CXCL12: Role in neuroinflammation

A novel phthalein component ameliorates neuroinflammation and cognitive dysfunction by suppressing the CXCL12/CXCR4 axis in rats with vascular dementia

ETHNOPHARMACOLOGICAL RELEVANCE

Chuanxiong, a plant of the Umbelliferae family, is a genuine medicinal herb from Sichuan Province. Phthalides are one of its main active components and exhibit good protective effect against cerebrovascular diseases. However, the mechanism by which phthalides exert neuroprotective effects is still largely unclear.

AIM OF THE STUDY

In this study, we extracted a phthalein component (named as QBT) from Ligusticum Chuanxiong, and investigated its neuroprotective effects against vascular dementia (VaD) rats and the underlying mechanism, focusing on the chemokine 12 (CXCL12)/chemokine (C-X-C motif) receptor 4 (CXCR4) axis.

METHODS

A rat model of VaD was established, and treated with QBT. Cognitive dysfunction in VaD rats was assessed using the Y-maze, new object recognition, and Morris water maze tests. Neuronal damage and inflammatory response in VaD rats were examined through Nissl staining, immunofluorescence, enzyme-linked immunospecific assay, and western blotting analysis. Furthermore, the effects of QBT on CXCL12/CXCR4 axis and its downstream signaling pathways, Janus kinase 2 (JAK2)/signal transducers and activators of transcription 3 (STAT3) and phosphatidylinositol 3 kinase (PI3K)/protein kinase B (AKT)/nuclear factor-κB (NF-κB), were investigated in VaD rats and BV2 microglial cells exposed to oxygen glucose deprivation.

RESULTS

QBT significantly alleviated cognitive dysfunction and neuronal damage in VaD rats, along with inhibition of VaD-induced over-activation of microglia and astrocytes and inflammatory response. Moreover, QBT exhibited anti-inflammatory effects by inhibiting the CXCL12/CXCR4 axis and its downstream JAK2/STAT3 and PI3K/AKT/NF-κB pathways, thereby attenuating the neuroinflammatory response both in vivo and in vitro.

CONCLUSION

QBT effectively mitigated neuronal damage and cognitive dysfunction in VaD rats, exerting neuroprotective effects by suppressing neuroinflammatory response through inhibition of the CXCL12/CXCR4 axis.

Loss of microRNA-15a/16-1 function promotes neuropathological and functional recovery in experimental traumatic brain injury

The diffuse axonal damage in white matter and neuronal loss, along with excessive neuroinflammation, hinder long-term functional recovery after traumatic brain injury (TBI). MicroRNAs (miRs) are small noncoding RNAs that negatively regulate protein-coding target genes in a posttranscriptional manner. Recent studies have shown that loss of function of the miR-15a/16-1 cluster reduced neurovascular damage and improved functional recovery in ischemic stroke and vascular dementia. However, the role of the miR-15a/16-1 cluster in neurotrauma is poorly explored. Here, we report that genetic deletion of the miR-15a/16-1 cluster facilitated the recovery of sensorimotor and cognitive functions, alleviated white matter/gray matter lesions, reduced cerebral glial cell activation, and inhibited infiltration of peripheral blood immune cells to brain parenchyma in a murine model of TBI when compared with WT controls. Moreover, intranasal delivery of the miR-15a/16-1 antagomir provided similar brain-protective effects conferred by genetic deletion of the miR-15a/16-1 cluster after experimental TBI, as evidenced by showing improved sensorimotor and cognitive outcomes, better white/gray matter integrity, and less inflammatory responses than the control antagomir-treated mice after brain trauma. miR-15a/16-1 genetic deficiency and miR-15a/16-1 antagomir also significantly suppressed inflammatory mediators in posttrauma brains. These results suggest miR-15a/16-1 as a potential therapeutic target for TBI.

Could Plasma CXCL12 Predict Ventricular Dysfunction in Patients with Severe Myocardial Infarction?

Plasma level of chemokine CXCL12 can predict adverse cardiovascular outcomes in patients with coronary artery disease, but data on its relationship with severity of coronary stenosis in cases of severe myocardial infarction (MI) are scarce and conflicting. The objective of this study was to investigate link between plasma CXCL12 levels and different grades of left ventricular ejection fraction (LVEF) in statin-treated and -untreated patients with severe MI. A total of 198 consecutive patients with first-time severe MI (ST-elevated myocardial infarction [STEMI], n  = 121 and non-ST-elevated myocardial infarction [NSTEMI], n  = 77) were recruited from Coronary Care Unit, King Abdulaziz University Hospital. They have one to two coronary arteries blocked ≥50%, or three arteries blocked 30 to 49%. Demographic and clinical criteria were collected and plasma CXCL12 level was measured. No correlations were detected between demographic and clinical criteria and CXCL12 level. While troponin peaks and LVEF significantly differed between STEMI and NSTEMI patients, CXCL12 level showed nonsignificant changes. Plasma CXCL12 levels decreased significantly in statin-treated patients compared with those untreated. From receiver operating characteristic (ROC) analysis, high CXCL12 levels were associated with no statin therapy. For STEMI and NSTEMI patients, area under the receiver operating characteristic curve for CXCL12 test were 0.685 and 0.820, while sensitivity and specificity values were 75.9 and 54.8%, and 73.1 and 84%, respectively. Plasma CXCL12 levels showed nonsignificant changes with different ranges of LVEF and troponin peaks. In patients with severe MI, irrespective of statin therapy, plasma CXCL12 showed no correlation with different ranges of LVEF suggesting that it cannot predict left ventricular dysfunction in these cases. However, cross-sectional design of this study is a limitation.

Secondary damage and neuroinflammation in the spinal dorsal horn mediate post-thalamic hemorrhagic stroke pain hypersensitivity: SDF1-CXCR4 signaling mediation

Central post-stroke pain (CPSP) is an intractable neuropathic pain, which can be caused by primary lesion of central somatosensory system. It is also a common sequelae of the thalamic hemorrhagic stroke (THS). So far, the underlying mechanisms of CPSP remain largely unknown. Our previous studies have demonstrated that SDF1-CXCR4 signaling in the hemorrhagic region contributes to the maintenance of the THS pain hypersensitivity via mediation of the thalamic neuroinflammation. But whether the spinal dorsal horn, an initial point of spinothalamic tract (STT), suffers from retrograde axonal degeneration from the THS region is still unknown. In this study, neuronal degeneration and loss in the spinal dorsal horn were detected 7 days after the THS caused by intra-thalamic collagenase (ITC) injection by immunohistochemistry, TUNEL staining, electron microscopy, and extracellular multi-electrode array (MEA) recordings, suggesting the occurrence of secondary apoptosis and death of the STT projecting neuronal cell bodies following primary THS via retrograde axonal degeneration. This retrograde degeneration was accompanied by secondary neuroinflammation characterized by an activation of microglial and astrocytic cells and upregulation of SDF1-CXCR4 signaling in the spinal dorsal horn. As a consequence, central sensitization was detected by extracellular MEA recordings of the spinal dorsal horn neurons, characterized by hyperexcitability of both wide dynamic range and nociceptive specific neurons to suprathreshold mechanical stimuli. Finally, it was shown that suppression of spinal neuroinflammation by intrathecal administration of inhibitors of microglia (minocycline) and astrocytes (fluorocitrate) and antagonist of CXCR4 (AMD3100) could block the increase in expression levels of Iba-1, GFAP, SDF1, and CXCR4 proteins in the dorsal spinal cord and ameliorate the THS-induced bilateral mechanical pain hypersensitivity, implicating that, besides the primary damage at the thalamus, spinal secondary damage and neuroinflammation also play the important roles in maintaining the central post-THS pain hypersensitivity. In conclusion, secondary neuronal death and neuroinflammation in the spinal dorsal horn can be induced by primary thalamic neural damage via retrograde axonal degeneration process. SDF1-CXCR4 signaling is involved in the mediation of secondary spinal neuroinflammation and THS pain hypersensitivity. This finding would provide a new therapeutic target for treatment of CPSP at the spinal level.

Extracellular Matrix Biomimetic Hydrogels, Encapsulated with Stromal Cell-Derived Factor 1, Improve the Composition of Foetal Tissue Grafts in a Rodent Model of Parkinson's Disease

Clinical studies have provided evidence for dopamine (DA) cell replacement therapy in Parkinson’s Disease. However, grafts derived from foetal tissue or pluripotent stem cells (PSCs) remain heterogeneous, with a high proportion of non-dopaminergic cells, and display subthreshold reinnervation of target tissues, thereby highlighting the need to identify new strategies to improve graft outcomes. In recent work, Stromal Cell-Derived Factor-1 (SDF1), secreted from meninges, has been shown to exert many roles during ventral midbrain DA development and DA-directed differentiation of PSCs. Related, co-implantation of meningeal cells has been shown to improve neural graft outcomes, however, no direct evidence for the role of SDF1 in neural grafting has been shown. Due to the rapid degradation of SDF1 protein, here, we utilised a hydrogel to entrap the protein and sustain its delivery at the transplant site to assess the impact on DA progenitor differentiation, survival and plasticity. Hydrogels were fabricated from self-assembling peptides (SAP), presenting an epitope for laminin, the brain’s main extracellular matrix protein, thereby providing cell adhesive support for the grafts and additional laminin–integrin signalling to influence cell fate. We show that SDF1 functionalised SAP hydrogels resulted in larger grafts, containing more DA neurons, increased A9 DA specification (the subpopulation of DA neurons responsible for motor function) and enhanced innervation. These findings demonstrate the capacity for functionalised, tissue-specific hydrogels to improve the composition of grafts targeted for neural repair.

SOX17 inhibits proliferation and invasion of neuroblastoma through CXCL12/CXCR4 signaling axis

SOX17 has been shown to be involved in the transcriptional regulation of CXCR4, and CXCL12 functions by binding to its receptor CXCR4. Here, we explored the expression of SOX17 in neuroblastoma (NB), its mutual regulation with CXCL12, and its effects on cancer cell proliferation, migration and invasion. Five human NB cell lines and 15 pairs of NB and adjacent tissue specimens were used, to conduct RT-qPCR, immunohistochemistry, western blot, ELISA, CCK-8, colony formation, Edu, transwell, chromatin immunoprecipitation (ChIP), and dual-luciferase assays, to study the role of SOX17 in NB. SOX17 levels were reduced in both NB tissues and cell lines. SOX17 inhibited NB tumor growth, migration and invasion in vivo and suppressed NB cell proliferation, migration, and invasion in vitro. SOX17 knockdown or overexpression revealed a negative correlation between SOX17 and CXCL12/CXCR4 pathway activation. ChIP and dual-luciferase assays in NB cells demonstrated that SOX17 significantly inhibited CXCL12 gene and protein levels by binding to CXCL12 promoter regions. In vivo and in vitro experiments using the CXCR4 antagonist, AMD3100, demonstrated that cell proliferation, migration and invasion were significantly abrogated by AMD3100 in NB cells with SOX17 knocked down. Further, AMD3100 impaired growth of NB tumors with SOX17 knocked down in mice. Importantly, SOX17 bound to the CXCL12 promoter, which then activated downstream targets to regulate cell viability, proliferation, and migration. In conclusion, our data demonstrate that SOX17 expression is repressed in NB tissues and cells, and that SOX17 suppresses NB tumor formation and proliferation through inhibition of CXCL12/CXCR4 signaling.

LINC00943 knockdown exerts neuroprotective effects in Parkinson's disease through regulates CXCL12 expression by sponging miR-7-5p

BACKGROUND

Parkinson's disease (PD) is a common neurodegenerative movement disorder, but the pathogenesis is still unclear. Long non-coding RNAs (lncRNAs) have been reported to play a prominent role in PD.

OBJECTIVE

This study is designed to explore the role and mechanism of long intergenic non-coding RNA 00943 (LINC00943) in the N-methyl-4-phenylpyridine (MPP⁺)-inducted PD model.

METHODS

LINC00943, microRNA-7-5p (miR-7-5p), and the chemokine (C-X-C motif) ligand 12 (CXCL12, also referred to as SDF-1) level were examined by real-time quantitative polymerase chain reaction (RT-qPCR). Cell viability and apoptosis were analyzed by 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2-H-tetrazolium bromide (MTT), and flow cytometry assays, severally. Protein levels of interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and CXCL12 were assessed by western blot assay. The ROS generation and SOD activity were detected by the corresponding kits. The binding relationship between miR-7-5p and LINC00943 or CXCL12 was predicted by Starbase and then verified by a dual-luciferase reporter and RNA Immunoprecipitation (RIP) assays.

RESULTS

LINC00943 and CXCL12 were increased, and miR-7-5p was decreased in MPP⁺-inducted SK-N-SH cells. LINC00943 silencing promoted cell viability, and repressed apoptosis and the inflammatory response in MPP⁺-treated SK-N-SH cells. The mechanical analysis discovered that LINC00943 acted as a sponge of miR-7-5p to regulate CXCL12 expression.

CONCLUSIONS

LINC00943 knockdown could attenuate MPP⁺-triggered neuron injury by regulating the miR-7-5p/CXCL12 axis, hinting at a promising therapeutic target for PD treatment.

The CXCL12-CXCR4 Signaling Axis Plays a Key Role in Cancer Metastasis and is a Potential Target for Developing Novel Therapeutics against Metastatic Cancer

Metastasis is the main cause of death in cancer patients; there is currently no effective treatment for cancer metastasis. This is primarily due to our insufficient understanding of the metastatic mechanisms in cancer. An increasing number of studies have shown that the C-X-C motif chemokine Ligand 12 (CXCL12) is overexpressed in various tissues and organs. It is a key niche factor that nurtures the pre-metastatic niches (tumorigenic soil) and recruits tumor cells (oncogenic "seeds") to these niches, thereby fostering cancer cell aggression and metastatic capabilities. However, the C-X-C motif chemokine Receptor 4 (CXCR4) is aberrantly overexpressed in various cancer stem/progenitor cells and functions as a CXCL12 receptor. CXCL12 activates CXCR4 as well as multiple downstream multiple tumorigenic signaling pathways, promoting the expression of various oncogenes. Activation of the CXCL12-CXCR4 signaling axis promotes Epithelial-Mesenchymal Transition (EMT) and mobilization of cancer stem/progenitor cells to pre-metastatic niches. It also nurtures cancer cells with high motility, invasion, and dissemination phenotypes, thereby escalating multiple proximal or distal cancer metastasis; this results in poor patient prognosis. Based on this evidence, recent studies have explored either CXCL12- or CXCR4-targeted anti-cancer therapeutics and have achieved promising results in the preclinical trials. Further exploration of this new strategy and its potent therapeutics effect against metastatic cancer through the targeting of the CXCL12- CXCR4 signaling axis may lead to a novel therapy that can clean up the tumor microenvironment ("soil") and kill the cancer cells, particularly the cancer stem/progenitor cells ("seeds"), in cancer patients. Ultimately, this approach has the potential to effectively treat metastatic cancer.

Overexpressed microRNA-103a-3p inhibits acute lower-extremity deep venous thrombosis via inhibition of CXCL12

Studies have shown that microRNAs (miRNAs) participate in almost all pathological and physiological processes including acute lower-extremity deep venous thrombosis (LEDVT). Here, this study was designed to elucidate the possible function of miR-103a-3p in acute LEDVT. Expression of miR-103a-3p and chemokine C-X-C motif ligand 12 (CXCL12) was initially quantified in plasma collected from 81 LEDVT patients. Then LEDVT mouse models were established by injection with 3% sodium pentobarbital. The interaction between miR-103a-3p and CXCL12 was identified by dual-luciferase reporter gene assay. After gain- and loss-of-function studies, interleukin-6 (IL-6) and IL-8 and tissue factor (TF) levels, and expression of plasminogen activator inhibitors (PAIs), von Willebrand factor (vWF), thromboxane A2 (TH-A2), F4/80, IL-12, Arginase-1 (Arg-1) and CD206 were determined using enzyme-linked immunosorbent assay (ELISA), reverse transcription quantitative polymerase chain reaction (RT-qPCR) and western blot analysis, respectively. miR-103a-3p was downregulated, while CXCL12 was upregulated in patients and mice with LEDVT. miR-103a-3p targets CXCL12 and inhibited its expression. Overexpressed miR-103a-3p or downregulated CXCL12 decreased expression of IL-6, IL-8, TF, PAIs, vWF, TH-A2, M1 markers (IL-6 and IL-12), yet increased expression of M2 markers (Arg-1 and CD206) in LEDVT mice. Additionally, upregulated miR-103a-3p or silencing CXCL12 suppressed thrombosis in LEDVT mice. However, overexpression of CXCL12 reversed the tendency mentioned above. Altogether, miR-103a-3p can potentially downregulate CXCL12 expression to disrupt inflammatory response and thrombosis, ultimately preventing the development of LEDVT. Our findings underscore a possible alternative therapeutic strategy to limit LEDVT.

Genetic variant in CXCL12 gene raises susceptibility to HPV infection and squamous intraepithelial lesions development: a case-control study

Background

Human papillomavirus (HPV) is the most common sexually transmitted virus in women worldwide. The persistence of the virus may cause warts that are considered benign lesions and low or high grade intraepithelial lesions (LSIL/HSIL). Immunological system plays an important role in the resolution of infections. In this context, we highlight the chemokines, which are important regulators in the development of viral infections and inflammation. Among which CXCL12 stands out, due to its pro-inflammatory features, acting as chemoattractant recruiting immune cells. Several polymorphisms were identified in CXCL12 gene including rs1801157 in the 3′-untranslated region, which is characterized by a substitution of a guanine for an adenine.

Methods

In this study, 195 women were classified as HPV non-infected and 169 as HPV-infected. HPV-DNA was detected by polymerase chain reaction (PCR) and the polymorphism was assessed in blood cells through restriction fragment length polymorphism analysis.

Results

HPV infection was more incident in women who had more than 4 sexual partners during lifetime (p = 0.007), among those who presented lower number of pregnancies (p = 0.017). HPV was more prevalent among allele A carriers confirmed by logistic regression analysis adjusted for several confounding factors [OR_ADJ = 4.985; CI_95% (2.85–8.72), p < 0.001]. An association between allele A carriers and HSIL development (p = 0.003) was also observed.

Conclusions

In the present study, we demonstrated that CXCL12 rs1801157 is independently associated with HPV infection and exerts influence in HSIL development, suggesting it as a promising susceptibility biomarker for HPV infection and lesions development.

Growth factor therapy sequesters inflammation in affording neuroprotection in cerebrovascular diseases

INTRODUCTION

In recent years, accumulating evidence has demonstrated the key role of inflammation in the progression of cerebrovascular diseases. Inflammation can persist over prolonged period of time after the initial insult providing a wider therapeutic window. Despite the acute endogenous upregulation of many growth factors after the injury, it is not sufficient to protect against inflammation and to regenerate the brain. Therapeutic approaches targeting both dampening inflammation and enhancing growth factors are likely to provide beneficial outcomes in cerebrovascular disease.

AREAS COVERED

In this mini review, we discuss major growth factors and their beneficial properties to combat the inflammation in cerebrovascular diseases. Emerging biotechnologies which facilitate the therapeutic effects of growth factors are also presented in an effort to provide insights into the future combination therapies incorporating both central and peripheral abrogation of inflammation. Expert commentary: Many studies discussed in this review have demonstrated the therapeutic effects of growth factors in treating cerebrovascular diseases. It is unlikely that one growth factor can be used to treat these complex diseases. Combination of growth factors and anti-inflammatory modulators may clinically improve outcomes for patients. In particular, transplantation of stem cells may be able to achieve both goals of modulating inflammation and upregulating growth factors. Large preclinical studies and multiple laboratory collaborations are needed to advance these findings from bench to bedside.

Central SDF-1/CXCL12 expression and its cardiovascular and sympathetic effects: the role of angiotensin II, TNF-α, and MAP kinase signaling

The chemokine stromal cell-derived factor-1 (SDF-1/CXCL12) and its receptors are expressed by neurons and glial cells in cardiovascular autonomic regions of the brain, including the hypothalamic paraventricular nucleus (PVN), and contribute to neurohumoral excitation in rats with ischemia-induced heart failure. The present study examined factors regulating the expression of SDF-1 in the PVN and mechanisms mediating its sympatho-excitatory effects. In urethane anesthetized rats, a 4-h intracerebroventricular (ICV) infusion of angiotensin II (ANG II) or tumor necrosis factor-α (TNF-α) in doses that increase mean blood pressure (MBP) and sympathetic drive increased the expression of SDF-1 in PVN. ICV administration of SDF-1 increased the phosphorylation of p44/42 mitogen-activated protein kinase (MAPK), JNK, and p38 MAPK in PVN, along with MBP, heart rate (HR), and renal sympathetic nerve activity (RSNA), but did not affect total p44/42 MAPK, JNK, and p38 MAPK levels. ICV pretreatment with the selective p44/42 MAPK inhibitor PD98059 prevented the SDF-1-induced increases in MBP, HR, and RSNA; ICV pretreatment with the selective JNK and p38 MAPK inhibitors attenuated but did not block these SDF-1-induced excitatory responses. ICV PD98059 also prevented the sympatho-excitatory response to bilateral PVN microinjections of SDF-1. ICV pretreatment with SDF-1 short-hairpin RNA significantly reduced ANG II- and TNF-α-induced phosphorylation of p44/42 MAPK in PVN. These findings identify TNF-α and ANG II as drivers of SDF-1 expression in PVN and suggest that the full expression of their cardiovascular and sympathetic effects depends upon SDF-1-mediated activation of p44/42 MAPK signaling.

Ischemic brain extract increases SDF-1 expression in astrocytes through the CXCR2/miR-223/miR-27b pathway

Ischemic cerebral stroke is one of the leading global causes of mortality and morbidity. Ischemic preconditioning (IPC) refers to a sublethal ischemia and resulting in tolerance to subsequent severe ischemic injury. Although several pathways are reportedly involved in IPC-mediated neuroprotection, the functional role of astrocytes is not fully understood. Stromal cell-derived factor-1 (SDF-1), a CXC chemokine produced mainly in astrocytes, is a ligand for chemokine receptor CXCR4. SDF-1 is reported to play a critical role in neuroprotection after stroke by mediating the migration of neuronal progenitor cells. We hypothesized that stimuli derived from ischemic brain were involved in the protective effects of IPC. To investigate this hypothesis, the mechanism in which ischemic brain extract (IBE) induced SDF-1 expression was investigated in C6 astrocytoma cells. IBE treatment of C6 cells increased SDF-1 expression compared to that in untreated or normal brain extract (NBE)-treated cells by downregulating SDF-1 targeting miRNA, miR-27b. MiR-223 was inversely upregulated in IBE-treated cells; overexpression of miR-223 decreased the expression of miR-27b by suppressing IKKα expression. Analysis of cytokine array data revealed an IBE associated enhanced expression of CINC-1 (CXCL1) and LIX1 (CXCL5). Knockdown or inhibition of their receptor, CXCR2, abolished IBE-mediated increased expression of SDF-1. These results were confirmed in primary cultured astrocytes. Taken together, the data demonstrate that IBE-elicited signals increase SDF-1 expression through the CXCR2/miR-223/miR-27b pathway in C6 astrocytoma cells and primary astrocytes, supporting the view that increased expression of SDF-1 by ischemic insults is a possible mechanism underlying therapeutic application of IPC.

HIV-associated neuropathogenesis: a systems biology perspective for modeling and therapy

Despite the development of powerful antiretroviral drugs, HIV-1 associated neurological disorders (HAND) will affect approximately half of those infected with HIV-1. Combined anti-retroviral therapy (cART) targets viral replication and increases T-cell counts, but it does not always control macrophage polarization, brain infection or inflammation. Moreover, it remains difficult to identify those at risk for HAND. New therapies that focus on modulating host immune response by making use of biological pathways could prove to be more effective than cART for the treatment of neuroAIDS. Additionally, while numerous HAND biomarkers have been suggested, they are of little use without methods for appropriate data integration and a systems-level interpretation. Machine learning, could be used to develop multifactorial computational models that provide clinicians and researchers with the ability to identify which factors (in what combination and relative importance) are considered important to outcome.

CXCL12-γ expression is inhibited in neuroinflammation

CXCL12 plays a protective role in CNS autoimmunity. Expression of CXCL12-γ, which has distinct structural and functional properties than the other isoforms of CXCL12, was determined in spinal cords of rats immunized to develop experimental autoimmune encephalomyelitis (EAE). CNS expression of CXCL12-γ was markedly lower in EAE-prone Dark Agouti rats than in EAE-resistant Albino Oxford rats, both in spinal cord homogenates and micro-blood vessels isolated from spinal cords. Inhibition of nitric oxide (NO) synthesis in DA rats upregulated, while donation of NO in AO rats downregulated CNS expression of CXCL12-γ. NO inhibited CXCL12-γ expression in astrocytes in vitro. A splice variant of CXCL12-γ which migrates into nucleolus was not detected in spinal cord or astrocytes. Thus, CXCL12-γ is expressed in the CNS after EAE induction, but its expression is markedly suppressed in spinal cord affected with full blown inflammation. NO is an important regulator of CXCL12-γ expression in neuroinflammation.

CXCR7 silencing attenuates cell adaptive response to stromal cell derived factor 1α after hypoxia

Previous studies have shown that chemotactic factor stromal-cell derived factor 1α (SDF1α) promotes cell recovery from hypoxic injury via its main receptor C-X-C chemokine receptor type (CXCR) 4. However, the role of its new receptor CXCR7 on cell repair against hypoxia and cell response to SDF1α remains largely unknown. In this study, neurons induced from hippocampal progenitor cells were pre-conditioned in hypoxia for 4 h and subsequently monitored to investigate the function of SDF1α on cell repair after hypoxia. Neurons were assessed for their cell morphology, actin filament polymerization and migration capability. SDF1α protein levels increased significantly 1 h after hypoxia compared to control (P<0.01), and it reached a peak at 24 h after hypoxia. Moreover, addition of SDF1α promoted neurite outgrowth and actin filament polymerization both in normoxic and hypoxic cells compared to untreated cells. Cell migration showed a time-dependent increase with SDF1α stimulation in both groups, and hypoxic cells illustrated a significant augment at 0.5 h, 1 h and 12 h after SDF1α application compared to normoxic cells (P<0.01). CXCR7 expression also increased with time dependence after hypoxia and demonstrated a two-fold upregulation compared to control at 24 h after hypoxia. With CXCR7 silencing, axon elongation and actin filament polymerization induced by SDF1α were inhibited sharply both in normoxic and hypoxic cells. CXCR7 silencing also leads to reduced hypoxic cell migration at 0.5 h, 1 h, 12 h, 24 h and 36 h after SDF1α application (P<0.01), but it failed to reduce normoxic cell migration induced by SDF1α at 0.5 h, 1 h and 12 h (P>0.05). 24 h SDF1α stimulation led to higher ERK1/2 phosphorylation compared to control, and ERK1/2 phosphorylation increased more in hypoxic cells than that in normoxic cells. This study suggested that CXCR7 plays an important role on cell repair processing induced by SDF1α, and CXCR7 silencing attenuates cell adaptive response to acute SDF1α stimulation (≤12 h) after hypoxia.