Interleukin-6 and cAMP induce stromal cell-derived factor-1 chemotaxis in astroglia by up-regulating CXCR4 cell surface expression. Implications for brain inflammation

Adenylyl cyclase 2 expression and function in neurological diseases

Adenylyl cyclases (Adcys) catalyze the formation of cAMP, a secondary messenger essential for cell survival and neurotransmission pathways in the CNS. Adcy2, one of ten Adcy isoforms, is highly expressed in the CNS. Abnormal Adcy2 expression and mutations have been reported in various neurological disorders in both rodents and humans. However, due to the lack of genetic tools, loss-of-function studies of Adcy2 are scarce. In this review, we summarize recent findings on Adcy2 expression and function in neurological diseases. Specifically, we first introduce the biochemistry, structure, and function of Adcy2 briefly. Next, the expression and association of Adcy2 in human patients and rodent models of neurodegenerative diseases (Alzheimer's disease and Parkinson's disease), psychiatric disorders (Tourette syndrome, schizophrenia, and bipolar disorder), and other neurological conditions (stress-associated disorders, stroke, epilepsy, and Lesch-Nyhan Syndrome) are elaborated. Furthermore, we discuss the pros and cons of current studies as well as key questions that need to be answered in the future. We hope to provide a focused review on Adcy2 that promotes future research in the field.

Differential CXCR4 expression on hematopoietic progenitor cells versus stem cells directs homing and engraftment

Gene therapy involves a substantial loss of hematopoietic stem and progenitor cells (HSPC) during processing and homing. Intra-BM (i.b.m.) transplantation can reduce homing losses, but prior studies have not yielded promising results. We studied the mechanisms involved in homing and engraftment of i.b.m. transplanted and i.v. transplanted genetically modified (GM) human HSPC. We found that i.b.m. HSPC transplantation improved engraftment of hematopoietic progenitor cells (HPC) but not of long-term repopulating hematopoietic stem cells (HSC). Mechanistically, HPC expressed higher functional levels of CXCR4 than HSC, conferring them a retention and homing advantage when transplanted i.b.m. Removing HPC and transplanting an HSC-enriched population i.b.m. significantly increased long-term engraftment over i.v. transplantation. Transient upregulation of CXCR4 on GM HSC-enriched cells, using a noncytotoxic portion of viral protein R (VPR) fused to CXCR4 delivered as a protein in lentiviral particles, resulted in higher homing and long-term engraftment of GM HSC transplanted either i.v. or i.b.m. compared with standard i.v. transplants. Overall, we show a mechanism for why i.b.m. transplants do not significantly improve long-term engraftment over i.v. transplants. I.b.m. transplantation becomes relevant when an HSC-enriched population is delivered. Alternatively, CXCR4 expression on HSC, when transiently increased using a protein delivery method, improves homing and engraftment specifically of GM HSC.

The Role of Tumor-Associated Myeloid Cells in Modulating Cancer Therapy

Myeloid cells include various cellular subtypes that are distinguished into mononuclear and polymorphonuclear cells, derived from either common myeloid progenitor cells (CMPs) or myeloid stem cells. They play pivotal roles in innate immunity since, following invasion by pathogens, myeloid cells are recruited and initiate phagocytosis and secretion of inflammatory cytokines into local tissues. Moreover, mounting evidence suggests that myeloid cells may also regulate cancer development by infiltrating the tumor to directly interact with cancer cells or by affecting the tumor microenvironment. Importantly, mononuclear phagocytes, including macrophages and dendritic cells (DCs), can have either a positive or negative impact on the efficacy of chemotherapy, radiotherapy as well as targeted anti-cancer therapies. Tumor-associated macrophages (TAMs), profusely found in the tumor stroma, can promote resistance to chemotherapeutic drugs, such as Taxol and Paclitaxel, whereas the suppression of TAMs can lead to an improved radiotherapy outcome. On the contrary, the presence of TAMs may be beneficial for targeted therapies as they can facilitate the accumulation of large quantities of nanoparticles carrying therapeutic compounds. Tumor infiltrating DCs, however, are generally thought to enhance cytotoxic therapies, including those using anthracyclines. This review focuses on the role of tumor-infiltrating and stroma myeloid cells in modulating tumor responses to various treatments. We herein report the impact of myeloid cells in a number of therapeutic approaches across a wide range of malignancies, as well as the efforts toward the elimination of myeloid cells or the exploitation of their presence for the enhancement of therapeutic efficacy against cancer.

Loss of Cxcr5 alters neuroblast proliferation and migration in the aged brain

Neurogenesis, the production of new neurons from neural stem cells, dramatically decreases during aging concomitantly with increased inflammation both systemically and in the brain. However, the precise role of inflammation and whether local or systemic factors drive the neurogenic decline during aging is poorly understood. Here, we identify CXCR5/5/CXCL13 signaling as a novel regulator of neurogenesis in the aged brain. The chemokine Cxcl13 was found to be upregulated in the brain during aging. Loss of its receptor, Cxcr5, led to increased proliferation and decreased numbers of neuroblasts in the aged subventricular zone (SVZ), together with accumulation of neuroblasts in the rostral migratory stream and olfactory bulb (OB), without increasing the amount of new mature neurons in the OB. The effect on proliferation and migration was specific to neuroblasts and likely mediated through increased levels of systemic IL-6 and local Cxcl12 expression in the SVZ. Our study raises the possibility of a new mechanism by which interplay between systemic and local alterations in inflammation regulates neurogenesis during aging.

Novel repair mechanisms in a renal ischaemia/reperfusion model: Subsequent saxagliptin treatment modulates the pro-angiogenic GLP-1/cAMP/VEGF, ANP/eNOS/NO, SDF-1α/CXCR4, and Kim-1/STAT3/HIF-1α/VEGF/eNOS pathways

The reno-protective effects of antidiabetic dipeptidyl peptidase (DPP)-4 inhibitors have been studied regarding their antioxidant and anti-inflammatory properties. However, the potential ability of saxagliptin to ameliorate renal injury by enhancing neovascularization has not been elucidated. To address this issue, saxagliptin (10 and 30 mg/kg) was administered to Wistar rats after the induction of renal ischaemia/reperfusion (I/R). Our results showed that saxagliptin operated through different axes to ameliorate I/R injury. By inhibiting DPP-4, saxagliptin maintained stromal cell-derived factor-1α expression and upregulated its chemokine receptor CXCR4 to trigger vasculogenesis through the enhanced migration of endothelial progenitor cells (EPCs). Additionally, this compound rescued the levels of glucagon-like peptide-1 and its downstream mediator cAMP to increase vascular endothelial growth factor (VEGF) and CXCR4 levels. Moreover, saxagliptin stimulated atrial natriuretic peptide/endothelial nitric oxide synthase to increase nitric oxide levels and provoke angiogenesis and renal vasodilation. In addition to inhibiting DPP-4, saxagliptin increased the renal kidney injury molecule-1/pY705-STAT3/hypoxia-inducible factor-1α/VEGF pathway to enhance angiogenesis. Similar to other gliptins, saxagliptin exerted its anti-inflammatory and antioxidant effects by suppressing the renal contents of p (S536)-nuclear factor-κB p65, tumour necrosis factor-α, monocyte chemoattractant protein-1, myeloperoxidase, and malondialdehyde while boosting the glutathione content. These events improved the histological structure and function of the kidney, as evidenced by decreased serum creatinine, blood urea nitrogen, and cystatin C and increased serum albumin. Accordingly, in addition to its anti-inflammatory and antioxidant activities, saxagliptin dose-dependently ameliorated I/R-induced renal damage by enhancing neovascularization through improved tissue perfusion and homing of bone marrow-derived EPCs to mediate repair processes.

Early pancreatic cancer lesions suppress pain through CXCL12-mediated chemoattraction of Schwann cells

Pancreatic ductal adenocarcinoma (PDAC) cells (PCC) have an exceptional propensity to metastasize early into intratumoral, chemokine-secreting nerves. However, we hypothesized the opposite process, that precancerous pancreatic cells secrete chemokines that chemoattract Schwann cells (SC) of nerves and thus induce ready-to-use routes of dissemination in early carcinogenesis. Here we show a peculiar role for the chemokine CXCL12 secreted in early PDAC and for its receptors CXCR4/CXCR7 on SC in the initiation of neural invasion in the cancer precursor stage and the resulting delay in the onset of PDAC-associated pain. SC exhibited cancer- or hypoxia-induced CXCR4/CXCR7 expression in vivo and in vitro and migrated toward CXCL12-expressing PCC. Glia-specific depletion of CXCR4/CXCR7 in mice abrogated the chemoattraction of SC to PCC. PDAC mice with pancreas-specific CXCL12 depletion exhibited diminished SC chemoattraction to pancreatic intraepithelial neoplasia and increased abdominal hypersensitivity caused by augmented spinal astroglial and microglial activity. In PDAC patients, reduced CXCR4/CXCR7 expression in nerves correlated with increased pain. Mechanistically, upon CXCL12 exposure, SC down-regulated the expression of several pain-associated targets. Therefore, PDAC-derived CXCL12 seems to induce tumor infiltration by SC during early carcinogenesis and to attenuate pain, possibly resulting in delayed diagnosis in PDAC.

Vildagliptin reduces plasma stromal cell-derived factor-1α in patients with type 2 diabetes compared with glimepiride

AIMS/INTRODUCTION

Dipeptidyl peptidase-4 inhibitors might have pleiotropic protective effects on cardiovascular disease (CVD), in contrast to sulfonylureas. Therefore, we compared various CVD risk factors between vildagliptin and glimepiride.

MATERIALS AND METHODS

We carried out a randomized, prospective and crossover trial. A total of 16 patients with type 2 diabetes whose glycated hemoglobin was >7% were randomized to add vildagliptin or glimepiride. After 12-week treatment, each drug was replaced with the other for another 12 weeks. Before and after each treatment, glucose homeostasis and CVD risk factors were assessed, and the continuous glucose monitoring system was applied to calculate glycemic variability.

RESULTS

The mean age of the participants was 60 years, 31% were men, body mass index 25.5 kg/m² and HbA1c 8.41%. Both vildagliptin and glimepiride significantly decreased glycated hemoglobin and glycemic variability indices. Despite the improved glucose homeostasis, favorable change of CVD markers was not prominent in both the arms, along with significant weight gain. Only plasma stromal cell-derived factor (SDF)-1α decreased by 30% in the vildagliptin arm. According to regression analyses, the reduction of SDF-1α was independently associated with vildagliptin usage and serum interleukin-6 changes, but white blood cells were not related with the SDF-1α changes.

CONCLUSION

Compared with glimepiride, vildagliptin arrestingly decreased plasma SDF-1α, and its clinical implications should be further investigated.

New insights into perineural invasion of pancreatic cancer: More than pain

Pancreatic cancer is one of the most malignant human tumors. Perineural invasion, whereby a cancer cell invades the perineural spaces surrounding nerves, is acknowledged as a gradual contributor to cancer aggressiveness. Furthermore, perineural invasion is considered one of the root causes of the recurrence and metastasis observed after pancreatic resection, and it is also an independent predictor of prognosis. Advanced research has demonstrated that the neural microenvironment is closely associated with perineural invasion in pancreatic cancer. Therapy targeting the molecular mechanism of perineural invasion may enable the durable clinical treatment of this formidable disease. This review provides an overview of the present status of perineural invasion, the relevant molecular mechanisms of perineural invasion, pain and hyperglycemia associated with perineural invasion in pancreatic cancer, and the targeted therapeutics based on these studies.

Astrocytes, therapeutic targets for neuroprotection and neurorestoration in ischemic stroke

Astrocytes are the most abundant cell type within the central nervous system. They play essential roles in maintaining normal brain function, as they are a critical structural and functional part of the tripartite synapses and the neurovascular unit, and communicate with neurons, oligodendrocytes and endothelial cells. After an ischemic stroke, astrocytes perform multiple functions both detrimental and beneficial, for neuronal survival during the acute phase. Aspects of the astrocytic inflammatory response to stroke may aggravate the ischemic lesion, but astrocytes also provide benefit for neuroprotection, by limiting lesion extension via anti-excitotoxicity effects and releasing neurotrophins. Similarly, during the late recovery phase after stroke, the glial scar may obstruct axonal regeneration and subsequently reduce the functional outcome; however, astrocytes also contribute to angiogenesis, neurogenesis, synaptogenesis, and axonal remodeling, and thereby promote neurological recovery. Thus, the pivotal involvement of astrocytes in normal brain function and responses to an ischemic lesion designates them as excellent therapeutic targets to improve functional outcome following stroke. In this review, we will focus on functions of astrocytes and astrocyte-mediated events during stroke and recovery. We will provide an overview of approaches on how to reduce the detrimental effects and amplify the beneficial effects of astrocytes on neuroprotection and on neurorestoration post stroke, which may lead to novel and clinically relevant therapies for stroke.

Strawberry notch homolog 2 is a novel inflammatory response factor predominantly but not exclusively expressed by astrocytes in the central nervous system

Interleukin‐6 (IL‐6) participates in the host response to injury and infection in the central nervous system (CNS). We identified strawberry notch homolog 2 (Sbno2) as an IL‐6‐stimulated gene in murine astrocytes. Sbno2 is a mouse homolog of the sno gene in Drosophila but little is known about the regulation or function of the mammalian gene. Here we examined the regulation of the Sbno2 gene in astrocytes in vitro and in the murine CNS following systemic endotoxin administration. In murine and human cultured astrocytes, Sbno2 gene expression was significantly upregulated in a dose‐ and time‐dependent fashion by hyper‐IL‐6 (IL‐6 + soluble IL‐6 receptor). The level of Sbno2 mRNA was also upregulated significantly in murine astrocytes by other glycoprotein130 cytokine‐family members and the pro‐inflammatory cytokines interleukin‐1 beta and tumor necrosis factor alpha. These changes were reflected by corresponding alterations in the level of the SBNO2 protein. Inhibiting protein synthesis resulted in higher Sbno2 mRNA and did not abolish the upregulation of Sbno2 mRNA mediated by hyper‐IL‐6. Inhibition of transcription led to a rapid reduction in hyper‐IL‐6‐induced Sbno2 mRNA in astrocytes suggesting that the Sbno2 mRNA is quite unstable. Following intra‐peritoneal lipopolysaccharide injection in mice, Sbno2 mRNA levels in the brain were significantly increased. Cellular localization studies revealed that this increase in Sbno2 mRNA occurred predominantly in astrocytes and in the choroid plexus and in some microglia, endothelial cells, and neurons. These findings are consistent with SBNO2 functioning as an acute inflammatory response gene in astrocytes as well as other cells in the CNS. GLIA 2015;63:1738–1752

Stromal-derived factor-1α/CXCL12-CXCR4 chemotactic pathway promotes perineural invasion in pancreatic cancer

Perineural invasion (PNI) is considered as an alternative route for the metastatic spread of pancreatic cancer cells; however, the molecular changes leading to PNI are still poorly understood. In this study, we show that the CXCL12/CXCR4 axis plays a pivotal role in the neurotropism of pancreatic cancer cells to local peripheral nerves. Immunohistochemical staining results revealed that CXCR4 elevation correlated with PNI in 78 pancreatic cancer samples. Both in vitro and in vivo PNI models were applied to investigate the function of the CXCL12/CXCR4 signaling in PNI progression and pathogenesis. The results showed that the activation of the CXCL12/CXCR4 axis significantly increased pancreatic cancer cells invasion and promoted the outgrowth of the dorsal root ganglia. CXCL12 derived from the peripheral nerves stimulated the invasion and chemotactic migration of CXCR4-positive cancer cells in a paracrine manner, eventually leading to PNI. In vivo analyses revealed that the abrogation of the activated signaling inhibited tumor growth and invasion of the sciatic nerve toward the spinal cord. These data indicate that the CXCL12/CXCR4 axis may be a novel therapeutic target to prevent the perineural dissemination of pancreatic cancer.

Absence of CCL2 and CCL3 Ameliorates Central Nervous System Grey Matter But Not White Matter Demyelination in the Presence of an Intact Blood-Brain Barrier

A broad spectrum of diseases is characterized by myelin abnormalities, oligodendrocyte pathology, and concomitant glia activation, among multiple sclerosis (MS). Our knowledge regarding the factors triggering gliosis and demyelination is scanty. Chemokines are pivotal for microglia and astrocyte activation and orchestrate critical steps during the formation of central nervous system (CNS) demyelinating lesions. Redundant functions of chemokines complicate, however, the study of their functional relevance. We used the cuprizone model to study redundant functions of two chemokines, CCL2/MCP1 and CCL3/MIP1α, which are critically involved in the pathological process of cuprizone-induced demyelination. First, we generated a mutant mouse strain lacking functional genes of both chemokines and demonstrated that double-mutant animals are viable, fertile, and do not present with gross abnormalities. Astrocytes and peritoneal macrophages, cultured form tissues of these animals did neither express CCL2 nor CCL3. Exposure to cuprizone resulted in increased CCL2 and CCL3 brain levels in wild-type but not mutant animals. Cuprizone-induced demyelination, oligodendrocyte loss, and astrogliosis were significantly ameliorated in the cortex but not corpus callosum of chemokine-deficient animals. In summary, we provide a novel powerful model to study the redundant function of two important chemokines. Our study reveals that chemokine function in the CNS redounds to region-specific pathophysiological events.

Radiation therapy-induced tumor invasiveness is associated with SDF-1-regulated macrophage mobilization and vasculogenesis

Radiation therapy (RT) remains the front-line treatment for high-grade gliomas; however, tumor recurrence remains the main obstacle for the clinical success of RT. Using a murine astrocytoma tumor cell line, ALTS1C1, the present study demonstrates that whole brain irradiation prolonged the survival of tumor-bearing mice, although the mice eventually died associated with increased tumor infiltration. Immunohistochemical (IHC) analysis indicated that RT decreased the microvascular density (MVD) of the primary tumor core, but increased the MVD of the tumor invasion front. RT also increased the number of tumor-associated macrophages (TAMs) and the expression of stromal cell-derived factor-1 (SDF-1) and hypoxia-inducible factor-1 (HIF-1) at the tumor invasion front. SDF-1 expression suppressed by siRNA (SDFkd tumors) showed a decrease in RT-enhanced tumor invasiveness, leading to prolonged survival of mice bearing these tumors. The invasion front in SDFkd tumors showed a lower MVD and TAM density than that in the islands of the control or irradiated ALTS1C1 tumors. Our results indicate that tumor-secreted SDF-1 is one key factor in RT-induced tumor invasiveness, and that it exerts its effect likely through macrophage mobilization and tumor revascularization.

The presumed atypical chemokine receptor CXCR7 signals through G(i/o) proteins in primary rodent astrocytes and human glioma cells

SDF-1/CXCL12 binds to the chemokine receptors, CXCR4 and CXCR7, and controls cell proliferation and migration during development, tumorigenesis, and inflammatory processes. It is currently assumed that CXCR7 would represent an atypical or scavenger chemokine receptor which modulates the function of CXCR4. Contrasting this view, we demonstrated recently that CXCR7 actively mediates SDF-1 signaling in primary astrocytes. Here, we provide evidence that CXCR7 affects astrocytic cell signaling and function through pertussis toxin-sensitive G(i/o) proteins. SDF-1-dependent activation of G(i/o) proteins and subsequent increases in intracellular Ca(2+) concentration persisted in primary rodent astrocytes with depleted expression of CXCR4, but were abolished in astrocytes with depleted expression of CXCR7. Moreover, CXCR7-mediated effects of SDF-1 on Erk and Akt signaling as well as on astrocytic proliferation and migration were all sensitive to pertussis toxin. Likewise, pertussis toxin abolished SDF-1-induced activation of Erk and Akt in CXCR7-only expressing human glioma cell lines. Finally, consistent with a ligand-biased function of CXCR7 in astrocytes, the alternate CXCR7 ligand, I-TAC/CXCL11, activated Erk and Akt through β-arrestin. The demonstration that SDF-1-bound CXCR7 activates G(i/o) proteins in astrocytes could help to explain some discrepancies previously observed for the function of CXCR4 and CXCR7 in other cell types.

Lipocalin-2 Is a chemokine inducer in the central nervous system: role of chemokine ligand 10 (CXCL10) in lipocalin-2-induced cell migration

The secreted protein lipocalin-2 (LCN2) has been implicated in diverse cellular processes, including cell morphology and migration. Little is known, however, about the role of LCN2 in the CNS. Here, we show that LCN2 promotes cell migration through up-regulation of chemokines in brain. Studies using cultured glial cells, microvascular endothelial cells, and neuronal cells suggest that LCN2 may act as a chemokine inducer on the multiple cell types in the CNS. In particular, up-regulation of CXCL10 by JAK2/STAT3 and IKK/NF-κB pathways in astrocytes played a pivotal role in LCN2-induced cell migration. The cell migration-promoting activity of LCN2 in the CNS was verified in vivo using mouse models. The expression of LCN2 was notably increased in brain following LPS injection or focal injury. Mice lacking LCN2 showed the impaired migration of astrocytes to injury sites with a reduced CXCL10 expression in the neuroinflammation or injury models. Thus, the LCN2 proteins, secreted under inflammatory conditions, may amplify neuroinflammation by inducing CNS cells to secrete chemokines such as CXCL10, which recruit additional inflammatory cells.

Interleukin-6, a mental cytokine

Almost a quarter of a century ago, interleukin-6 (IL-6) was discovered as an inflammatory cytokine involved in B cell differentiation. Today, IL-6 is recognized to be a highly versatile cytokine, with pleiotropic actions not only in immune cells, but also in other cell types, such as cells of the central nervous system (CNS). The first evidence implicating IL-6 in brain-related processes originated from its dysregulated expression in several neurological disorders such as multiple sclerosis, Alzheimer's disease and Parkinson's disease. In addition, IL-6 was shown to be involved in multiple physiological CNS processes such as neuron homeostasis, astrogliogenesis and neuronal differentiation. The molecular mechanisms underlying IL-6 functions in the brain have only recently started to emerge. In this review, an overview of the latest discoveries concerning the actions of IL-6 in the nervous system is provided. The central position of IL-6 in the neuroinflammatory reaction pattern, and more specifically, the role of IL-6 in specific neurodegenerative processes, which accompany Alzheimer's disease, multiple sclerosis and excitotoxicity, are discussed. It is evident that IL-6 has a dichotomic action in the CNS, displaying neurotrophic properties on the one hand, and detrimental actions on the other. This is in agreement with its central role in neuroinflammation, which evolved as a beneficial process, aimed at maintaining tissue homeostasis, but which can become malignant when exaggerated. In this perspective, it is not surprising that 'well-meant' actions of IL-6 are often causing harm instead of leading to recovery.

Putative mechanisms of cognitive dysfunction in chemotherapy-naïve diffuse large B-cell lymphoma: a case report and review of the literature

Cognitive impairment is now recognized as a frequent consequence of treatments for cancers localized outside the central nervous system (CNS). In contrast, little attention has been given to the potentially deleterious cognitive effects from non-CNS cancers themselves. The present case study proposes that cognitive deficits occur in a subset of treatment-naive patients with diffuse large B-cell lymphoma in whom no gross evidence of lymphoma-related CNS involvement is apparent. Evidence is presented from a case study and elaborate putative mechanisms centering on deleterious effects of B-cell-mediated inflammatory cytokine secretion on neurons. Moreover, this case study speculates that genetic variability involving apolipoprotein E or other factors may mediate cognitive variability among these patients.

CXCR7 is an active component of SDF-1 signalling in astrocytes and Schwann cells

The alternative SDF-1 (stromal cell derived factor-1) receptor, CXCR7, has been suggested to act as either a scavenger of extracellular SDF-1 or a modulator of the primary SDF-1 receptor, CXCR4. CXCR7, however, also directly affects the function of various tumor-cell types. Here, we demonstrate that CXCR7 is an active component of SDF-1 signalling in astrocytes and Schwann cells. Cultured cortical astrocytes and peripheral nerve Schwann cells exhibit comparable total and cell-surface levels of expression of both SDF-1 receptors. Stimulation of astrocytes with SDF-1 resulted in the temporary activation of Erk1/2, Akt and PKCzeta/lambda, but not p38 and PKCalpha/beta. Schwann cells showed SDF-1-induced activation of Erk1/2, Akt and p38, but not PKCalpha/beta and PKCzeta/lambda. The respective signalling pattern remained fully inducible in astrocytes from CXCR4-deficient mice, but was abrogated following depletion of astrocytic CXCR7 by RNAi. In Schwann cells, RNAi-mediated depletion of either CXCR4 or CXCR7 silenced SDF-1 signalling. The findings of the astrocytic receptor-depletion experiments were reproduced by CXCR7 antagonist CCX754, but not by CXCR4 antagonist AMD3100, both of which abolished astrocytic SDF-1 signalling. Further underlining the functional importance of CXCR7 signalling in glial cells, we show that the mitogenic effects of SDF-1 on both glial cell types are impaired upon depleting CXCR7.

Nuclear factor-kappaB activation regulates cyclooxygenase-2 induction in human astrocytes in response to CXCL12: role in neuronal toxicity

Neurodegenerative and neuroinflammatory disorders are commonly associated with local chemokine release. In other way, emerging data indicate that the prostaglandin E2 (PGE(2)), one of the major prostaglandins produced in the brain, play a central role in several pathological diseases. In this study, we investigated the relationship between CXCL12, cyclooxygenase (COX)-2 and PGE(2) in human brain cells. CXCL12 induced COX-2 and secretion of PGE(2) in a dose-dependent manner in human astrocytes. This induction was abolished by treatment with pertussis toxin and AMD3100, confirming the role of CXCR4 signaling. The nuclear factor-kappaB involvement was confirmed by using pyrrolidine dithiocarbamate, and with transient transfection assays. Over-expression of inhibitory proteins of nuclear factor-kappaB abrogated COX-2 induction, and CXCL12 induced p65/relA translocation. Culture supernatants from CXCL12-treated astrocytes reduced viability of neuroblastoma cells, and COX inhibitors abrogated this toxicity. Therefore, the relationship between chemokines and PGs could differentially influence the pathogenic network responsible for neurodegeneration.

Spatio-temporal changes of SDF1 and its CXCR4 receptor in the dorsal root ganglia following unilateral sciatic nerve injury as a model of neuropathic pain

There is a growing evidence that chemokines and their receptors play a role in inducing and maintaining neuropathic pain. In the present study, unilateral chronic constriction injury (CCI) of rat sciatic nerve under aseptic conditions was used to investigate changes for stromal derived factor-1 (SDF1) and its CXCR4 receptor in lumbal (L4-L5) and cervical (C7-C8) dorsal root ganglia (DRG) from both sides of naïve, CCI-operated and sham-operated rats. All CCI-operated rats displayed mechanical allodynia and thermal hyperalgesia in hind paws ipsilateral to CCI, but forepaws exhibited only temporal changes of sensitivity not correlated with alterations in SDF1 and CXCR4 proteins. Naïve DRG displayed immunofluorescence for SDF1 (SDF1-IF) in the satellite glial cells (SGC) and CXCR4-IF in the neuronal bodies with highest intensity in small- and medium-sized neurons. Immunofluorescence staining and Western blot analysis confirmed that unilateral CCI induced bilateral alterations of SDF1 and CXCR4 proteins in both L4-L5 and C7-C8 DRG. Only lumbal DRG were invaded by ED-1+ macrophages exhibiting SDF1-IF while elevation of CXCR4-IF was found in DRG neurons and SGC but not in ED-1+ macrophages. No attenuation of mechanical allodynia, but reversed thermal hyperalgesia, in ipsi- and contralateral hind paws was found in CCI-operated rats after i.p. administration of CXCR4 antagonist (AMD3100). These results indicate that SDF1/CXCR4 changes are not limited to DRG associated with injured nerve but that they also spread to DRG non-associated with such nerve. Functional involvement of these alterations in DRG non-associated with injured nerve in neuropathic pain remains to be elucidated.

Dexamethasone and hypoxia upregulate CXCR4 expression in myeloma cells

We investigated the modulation of CXCR4 expression by cytokines, dexamethasone, and hypoxia in myeloma cells in vitro. Tumor necrosis factor-alpha (TNF-alpha), transforming growth factor-beta1 (TGF-beta1), and vascular endothelial growth factor (VEGF) enhanced CXCR4 expression in RPMI8226 cells. In the myeloma cell lines examined and primary bone marrow (BM) CD138+ cells, dexamethasone enhanced CXCR4 expression both in the cytoplasm and on the cell surface, while downregulating SDF-1 expression and secretion in BM stromal cells. Incubation of cells under hypoxic conditions (1% O(2)) also induced upregulation of CXCR4 in the cytoplasm and on the cell surface and enhanced chemotaxis in response to stromal cell-derived factor-1 (SDF-1). Cell surface CXCR4 expression was more prominent in annexin V-positive apoptotic cells. Given the roles of the SDF-1/CXCR4 axis in the development and progression of myeloma, CXCR4-downregulating agents may enhance the antitumor effects of dexamethasone.

Chemokines released from astrocytes promote chemokine receptor 5-mediated neuronal cell differentiation

Astrocytes are one of major glial cell types in the central nervous system (CNS), and can support many functions of neuronal cells. In the present study, we demonstrated that the differentiation of rat embryonic neuronal cells was promoted by treatment with astrocyte and microglia-conditioned medium. Cytokine assays identified that the IL-4, MIP-1, KC, and RANTES as were released from astrocyte, and these chemokines promote differentiation of rat embryonic neuronal cells. However, chemokine-promoted neuronal cell differentiation was suppressed by antibodies of these chemokines and their receptor (CCR5). CCR5 and neuronal cell differentiation marker proteins were found to be colocalized, and their expressions were enhanced by chemokines. Furthermore, the differentiation of neuronal cells from CCR5 knock-out mice and of neuronal cells from mice knocked down with the CCR5 siRNA were significantly reduced and delayed. Bradykinin elevated calcium influx in the embryonic neuronal cells. These data suggest that specific chemokines derived from astrocytes may significantly have influence on the CCR5-mediated differentiation of embryonic neuronal cells.

Cytokines and myelination in the central nervous system

Myelin abnormalities that reflect damage to developing and mature brains are often found in neurological diseases with evidence of inflammatory infiltration and microglial activation. Many cytokines are virtually undetectable in the uninflamed central nervous system (CNS), so that their rapid induction and sustained elevation in immune and glial cells contributes to dysregulation of the inflammatory response and neural cell homeostasis. This results in aberrant neural cell development, cytotoxicity, and loss of the primary myelin-producing cells of the CNS, the oligodendrocytes. This article provides an overview of cytokine and chemokine activity in the CNS with relevance to clinical conditions of neonatal and adult demyelinating disease, brain trauma, and mental disorders with observed white matter defects. Experimental models that mimic human disease have been developed in order to study pathogenic and therapeutic mechanisms, but have shown mixed success in clinical application. However, genetically altered animals, and models of CNS inflammation and demyelination, have offered great insight into the complexities of neuroimmune interactions that impact oligodendrocyte function. The intracellular signaling pathways of selected cytokines have also been highlighted to illustrate current knowledge of receptor-mediated events. By learning to interpret the actions of cytokines and by improving methods to target appropriate predictors of disease risk selectively, a more comprehensive understanding of altered immunoregulation will aid in the development of advanced treatment options for patients with inflammatory white matter disorders.

Interleukin-6 acts in the fashion of a classical chemokine on monocytic cells by inducing integrin activation, cell adhesion, actin polymerization, chemotaxis, and transmigration

Macrophages contribute to the innate immune response by eliminating bacteria, viral particles, and apoptotic bodies. They develop from circulating monocytes. In case of an infection, monocytes attach to the endothelial cells of the blood vessels, migrate along the endothelial cells, leave the circulatory system to enter the inflammatory tissue, and differentiate into macrophages. Cell migration is induced frequently by chemokines that act through G-protein-coupled receptors. Only a few cytokines signaling through single-transmembrane domain receptors have been shown to induce cell migration. Often, this potential depends on the induction of classical chemokines and is not a direct cellular effect. Here, we discovered IL-6 as a potent stimulant for monocytic cell migration. Furthermore, we present data about IL-6-induced integrin activation, cell attachment, actin polymerization, fibronectin-dependent migration, and transmigration through a layer of endothelial cells. Our results show that IL-6 fulfills all biological properties to mediate cell migration of monocytic cells, which may contribute to the proinflammatory potential of IL-6.

Functional reconstitution of the human chemokine receptor CXCR4 with G(i)/G (o)-proteins in Sf9 insect cells

The chemokine stromal cell-derived factor-1alpha (SDF-1alpha) binds to the chemokine receptor CXCR4 that couples to pertussis toxin-sensitive G-proteins of the G(i)/G(o)-family. CXCR4 plays a role in the pathogenesis of autoimmune diseases, human immunodeficiency virus infection and various tumors, fetal development as well as endothelial progenitor and T-cell recruitment. To this end, most CXCR4 studies have focused on the cellular level. The aim of this study was to establish a reconstitution system for the human CXCR4 that allows for the analysis of receptor/G-protein coupling at the membrane level. We wished to study specifically constitutive CXCR4 activity and the G-protein-specificity of CXCR4. We co-expressed N- and C-terminally epitope-tagged human CXCR4 with various G(i)/G(o)-proteins and regulator of G-protein signaling (RGS)-proteins in Sf9 insect cells. Expression of CXCR4, G-proteins, and RGS-proteins was verified by immunoblotting. CXCR4 coupled more effectively to Galpha(i1) and Galpha(i2) than to Galpha(i3) and Galpha(o) and insect cell G-proteins as assessed by SDF-1alpha-stimulated high-affinity steady-state GTP hydrolysis. The RGS-proteins RGS4 and GAIP enhanced SDF-1alpha-stimulated GTP hydrolysis. SDF-1alpha stimulated [(35)S]guanosine 5'-[gamma-thio]triphosphate (GTPgammaS) binding to Galpha(i2). RGS4 did not enhance GTPgammaS binding. Na(+) salts of halides did not reduce basal GTPase activity. The bicyclam, 1-[[1,4,8,11-tetrazacyclotetradec-1-ylmethyl)phenyl]methyl]-1,4,8,11-tetrazacyclotetradecane (AMD3100), acted as CXCR4 antagonist but was devoid of inverse agonistic activity. Halides reduced the maximum SDF-1alpha-stimulated GTP hydrolysis in the order of efficacy I(-) > Br(-) > Cl(-). In addition, salts reduced the potency of SDF-1alpha at activating GTP hydrolysis. From our data, we conclude the following: (1) Sf9 cells are a suitable system for expression of functionally intact human CXCR4; (2) Human CXCR4 couples effectively to Galpha(i1) and Galpha(i2); (3) There is no evidence for constitutive activity of CXCR4; (4) RGS-proteins enhance agonist-stimulated GTP hydrolysis, showing that GTP hydrolysis becomes rate-limiting in the presence of SDF-1alpha; (5) By analogy to previous observations made for the beta(2)-adrenoceptor coupled to G(s), the inhibitory effects of halides on agonist-stimulated GTP hydrolysis may be due to increased GDP-affinity of G(i)-proteins, reducing the efficacy of CXCR4 at stimulating nucleotide exchange.

Tonic activation of CXC chemokine receptor 4 in immature granule cells supports neurogenesis in the adult dentate gyrus

Stromal-cell-derived factor-1 (SDF-1) and its receptor CXC chemokine receptor 4 (CXCR4) play a well-established role during embryonic development of dentate gyrus granule cells. However, little is known about the regulation and function of CXCR4 in the postnatal dentate gyrus. Here, we identify a striking mismatch between intense CXCR4 mRNA and limited CXCR4 protein expression in adult rat subgranular layer (SGL) neurons. We demonstrate that CXCR4 protein expression in SGL neurons is progressively lost during postnatal day 15 (P15) to P21. This loss of CXCR4 protein expression was paralleled by a reduction in the number of SDF-1-responsive SGL neurons and a massive upregulation of SDF-1 mRNA in granule cells. Intraventricular infusion of the CXCR4-antagonist AMD3100 dramatically increased CXCR4 protein expression in SGL neurons, suggesting that CXCR4 is tonically activated and downregulated by endogenous SDF-1. Infusion of AMD3100 also facilitated detection of CXCR4 protein in bromodeoxyuridine-, nestin-, and doublecortin-labeled cells and showed that the vast majority of adult-born granule cells transiently expressed CXCR4. Chronic AMD3100 administration impaired formation of new granule cells as well as neurogenesis-dependent long-term recognition of novel objects. Therefore, our findings suggest that tonic activation of CXCR4 in newly formed granule cells by endogenous SDF-1 is essential for neurogenesis-dependent long-term memory in the adult hippocampus.

Antiinflammatory cAMP signaling and cell migration genes co-opted by the anthrax bacillus

Bacillus anthracis, the etiologic agent of anthrax, avoids immune surveillance and commandeers host macrophages as a vehicle for lymphatic spreading. Here, we show that B. anthracis edema toxin (ET), via its adenylyl cyclase activity, dramatically increases the motility of infected macrophages and the expression of vascular endothelial growth factor. The transcription factor CREB and the syndecan-1 gene, a CREB target, play crucial roles in ET-induced macrophage migration. These molecular and cellular responses occur in macrophages engaged in antiinflammatory G protein-coupled receptor activation, thus illustrating a common signaling circuitry controlling resolution of inflammation and host cell hijacking by B. anthracis.

Stromal-derived factor-1 and inflammatory cytokines in retinal vein occlusion

PURPOSE

To identify the roles of stromal-derived factor (SDF-1) and inflammatory cytokines in retinal vein occlusion (RVO).

METHODS

Samples were collected by vitrectomy and the levels of SDF-1, vascular endothelial growth factor, and inflammatory cytokines (interleukins [IL-1beta, IL-6, IL-8, IL-10, IL-12p70]; tumor necrosis factor-alpha) were measured in 20 eyes with RVO, and 9 eyes with epiretinal membrane served as negative controls. Four eyes with inflammatory diseases were also investigated.

RESULTS

SDF-1 levels in active RVO (A-RVO; 4 eyes with iris neovascularization) were significantly higher than those in quiescent RVO (Q-RVO; 16 eyes without iris neovascularization) and the negative controls (p < .01), whereas there were no significant difference between the Q-RVO and the negative controls. There were no significant correlations between the concentrations of SDF-1 and other cytokines.

CONCLUSIONS

Elevation of intravitreous SDF-1 levels in A-RVO but not Q-RVO suggested a pivotal role of SDF-1 in angiogenic changes during RVO.

Multiple roles of chemokine CXCL12 in the central nervous system: a migration from immunology to neurobiology

Chemotactic cytokines (chemokines) have been traditionally defined as small (10-14kDa) secreted leukocyte chemoattractants. However, chemokines and their cognate receptors are constitutively expressed in the central nervous system (CNS) where immune activities are under stringent control. Why and how the CNS uses the chemokine system to carry out its complex physiological functions has intrigued neurobiologists. Here, we focus on chemokine CXCL12 and its receptor CXCR4 that have been widely characterized in peripheral tissues and delineate their main functions in the CNS. Extensive evidence supports CXCL12 as a key regulator for early development of the CNS. CXCR4 signaling is required for the migration of neuronal precursors, axon guidance/pathfinding and maintenance of neural progenitor cells (NPCs). In the mature CNS, CXCL12 modulates neurotransmission, neurotoxicity and neuroglial interactions. Thus, chemokines represent an inherent system that helps establish and maintain CNS homeostasis. In addition, growing evidence implicates altered expression of CXCL12 and CXCR4 in the pathogenesis of CNS disorders such as HIV-associated encephalopathy, brain tumor, stroke and multiple sclerosis (MS), making them the plausible targets for future pharmacological intervention.

Astrocytes--friends or foes in multiple sclerosis?

In multiple sclerosis (MS), the presence of demyelinating plaques has concentrated researchers' minds on the role of the oligodendrocyte in its pathophysiology. Recently, with the rediscovery of early and widespread loss of axons in the disease, new emphasis has been put on the role of axons and axon-oligodendrocyte interactions in MS. Despite the fact that, in 1904, Müller claimed that MS was a disease of astrocytes, more recently, astrocytes have taken a back seat, except as the cells that form the final glial scar after all hope of demyelination is over. However, perhaps it is time for the return of the astrocyte to popularity in the pathogenesis of MS, with recent reports on the dual role of astrocytes in aiding degeneration and demyelination, by promoting inflammation, damage of oligodendrocytes and axons, and glial scarring, but also in creating a permissive environment for remyelination by their action on oligodendrocyte precursor migration, oligodendrocyte proliferation, and differentiation. We review these findings to try to provide a cogent view of astrocytes in the pathology of MS.

Expression profiling identifies a molecular signature of reactive astrocytes stimulated by cyclic AMP or proinflammatory cytokines

Specialized glia, termed reactive astrocytes, accompany numerous pathologic conditions affecting the central nervous system, including stroke, multiple sclerosis, and neoplasia. To better define this important cell type, we employed high-density microarray gene expression profiling using two in vitro models of reactive gliosis (stimulation with dbcAMP or IL-1beta/IFNgamma). We identified 44 differentially expressed transcripts common to both in vitro models and demonstrated that a subset of these genes are also differentially expressed in response to experimental autoimmune encephalomyelitis and focal cerebral ischemia in vivo. Moreover, this pattern of differential gene expression is not observed in hyperproliferating or neoplastic glia.

The CXCR5 chemokine receptor is expressed by carcinoma cells and promotes growth of colon carcinoma in the liver

The chemokine receptor CXCR5 is expressed by B cells and certain T cells and controls their migration into and within lymph nodes. Its ligand BCA-1/CXCL13 is present in lymph nodes and spleen and also in the liver. Surprisingly, we detected CXCR5 in several mouse and human carcinoma cell lines. CXCR5 was particularly prominent in pancreatic carcinoma cell lines and was also detected by immunohistochemistry in 7 of 18 human pancreatic carcinoma tissues. Expression in CT26 colon carcinoma was low in vitro, up-regulated in vivo, and rapidly lost when cells were explanted in vitro. CXCL13 strongly promoted proliferation of CXCR5-transfected CT26 cells in vitro. In the liver, after intrasplenic injection, these CXCR5 transfectants initially grew faster than controls, but the growth rate of control tumors accelerated later to become similar to the transfectants, likely due to the up-regulation of CXCR5. Inhibition of CXCR5 function, by trapping CXCR5 in the endoplasmic reticulum using a CXCL13-KDEL "intrakine," had no effect on initial growth of liver foci but later caused a prolonged growth arrest. In contrast, s.c. and lung tumors of CXCR5- and intrakine-transfected cells grew at similar rates as controls. We conclude that expression of CXCR5 on tumor cells promotes the growth of tumor cells in the liver and, at least for CT26 cells, seems to be required for outgrowth to large liver tumors. Given the limited expression on normal cells, CXCR5 may constitute an attractive target for therapy, particularly for pancreatic carcinoma.

Autocrine factors that sustain glioma invasion and paracrine biology in the brain microenvironment

Invasion is a defining hallmark of glioblastoma multiforme, just as metastasis characterizes other high-grade tumors. Glial tumors invariably recur due to the regrowth of invasive cells, which are unaffected by standard treatment modalities. Drivers of glioma invasion include autocrine signals propagated by secreted factors that signal through receptors on the tumor. These secreted factors are able to diffuse through the peritumoral stroma, thereby influencing parenchymal cells that surround the tumor mass. Here we describe various autocrine motility factors that are expressed by invasive glioma cells and explore the effects that they may have on normal cells present in the path of invasion. Conversely, normal brain parenchymal cells secrete ligands that can stimulate receptors on invasive glioma cells and potentially facilitate glioma invasion or create a permissive microenvironment for malignant progression. Parallel observations have been made for solid tumors of epithelial origin, in which parenchymal and stromal cells either support or suppress tumor invasion. Most autocrine and paracrine interactions involved in glioma invasion constitute known signaling systems in stages of central nervous system development that involve the migration of precursor cells that populate the developing brain. Key paracrine interactions between glioma cells and the brain microenvironment can influence glioma pathobiology and therefore contribute to its poor prognosis. Current therapies for glioma that could have an impact on paracrine communication between tumors and normal cells are discussed. We suggest that cells in the normal brain parenchyma be considered as potential targets for adjuvant therapies to control glioma growth because such cells are less likely to develop resistance than glioma cells.

Neuronal chemokines: versatile messengers in central nervous system cell interaction

Whereas chemokines are well known for their ability to induce cell migration, only recently it became evident that chemokines also control a variety of other cell functions and are versatile messengers in the interaction between a diversity of cell types. In the central nervous system (CNS), chemokines are generally found under both physiological and pathological conditions. Whereas many reports describe chemokine expression in astrocytes and microglia and their role in the migration of leukocytes into the CNS, only few studies describe chemokine expression in neurons. Nevertheless, the expression of neuronal chemokines and the corresponding chemokine receptors in CNS cells under physiological and pathological conditions indicates that neuronal chemokines contribute to CNS cell interaction. In this study, we review recent studies describing neuronal chemokine expression and discuss potential roles of neuronal chemokines in neuron-astrocyte, neuron-microglia, and neuron-neuron interaction.

Progesterone reduces the migration of mast cells toward the chemokine stromal cell-derived factor-1/CXCL12 with an accompanying decrease in CXCR4 receptors

Mast cell recruitment is implicated in many physiological functions and several diseases. It depends on microenvironmental factors, including hormones. We have investigated the effect of progesterone on the migration of HMC-1(560) mast cells toward CXCL12, a chemokine that controls the migration of mast cells into tissues. HMC-1(560) mast cells were incubated with 1 nM to 1 microM progesterone for 24 h. Controls were run without progesterone. Cell migration toward CXCL12 was monitored with an in vitro assay, and statistical analysis of repeated experiments revealed that progesterone significantly reduced cell migration without increasing the number of apoptotic cells (P = 0.0084, n = 7). Differences between progesterone-treated and untreated cells were significant at 1 microM (P < 0.01, n = 7). Cells incubated with 1 microM progesterone showed no rearrangment of actin filaments in response to CXCL12. Progesterone also reduced the calcium response to CXCL12 and Akt phosphorylation. Cells incubated with progesterone had one-half the control concentrations of CXCR4 (mRNA, total protein, and membrane-bound protein). Progesterone also inhibited the migration of HMC-1(560) cells transfected with hPR-B-pSG5 plasmid, which contained 2.5 times as much PR-B as the control. These transfected cells responded differently (P < 0.05, n = 5) from untreated cells to 1 nM progesterone. We conclude that progesterone reduces mast cell migration toward CXCL12 and that CXCR4 may be a progesterone target in mast cells.

Adenosine upregulates CXCR4 and enhances the proliferative and migratory responses of human carcinoma cells to CXCL12/SDF-1alpha

The level of expression of the chemokine receptor CXCR4 has been shown to play a crucial role in determining the ability of cancer cells to metastasize from the primary tumor and become established in tissue sites that are rich in the CXCR4 ligand CXCL12/SDF-1alpha. High CXCR4 expression on cancer cells is associated with an increased risk of recurrence and poorer overall survival. We propose that local tissue mediators within the primary tumor or at secondary sites may modulate the level of CXCR4 expression and, therefore, potentially affect the ability of the cancer cells to metastasize. The purine nucleoside adenine-9-beta-D-ribofuranoside (adenosine) is generated at high concentrations within the extracellular fluid of solid tumors because of their hypoxia. We show here that adenosine acts through A(2A) and A(2B) adenosine receptors on human colorectal carcinoma cells to upregulate CXCR4 mRNA expression up to 10-fold and selectively increases cell-surface CXCR4 protein up to 3-fold. This increase in cell-surface CXCR4 enables the carcinoma cells to migrate toward CXCL12, and enhances their proliferation in response to CXCL12. Adenosine may therefore be one of the factors within the tumor microenvironment that facilitates tumor dissemination, by upregulating CXCR4 on certain cancer cells and enhancing cellular responses to CXCL12.

A role for CXCL12 (SDF-1alpha) in the pathogenesis of multiple sclerosis: regulation of CXCL12 expression in astrocytes by soluble myelin basic protein

The pathogenic mechanisms that contribute to multiple sclerosis (MS) include leukocyte chemotaxis into the central nervous system (CNS) and the production of inflammatory mediators, resulting in oligodendrocyte damage, demyelination, and neuronal injury. Thus, factors that regulate leukocyte entry may contribute to early events in MS, as well as to later stages of lesion pathogenesis. CXCL12 (SDF-1alpha), a chemokine essential in CNS development and a chemoattractant for resting and activated T cells, as well as monocytes, is constitutively expressed at low levels in the CNS and has been implicated in T cell and monocyte baseline trafficking. To determine whether CXCL12 is increased in MS, immunohistochemical analyses of lesions of chronic active and chronic silent MS were performed. CXCL12 protein was detected on endothelial cells (EC) in blood vessels within normal human brain sections and on a small number of astrocytes within the brain parenchyma. In active MS lesions, CXCL12 levels were high on astrocytes throughout lesion areas and on some monocytes/macrophages within vessels and perivascular cuffs, with lesser staining on EC. In silent MS lesions, CXCL12 staining was less than that observed in active MS lesions, and also was detected on EC and astrocytes, particularly hypertrophic astrocytes near the lesion edge. Experiments in vitro demonstrated that IL-1beta and myelin basic protein (MBP) induced CXCL12 in astrocytes by signaling pathways involving ERK and PI3-K. Human umbilical vein EC did not produce CXCL12 after treatment with MBP or IL-1beta. However, these EC cultures expressed CXCR4, the receptor for CXCL12, suggesting that this chemokine may activate EC to produce other mediators involved in MS. In agreement, EC treatment with CXCL12 was found to upregulate CCL2 (MCP-1) and CXCL8 (IL-8) by PI3-K and p38-dependent mechanisms. Our findings suggest that increased CXCL12 may initiate and augment the inflammatory response during MS.

Mice deficient in the chemokine receptor CXCR4 exhibit impaired limb innervation and myogenesis

The chemokine CXCL12/SDF-1 and its receptor CXCR4 regulate the development and the function of the hematopoietic system and control morphogenesis of distinct brain areas. Here, we demonstrate that inactivation of CXCR4 results in a massive loss of spinal cord motoneurons and dorsal root ganglion neurons and, subsequently, in a reduced innervation of the developing mouse fore- and hindlimbs. However, only the death of sensory neurons seems to be a direct consequence of receptor inactivation as suggested by the observations that DRG neurons, but not motoneurons, of wild-type animals express CXCR4 and respond to CXCL12 with an increase in cell survival. In contrast, the increased death of motoneurons in CXCR4-deficient animals seems to result from impaired limb myogenesis and a subsequent loss of muscle-derived neurotrophic support. In summary, our findings unravel a previously unrecognized complex role of CXCL12/CXCR4 in the control of limb neuromuscular development.

Andrograpanin, a compound isolated from anti-inflammatory traditional Chinese medicine Andrographis paniculata, enhances chemokine SDF-1alpha-induced leukocytes chemotaxis

Andrographis paniculata is a traditional Chinese medicine (TCM) that has been effectively used for treatment of infection, inflammation, cold, fever, and diarrhea in China. However, mechanism of its therapeutic function is not well known. In the current study, we showed one of its components, andrograpanin, could enhance chemokine stromal cell-derived factor-1alpha (SDF-1alpha) induced chemotaxis in Jurkat and THP-1 cells. Further study demonstrated that this kind of effect was CXC chemokine receptor-4 (CXCR4) specific, since andrograpanin could not enhance other chemokines, such as RANTES, monocyte chemotactic protein-1 (MCP-1), etc. induced cell chemotaxis. Mechanisms of andrograpanin exerting its effect were not directly in the receptor and G protein coupling level because it had no effect on the binding of SDF-1 to CXCR4, SDF-1 induced G protein activation and adenyly cyclase inhibition. However, receptor internalization might be involved, since we found it significantly reduced SDF-1alpha-induced CXCR4 internalization.

cAMP-induced PKCzeta activation increases functional CXCR4 expression on human CD34+ hematopoietic progenitors

Chemokines are key regulators of hematopoiesis and host defense. We report here that functional expression of the chemokine receptor CXCR4 on human immature CD34+ hematopoietic progenitors was increased as a result of sustained elevation in cellular cAMP by dbcAMP and prostaglandin E2. This effect of cAMP was specifically mediated by PKCzeta activity. CXCR4 expression and PKCzeta activation by cAMP were decreased after the inhibition of cAMP effector-Rap1 by Spa1 overexpression. Interference with the activation of Rac1, a downstream target of Rap1, prevented the cAMP-induced increase in PKCzeta activity and CXCR4 levels. Functional manifestation of the effects of cAMP-elevating agents revealed an increased ability of human CD34+ cells to transmigrate the bone marrow (BM) endothelial layer and adhere to BM stroma in vitro, and it augmented the homing potential to the BM and spleens of immunodeficient mice in a Rac1- and a PKCzeta-dependent manner. cAMP- and TNFalpha-stimulated pathways converged in PKCzeta-activated CXCR4 expression and MMP-2/MMP-9 secretion. cAMP treatment had a beneficial effect on CD34+ cell survival in a PKCzeta-mediated fashion. Taken together, our data reveal major roles for cAMP-induced PKCzeta activation in signaling governing the motility and development of CD34+ cells.

Enhanced production of interleukin 6 in peripheral blood monocytes stimulated with mucins secreted into the bloodstream

PURPOSE

It has been reported that tumor progression is correlated with the serum level of interleukin 6 (IL-6). The purpose of this study was to investigate by what mechanism, other than production from tumor cell, the serum level of IL-6 is elevated in the tumor-bearing state.

EXPERIMENTAL DESIGN

Monocytes from healthy donors were cultured in the presence of sera from colon cancer patients, and the activity to elevate IL-6 production was estimated. This activity of serum was also examined after various biochemical treatments.

RESULTS

When monocytes from healthy donors were cultured in the presence of sera from patients with colon cancer, secretion of IL-6 from the cells was markedly elevated. Serum proteins were fractionated on Sepharose 4B and the activity to elevate IL-6 production was found in the excluded fractions. Sialyl Tn antigen was detected in these same fractions. By excluding some mucins from the serum, the inducing activity was reduced to 40% of the original level. Furthermore, we purified mucins from the conditioned medium of colon cancer cells. Production of IL-6 was effectively elevated by a small amount of purified mucins in a dose-dependent manner. When the inducing activity was examined in the presence of binding or competitive inhibitors to the scavenger receptor, the effect was remarkably reduced.

CONCLUSIONS

Mucins secreted from colon cancer cells into the bloodstream induce production of IL-6 in peripheral blood monocytes through the scavenger receptor, which may be responsible for the high level of serum IL-6 in colon cancer patients.

Chemokine-induced recruitment of genetically modified bone marrow cells into the CNS of GM1-gangliosidosis mice corrects neuronal pathology

Bone marrow cells (BMCs) could correct some pathologic conditions of the central nervous system (CNS) if these cells would effectively repopulate the brain. One such condition is G(M1)-gangliosidosis, a neurodegenerative glycosphingolipidosis due to deficiency of lysosomal beta-galactosidase (beta-gal). In this disease, abnormal build up of G(M1)-ganglioside in the endoplasmic reticulum of brain cells results in calcium imbalance, induction of an unfolded protein response (UPR), and neuronal apoptosis. These processes are accompanied by the activation/proliferation of microglia and the production of inflammatory cytokines. Here we demonstrate that local neuroinflammation promotes the selective activation of chemokines, such as stromal-cell-derived factor 1 (SDF-1), macrophage inflammatory protein 1-alpha (MIP-1alpha), and MIP-1beta, which chemoattract genetically modified BMCs into the CNS. Mice that underwent bone marrow transplantation showed increased beta-gal activity in different brain regions and reduced lysosomal storage. Decreased production of chemokines and effectors of the UPR as well as restoration of neurologic functions accompanied this phenotypic reversion. Our results suggest that beta-gal-expressing bone marrow (BM)-derived cells selectively migrate to the CNS under a gradient of chemokines and become a source of correcting enzyme to deficient neurons. Thus, a disease condition such as G(M1)-gangliosidosis, which is characterized by neurodegeneration and neuroinflammation, may influence the response of the CNS to ex vivo gene therapy.

Expression of CXCR4 and Its Down-Regulation by IFN-γ in Head and Neck Squamous Cell Carcinoma

PURPOSE

The functional expression of CXCR4, which plays roles in cell migration and proliferation in response to its unique ligand stromal cell-derived factor-1 (SDF-1), has been reported in variety of carcinomas. However, CXCR4 expression and its functional role in head and neck squamous cell carcinomas (HNSCC) remain unclear. In this study, we investigated CXCR4 expression and analyzed its functions in HNSCC cell lines. We also attempted to regulate CXCR4 expression using cytokines, such as interleukin-1beta, tumor necrosis factor-alpha, and IFN-gamma. Finally, we investigated correlation between CXCR4 expression and clinical features in patients with HNSCC.

EXPERIMENTAL DESIGN

Six HNSCC cell lines were used in this study. Reverse transcription-PCR and flow cytometry analysis were shown for CXCR4 expressions with or without stimulations of cytokines. SDF-1-mediated cell migration was assayed in Matrigel-coated chemotaxis chamber. The SDF-1-mediated cell proliferation was analyzed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The SDF-1-mediated signaling pathways were analyzed by Western blot analysis. Biopsy specimens from 56 patients with HNSCC were used for immunohistologic analysis.

RESULTS

The significant CXCR4 expression was found in HSQ-89, IMC-3, and Nakamura cells. The SDF-1-mediated cell migration and proliferation were observed in CXCR4-positive cells. SDF-1 also promoted rapid phosphorylation of extracellular signal-regulated kinase 1/2 and Akt signaling pathways in CXCR4-positive cells. The SDF-1-mediated cell migration and proliferation of CXCR4-positive cells were inhibited by neutralization of CXCR4. Among three cytokines tested, IFN-gamma significantly reduced CXCR4 expression and SDF-1-induced cell migration and proliferation of CXCR4-positive cells. Immunohistologic analysis revealed that patients with advanced neck status and patients who developed distant metastases showed significantly higher CXCR4 expression, and the cause-specific survival of patients with CXCR4-expression was significantly shorter. Furthermore, multivariate analysis confirmed that CXCR4 positive was the independent factor for cause-specific death.

CONCLUSION

Our results may provide an insight into future therapeutic agent that inhibits tumor metastasis and progression via down-regulating CXCR4 expression in patients with HNSCC.

In vivo cytokine secretion and NF-kappaB activation around titanium and copper implants

The early biological response at titanium (Ti), copper (Cu)-coated Ti and sham sites was evaluated in an in vivo rat model. Material surface chemical and topographical properties were characterized using Auger electron spectroscopy, energy dispersive X-ray spectroscopy and interferometry, respectively. The number of leukocytes, cell types and cell viability (release of lactate dehydrogenase) were determined in the implant-interface exudate. The contents of activated nuclear transcription factor NF-kappaB, interleukin-6 (IL-6) and interleukin-10 (IL-10) were determined by enzyme linked immunosorbent assay. An increase in the number of leukocytes, in particular, polymorphonuclear leukocytes, was observed between 12 and 48 h around Cu. A marked decrease of exudate cell viability was found around Cu after 48 h. The total amounts of activated NF-kappaB after 12 h was highest in Ti exudates whereas after 48 h the highest amount of NF-kappaB was detected around Cu. The levels of cytokine IL-6 were consistently high around Cu at both time periods. No differences in IL-10 contents were detected, irrespective of material/sham and time. The results show that materials with different toxicity grades (titanium with low and copper with high toxicity) exhibit early differences in the activation of NF-kappaB, extracellular expression and secretion of mediators, causing major differences in inflammatory cell accumulation and death in vivo.

Laminar shear stress inhibits CXCR4 expression on endothelial cells: functional consequences for atherogenesis

Laminar shear stress (LSS) represents a major athero-protective stimulus. However, the mechanisms for this effect are poorly characterized. As chemokine receptors modulate endothelial cell functions, we hypothesized that at least some LSS effects on endothelial cells (ECs) may be due to LSS-dependent changes in chemokine receptor expression and function. Exposure of Human umbilical vein endothelial cells (HUVECs) to 15 dynes/cm2/sec(-1) LSS strongly inhibited CXC chemokine receptor 4 (CXCR4) expression at the transcriptional level and impaired stromal-derived factor (SDF)-1/CXCL12-driven chemotaxis. On the contrary, low shear stress (SS; 4 dynes/cm2/sec(-1)) only marginally affected CXCR4 expression when compared with static control cells. Differently from CXCR4, the expression of SDF-1 mRNA was not affected by LSS treatment. CXCR4 overexpression induced a dose-dependent endothelial cell apoptosis that was enhanced by SDF-1 treatment and was caspase-dependent. CXCR4 overexpression inhibited the LSS-mediated antiapoptotic effect on ECs and was associated to impairment of LSS-induced ERK1/2 phosphorylation. These findings suggest that LSS-induced CXCR4 down-regulation may contribute to endothelial cell survival. Interestingly, the expression of the proatherogenic chemokines MCP-1 and IL-8 was induced by SDF-1 treatment and by CXCR4 overexpression in HUVECs. Further, the known LSS-induced inhibition of MCP-1 expression was impaired in CXCR4 overexpressing ECs. Finally, CXCR4 was abundantly expressed by human atherosclerotic plaque endothelium that is exposed to low/absent shear stress, while it was poorly expressed by minimally diseased carotid artery endothelium. In conclusion, LSS-dependent CXCR4 down-regulation may contribute to atheroprotection by favoring the integrity of the endothelial barrier and by inhibiting MCP-1 and IL-8 expression.