p.) and evaluating consequent immunoreactivity. Exercise increased bromodeoxyuridine immunoreactivity in dentate gyrus, but not in other brain regions studied. Self-administration of ethanol decreased bromodeoxyuridine immunoreactivity by approximately 60% (P <.01) in dentate gyrus; 70% (P <.001), in forebrain; and 80% (P <.001), in corpus callosum. Findings for exercise and ethanol consumption combined were remarkably similar to those for exercise alone. The opposing effects of ethanol consumption and exercise on neurogenesis could contribute to the CNS pathology and health benefits, respectively, of these two behaviors.

Ethanol inhibition of neural stem cell differentiation is reduced by neurotrophic factors

BACKGROUND

Ethanol exposure during development leads to various forms of neuronal damage. Because neural stem cells (NSCs) play a pivotal role in the development and maturation of the central nervous system, it is important to understand the effect of ethanol on NSC differentiation. In this study, we investigated the effect of ethanol on differentiation of cultured NSCs in the presence and absence of neurotrophic factors.

METHODS

NSCs were derived from rat embryos on embryonic day 14. Cells were exposed to ethanol with or without neurotrophic factors, insulin-like growth factor-1 (IGF-1), or brain-derived neurotrophic factor (BDNF). The effect of ethanol on differentiation was quantified by measurement of optical density of each sample following to microtubule-associated protein 2 enzyme-linked immunosorbent assay and counting of the number of microtubule-associated protein 2-positive cells microscopically. In addition, cell viability of cultured cortical neurons that were exposed to similar concentrations of ethanol was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay.

RESULTS

Ethanol (20-100 mM) inhibited NSC differentiation induced by basic fibroblast growth factor removal, whereas those concentrations of ethanol did not affect neuronal survival. Both IGF-1 and BDNF promoted generation of neurons in the absence of ethanol. Moreover, they suppressed the inhibitory effect of ethanol on NSC differentiation.

CONCLUSIONS

Ethanol inhibited NSC differentiation at concentrations much lower than what compromised neuronal survival. Ethanol-induced differential inhibition was reduced by both IGF-1 and BDNF. These results suggest that ethanol inhibits stem cell differentiation through alteration of cellular pathways related to neurotrophic factor signaling.

OX40 Signals during Priming on Dendritic Cells Inhibit CD4 T Cell Proliferation: IL-4 Switches off OX40 Signals Enabling Rapid Proliferation of Th2 Effectors

In this study we examined the role and regulation of OX40 signals during CD4 T cell priming on dendritic cells (DCs). Contrary to expectation, OX40-deficient cells proliferated more rapidly than their normal counterparts, particularly when stimulated with peptide in the absence of added cytokines. This proliferative advantage was not apparent for Th2-differentiated cells. When the reasons for this were investigated, we found that the cytokine IL-4 specifically down-regulated expression of OX40 ligand on T, B, and DCs, but not on the CD4(+)CD3(-) cells linked with selection of Th2 cells into the memory compartment. OX40 ligand expression was also down-regulated on rapidly proliferating Th1 effectors. These data are compatible with OX40 signals acting during priming as a check on naive T cell proliferation while T cells integrate additional DC signals. This would serve to limit inappropriate T cell responses. In contrast, OX40 signals from CD4(+)CD3(-) cells located in the outer T zone select proliferating Th2 effectors into the memory T cell pool.

Inhibition of islet amyloid polypeptide fibril formation: a potential role for heteroaromatic interactions

The formation of amyloid fibril is associated with major human diseases, including Alzheimer's disease, prion diseases, and type 2 diabetes. Methods for efficient inhibition of amyloid fibril formation are therefore highly clinically important. A principal approach for the inhibition of amyloid formation is based on the use of modified molecular recognition elements. Here, we demonstrate efficient inhibition of amyloid formation of the type 2 diabetes-related human islet amyloid polypeptide (hIAPP) by a modified aromatic peptide fragment and a small aromatic polyphenol molecule. A molecular recognition assay using peptide array analysis suggested that molecular recognition between hIAPP and its core amyloidogenic module is mediated by aromatic rather than hydrophobic interactions. To study the possible effect of aromatic interactions on inhibition of hIAPP fibril formation, we have used peptide and small molecule inhibitors. The addition of a nonamyloidogenic peptide analogue of the core module NFGAILSS, in which phenylalanine was substituted with tyrosine (NYGAILSS), resulted in substantial inhibition of fibril formation by hIAPP. The inhibition was significantly stronger than the one achieved using a beta-sheet breaker-conjugated peptide NFGAILPP. On the basis of the molecular arrangement of the tyrosine-phenylalanine interaction, we suggest that the inhibition stems from the geometrical constrains of the heteroaromatic benzene-phenol interaction. In line with this notion, we demonstrate remarkable inhibition of hIAPP fibril formation and cytotoxicity toward pancreatic beta-cells by a small polyphenol molecule, the nontoxic phenol red compound. Taken together, our results provide further experimental support for the potential role of aromatic interactions in amyloid formation and establish a novel approach for its inhibition.

Inhibition of Nogo: a key strategy to increase regeneration, plasticity and functional recovery of the lesioned central nervous system

In the adult central nervous system (CNS) myelin and oligodendrocytes, Nogo-A exerts a growth inhibitory function leading to restricted axonal regeneration. After development of different anti-Nogo-A antibodies and other Nogo-A blocking reagents their application has recently been studied in various in vivo animal models of spinal cord injury and stroke. These studies show that intracerebral application of Nogo-A-inactivating reagents leads to enhanced regeneration and compensatory sprouting, structural reorganization or plasticity, and functional recovery as seen in different behavioural analyses.

Genetic manipulation of telomerase in HIV-specific CD8+ T cells: enhanced antiviral functions accompany the increased proliferative potential and telomere length stabilization

A large proportion of the CD8(+) T cell pool in persons chronically infected with HIV consists of cells that show features of replicative senescence, an end stage characterized by irreversible cell cycle arrest, multiple genetic and functional changes, and shortened telomeres. The objective of our research was to determine whether constitutive expression of the gene for the human telomerase (hTERT) can prevent senescence-induced impairments in human virus-specific CD8(+) T cells, particularly in the context of HIV-1 disease. Our results indicate that hTERT-expressing HIV-specific CD8(+) lymphocytes show both an enhanced and sustained capacity to inhibit HIV-1 replication in in vitro coculture experiments, as well as prolonged ability to produce IFN-gamma and TNF-alpha in response to stimulation with HIV-1-derived peptides, as compared with vector-transduced controls. Loss of CD28 expression, the signature change of replicative senescence in cell culture, was retarded in those CD8(+) T cell cultures that had high levels of CD28 at the time of hTERT transduction. These findings suggest that telomere shortening may be the primary driving force behind several aspects of CD8(+) T cell dysfunction associated with replicative senescence. We also demonstrate reduced accumulation of the p16(INK4a) and p21(WAF1) cell cycle inhibitors in hTERT-transduced lymphocytes, providing a possible mechanism by which stable hTERT expression is able to circumvent the senescence barrier in CD8(+) T cells. Given the key role of CD8(+) T cell function in controlling a variety of acute and latent viral infections, approaches to retard the functional decrements associated with replicative senescence may lead to novel types of immunotherapy.

Targeting IL-15 receptor-bearing cells with an antagonist mutant IL-15/Fc protein prevents disease development and progression in murine collagen-induced arthritis

It has been suggested that the inflammatory cytokine IL-15 plays an important role in the development of several autoimmune diseases, including rheumatoid arthritis. We have generated a unique lytic and antagonistic IL-15 mutant/Fcgamma2a fusion protein (CRB-15) that targets the IL-15R. In the present study we examined the effects of targeting the IL-15R on the prevention and treatment of collagen-induced arthritis (CIA) in mice and probed the possible mechanisms of action of this IL-15 mutant/Fcgamma2a protein. Upon immunization with type II collagen, DBA/1 mice develop severe articular inflammation and destruction. Treatment of DBA/1 mice with a brief course of CRB-15 at the time of type II collagen challenge markedly inhibited the incidence and severity of arthritis. Moreover, in animals with ongoing established arthritis, treatment with CRB-15 effectively blocked disease progression compared with that in control-treated animals. The therapeutic effect of CRB-15 on either disease development or disease progression is remarkably stable, because withdrawal of treatment did not lead to disease relapse. A detailed analysis revealed that treatment with CRB-15 decreased synovitis in the joints; reduced bone erosion and cartilage destruction; reduced in situ production of the proinflammatory cytokines TNF-alpha, IL-1beta, IL-6, and IL-17; and decreased the responder frequency of autoreactive T cells. Our study suggests that the effective targeting of IL-15R-triggered events with CRB-15 can be of therapeutic importance in the treatment of rheumatoid arthritis.

An IL-4R alpha allelic variant, I50, acts as a gain-of-function variant relative to V50 for Stat6, but not Th2 differentiation

Signaling through the IL-4R alpha-chain (IL-4Ralpha) is crucial for the development of Th2 cells, central effectors in atopic disease. Alleles of the IL-4Ralpha have been identified that have been variably associated with increased incidence of allergic disease, but there is little direct evidence that any variant is sufficient to alter a target that determines allergic pathophysiology or susceptibility. Variants of IL-4Ralpha encoding isoleucine instead of valine at position 50 (I50 vs V50, respectively) can signal increased Stat6-dependent transcriptional activity, whether in an I50, Q551 or I50, R551 haplotype. Strikingly, signaling through these receptors did not increase the efficiency of Th2 development or the IL-4 mediated repression of Th1 development or a target gene, IL-18Ralpha. Further, IL-4-induced proliferation was similar for Th2 cells independent of the variant expressed. Together these findings indicate that IL-4Ralpha variants that exhibit gain-of-function with respect to Stat6 do not act directly through alterations in Th2/Th1 induction after Ag exposure. The data further suggest that for such variants, any mechanistic involvement is based on a role in cellular targets of Th2 cytokines.

Identification of insulin receptor substrate proteins as key molecules for the TβR‐V/LRP‐1‐mediated growth inhibitory signaling cascade in epithelial and myeloid cells

The type V TGF-beta receptor (TbetaR-V) mediates IGF-independent growth inhibition by IGFBP-3 and mediates growth inhibition by TGF-beta1 in concert with the other TGF-beta receptor types. TbetaR-V was recently found to be identical to LRP-1. Here we find that insulin and (Q3A4Y15L16) IGF-I (an IGF-I analog that has a low affinity for IGFBP-3) antagonize growth inhibition by IGFBP-3 in mink lung epithelial cells (Mv1Lu cells) stimulated by serum. In these cells, IGFBP-3 induces serine-specific dephosphorylation of IRS-1 and IRS-2. The IGFBP-3-induced dephosphorylation of IRS-2 is prevented by cotreatment of cells with insulin, (Q3A4Y15L16) IGF-I, or TbetaR-V/LRP-1 antagonists. The magnitude of the IRS-2 dephosphorylation induced by IGFBP-3 positively correlates with the degree of growth inhibition by IGFBP-3 in Mv1Lu cells and mutant cells derived from Mv1Lu cells. Stable transfection of murine 32D myeloid cells (which lack endogenous IRS proteins and are insensitive to growth inhibition by IGFBP-3) with IRS-1 or IRS-2 cDNA confers sensitivity to growth inhibition by IGFBP-3; this IRS-mediated growth inhibition can be completely reversed by insulin in 32D cells stably expressing IRS-2 and the insulin receptor. These results suggest that IRS-1 and IRS-2 are key molecules for the TbetaR-V/LRP-1-mediated growth inhibitory signaling cascade.

A nuclear localization sequence endows human pancreatic ribonuclease with cytotoxic activity

Some members of the ribonuclease superfamily, such as Onconase, are cytotoxic to cancer cells. This is not the case for human pancreatic ribonuclease. This lack of cytotoxicity is probably a result of the inhibition exerted by the cytosolic ribonuclease inhibitor once the protein has reached the cytosol. Until now, all cytotoxic human pancreatic ribonuclease variants have been described as being resistant to the inhibitor. Here, we report on the characterization of a cytotoxic variant of human pancreatic ribonuclease which has an Arg triplet introduced onto one of its surface-exposed loops. Despite its sensitivity to the inhibitor, this variant, called PE5, was only 5-15 times less cytotoxic than Onconase. When it was taken up by cells, it was only observed within late compartments of the endocytic pathway, probably because the number of molecules transported to the cytosol was too small to allow their visualization. Nuclear import assays showed that the Arg triplet endows PE5 with a nuclear localization signal. In these experiments, PE5 was efficiently transported to the nucleus where it was initially localized in the nucleolus. Although the Arg introduction modified the net charge of the protein and somehow impaired recognition by the cytosolic inhibitor, control variants, which had the same number of charges or were not recognized by the inhibitor, were not toxic. We concluded that targeting a ribonuclease to the nucleus results in cytotoxicity. This effect is probably due to ribonuclease interference with rRNA processing and ribosome assembly within the nucleolus.

Evasion from NK cell immunity by MHC class I chain-related molecules expressing colon adenocarcinoma

Evasion of host immune responses is well documented for viruses and may also occur during tumor immunosurveillance. The mechanisms involve alterations in MHC class I expression, Ag processing and presentation, chemokine and cytokine production, and lymphocyte receptor expression. Epithelial tumors overexpress MHC class I chain-related (MIC) molecules, which are ligands for the activating receptor NKG2D on NK and T cells. We report that NK cells from patients with colorectal cancer lack expression of activating NKG2D and chemokine CXCR1 receptors, both of which are internalized. Serum levels of soluble MIC (sMIC) are elevated and are responsible for down-modulation of NKG2D and CXCR1. In contrast, high serum levels of CXC ligands, IL-8, and epithelial-neutrophil-activating peptide (ENA-78) do not down-modulate CXCR1. In vitro, internalization of NKG2D and CXCR1 occurs within 4 and 24 h, respectively, of incubating normal NK cells with sMIC-containing serum. Furthermore, natural cytotoxicity receptor NKp44 and chemokine receptor CCR7 are also down-modulated in IL-2-activated NK cells cocultured in MIC-containing serum-an effect secondary to the down-modulation of NKG2D and not directly caused by physical association with sMIC. The patients' NK cells up-regulate expression of NKG2D, NKp44, CXCR1, and CCR7 when cultured in normal serum or anti-MIC Ab-treated autologous serum. NKG2D(+) but not NKG2D(-) NK cells are tumoricidal in vitro, and in vivo they selectively traffic to the xenografted carcinoma, form immunological synapse with tumor cells, and significantly retard tumor growth in the SCID mice. These results suggest that circulating sMIC in the cancer patients deactivates NK immunity by down-modulating important activating and chemokine receptors.

Glutathione S-Transferases (GSTs) Inhibit Transcriptional Activation by the Peroxisomal Proliferator-Activated Receptor γ (PPARγ) Ligand, 15-Deoxy-Δ12,14Prostaglandin J2 (15-d-PGJ2)

15-Deoxy-Delta(12,14)prostaglandin J(2) (15-d-PGJ(2)), a terminal metabolite of the J-series cyclopentenone prostaglandins, influences a variety of cellular processes including gene expression, differentiation, growth, and apoptosis. As a ligand of peroxisomal proliferator-activated receptor gamma (PPAR gamma), 15-d-PGJ(2) can transactivate PPAR gamma-responsive promoters. Previously, we showed that multidrug resistance proteins MRP1 and MRP3 attenuate cytotoxic and transactivating activities of 15-d-PGJ(2) in MCF7 breast cancer cells. Attenuation was glutathione-dependent and was associated with formation of the glutathione conjugate of 15-d-PGJ(2), 15-d-PGJ(2)-SG, and its active efflux by MRP. Here we have investigated whether the glutathione S-transferases (GST) can influence biological activities of 15-d-PGJ(2). MCF7 cells were stably transduced with human cytosolic GST isozymes M1a, A1, or P1a. These GSTs had no effect on 15-d-PGJ(2) cytotoxicity when expressed either alone or in combination with MRP1. However, expression of any of the three GSTs significantly inhibited 15-d-PGJ(2)-dependent transactivation of a PPAR gamma-responsive reporter gene. The degree of inhibition correlated with the level of GST expressed. Under physiologic conditions, the nonenzymatic rate of 15-d-PGJ(2) conjugation with glutathione was significant. Of the three GST isozymes, only GSTM1a-1a further stimulated the rate of 15-d-PGJ(2)-SG formation. Moreover, GSTM1a-1a rate enhancement was only a transient burst that was complete within 15 s. Hence, catalysis plays little, if any, role in GST inhibition of 15-d-PGJ(2)-dependent transactivation. In contrast, inhibition of transactivation was associated with strong GST/15-d-PGJ(2) interactions. Potent inhibition by 15-d-PGJ(2) and 15-d-PGJ(2)-SG of GST activity was observed with K(i) in the 0.15-2.0 microM range for the three GST isozymes, results suggesting avid associations between GST and 15-d-PGJ(2) or 15-d-PGJ(2)-SG. Electrospray ionization mass spectrometry (ESI/MS) studies revealed no stable adducts of GST and 15-d-PGJ(2) indicating that GST/15-d-PGJ(2) interactions are primarily noncovalent. These results are consistent with a mechanism of GST-mediated inhibition of transactivation in which GST binds 15-d-PGJ(2) and 15-d-PGJ(2)-SG thereby sequestering the ligands in the cytosol away from their nuclear target, PPAR gamma.

Timing of IFN-beta exposure during human dendritic cell maturation and naive Th cell stimulation has contrasting effects on Th1 subset generation: a role for IFN-beta-mediated regulation of IL-12 family cytokines and IL-18 in naive Th cell differentiation

Type I IFNs, IFN-alpha and IFN-beta, are early effectors of innate immune responses against microbes that can also regulate subsequent adaptive immunity by promoting antimicrobial Th1-type responses. In contrast, the ability of IFN-beta to inhibit autoimmune Th1 responses is thought to account for some of the beneficial effects of IFN-beta therapy in the treatment of relapsing remitting multiple sclerosis. To understand the basis of the paradoxical effects of IFN-beta on the expression of Th1-type immune responses, we developed an in vitro model of monocyte-derived dendritic cell (DC)-dependent, human naive Th cell differentiation, in which one can observe both positive and negative effects of IFN-beta on the generation of Th1 cells. In this model we found that the timing of IFN-beta exposure determines whether IFN-beta will have a positive or a negative effect on naive Th cell differentiation into Th1 cells. Specifically, the presence of IFN-beta during TNF-alpha-induced DC maturation strongly augments the capacity of DC to promote the generation of IFN-gamma-secreting Th1 cells. In contrast, exposure to IFN-beta during mature DC-mediated primary stimulation of naive Th cells has the opposite effect, in that it inhibits Th1 cell polarization and promotes the generation of an IL-10-secreting T cell subset. Studies with blocking mAbs and recombinant cytokines indicate that the mechanism by which IFN-beta mediates these contrasting effects on Th1 cell generation is at least in part by differentially regulating DC expression of IL-12 family cytokines (IL-12 and/or IL-23, and IL-27) and IL-18.

Novel and detrimental effects of lipopolysaccharide on in vitro generation of immature dendritic cells: involvement of mitogen-activated protein kinase p38

Dendritic cells (DCs) are recognized as major players in the regulation of immune responses to a variety of Ags, including bacterial agents. LPS, a Gram-negative bacterial cell wall component, has been shown to fully activate DCs both in vitro and in vivo. LPS-induced DC maturation involves activation of p38, extracellular signal-regulated kinase (ERK)/mitogen-activated protein kinases, and NF-kappaB. Blocking p38 inhibits LPS-induced maturation of DCs. In this study we investigated the role of LPS in the in vitro generation of immature DCs. We report here that in contrast to the observed beneficial effects on DCs, the presence of LPS in monocyte culture retarded the generation of immature DCs. LPS not only impaired the morphology and reduced the yields of the cultured cells, but also inhibited the up-regulation of surface expression of CD1a, costimulatory and adhesion molecules. Furthermore, LPS up-regulated the secretion of IL-1beta, IL-6, IL-8, IL-10, and TNF-alpha; reduced Ag presentation capacity; and inhibited phosphorylation of ERK, but activated p38, leading to a reduced NF-kappaB activity in treated cells. Neutralizing Ab against IL-10, but not other cytokines, partially blocked the effects of LPS. Inhibiting p38 (by inhibitor SB203580) restored the morphology, phenotype, and Ag presentation capacity of LPS-treated cells. SB203580 also inhibited LPS-induced production of IL-1beta, IL-10, and TNF-alpha; enhanced IL-12 production; and recovered the activity of ERK and NF-kappaB. Thus, our study reveals that LPS has dual effects on DCs that are biologically important: activating existing DCs to initiate an immune response, and inhibiting the generation of new DCs to limit such a response.

Cutting Edge: NF-κB2 Is a Negative Regulator of Dendritic Cell Function

RelB, a member of the NF-kappaB family of transcription factors, is essential for dendritic cell (DC) maturation. Recent findings indicate that RelB is exclusively regulated through its interaction with cytoplasmic NF-kappaB2/p100. The studies presented in this report show that DCs lacking NF-kappaB2 have dramatically enhanced RelB activity, associated with increased MHC class II and costimulatory molecule expression and an enhanced ability to induce CD4(+) T cell responses. These studies identify a novel role for NF-kappaB2 in the negative regulation of RelB-induced DC maturation, with critical consequences for the regulation of adaptive immune responses.