Chemokine-like factor 1, a novel cytokine, induces nerve cell migration through the non-extracellular Ca2+-dependent tyrosine kinases pathway

CKLF1 in cardiovascular and cerebrovascular diseases

Chemokine like factor 1 (CKLF1) is a novel atypical chemokine, playing a crucial role in cardiovascular and cerebrovascular diseases (CCVDs) demonstrated by a growing body of works. In cardiovascular diseases including atherosclerosis and myocardial infarction, meanwhile in cerebrovascular diseases such as ischemic stroke and hemorrhagic stroke, the expression levels of CKLF1 change markedly, which triggers downstream signaling pathways by binding with its functional receptors, and then exerts multiple effects to participate in the occurrence and development of these CCVDs. The functional roles of CKLF1 are dynamic and CKLF1 may act as a double-edged sword. The CCVDs-promoting role is related to recruiting inflammatory cells, enhancing the proliferation of vascular smooth muscle cells and endothelial cells, while the CCVDs-suppressing role may correlate with migration of nerve cells and promotion of hematopoietic stem cell proliferation which contributes to disease recovery. Based on this, the paper intends to review expression shifts, potential roles, and molecular mechanisms of CKLF1 in CCVDs, and the current status of CKLF1 targeted therapeutic strategies is also included. We hope this review may provide a valuable reference for using CKLF1 as a diagnostic and prognostic biomarker for CCVDs or developing novel treatments.

The origin, evolution, and molecular diversity of the chemokine system

Chemokine signalling performs key functions in cell migration via chemoattraction, such as attracting leukocytes to the site of infection during host defence. The system consists of a ligand, the chemokine, usually secreted outside the cell, and a chemokine receptor on the surface of a target cell that recognises the ligand. Several noncanonical components interact with the system. These include a variety of molecules that usually share some degree of sequence similarity with canonical components and, in some cases, are known to bind to canonical components and/or to modulate cell migration. Whereas canonical components have been described in vertebrate lineages, the distribution of the noncanonical components is less clear. Uncertainty over the relationships between canonical and noncanonical components hampers our understanding of the evolution of the system. We used phylogenetic methods, including gene-tree to species-tree reconciliation, to untangle the relationships between canonical and noncanonical components, identify gene duplication events, and clarify the origin of the system. We found that unrelated ligand groups independently evolved chemokine-like functions. We found noncanonical ligands outside vertebrates, such as TAFA "chemokines" found in urochordates. In contrast, all receptor groups are vertebrate-specific and all-except ACKR1-originated from a common ancestor in early vertebrates. Both ligand and receptor copy numbers expanded through gene duplication events at the base of jawed vertebrates, with subsequent waves of innovation occurring in bony fish and mammals.

Role of chemokine-like factor 1 as an inflammatory marker in diseases

Immunoinflammatory mechanisms have been incrementally found to be involved in the pathogenesis of multiple diseases, with chemokines being the main drivers of immune cell infiltration in the inflammatory response. Chemokine-like factor 1 (CKLF1), a novel chemokine, is highly expressed in the human peripheral blood leukocytes and exerts broad-spectrum chemotactic and pro-proliferative effects by activating multiple downstream signaling pathways upon binding to its functional receptors. Furthermore, the relationship between CKLF1 overexpression and various systemic diseases has been demonstrated in both in vivo and in vitro experiments. In this context, it is promising that clarifying the downstream mechanism of CKLF1 and identifying its upstream regulatory sites can yield new strategies for targeted therapeutics of immunoinflammatory diseases.

CKLF1 Enhances Inflammation-Mediated Carcinogenesis and Prevents Doxorubicin-Induced Apoptosis via IL6/STAT3 Signaling in HCC

PURPOSE

Hepatocellular carcinoma (HCC), one of the most common and deadliest malignancies worldwide, has a poor prognosis, owing to its high potential for vascular invasion and metastasis and the lack of biomarkers for early diagnosis. Thus, it must be a crucial factor for investigating therapeutic strategies for HCC to identify the functional molecular targets. Here, we reported a novel chemokine, CKLF1, that might act as a pivotal modulator in the invasion and metastasis of HCC and could serve as an attractive target for cancer therapy.

EXPERIMENTAL DESIGN

Bioinformatics analysis, PCR, Western blotting, and IHC were performed to detect the expression of CKLF1 in HCC. The function of CKLF1 was demonstrated by a series of in vitro and in vivo experiments. Pharmacologic treatment, flow cytometry, and Western blotting were carried out to demonstrate the potential mechanisms of CKLF1.

RESULTS

We proved that CKLF1 was overexpressed in HCC tissues and was related to tumor stage, vascular invasion, and patient survival. Then, functional assays showed that CKLF1 promoted hepatocellular carcinogenesis and metastatic potential. Finally, the IL6/STAT3 signaling pathway was involved in the mechanistic investigation. The results demonstrated that CKLF1 enhanced the progression of HCC and prevented doxorubicin-induced apoptosis through activating the IL6/STAT3 pathway.

CONCLUSIONS

These data showed that CKLF1 inhibited apoptosis and promoted malignant transformation through the IL6/STAT3 pathway, and ultimately enhanced the development and metastasis of HCC. Thus, our work revealed that CKLF1 was a significant prognostic factor of HCC and might be a potential molecular therapeutic target for HCC.

IMM-H004, a coumarin derivative, attenuated brain ischemia/reperfusion injuries and subsequent inflammation in spontaneously hypertensive rats through inhibition of VCAM-1

We studied the effect of IMM-H004 in treating brain I/R injury in spontaneously hypertensive rats and showed that IMM-H004 could efficiently ameliorate neurological defects and infarct volume in a time and dose dependent manner.

Phosphodiesterase-4D Knock-down in the Prefrontal Cortex Alleviates Chronic Unpredictable Stress-Induced Depressive-Like Behaviors and Memory Deficits in Mice

Phosphodiesterase 4 (PDE4) has four isoforms (PDE4A-D) with at least 25 splice variants. PDE4 subtype nonselective inhibitors produce potent antidepressant-like and cognition-enhancing effects via increased intracellular cyclic AMP (cAMP) signaling in the brain. Our previous data have demonstrated that long-form PDE4Ds appear to be involved in these pharmacological properties of PDE4 inhibitors in the normal animals. However, it is not clear whether long-form PDE4Ds are critical for the behaviors and related cellular signaling/neuronal plasticity/neuroendocrine alterations in the depressed animals. In the present study, animals exposed to the chronic unpredictable stress (CUS), a rodent model of depression, exhibited elevated corticosterone, depressive-like behavior, memory deficits, accompanied with decreased cAMP-PKA-CREB and cAMP-ERK1/2-CREB signaling and neuroplasticity. These alterations induced by CUS were reversed by RNA interference (RNAi)-mediated prefrontal cortex long-form PDE4Ds (especially PDE4D4 and PDE4D5) knock-down, similar to the effects of the PDE4 subtype nonselective inhibitor rolipram. Furthermore, these effects of RNAi were not enhanced by rolipram. These data indicate a predominant role of long-form PDE4Ds in the pharmacotherapies of PDE4 inhibitors for depression and concomitant memory deficits. Long-form PDE4Ds, especially PDE4D4 and PDE4D5, appear to be the promising targets for the development of antidepressants with high therapeutic indices.

Chemokine-like factor 1-derived C-terminal peptides induce the proliferation of dermal microvascular endothelial cells in psoriasis

Psoriasis is an inflammatory disease characterized by the abnormal proliferation of skin cells, including dermal microvascular endothelial cells. Recently, chemokine-like factor 1 (CKLF1) was found to participate in the local inflammation and cell proliferation. To explore its role in the pathogenesis of psoriasis, the expression of both CKLF1 and its receptor (CCR4) was determined in the psoriatic lesions. Also, the effect of the C-terminal peptides (C19 and C27) of CKLF1 on the proliferation of human umbilical vein endothelial cells was studied in vitro. By immunohistochemistry and immunofluorescence, the expression of both CKLF1 and CCR4 was determined in the psoriatic lesions. The effect of C-terminal peptides on human umbilical vein endothelial cells (HUVECs) was studied in vitro by the evaluation of cell proliferation and apoptosis. The in vivo assessment was performed accordingly through the subcutaneous injection peptides on BALB/c mice. The results showed that, by immunohistochemistry, both CKLF1 and CCR4 were increasingly expressed in psoriatic lesions as compared to normal skins. Moreover, the primary umbilical vein endothelial cells exhibited higher proliferation ratio under the C19 or C27 stimulation, which was even enhanced by the addition of psoriatic sera or TNF-α. Furthermore, the enhancement of peptide simulation was accompanied with the activation of ERK1/2-MAPKs pathway. In addition, such effect of C19 and C27 was mirrored by the hyperproliferation of cutaneous microvessels in BALB/c mice that were subcutaneously injected with the two peptides. Therefore, we concluded that CKLF1 plays a role in the pathogenesis of psoriasis by promoting the proliferation of microvascular endothelial cells that possibly correlates with ERK1/2-MAPKs activation.

Neutralization of chemokine-like factor 1, a novel C-C chemokine, protects against focal cerebral ischemia by inhibiting neutrophil infiltration via MAPK pathways in rats

Background

Inflammation plays a key role in the pathophysiology of ischemic stroke. Some proinflammatory mediators, such as cytokines and chemokines, are produced in stroke. Chemokine-like factor 1 (CKLF1), as a novel C-C chemokine, displays chemotactic activities in a wide spectrum of leukocytes and plays an important role in brain development. In previous studies, we have found that the expression of CKLF1 increased in rats after focal cerebral ischemia and treatment with the CKLF1 antagonist C19 peptide decreased the infarct size and water content. However, the role of CKLF1 in stroke is still unclear. The objective of the present study was to ascertain the possible roles and mechanism of CKLF1 in ischemic brain injury by applying anti-CKLF1 antibody.

Methods

Male Sprague–Dawley rats were subjected to one-hour middle cerebral artery occlusion. Antibody to CKLF1 was applied to the right cerebral ventricle immediately after reperfusion; infarct volume and neurological score were measured at 24 and 72 hours after cerebral ischemia. RT-PCR, Western blotting and ELISA were utilized to characterize the expression of adhesion molecules, inflammatory factors and MAPK signal pathways. Immunohistochemical staining and myeloperoxidase activity was used to determine the extent of neutrophil infiltration.

Results

Treatment with anti-CKLF1 antibody significantly decreased neurological score and infarct volume in a dose-dependent manner at 24 and 72 hours after cerebral ischemia. Administration with anti-CKLF1 antibody lowered the level of inflammatory factors TNF-α, IL-1β, MIP-2 and IL-8, the expression of adhesion molecules ICAM-1 and VCAM-1 in a dose-dependent manner. The results of immunohistochemical staining and detection of MPO activity indicated that anti-CKLF1 antibody inhibited neutrophil infiltration. Further studies suggested MAPK pathways associated with neutrophil infiltration in cerebral ischemia.

Conclusions

Selective inhibition of CKLF1 activity significantly protects against ischemia/reperfusion injury by decreasing production of inflammatory mediators and expression of adhesion molecules, thereby reducing neutrophils recruitment to the ischemic area, possibly via inhibiting MAPK pathways. Therefore, CKLF1 may be a novel target for the treatment of stroke.

RNA interference-mediated phosphodiesterase 4D splice variants knock-down in the prefrontal cortex produces antidepressant-like and cognition-enhancing effects

BACKGROUND AND PURPOSE

Phosphodiesterase 4 (PDE4) inhibitors produce potent antidepressant-like and cognition-enhancing effects. However, their clinical utility is limited by the major side effect of emesis, which appears to be PDE4 isoform-specific. Although PDE4D subtype plays the pivotal role in these therapeutic profiles, it is also the primary subtype responsible for emesis. Therefore, the aim of present research was to investigate whether long-form PDE4D variants mediate antidepressant-like and cognition-enhancing effects, but are irrespective with emesis.

EXPERIMENTAL APPROACH

In mice microinfused with lentiviral vectors that contained shRNA-mir hairpin structure targeting long-form PDE4Ds into bilateral prefrontal cortices, the tail-suspension and forced-swim tests were used to measure antidepressant-like effects; novel object recognition and Morris water-maze tasks were used to determine cognition-enhancing effects. The emetic potential was assessed by alpha2 adrenergic receptor-mediated anaesthesia, a surrogate measure of emesis. Intracellular cAMP signalling was analysed by time-resolved FRET immunoassay and Western-blot. Dendritic complexity was assessed by Golgi staining.

KEY RESULTS

Microinfusions of lentiviral PDE4D-shRNA down-regulated PDE4D4 and PDE4D5, and imitated the antidepressant-like and cognition-enhancing effects of the prototypical PDE4 inhibitor rolipram. The behavioural effects were related to dendritic complexity and mediated by the increased cAMP signalling. In addition, these effects were not enhanced in the presence of rolipram. Finally, while rolipram shortened the duration of combined anaesthesia, RNA interference-mediated PDE4D knock-down in the prefrontal cortex did not.

CONCLUSION AND IMPLICATIONS

These data suggest that long-form PDE4Ds, at least PDE4D4 and PDE4D5, may be the promising targets for the development of PDE4 variant-selective inhibitors as the new pharmacotherapies for depressive disorders and neurodegenerative diseases involving memory deficits.

Gene expression analysis reveals schizophrenia-associated dysregulation of immune pathways in peripheral blood mononuclear cells

Peripheral blood mononuclear cells (PBMCs) represent an accessible tissue source for gene expression profiling in schizophrenia that could provide insight into the molecular basis of the disorder. This study used the Illumina HT_12 microarray platform and quantitative real time PCR (QPCR) to perform mRNA expression profiling on 114 patients with schizophrenia or schizoaffective disorder and 80 non-psychiatric controls from the Australian Schizophrenia Research Bank (ASRB). Differential expression analysis revealed altered expression of 164 genes (59 up-regulated and 105 down-regulated) in the PBMCs from patients with schizophrenia compared to controls. Bioinformatic analysis indicated significant enrichment of differentially expressed genes known to be involved or associated with immune function and regulating the immune response. The differential expression of 6 genes, EIF2C2 (Ago 2), MEF2D, EVL, PI3, S100A12 and DEFA4 was confirmed by QPCR. Genome-wide expression analysis of PBMCs from individuals with schizophrenia was characterized by the alteration of genes with immune system function, supporting the hypothesis that the disorder has a significant immunological component in its etiology.

Sex-biased genetic effects on gene regulation in humans

Human regulatory variation, reported as expression quantitative trait loci (eQTLs), contributes to differences between populations and tissues. The contribution of eQTLs to differences between sexes, however, has not been investigated to date. Here we explore regulatory variation in females and males and demonstrate that 12%–15% of autosomal eQTLs function in a sex-biased manner. We show that genes possessing sex-biased eQTLs are expressed at similar levels across the sexes and highlight cases of genes controlling sexually dimorphic and shared traits that are under the control of distinct regulatory elements in females and males. This study illustrates that sex provides important context that can modify the effects of functional genetic variants.

Developmental expression of chemokine-like factor 1, a novel member of chemokines family, in postnatal rat cerebral cortex

Chemokine-like factor 1 (CKLF1) has been implicated to induce the migration of neuroblastoma cells and is abundant in fetal brain but scarce in adult brain. Given the importance of neural cell migration in brain development, it is possible that the chemotaxis of CKLF1 is required during brain development. Therefore, it is essential to know the detailed expression profiles of CKLF1 during brain development first. However, the developmental expression patterns of CKLF1 still remain unclear. We aimed to investigate the temporal and spatial expressions of CKLF1 during cerebral cortex postnatal development in rats. By reverse-transcription PCR/immunoblotting at multiple time points, the mRNA/protein expressions of CKLF1 were in abundance at birth, then decreased progressively within the next two weeks and almost disappeared in adulthood. By immunohistochemistry staining, an obvious expression of CKLF1 was observed in the cerebral cortex, hippocampus, olfactory bulb, some specific nuclei and commissural fibers. Concluding, the temporal expression pattern of CKLF1 was coincident with the postnatal developmental stages and the spatial locations of CKLF1 were some destinations of neural cell migration or regions where myelination normally occurs during cerebrum postnatal development.

Expression of chemokine-like factor 1 after focal cerebral ischemia in the rat

Cerebral ischemic injury is associated with the induction of a series of pro-inflammatory mediators such as cytokines and chemokines. The chemokine-like factor 1(CKLF1), as a novel human cytokine, displays chemotactic activities in a wide spectrum of leukocytes. The present study was conducted to determine if CKLF1 was produced in the brain of rats subjected to transient middle cerebral artery occlusion (TMCAO). Therefore, RT-PCR, Western blot and immunohistochemistry were utilized to characterize the expression of CKLF1 at different times after TMCAO. The result showed that almost no expression of CKLF1 was found in the sham-operated or contralateral cerebral cortex and hippocampus. CKLF1 expression significantly increased in the ischemic cerebral cortex and hippocampus, elevating at 12 h and peaking at 2 days after reperfusion. CKLF1 positive staining was mainly present in the cerebral cortex, hippocampus, thalamus, and hypothalamus. These results demonstrate that the expression of CKLF1 increases after focal cerebral ischemia in rat brain. Thus, CKLF1 may be a potential therapeutic target for cerebral ischemia.