The effects of the selective and non-peptide CXCR2 receptor antagonist SB225002 on acute and long-lasting models of nociception in mice

Dual Role of CXCL8 in Maintaining the Mesenchymal State of Glioblastoma Stem Cells and M2-Like Tumor-Associated Macrophages

PURPOSE

The dynamic interplay between glioblastoma stem cells (GSC) and tumor-associated macrophages (TAM) sculpts the tumor immune microenvironment (TIME) and promotes malignant progression of glioblastoma (GBM). However, the mechanisms underlying this interaction are still incompletely understood. Here, we investigate the role of CXCL8 in the maintenance of the mesenchymal state of GSC populations and reprogramming the TIME to an immunosuppressive state.

EXPERIMENTAL DESIGN

We performed an integrative multi-omics analyses of RNA sequencing, GBM mRNA expression datasets, immune signatures, and epigenetic profiling to define the specific genes expressed in the mesenchymal GSC subsets. We then used patient-derived GSCs and a xenograft murine model to investigate the mechanisms of tumor-intrinsic and extrinsic factor to maintain the mesenchymal state of GSCs and induce TAM polarization.

RESULTS

We identified that CXCL8 was preferentially expressed and secreted by mesenchymal GSCs and activated PI3K/AKT and NF-κB signaling to maintain GSC proliferation, survival, and self-renewal through a cell-intrinsic mechanism. CXCL8 induced signaling through a CXCR2-JAK2/STAT3 axis in TAMs, which supported an M2-like TAM phenotype through a paracrine, cell-extrinsic pathway. Genetic- and small molecule-based inhibition of these dual complementary signaling cascades in GSCs and TAMs suppressed GBM tumor growth and prolonged survival of orthotopic xenograft-bearing mice.

CONCLUSIONS

CXCL8 plays critical roles in maintaining the mesenchymal state of GSCs and M2-like TAM polarization in GBM, highlighting an interplay between cell-autonomous and cell-extrinsic mechanisms. Targeting CXCL8 and its downstream effectors may effectively improve GBM treatment.

A novel gedunin-2-hydroxypropyl-β-cyclodextrin inclusion complex improves anti-nociceptive and anti-inflammatory activities of gedunin in rodents

Gedunin is a bioactive compound, obtained from Entandrophragma angolense (EA), which has limited therapeutic usefulness due to poor aqueous solubility and first-pass effects. Cyclodextrins are cyclic oligosaccharides that form complexes with poorly soluble compounds, thus enhancing their pharmacological activity. In this article, we evaluated the pharmacological activities of gedunin-2-hydroxypropyl-β-cyclodextrin complex (GCD) in rodents. The antinociceptive activity of GCD (50, 100, 200 mg/kg) and Gedunin (50mg/kg) was tested in acetic acid-induced writhing and formalin-induced paw licking in mice. The anti-inflammatory activity was investigated in carrageenan-induced paw oedema and air pouch inflammation models in rats. Leucocytes counts, Tumour Necrosis Factor-alpha (TNF-α) level, nitric oxide, malondialdehyde, reduced glutathione, and myeloperoxidase enzyme activities were assessed in the air pouch exudate. The GCD (200mg/kg) significantly decreased writhing response, reduced licking duration and decreased oedema compared with gedunin and control. Exudate volume and leucocyte count were significantly reduced by GCD (200 mg/kg), it decreased myeloperoxidase activity and inhibited TNF-α release. The carrageenan-induced GSH depletion, increased malondialdehyde and nitrite levels were significantly reversed by GCD (200 mg/kg) relative to gedunin and control.  The GCD complex demonstrated significant antinociceptive and anti-inflammatory activities relative to gedunin alone via mechanisms associated with inhibition of oxidative stress and inflammation in rodents.

The Importance of CXCL1 in Physiology and Noncancerous Diseases of Bone, Bone Marrow, Muscle and the Nervous System

This review describes the role of CXCL1, a chemokine crucial in inflammation as a chemoattractant for neutrophils, in physiology and in selected major non-cancer diseases. Due to the vast amount of available information, we focus on the role CXCL1 plays in the physiology of bones, bone marrow, muscle and the nervous system. For this reason, we describe its effects on hematopoietic stem cells, myoblasts, oligodendrocyte progenitors and osteoclast precursors. We also present the involvement of CXCL1 in diseases of selected tissues and organs including Alzheimer’s disease, epilepsy, herpes simplex virus type 1 (HSV-1) encephalitis, ischemic stroke, major depression, multiple sclerosis, neuromyelitis optica, neuropathic pain, osteoporosis, prion diseases, rheumatoid arthritis, tick-borne encephalitis (TBE), traumatic spinal cord injury and West Nile fever.

Inhibition of Spinal Interleukin-33 Attenuates Peripheral Inflammation and Hyperalgesia in Experimental Arthritis

Accumulating evidence indicates that the continuous and intense nociceptive from inflamed tissue may increase the excitability of spinal dorsal horn neurons, which can signal back and modulate peripheral inflammation. Previous studies have demonstrated that spinal interleukin (IL)-33 contributes to the hyperexcitability of spinal dorsal horn neurons. This study was undertaken to investigate whether spinal IL-33 can also influence a peripheral inflammatory response in a rat model of arthritis. Lentivirus-delivered short hairpin RNA targeting IL-33 (LV-shIL-33) was constructed for gene silencing. Rats with adjuvant-induced arthritis (AIA) were injected intrathecally with LV-shIL-33 3 days before the complete Freund's adjuvant (CFA) injection. During an observation period of 21 days, pain-related behavior and inflammation were assessed. In addition, the expression of spinal proinflammatory cytokines and the activation of spinal extracellular signal-regulated kinase (ERK) and nuclear factor-κB (NF-κB) pathways were evaluated on 9 days after CFA treatment. The existence of tissue injury or inflammation in rats with AIA resulted in the upregulation of spinal IL-33, which is predominantly expressed in neurons, astrocytes, and oligodendrocytes. Intrathecal administration of LV-shIL-33 significantly alleviated hyperalgesia, paw swelling, and joint destruction, and attenuated the expression of proinflammatory cytokines [IL-6, IL-1β, and tumor necrosis factor-α (TNF-α)], as well as the activation of ERK and NF-κB/p65 in the spinal cord. Our data suggest that spinal IL-33 contributes to the development of both peripheral inflammation and hyperalgesia. Thus, interference with IL-33 at the spinal level might represent a novel therapeutic target for painful inflammatory disorders.

The neuroprotection of hyperbaric oxygen therapy against traumatic brain injury via NF-κB/MAPKs-CXCL1 signaling pathways

It is well known that hyperbaric oxygen (HBO) therapy achieves neuroprotective effects by modulating neuroinflammatory responses. However, its underlying therapeutic mechanisms are not yet fully elucidated. Based on our previous studies, we further investigated whether HBO therapy exerts neuroprotective effects in vivo by regulating the nuclear factor-kappa B (NF-κB)/ mitogen-activated protein kinases (MAPKs) chemokine (C-X-C motif) ligand (CXCL)1 inflammatory pathway. In our study, a rat model of traumatic brain injury (TBI) was established by controlled cortical impact (CCI) to verify that the expression of CXCL1 and chemokine (C-X-C motif) receptor (CXCR)2 increased after TBI, and CXCL1 was mainly expressed in astrocytes, while CXCR2 was mainly expressed in neurons. Increased apoptosis of cortical nerve cells in the injured cortex was also found after TBI. Reduced nerve cell apoptosis with improved neurological function was observed after application of a CXCR2 antagonist. The expression of phospho-extracellular signal-regulated kinase (p-ERK), phospho-c-Jun N-terminal kinase (p-JNK) and p-NF-κB increased after TBI, and application of ERK, JNK and NF-κB inhibitors decreased expression of CXCL1 and CXCR2 in rats. We further found that HBO therapy down-regulated the expression of p-ERK, p-JNK, p-NF-κB, CXCL1, and CXCR2, and reduced nerve cell apoptosis, improved the neurological function of TBI rats, and ultimately alleviated the secondary injury. In conclusion, HBO therapy may exert neuroprotective effect by regulating the NF-κB/MAPKs (JNK and ERK)-CXCL1 inflammatory pathways following TBI, which probably provide the theoretical and experimental basis for the clinical application of HBO therapy in the treatment of TBI.

Selection of a picomolar antibody that targets CXCR2-mediated neutrophil activation and alleviates EAE symptoms

Receptors and their ligands are important therapeutic targets for about one third of marketed drugs. Here, we describe an epitope-guided approach for selection of antibodies that modulate cellular signaling of targeted receptors. We chose CXC chemokine receptor 2 (CXCR2) in the G-protein coupled receptor superfamily as receptor and a CXCR2 N-terminal peptide for antibody selection. We obtain a highly selective, tight-binding antibody from a 10¹¹-member antibody library using combinatorial enrichment. Structural and Hydrogen-Deuterium-Exchange mass spectrometry analyses demonstrate antibody interaction with an N-terminal region of CXCR2 that is part of the IL-8 epitope. The antibody strongly inhibits IL-8-induced and CXCR2-mediated neutrophil chemotaxis in vitro and alleviates hCXCR2-dependent experimental autoimmune encephalomyelitis symptoms in mice. As inappropriate neutrophil migration accompanies many diseases including inflammatory bowel disease, glomerulonephritis, allergic asthma, chronic obstructive pulmonary disease, and cancer, this antibody has potential for development as a therapeutic agent, akin to anti-TNF antibodies. However, an important difference here is that the antibody targets the chemokine receptor and competes with natural ligand, rather than targeting the ligand itself.

CXCR2 is central to neutrophil chemotaxis and hence to some inflammatory diseases. Here the authors demonstrate the value of an epitope-guided antibody panning method to develop a tight binding anti-hCXCR2 antibody, along with crystal structures of this antibody and antigen, that can block neutrophil chemotaxis and protect mice in an EAE model.

Effects of CGRP-Primed Dental Pulp Stem Cells on Trigeminal Sensory Neurons

Dental pulp stem cells (DPSCs) are important in tooth physiology, contributing to development, repair, regeneration, and immunomodulatory processes. However, their role in inflammatory mechanisms underlying pulpitis is not well understood. We evaluated the influence of DPSCs stimulated with calcitonin gene-related peptide (CGRP), a proinflammatory neuropeptide, on the expression of mediators released from DPSCs and the effect of these mediators on sensory neuron activity. Human DPSCs were treated with either control media or media containing CGRP (10^-8 M) for 7 d, and the conditioned media (CM) containing DPSC-released mediators was collected. The expression of cytokines and chemokines from DPSCs was evaluated by reverse transcription quantitative polymerase chain reaction. The effects of the CM from CGRP-primed DPSCs (primed DPSC-CM) were evaluated on sensory afferents by using primary cultures of mouse trigeminal neurons and an organotypic model of cultured human pulp slices. Mouse trigeminal neurons and human pulp explants were pretreated for 24 h with control or primed DPSC-CM and then stimulated with capsaicin. Afferent activity was measured by quantifying the response to capsaicin via live cell calcium imaging in mouse neurons and CGRP released from pulp explants. Gene expression analysis showed that primed DPSCs overexpressed some proinflammatory cytokines and chemokines, including chemokines CXCL1 and CXCL8, which are both agonists of the receptor CXCR2 expressed in sensory neurons. Primed DPSC-CM increased human pulp sensory afferent activity as compared with control DPSC-CM. Similarly, primed DPSC-CM increased the intensity of calcium responses in cultured mouse trigeminal neurons. Furthermore, the CXCR2 antagonist SB225002 prevented trigeminal neuron sensitization to capsaicin induced by primed DPSC-CM. In conclusion, mediators released by DPSCs, primed with the proinflammatory mediator CGRP, induce neuronal sensitization through CXCR2 receptor. These data suggest that DPSCs might contribute to pain symptoms that develop in pulpitis.

CXC Chemokine Receptors in the Tumor Microenvironment and an Update of Antagonist Development

Chemokine receptors, a diverse group within the seven-transmembrane G protein-coupled receptor superfamily, are frequently overexpressed in malignant tumors. Ligand binding activates multiple downstream signal transduction cascades that drive tumor growth and metastasis, resulting in poor clinical outcome. These receptors are thus considered promising targets for anti-tumor therapy. This article reviews recent studies on the expression and function of CXC chemokine receptors in various tumor microenvironments and recent developments in cancer therapy using CXC chemokine receptor antagonists.

Chemokines: A Potential Therapeutic Target to Suppress Autoimmune Arthritis

BACKGROUND

Chemokines are a family of low molecular weight proteins that induce chemotaxis of inflammatory cells, which mainly depends on the recognition of a chemo-attractant gradient and interaction with the substratum. In Rheumatoid Arthritis (RA), abundant chemokines are expressed in synovial tissue, cause inflammatory cells migration into the inflamed joint that necessitates the formation of new blood vessels i.e. angiogenesis. Over the decades, studies showed that continuous inflammation may lead to the loss of tissue architecture and function, causing severe disability and cartilage destruction. In spite of the advancement of modern drug therapy, thousands of arthritic patients suffer mortality and morbidity globally. Thus, there is an urgent need for the development of novel therapeutic agents for the treatment of RA.

METHODS

This review is carried out throughout a non-systematic search of the accessible literature, will provide an overview of the current information of chemokine in RA and also exploring the future perspective of the vital role of targeting chemokine in RA treatment.

RESULTS

Since, chemokines are associated with inflammatory cells/leucocyte migration at the site of inflammation in chronic inflammatory diseases and hence, blockade or interference with chemokines activity showing a potential approach for the development of new anti-inflammatory agents. Currently, results obtained from both preclinical and clinical studies showed significant improvement in arthritis.

CONCLUSION

This review summarizes the role of chemokines and their receptors in the pathogenesis of RA and also indicates possible interactions of chemokines/receptors with various synthetic and natural compounds that may be used as a potential therapeutic target in the future for the treatment of RA.

Pharmacological Blockade of Spinal CXCL3/CXCR2 Signaling by NVP CXCR2 20, a Selective CXCR2 Antagonist, Reduces Neuropathic Pain Following Peripheral Nerve Injury

Recently, the role of CXCR2 in nociception has been noted. Our studies provide new evidence that the intrathecal administration of its CINC ligands (Cytokine-Induced Neutrophil Chemoattractant; CXCL1-3) induces pain-like behavior in naïve mice, and the effect occurring shortly after administration is associated with the neural location of CXCR2, as confirmed by immunofluorescence. RT-qPCR analysis showed, for the first time, raised levels of spinal CXCR2 after chronic constriction injury (CCI) of the sciatic nerve in rats. Originally, on day 2, we detected escalated levels of the spinal mRNA of all CINCs associated with enhancement of the protein level of CXCL3 lasting until day 7. Intrathecal administration of CXCL3 neutralizing antibody diminished neuropathic pain on day 7 after CCI. Interestingly, CXCL3 is produced in lipopolysaccharide-stimulated microglial, but not astroglial, primary cell cultures. We present the first evidence that chronic intrathecal administrations of the selective CXCR2 antagonist, NVP CXCR2 20, attenuate neuropathic pain symptoms and CXCL3 expression after CCI. Moreover, in naïve mice, this antagonist prevented CXCL3-induced hypersensitivity. However, NVP CXCR2 20 did not diminish glial activation, thus not enhancing morphine/buprenorphine analgesia. These results provide novel insight into the crucial role of CXCR2 in neuropathy based on CXCL3 modulation, which may become a potential therapeutic target in pain treatment.

Spinal blockage of CXCL1 and its receptor CXCR2 inhibits paclitaxel-induced peripheral neuropathy in mice

Painful peripheral neuropathy is the most dose-limiting side effect of paclitaxel (PTX), a widely used anti-cancer drug to treat solid tumours. The understanding of the mechanisms involved in this side effect is crucial to the development of new therapeutic approaches. CXCL1 chemokine and its receptor CXCR2 have been pointed as promising targets to treat chronic pain. Herein, we sought to evaluate the possible involvement of CXCL1 and CXCR2 in the pathogenesis of PTX-induced neuropathic pain in mice. PTX treatment led to increased levels of CXCL1 in both dorsal root ganglion and spinal cord samples. Systemic treatment with the anti-CXCL1 antibody (10 μg/kg, i.v.) or the selective CXCR2 antagonist (SB225002, 3 mg/kg, i.p.) had minor effect on PTX-induced mechanical hypersensitivity. On the other hand, the intrathecal (i.t.) treatment with anti-CXCL1 (1 ng/site) or SB225002 (10 μg/site) consistently inhibited the nociceptive responses of PTX-treated mice. Similar results were obtained by inhibiting the PI3Kγ enzyme a downstream pathway of CXCL1/CXCR2 signalling with either the selective AS605240 (5 μg/site, i.t.) or the non-selective wortmannin PI3K inhibitor (0.4 μg/site, i.t.). Overall, the data indicates that the up-regulation of CXCL1 is important for the development and maintenance of PTX-induced neuropathic pain in mice. Therefore, the spinal blockage of CXCL1/CXCR2 signalling might be a new innovative therapeutic approach to treat this clinical side effect of PTX.

2-Allylphenol Reduces IL-1β and TNF-α, Promoting Antinociception through Adenosinergic, Anti-Inflammatory, and Antioxidant Mechanisms

2-Allylphenol (2-AP) is a synthetic phenylpropanoid, structurally related to cardanol, thymol, and ortho-eugenol. Phenylpropanoids are described in the literature as being capable of promoting biological activity. Due to the similarity between 2-AP and other bioactive phenylpropanoids, the present research aims at evaluating the antioxidant, antinociceptive, and anti-inflammatory potential of 2-AP in silico, in vitro, and in vivo. At 30 min prior to the start of in vivo pharmacological testing, administration of 2-AP (25, 50, 75, and 100 mg/kg i.p.), morphine (6 mg/kg i.p.), dexamethasone (2 mg/kg s.c.), or vehicle alone was performed. In the acetic acid-induced abdominal writhing tests, pretreatment with 2-AP significantly reduced the number of abdominal writhes, as well as decreased licking times in the glutamate and formalin tests. Investigation of the mechanism of action using the formalin model led to the conclusion that the opioid system does not participate in its activity. However, the adenosinergic system is involved. In the peritonitis tests, 2-AP inhibited leukocyte migration and reduced releases of proinflammatory mediators TNF-α and IL-1β. In vitro antioxidant assays demonstrated that 2-AP presents significant ability to sequester superoxide radicals. In silico docking studies confirmed interaction between 2-AP and the adenosine A2a receptor through hydrogen bonds with the critical asparagine 253 residues present in the active site. Investigation of 2-AP demonstrated its nociception inhibition and ability to reduce reactive oxygen species. Its interaction with A2a receptors may well be related to proinflammatory cytokines TNF-α and IL-1β reduction activity, corroborating its antinociceptive effect.

SB225002 inhibits prostate cancer invasion and attenuates the expression of BSP, OPN and MMP‑2

The mechanisms of malignant cell metastasis to secondary sites are complex and multifactorial. Studies have demonstrated that small integrin-binding ligand N-linked glycoproteins (SIBLINGs), particularly bone sialoprotein (BSP) and osteopontin (OPN), are involved in neoplastic growth and metastasis. SIBLINGs promote malignant cell invasion and metastasis by enhancing matrix metalloproteinase 2 (MMP-2) and MMP-9 expression. Moreover, BSP and OPN can combine with integrin, which is located on the tumor cell surface, to further promote the malignant behavior of tumor cells. In the present study, we investigated whether SB225002, a specific CXCR2 receptor antagonist, can inhibit prostate cancer cell expression of BSP and OPN and reduce cancer cell invasion ability. A series of experiments showed that after SB225002 treatment, the proliferation, invasion and migration of two androgen-independent prostate cancer cell lines were inhibited, but this inhibitory effect was not observed on androgen-dependent prostate cancer cells. Western blotting showed that the PI3K signaling pathway could regulate the expression of SIBLING and MMP family proteins, and SB22055 could reduce the expression of BSP, OPN and MMP-2 in prostate cancer cells by inhibiting AKT/mTOR phosphorylation. Finally, in vivo experiments confirmed that SB225002 inhibited the proliferation of prostate cancer cells in vivo, and the expression levels of BSP, OPN and MMP-2 were also inhibited.

Inhibitory effects of Dianthi Herba ethanolic extract on inflammatory and nociceptive responses in murine macrophages and mouse models of abdominal writhing and ear edema

ETHNOPHARMACOLOGICAL RELEVANCE

Dianthi Herba is a traditional herbal medicine used to treat inflammatory-related diseases including acute pyelonephritis, cystitis, laryngopharyngitis, and urethritis.

AIM OF THE STUDY

We investigated the effects of Dianthi Herba ethanolic extract (DH) on lipopolysaccharide (LPS)-mediated inflammatory responses in murine macrophages including RAW 264.7 cell line and mouse peritoneal macrophages as well as nociceptive and edema mouse models.

MATERIALS AND METHODS

The biological effects of DH on inflammatory cytokine, mediator, and related protein production were assessed using enzyme-linked immunosorbent assay (ELISA), Western blotting, and real-time reverse transcription-polymerase chain reaction (real-time RT-PCR). Additionally, Western blotting was performed to investigate intracellular signaling pathways, and the anti-nociceptive activity of three doses of DH (100, 200, and 300mg/kg) against acetic acid-induced writhing responses and its inhibitory effects on xylene-induced ear edema were researched in mice through oral administration.

RESULTS

DH treatment significantly inhibited nitric oxide (NO) secretion and inflammatory cytokine production in RAW 264.7 cells and mouse peritoneal macrophages and induced heme oxygenase (HO)-1 expression. DH strongly inhibited the transcriptional activity of nuclear factor (NF)-κB and phosphorylation of mitogen-activated protein kinases (MAPK) in LPS-stimulated macrophages. Meanwhile, DH exerted anti-nociceptive effects on writhing responses and anti-edema effects in mice.

CONCLUSION

We confirmed the anti-inflammatory activities and inhibitory mechanism of DH in macrophages and clarified its inhibitory effects in vivo. These findings illustrate the therapeutic potential of DH as a natural anti-inflammatory agent.

IL-33/ST2 signaling contributes to radicular pain by modulating MAPK and NF-κB activation and inflammatory mediator expression in the spinal cord in rat models of noncompressive lumber disk herniation

BACKGROUND

Immune and inflammatory responses occurring in the spinal cord play a pivotal role in the progression of radicular pain caused by intervertebral disk herniation. Interleukin-33 (IL-33) orchestrates inflammatory responses in a wide range of inflammatory and autoimmune disorders of the nervous system. Thus, the purpose of this study is to investigate the expression of IL-33 and its receptor ST2 in the dorsal spinal cord and to elucidate whether the inhibition of spinal IL-33 expression significantly attenuates pain-related behaviors in rat models of noncompressive lumbar disc herniation.

METHODS

Lentiviral vectors encoding short hairpin RNAs that target IL-33 (LV-shIL-33) were constructed for gene silencing. Rat models of noncompressive lumber disk herniation were established, and the spines of rats were injected with LV-shIL-33 (5 or 10 μl) on the first day after the operation. Mechanical thresholds were evaluated during an observation period of 21 days. Moreover, the expression levels of spinal tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6), and cyclooxygenase 2 (COX-2) and the activation of the mitogen-activated protein kinases (MAPK) and nuclear factor-κB (NF-κB) pathways were evaluated to gain insight into the mechanisms related to the contribution of IL-33/ST2 signaling to radicular pain.

RESULTS

The application of nucleus pulposus (NP) to the dorsal root ganglion (DRG) induced an increase in IL-33 and ST2 expression in the spinal cord, mainly in the dorsal horn neurons, astrocytes, and oligodendrocytes. Spinally delivered LV-shIL-33 knocked down the expression of IL-33 and markedly attenuated mechanical allodynia. In addition, spinal administration of LV-shIL-33 reduced the overexpression of spinal IL-1β, TNF-α, and COX-2 and attenuated the activation of C-Jun N-terminal kinase (JNK), extracellular signal-regulated kinase (ERK), and NF-κB/p65 but not p38.

CONCLUSIONS

This study indicates that spinal IL-33/ST2 signaling plays an important role in the development and progression of radicular pain in rat models of noncompressive lumber disk herniation. Thus, the inhibition of spinal IL-33 expression may provide a potential treatment to manage radicular pain caused by intervertebral disk herniation.

Chemokines in neuron-glial cell interaction and pathogenesis of neuropathic pain

Neuropathic pain resulting from damage or dysfunction of the nervous system is a highly debilitating chronic pain state and is often resistant to currently available treatments. It has become clear that neuroinflammation, mainly mediated by proinflammatory cytokines and chemokines, plays an important role in the establishment and maintenance of neuropathic pain. Chemokines were originally identified as regulators of peripheral immune cell trafficking and were also expressed in neurons and glial cells in the central nervous system. In recent years, accumulating studies have revealed the expression, distribution and function of chemokines in the spinal cord under chronic pain conditions. In this review, we provide evidence showing that several chemokines are upregulated after peripheral nerve injury and contribute to the pathogenesis of neuropathic pain via different forms of neuron-glia interaction in the spinal cord. First, chemokine CX3CL1 is expressed in primary afferents and spinal neurons and induces microglial activation via its microglial receptor CX3CR1 (neuron-to-microglia signaling). Second, CCL2 and CXCL1 are expressed in spinal astrocytes and act on CCR2 and CXCR2 in spinal neurons to increase excitatory synaptic transmission (astrocyte-to-neuron signaling). Third, we recently identified that CXCL13 is highly upregulated in spinal neurons after spinal nerve ligation and induces spinal astrocyte activation via receptor CXCR5 (neuron-to-astrocyte signaling). Strategies that target chemokine-mediated neuron-glia interactions may lead to novel therapies for the treatment of neuropathic pain.

Direct Macromolecular Drug Delivery to Cerebral Ischemia Area using Neutrophil-Mediated Nanoparticles

Delivery of macromolecular drugs to the brain is impeded by the blood brain barrier. The recruitment of leukocytes to lesions in the brain, a typical feature of neuroinflammation response which occurs in cerebral ischemia, offers a unique opportunity to deliver drugs to inflammation sites in the brain. In the present study, cross-linked dendrigraft poly-L-lysine (DGL) nanoparticles containing cis-aconitic anhydride-modified catalase and modified with PGP, an endogenous tripeptide that acts as a ligand with high affinity to neutrophils, were developed to form the cl PGP-PEG-DGL/CAT-Aco system. Significant binding efficiency to neutrophils, efficient protection of catalase enzymatic activity from degradation and effective transport to receiver cells were revealed in the delivery system. Delivery of catalase to ischemic subregions and cerebral neurocytes in MCAO mice was significantly enhanced, which obviously reducing infarct volume in MCAO mice. Thus, the therapeutic outcome of cerebral ischemia was greatly improved. The underlying mechanism was found to be related to the inhibition of ROS-mediated apoptosis. Considering that neuroinflammation occurs in many neurological disorders, the strategy developed here is not only promising for treatment of cerebral ischemia but also an effective approach for various CNS diseases related to inflammation.

An adaptive signaling network in melanoma inflammatory niches confers tolerance to MAPK signaling inhibition

Mitogen-activated protein kinase (MAPK) pathway antagonists induce profound clinical responses in advanced cutaneous melanoma, but complete remissions are frustrated by the development of acquired resistance. Before resistance emerges, adaptive responses establish a mutation-independent drug tolerance. Antagonizing these adaptive responses could improve drug effects, thereby thwarting the emergence of acquired resistance. In this study, we reveal that inflammatory niches consisting of tumor-associated macrophages and fibroblasts contribute to treatment tolerance through a cytokine-signaling network that involves macrophage-derived IL-1β and fibroblast-derived CXCR2 ligands. Fibroblasts require IL-1β to produce CXCR2 ligands, and loss of host IL-1R signaling in vivo reduces melanoma growth. In tumors from patients on treatment, signaling from inflammatory niches is amplified in the presence of MAPK inhibitors. Signaling from inflammatory niches counteracts combined BRAF/MEK (MAPK/extracellular signal-regulated kinase kinase) inhibitor treatment, and consequently, inhibiting IL-1R or CXCR2 signaling in vivo enhanced the efficacy of MAPK inhibitors. We conclude that melanoma inflammatory niches adapt to and confer drug tolerance toward BRAF and MEK inhibitors early during treatment.

TRESK contributes to pain threshold changes by mediating apoptosis via MAPK pathway in the spinal cord

The mechanism underlying neuropathic pain (NP) is complex and has not been fully elucidated. The TWIK-related spinal cord K⁺ (TRESK) is the major background potassium current in dorsal root ganglia (DRG), we found that mitogen-activated protein kinase (MAPK) signal pathway were activated in spinal cord accompanied by TRESK down regulation in response to NP. Therefore, we investigated whether TRESK mediates inflammation and apoptosis by MAPK pathway in the spinal cord of NP rats. SNI rats exhibited reduced TRESK expression in DRG and spinal cord and higher sensitivity to mechanical stimuli but no effect on thermal stimuli. Intrathecal injections of TRESK overexpressing adenovirus alleviated mechanical allodynia, inhibited phosphorylation of extracellular signal-regulated kinase (ERK) and p38, and decreased inflammatory reactions and apoptosis in the spinal cords of SNI rats. Down regulation of TRESK in DRG and spinal cord was detected in normal rats after intrathecal TRESK shRNA lentivirus injection, which induced mechanical allodynia but had no effect on pain thresholds for heat stimulation. Phosphorylated ERK and p38 were increased in the spinal cord. Intrathecal injection of an ERK antagonist (PD98059) and p38 antagonist (SB203580) prevented ERK and p38 activation in the spinal cord and mechanical allodynia induced by TRESK shRNA lentivirus. In conclusion, our study clearly demonstrated an important role for TRESK in NP and that TRESK regulation contributes to pain sensitivity mediates inflammation and apoptosis by ERK and p38 MAPK signaling in the spinal cord.

Chemokine receptor CXCR2 in dorsal root ganglion contributes to the maintenance of inflammatory pain

Chemokines and their receptors have been demonstrated to be important contributors to the development and maintenance of chronic pain. Recent studies showed that chemokine (C-X-C motif) ligand 1 (CXCL1) and its major receptor CXCR2 are respectively expressed in astrocytes and neurons in the spinal cord and are involved in the maintenance of neuropathic pain and inflammatory pain via astrocytic-neuronal interaction. Here we investigated how CXCL1 and CXCR2 are regulated in the dorsal root ganglion (DRG) after peripheral injection of complete Freund's adjuvant (CFA) and its implication in inflammatory pain. CFA induced rapid increase of CXCL1 mRNA and protein in the DRG. Double immunostaining showed that CXCL1 was colocalized with calcitonin gene-related peptide (CGRP), isolectin B4 (IB4), and neurofilament 200 (NF200). Furthermore, CXCR2 mRNA was increased 3h after CFA injection and maintained for more than 3 days. CXCR2 protein was also increased and colocalized with CGRP, IB4, and NF200. Finally, perisciatic nerve injection of CXCR2 siRNA to specifically knock down CXCR2 in the DRG effectively attenuated CFA-induced mechanical allodynia and heat hyperalgesia, and the effect maintained for more than 5 days. Taken together, our results demonstrated that CXCL1 and CXCR2 may regulate the maintenance of inflammatory pain via an autocrine/paracrine way in DRG neurons.

Resolvin D1 Inhibits Mechanical Hypersensitivity in Sciatica by Modulating the Expression of Nuclear Factor-κB, Phospho-extracellular Signal–regulated Kinase, and Pro- and Antiinflammatory Cytokines in the Spinal Cord and Dorsal Root Ganglion

Background

Accumulating evidence indicates that spinal inflammatory and immune responses play an important role in the process of radicular pain caused by intervertebral disk herniation. Resolvin D1 (RvD1) has been shown to have potent antiinflammatory and antinociceptive effects. The current study was undertaken to investigate the analgesic effect of RvD1 and its underlying mechanism in rat models of noncompressive lumbar disk herniation.

Methods

Rat models of noncompressive lumber disk herniation were established, and mechanical thresholds were evaluated using the von Frey test during an observation period of 21 days (n = 8/group). Intrathecal injection of vehicle or RvD1 (10 or 100 ng) was performed for three successive postoperative days. On day 7, the ipsilateral spinal dorsal horns and L5 dorsal root ganglions (DRGs) were removed to assess the expressions of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), IL-10, and transforming growth factor-β1 (TGF-β1) and the activation of nuclear factor-κB (NF-κB)/p65 and phospho-extracellular signal–regulated kinase (p-ERK) signaling (n = 30/group).

Results

The application of nucleus pulposus to L5 DRG induced prolonged mechanical allodynia, inhibited the production of IL-10 and TGF-β1, and up-regulated the expression of TNF-α, IL-1β, NF-κB/p65, and p-ERK in the spinal dorsal horns and DRGs. Intrathecal injection of RvD1 showed a potent analgesic effect, inhibited the up-regulation of TNF-α and IL-1β, increased the release of IL-10 and TGF-β1, and attenuated the expression of NF-κB/p65 and p-ERK in a dose-dependent manner.

Conclusions

The current study showed that RvD1 might alleviate neuropathic pain via regulating inflammatory mediators and NF-κB/p65 and p-ERK pathways. Its antiinflammatory and proresolution properties may offer novel therapeutic approaches for the management of neuropathic pain.

SB225002 Induces Cell Death and Cell Cycle Arrest in Acute Lymphoblastic Leukemia Cells through the Activation of GLIPR1

Acute Lymphoblastic Leukemia (ALL) is the most frequent childhood malignancy. In the effort to find new anti-leukemic agents, we evaluated the small drug SB225002 (N-(2-hydroxy-4-nitrophenyl)-N’-(2-bromophenyl)urea). Although initially described as a selective antagonist of CXCR2, later studies have identified other cellular targets for SB225002, with potential medicinal use in cancer. We found that SB225002 has a significant pro-apoptotic effect against both B- and T-ALL cell lines. Cell cycle analysis demonstrated that treatment with SB225002 induces G2-M cell cycle arrest. Transcriptional profiling revealed that SB225002-mediated apoptosis triggered a transcriptional program typical of tubulin binding agents. Network analysis revealed the activation of genes linked to the JUN and p53 pathways and inhibition of genes linked to the TNF pathway. Early cellular effects activated by SB225002 included the up-regulation of GLIPR1, a p53-target gene shown to have pro-apoptotic activities in prostate and bladder cancer. Silencing of GLIPR1 in B- and T-ALL cell lines resulted in increased resistance to SB225002. Although SB225002 promoted ROS increase in ALL cells, antioxidant N-Acetyl Cysteine pre-treatment only modestly attenuated cell death, implying that the pro-apoptotic effects of SB225002 are not exclusively mediated by ROS. Moreover, GLIPR1 silencing resulted in increased ROS levels both in untreated and SB225002-treated cells. In conclusion, SB225002 induces cell cycle arrest and apoptosis in different B- and T-ALL cell lines. Inhibition of tubulin function with concurrent activation of the p53 pathway, in particular, its downstream target GLIPR1, seems to underlie the anti-leukemic effect of SB225002.

Inhibitory Effects of Epimedium Herb on the Inflammatory Response In Vitro and In Vivo

Epimedium Herb (EH) is a medicinal herb used in traditional Eastern Asia. In this study described, we investigated the biological effects of Epimedium Herb water extract (EHWE) on lipopolysaccharide (LPS)-mediated inflammation in macrophages and local inflammation in vivo. We also investigated the biological effects of EHWE on the production of inflammatory mediators, pro-inflammatory cytokines and related products, as well as nuclear factor κB (NF-κB) and mitogen-activated protein kinase (MAPK) activation in LPS-stimulated macrophages. The analgesic effect of the acetic acid-induced writhing response and inhibitory activity on xylene-induced ear edema was also evaluated in mice. EHWE exhibited anti-inflammatory effects by inhibiting the production of nitric oxide (NO), interleukin (IL)-6 and IL-1β. In addition, EHWE strongly suppressed inducible nitric oxide synthase (iNOS), a NO synthesis enzyme, induced heme oxygenase-1 (HO-1) expression, and inhibited NF-κB activation as well as MAPK pathway phosphorylation. Furthermore, EHWE exhibited an analgesic effect on the writhing response and an inhibitory effect on ear edema in mice. For the first time, we demonstrated the anti-inflammatory effects and inhibitory mechanism in macrophages, as well as the inhibitory activity of EHWE in vivo. Our results indicate a potential use of EHWE as an inflammatory therapeutic agent developed from a natural substance.

An in vivo and in vitro assessment of the anti-inflammatory, antinociceptive, and immunomodulatory activities of Clematis terniflora DC. extract, participation of aurantiamide acetate

AIM

Clematis terniflora DC. has been widely used as a traditional Chinese medicine for the treatment of tonsillitis, rheumatoid arthritis, and prostatitis. Despite its widespread use in China, there are currently no studies systematically examined its therapeutic effects and mechanism of action. As such, the present study was conducted to evaluate the anti-inflammatory, antinociceptive, and immunomodulatory effects of C. terniflora DC. using rodent and cellular models.

METHODS

The anti-inflammatory properties of the 70% ethanol eluted fraction of the 70% ethanol extract of C. terniflora DC. (EECTD) were evaluated using the xylene-induced ear swelling test, the carrageenan-induced edema model, and the cotton pellet granuloma method. Its antinociceptive activities were determined using both the acetic acid-induced writhing test and the hot plate assay. In parallel, we conducted an in vitro assay in LPS-induced RAW264.7 cells to examine the anti-inflammatory effects of EECTD and its purified form, aurantiamide acetate (AA) on inhibition of nitric oxide (NO) and prostaglandin E2 (PGE2) release.

RESULTS

EECTD (300mg/kg) significantly reduced the number of writhing, extended the pain response latency, and suppressed xylene-induced ear swelling. Each EECTD treatment group also had significant inhibition of cotton granulation formation in addition to reduced carrageenan-induced paw edema. EECTD was also shown to alleviate signs of inflammation in histopathological paw sections. However, it had a less noticeable effect on mouse ear swelling in the delayed type hypersensitivity test. A purified compound was isolated from EECTD and its structure was identified as AA. In vitro experimental results showed that both EECTD and AA were able to significantly inhibit the release of pro-inflammatory cytokines NO and PGE2 on LPS-induced RAW264.7 cells.

CONCLUSION

These results suggest that EECTD has significant anti-inflammatory and antinociceptive activities, partially related to one of the active substances identified as AA. We hypothesize that these effects are related to its ability to inhibit the production of cytokines NO and PGE2. However, further work will be needed to determine its exact mechanism of action.

The antihypersensitive and antiinflammatory activities of a benzofuranone derivative in different experimental models in mice: the importance of the protein kinase C pathway

BACKGROUND

Benzofuranone (BF1) was synthesized and its effects evaluated on mechanical hypersensitivity and paw edema models induced by different agents and on neuropathic pain induced by partial ligation of the sciatic nerve. An attempt was also made to elucidate the mechanism of action.

METHODS

Swiss mice were used for the tests. Hypersensitivity was induced by intraplantar injection of carrageenan, bradykinin (BK), prostaglandin E2 (PGE2), epinephrine, lipopolysaccharide, or complete Freund adjuvant or by using a neuropathic pain model (evaluated with von Frey filament 0.6 g). The antiinflammatory effects were investigated in a paw edema model induced by carrageenan, PGE2, and BK (measured with a plethysmometer). The involvement of protein kinase C (PKC) was investigated through a nociception model induced by phorbol myristate acetate.

RESULTS

BF1 inhibited the hypersensitivity and paw edema induced by intraplantar injection of carrageenan, BK, and PGE2 (P < 0.001), and it was effective in reducing the hypersensitivity evoked by complete Freund adjuvant or epinephrine (P < 0.001) but not by lipopolysaccharide (P = 0.2570). BF1 inhibited the licking behavior induced by phorbol myristate acetate (P < 0.001), suggesting involvement of the PKC pathway. A reduction in hypersensitivity of mice submitted to partial ligation of the sciatic nerve (P < 0.001) was observed, with inhibition of neutrophil migration and interleukin-1β production into the spinal cord. BF1 treatment did not interfere with locomotor activity (P = 0.0783) and thermal withdrawal threshold (P = 0.5953), which are important adverse effects of other analgesics.

CONCLUSIONS

BF1 has dose-dependent antihypersensitive and antiinflammatory effects in both acute and chronic models of pain and inflammation, possibly mediated through interference with the PKC activation pathway. The easy and fast synthesis of this compound, low-cost, low-concentration-requirement, and once-daily-administration drug suggest it as a candidate for future clinical studies.

Antinociceptive and anti-inflammatory activities of Cuscuta chinensis seeds in mice

The seeds of Cuscuta chinensis, Cuscutae Semen, are commonly used as a medicinal material for treating the aching and weakness of the loins and knees, tonifying the defects of the liver and the kidney, and treating the diarrhea due to hypofunction of the kidney and the spleen. Since aching and inflammation are highly correlated with such diseases, the aim of this study is to investigate the possible antinociceptive and anti-inflammatory mechanisms of the seeds of C. chinensis. The antinociceptive effect of the seeds of C. chinensis was evaluated via the acetic acid-induced writhing response and formalin-induced paw licking methods. The anti-inflammatory effect was evaluated via the λ-carrageenan induced mouse paw edema method. The results found that 100 and 500 mg/kg of the methanol extract of the seeds of C. chinensis( CC MeOH ) significantly decreased (p < 0.01 and p < 0.001, respectively) the writhing response in the acetic acid assay. Additionally, 20-500 mg/kg of CC MeOH significantly decreased licking time at the early (20 and 100 mg/kg, p < 0.001) and late phases (100 mg/kg, p < 0.01; 500 mg/kg, p < 0.001) of the formalin test, respectively. Furthermore, CC MeOH (100 and 500 mg/kg) significantly decreased (p < 0.01 and p < 0.001, respectively) edema paw volume four hours after λ-carrageenan had been injected. The results in the following study also revealed that the anti-inflammatory mechanism of CC MeOH may be due to declined levels of NO and MDA in the edema paw by increasing the activities of SOD, GPx and GRd in the liver. In addition, CC MeOH also decreased IL-1β, IL-6, NF-κB, TNF-α, and COX-2 levels. This is the first study to demonstrate the possible mechanisms for the antinociceptive and anti-inflammatory effects of CC MeOH in vivo. Thus, it provides evidence for the treatment of Cuscutae Semen in inflammatory diseases.

Pharmacological inhibition of CXCR2 chemokine receptors modulates paraquat-induced intoxication in rats

Paraquat (PQ) is an agrochemical agent commonly used worldwide, which is allied to potential risks of intoxication. This herbicide induces the formation of reactive oxygen species (ROS) that ends up compromising various organs, particularly the lungs and the brain. This study evaluated the deleterious effects of paraquat on the central nervous system (CNS) and peripherally, with special attempts to assess the putative protective effects of the selective CXCR2 receptor antagonist SB225002 on these parameters. PQ-toxicity was induced in male Wistar rats, in a total dose of 50 mg/kg, and control animals received saline solution at the same schedule of administration. Separate groups of animals were treated with the selective CXCR2 antagonist SB225002 (1 or 3 mg/kg), administered 30 min before each paraquat injection. The major changes found in paraquat-treated animals were: decreased body weight and hypothermia, nociception behavior, impairment of locomotor and gait capabilities, enhanced TNF-α and IL-1β expression in the striatum, and cell migration to the lungs and blood. Some of these parameters were reversed when the antagonist SB225002 was administered, including recovery of physiological parameters, decreased nociception, improvement of gait abnormalities, modulation of striatal TNF-α and IL-1β expression, and decrease of neutrophil migration to the lungs and blood. Taken together, our results demonstrate that damage to the central and peripheral systems elicited by paraquat can be prevented by the pharmacological inhibition of CXCR2 chemokine receptors. The experimental evidence presented herein extends the comprehension on the toxicodynamic aspects of paraquat, and opens new avenues to treat intoxication induced by this herbicide.

Opioids enhance CXCL1 expression and function after incision in mice

Chronic opioid consumption increases postoperative pain. Epigenetic changes related to chronic opioid use and surgical incision may be partially responsible for this enhancement. The CXCL1/CXCR2 signaling pathway, implicated in several pain models, is known to be epigenetically regulated via histone acetylation. The current study was designed to investigate the role of CXCL1/CXCR2 signaling in opioid-enhanced incisional sensitization and to elucidate the possible epigenetic mechanism underlying CXCL1/CXCR2 pathway-mediated regulation of nociceptive sensitization in mice. Chronic morphine treatment generated mechanical and thermal nociceptive sensitization and also significantly exacerbated incision-induced mechanical allodynia. Peripheral but not central messenger RNA levels of CXCL1 and CXCR2 were increased after incision. The source of peripheral CXCL1 appeared to be wound area neutrophils. Histone H3 subunit acetylated at the lysine 9 position (AcH3K9) was increased in infiltrating dermal neutrophils after incision and was further increased in mice with chronic morphine treatment. The association of AcH3K9 with the promoter region of CXCL1 was enhanced in mice after chronic morphine treatment. The increase in CXCL1 near wounds caused by chronic morphine pretreatment was mimicked by pharmacologic inhibition of histone deacetylation. Finally, local injection of CXCL1 induced mechanical sensitivity in naive mice, whereas blocking CXCR2 reversed mechanical hypersensitivity after hind paw incision.

PERSPECTIVE

Peripheral CXCL1/CXCR2 signaling helps to control nociceptive sensitization after incision, and epigenetic regulation of CXCL1 expression explains in part opioid-enhanced incisional allodynia in mice. These results suggest that targeting CXCL1/CXCR2 signaling may be useful in treating nociceptive sensitization, particularly for postoperative pain in chronic opioid-consuming patients.

Activation of spinal NF-κB/p65 contributes to peripheral inflammation and hyperalgesia in rat adjuvant-induced arthritis

OBJECTIVE

It is known that noxious stimuli from inflamed tissue may increase the excitability of spinal dorsal horn neurons (a process known as central sensitization), which can signal back and contribute to peripheral inflammation. However, the underlying mechanisms have yet to be fully defined. A number of recent studies have indicated that spinal NF-κB/p65 is involved in central sensitization, as well as pain-related behavior. Thus, the aim of this study was to determine whether NF-κB/p65 can facilitate a peripheral inflammatory response in rat adjuvant-induced arthritis (AIA).

METHODS

Lentiviral vectors encoding short hairpin RNAs that target NF-κB/p65 (LV-shNF-κB/p65) were constructed for gene silencing. The spines of rats with AIA were injected with LV-shNF-κB/p65 on day 3 or day 10 after treatment with Freund's complete adjuvant (CFA). During an observation period of 20 days, pain-related behavior, paw swelling, and joint histopathologic changes were evaluated. Moreover, the expression levels of spinal tumor necrosis factor α (TNFα), interleukin-1β (IL-1β), and cyclooxygenase 2 (COX-2) were assessed on day 14 after CFA treatment.

RESULTS

The presence of peripheral inflammation in rats with AIA induced an increase in NF-κB/p65 expression in the spinal cord, mainly in the dorsal horn neurons and astrocytes. Delivery of LV-shNF-κB/p65 to the spinal cord knocked down the expression of NF-κB/p65 and significantly attenuated hyperalgesia, paw edema, and joint destruction. In addition, spinal delivery of LV-shNF-κB/p65 reduced the overexpression of spinal TNFα, IL-1β, and COX-2.

CONCLUSION

These findings indicate that spinal NF-κB/p65 plays an important role in the initiation and development of both peripheral inflammation and hyperalgesia. Thus, inhibition of spinal NF-κB/p65 expression may provide a potential treatment to manage painful inflammatory disorders.

Chemokine CXCL1 enhances inflammatory pain and increases NMDA receptor activity and COX-2 expression in spinal cord neurons via activation of CXCR2

Recent studies have shown that CXCL1 upregulation in spinal astrocytes is involved in the maintenance of neuropathic pain. However, whether and how CXCL1 regulates inflammatory pain remains unknown. Here we show that intraplantar injection of CFA increased mRNA and protein expressions of CXCL1 and its major receptor CXCR2 in the spinal cord at 6h and 3days after the injection. Immunofluorescence double staining showed that CXCL1 and CXCR2 were expressed in spinal astrocytes and neurons, respectively. Intrathecal injection of CXCL1 neutralizing antibody or CXCR2 antagonist SB225002 attenuated CFA-induced mechanical and heat hypersensitivity on post-CFA day 3. Patch-clamp recordings showed that CXCL1 potentiated NMDA-induced currents in lamina II neurons via CXCR2, and this potentiation was further increased in CFA-treated mice. Furthermore, intrathecal injection of CXCL1 increased COX-2 expression in dorsal horn neurons, which was blocked by pretreatment with SB225002 or MEK (ERK kinase) inhibitor PD98059. Finally, pretreatment with SB225002 or PD98059 decreased CFA-induced heat hyperalgesia and COX-2 mRNA/protein expression and ERK activation in the spinal cord. Taken together, our data suggest that CXCL1, upregulated and released by spinal astrocytes after inflammation, acts on CXCR2-expressing spinal neurons to increase ERK activation, synaptic transmission and COX-2 expression in dorsal horn neurons and contributes to the pathogenesis of inflammatory pain.

The role(s) of cytokines/chemokines in urinary bladder inflammation and dysfunction

Bladder pain syndrome (BPS)/interstitial cystitis (IC) is a chronic pain syndrome characterized by pain, pressure, or discomfort perceived to be bladder related and with at least one urinary symptom. It was recently concluded that 3.3-7.9 million women (>18 years old) in the United States exhibit BPS/IC symptoms. The impact of BPS/IC on quality of life is enormous and the economic burden is significant. Although the etiology and pathogenesis of BPS/IC are unknown, numerous theories including infection, inflammation, autoimmune disorder, toxic urinary agents, urothelial dysfunction, and neurogenic causes have been proposed. Altered visceral sensations from the urinary bladder (i.e., pain at low or moderate bladder filling) that accompany BPS/IC may be mediated by many factors including changes in the properties of peripheral bladder afferent pathways such that bladder afferent neurons respond in an exaggerated manner to normally innocuous stimuli (allodynia). The goals for this review are to describe chemokine/receptor (CXCL12/CXCR4; CCL2/CCR2) signaling and cytokine/receptor (transforming growth factor (TGF-β)/TGF-β type 1 receptor) signaling that may be valuable LUT targets for pharmacologic therapy to improve urinary bladder function and reduce somatic sensitivity associated with urinary bladder inflammation.

Anti-inflammatory and anti-hypersensitive effects of the crude extract, fractions and triterpenes obtained from Chrysophyllum cainito leaves in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Chrysophyllum cainito, popularly known as "star apple", caimito, "abiu-roxo" or "abiu-do-Pará", is a tree of about 25m in height. Besides its culinary use, it is also used in folk medicine for the treatment of diabetes mellitus and several inflammatory diseases.

MATERIALS AND METHODS

The crude methanolic extract (CME) was submitted to phytochemical studies for obtaining fractions and isolated compounds. They were monitored by thin-layer-chromatography (TLC). The biological activity was evaluated in mice using the carrageenan-induced mechanical hypersensitivity and paw oedema. Biochemical assays, such as myeloperoxidase (MPO) and activity and cytokines levels quantification, were carried out to analyse the involvement of neutrophil migration and IL-1β and TNFα production. Some adverse effects were investigated using the open-field and rota-rod tests, and it was also measured the rectal temperature.

RESULTS

This study demonstrates, for the first time, the anti-hypersensitivity and anti-inflammatory effects of CME, fractions and two isolated triterpenes obtained from the leaves of Chrysophyllum cainito on carrageenan-induced hypersensitivity and paw-oedema. The mice treated with CME or chloroform fraction (CHCl3) presented reduction in mechanical hypersensitivity. The effect of the CME seemed to be partially related to the anti-inflammatory activity, as the paw-oedema and MPO activity were also significantly inhibited. The isolated compound Lup-20(29)-en-3β-O-hexanoate demonstrated more reduction of the hypersensitivity than 3β-Lup-20(29)-en-3-yl acetate, suggesting that this molecule might be partially responsible for the biological effects obtained with CME and CHCl3 fractions. Finally, animals treated with CME and CHCl3 did not present changes in locomotor activity, motor performance or body temperature.

CONCLUSIONS

Our data demonstrates, for the first time, that the crude extract, fractions and pure compounds obtained from the Chrysophyllum cainito leaves possess important anti-hypersensitive properties against inflammatory pain in mice. The mechanisms through which Chrysophyllum cainito exerts its anti-hypersensitive actions are still unclear, and require further investigation; however, this could well constitute a new and attractive alternative for the management of persistent inflammatory and neuropathic pain in humans.

Role of CXCR2 and TRPV1 in functional, inflammatory and behavioural changes in the rat model of cyclophosphamide-induced haemorrhagic cystitis

BACKGROUND AND PURPOSE

Cyclophosphamide induces urotoxicity characterized by the development of cystitis, which involves bladder overactivity and inflammation. Here, we investigated the roles of chemokine receptor 2 (CXCR2) and transient receptor potential vanilloid 1 (TRPV1) channels in a rat model of cyclophosphamide-induced cystitis.

EXPERIMENTAL APPROACH

Cystitis induced by cyclophosphamide in rats was assessed by gross morphology, histology and immunohistochemistry of bladder tissue. mRNA for CXCR2 and TRPV1 channels were measured by RT-PCR. Nociceptive responses in paw and abdomen, along with cystometric measures were recorded.

KEY RESULTS

Cyclophosphamide, i.p., induced pain behaviour, bladder inflammation and voiding dysfunction. The CXCR2 antagonist, SB225002, the TRPV1 channel antagonist, SB366791 or their combination reduced the mechanical hypersensitivity of paw and abdominal area and nociceptive behaviour after cyclophosphamide. Cyclophosphamide-induced cystitis was characterized by haemorrhage, oedema, neutrophil infiltration and other inflammatory changes, which were markedly decreased by the antagonists. Up-regulation of CXCR2 and TRPV1 mRNA in the bladder after cyclophosphamide was inhibited by SB225002, SB366791 or their combination. Expression of CXCR2 and TRPV1 channels was increased in the urothelium after cyclophosphamide. Bladder dysfunction was shown by increased number of non-voiding contractions (NVCs) and bladder pressures and a reduction in bladder capacity (BC), voided volume (VV) and voiding efficiency (VE). SB225002 or its combination with SB366791 reduced bladder pressures, whereas SB225002, SB366791 or their combination increased BC, VV and VE, and also reduced the number of NVCs.

CONCLUSIONS AND IMPLICATIONS

CXCR2 and TRPV1 channels play important roles in cyclophosphamide-induced cystitis in rats and could provide potential therapeutic targets for cystitis.

Epigenetic regulation of spinal CXCR2 signaling in incisional hypersensitivity in mice

BACKGROUND

The regulation of gene expression in nociceptive pathways contributes to the induction and maintenance of pain sensitization. Histone acetylation is a key epigenetic mechanism controlling chromatin structure and gene expression. Chemokine CC motif receptor 2 (CXCR2) is a proinflammatory receptor implicated in neuropathic and inflammatory pain and is known to be regulated by histone acetylation in some settings. The authors sought to investigate the role of histone acetylation on spinal CXCR2 signaling after incision.

METHODS

Groups of 5-8 mice underwent hind paw incision. Suberoylanilide hydroxamic acid and anacardic acid were used to inhibit histone deacetylase and histone acetyltransferase, respectively. Behavioral measures of thermal and mechanical sensitization as well as hyperalgesic priming were used. Both message RNA quantification and chromatin immunoprecipitation analysis were used to study the regulation of CXCR2 and ligand expression. Finally, the selective CXCR2 antagonist SB225002 was administered intrathecally to reveal the function of spinal CXCR2 receptors after hind paw incision.

RESULTS

Suberoylanilide hydroxamic acid significantly exacerbated mechanical sensitization after incision. Conversely, anacardic acid reduced incisional sensitization and also attenuated incision-induced hyperalgesic priming. Overall, acetylated histone H3 at lysine 9 was increased in spinal cord tissues after incision, and enhanced association of acetylated histone H3 at lysine 9 with the promoter regions of CXCR2 and keratinocyte-derived chemokine (CXCL1) was observed as well. Blocking CXCR2 reversed mechanical hypersensitivity after hind paw incision.

CONCLUSIONS

Histone modification is an important epigenetic mechanism regulating incision-induced nociceptive sensitization. The spinal CXCR2 signaling pathway is one epigenetically regulated pathway controlling early and latent sensitization after incision.

Comparison of active constituents, acute toxicity, anti-nociceptive and anti-inflammatory activities of Porana sinensis Hemsl., Erycibe obtusifolia Benth. and Erycibe schmidtii Craib

ETHNOPHARMACOLOGICAL RELEVANCE

Erycibe obtusifolia and Erycibe schmidtii, which belong to the same genus as Erycibe, are widely used in traditional medicine for the treatment of joint pain and rheumatoid arthritis (RA). Porana sinensis has become a widely used substitute for Erycibe obtusifolia and Erycibe schmidtii as they have declined in the wild. In the present work, the content of the main active components, the acute toxicity, the anti-nociceptive and anti-inflammatory activities of Porana sinensis, Erycibe obtusifolia and Erycibe schmidtii were compared, and the mechanisms of anti-nociceptive and anti-inflammatory activities were discussed.

MATERIALS AND METHODS

A quantitative HPLC (high performance liquid chromatography) method was first developed to compare the content of the main active components (scopoletin, scopolin and chlorogenic acid). The anti-inflammatory and anti-nociceptive activities of 40% ethanolic extracts of the three plants were compared using the models of xylene-induced ear edema, formalin-induced inflammation, carrageenan-induced air pouch inflammation, acetic acid-induced writhing and formalin-induced nociception. The acute toxicity of the 40% ethanolic extracts of the three plants was studied.

RESULTS

The assay suggested a large content of scopoletin, scopolin and chlorogenic acid in the three plants. The 40% ethanolic extracts of the three plants were almost non-toxic at the dose of 5g/kg and all of them showed significant anti-inflammatory effects in the tests of xylene-induced ear edema and formalin-induced inflammation. In the carrageenan-induced air pouch inflammation test, the synthesis of PGE2 was significantly inhibited by all the extracts. They significantly inhibited the number of contortions induced by acetic acid and the second phase of the formalin-induced licking response. Naloxone was not able to reverse the analgesic effect of these extracts.

CONCLUSION

The study identifies the similarity of the three plants in their main active components as well as acute toxicity, anti-nociceptive and anti-inflammatory activities. It supports the use of Porana sinensis as a suitable substitute, but further studies are needed to confirm this.

Chemokines as peripheral pain mediators

Multiple lines of evidence support the notion that much if not most chronic pain is dependent on on-going peripheral activity in nociceptors. This is not to say that central changes are unimportant, only that much of the central change is supported by a peripheral drive. This begs the question of what causes this peripheral drive. In some instances, particularly in association with peripheral nerve injury, nociceptors may become spontaneously active because of alterations in ion channel function or expression. But in most cases nociceptor activity arises because of the actions of peripheral mediators released by injured or damaged tissue. Some of these mediators are well known, such as the prostanoids. Others have more recently been identified, such as nerve growth factor (NGF). However, the limited efficacy of existing analgesic therapies strongly suggests that other important pain mediators exist. Here we discuss the evidence that a family of secreted proteins, the chemokines - well known for their actions in regulating immune cell migration - also play an important role in sustaining abnormal nociceptor activity in persistent pain states.

Molecular mechanisms of the antitumor activity of SB225002: a novel microtubule inhibitor

SB225002 (SB) is an IL-8 receptor B (IL-8RB) antagonist that has previously been shown to inhibit IL-8-based cancer cell invasion, and to possess in vivo anti-inflammatory and anti-nociceptive effects. The present study presented an evidence for the cell cycle-targeting activity of SB in a panel of p53-mutant human cancer cell lines of different origin, and investigated the underlying molecular mechanisms. A combination of cell cycle analysis, immunocytometry, immunoblotting, and RNA interference revealed that SB induced a BubR1-dependent mitotic arrest. Mechanistically, SB was shown to possess a microtubule destabilizing activity evidenced by hyperphosphorylation of Bcl2 and BclxL, suppression of microtubule polymerization and induction of a prometaphase arrest. Molecular docking studies suggested that SB has a good affinity toward vinblastine-binding site on β-tubulin subunit. Of note, SB265610 which is a close structural analog of SB225002 with a potent IL-8RB antagonistic activity did not exhibit a similar antimitotic activity. Importantly, in P-glycoprotein overexpressing NCI/Adr-Res cells the antitumor activity of SB was unaffected by multidrug resistance. Interestingly, the mechanisms of SB-induced cell death were cell-line dependent, where in invasive hepatocellular carcinoma HLE cells the significant contribution of BAK-dependent mitochondrial apoptosis was demonstrated. Conversely, SB activated p38 MAPK signaling in colorectal adenocarcinoma cells SW480, and pharmacologic inhibition of p38 MAPK activity revealed its key role in mediating SB-induced caspase-independent cell death. In summary, the present study introduced SB as a promising antitumor agent which has the potential to exert its activity through dual mechanisms involving microtubules targeting and interference with IL-8-drivin cancer progression.

Sensory and signaling mechanisms of bradykinin, eicosanoids, platelet-activating factor, and nitric oxide in peripheral nociceptors

Peripheral mediators can contribute to the development and maintenance of inflammatory and neuropathic pain and its concomitants (hyperalgesia and allodynia) via two mechanisms. Activation or excitation by these substances of nociceptive nerve endings or fibers implicates generation of action potentials which then travel to the central nervous system and may induce pain sensation. Sensitization of nociceptors refers to their increased responsiveness to either thermal, mechanical, or chemical stimuli that may be translated to corresponding hyperalgesias. This review aims to give an account of the excitatory and sensitizing actions of inflammatory mediators including bradykinin, prostaglandins, thromboxanes, leukotrienes, platelet-activating factor, and nitric oxide on nociceptive primary afferent neurons. Manifestations, receptor molecules, and intracellular signaling mechanisms of the effects of these mediators are discussed in detail. With regard to signaling, most data reported have been obtained from transfected nonneuronal cells and somata of cultured sensory neurons as these structures are more accessible to direct study of sensory and signal transduction. The peripheral processes of sensory neurons, where painful stimuli actually affect the nociceptors in vivo, show marked differences with respect to biophysics, ultrastructure, and equipment with receptors and ion channels compared with cellular models. Therefore, an effort was made to highlight signaling mechanisms for which supporting data from molecular, cellular, and behavioral models are consistent with findings that reflect properties of peripheral nociceptive nerve endings. Identified molecular elements of these signaling pathways may serve as validated targets for development of novel types of analgesic drugs.

Analgesic and Anti-Inflammatory Activities of Methanol Extract of Cissus repens in Mice

The aim of this study was to investigate possible analgesic and anti-inflammatory mechanisms of the CR_MeOH. Analgesic effect was evaluated in two models including acetic acid-induced writhing response and formalin-induced paw licking. The anti-inflammatory effect was evaluated by λ-carrageenan-induced mouse paw edema and histopathologic analyses. The results showed that CR_MeOH (500 mg/kg) decreased writhing response in the acetic acid assay and licking time in the formalin test. CR_MeOH (100 and 500 mg/kg) significantly decreased edema paw volume at 4th to 5th hours after λ-carrageenan had been injected. Histopathologically, CR_MeOH abated the level of tissue destruction and swelling of the edema paws. These results were indicated that anti-inflammatory mechanism of CR_MeOH may be due to declined levels of NO and MDA in the edema paw through increasing the activities of SOD, GPx, and GRd in the liver. Additionally, CR_MeOH also decreased IL-1β, IL-6, NFκB, TNF-α, COX-2, and iNOS levels. The contents of two active ingredients, ursolic acid and lupeol, were quantitatively determined. This paper demonstrated possible mechanisms for the analgesic and anti-inflammatory effects of CR_MeOH and provided evidence for the classical treatment of Cissus repens in inflammatory diseases.

Analgesic and Anti-Inflammatory Activities of Methanol Extract of Ficus pumila L. in Mice

This study investigated possible analgesic and anti-inflammatory mechanisms of the methanol extract of Ficus pumila (FP_MeOH). Analgesic effects were evaluated in two models including acetic acid-induced writhing response and formalin-induced paw licking. The results showed FP_MeOH decreased writhing response in the acetic acid assay and licking time in the formalin test. The anti-inflammatory effect was evaluated by λ-carrageenan-induced mouse paw edema and histopathological analyses. FP_MeOH significantly decreased the volume of paw edema induced by λ-carrageenan. Histopathologically, FP_MeOH abated the level of tissue destruction and swelling of the edema paws. This study indicated anti-inflammatory mechanism of FP_MeOH may be due to declined levels of NO and MDA in the edema paw through increasing the activities of SOD, GPx, and GRd in the liver. Additionally, FP_MeOH also decreased the level of inflammatory mediators such as IL-1β, TNF-α, and COX-2. HPLC fingerprint was established and the contents of three active ingredients, rutin, luteolin, and apigenin, were quantitatively determined. This study provided evidence for the classical treatment of Ficus pumila in inflammatory diseases.

TRPM2 contributes to inflammatory and neuropathic pain through the aggravation of pronociceptive inflammatory responses in mice

Accumulating evidence suggests that neuroimmune interactions contribute to pathological pain. Transient receptor potential melastatin 2 (TRPM2) is a nonselective Ca²⁺-permeable cation channel that acts as a sensor for reactive oxygen species. TRPM2 is expressed abundantly in immune cells and is important in inflammatory processes. The results of the present study show that TRPM2 plays a crucial role in inflammatory and neuropathic pain. While wild-type and TRPM2 knock-out mice showed no difference in their basal sensitivity to mechanical and thermal stimulation, nocifensive behaviors in the formalin test were reduced in TRPM2 knock-out mice. In carrageenan-induced inflammatory pain and sciatic nerve injury-induced neuropathic pain models, mechanical allodynia and thermal hyperalgesia were attenuated in TRPM2 knock-out mice. Carrageenan-induced inflammation and sciatic nerve injury increased the expression of TRPM2 mRNA in the inflamed paw and around the injured sciatic nerve, respectively. TRPM2 deficiency diminished the infiltration of neutrophils and the production of chemokine (C-X-C motif) ligand-2 (CXCL2), a major chemokine that recruits neutrophils, but did not alter the recruitment of F4/80-positive macrophages in the inflamed paw or around the injured sciatic nerve. Microglial activation after nerve injury was suppressed in the spinal cord of TRPM2 knock-out mice. Furthermore, CXCL2 production and inducible nitric oxide synthase induction were diminished in cultured macrophages and microglia derived from TRPM2 knock-out mice. Together, these results suggest that TRPM2 expressed in macrophages and microglia aggravates peripheral and spinal pronociceptive inflammatory responses and contributes to the pathogenesis of inflammatory and neuropathic pain.

Antihyperalgesic activity of the methanol extract and some constituents obtained from Polygala cyparissias (Polygalaceae)

Polygala cyparissias, used in folk medicine as an anaesthetic, has already demonstrated antinociceptive activity against acute pain. In this study, we investigated the antihyperalgesic activity of the P. cyparissias methanol extract (PCME) from which the following compounds were isolated: α-spinasterol (PC1), 1,3-dihydroxy-7-methoxyxanthone (PC2), 1,7-dihydroxy-2,3-methylenedioxyxanthone (PC3) and 1,3,6,8-tetrahydroxy-2,7-dimethoxyxanthone (PC4). The antihyperalgesic effect was evaluated using experimental models of persistent pain induced by carrageenan, lipopolysaccharide (LPS), Freund's Complete Adjuvant (CFA), PGE(2) or epinephrine. The partial ligation of the sciatic nerve (PLSN) model was also used. In inflammatory hyperalgesia induced by carrageenan, LPS, CFA or PGE(2), the inhibition values obtained with the PCME treatment were 68 ± 3%, 89 ± 5%, 43 ± 3% and 40 ± 4%, respectively. In epinephrine-induced hyperalgesia, the extract was effective, reducing 99 ± 11% of response frequency, while in PLSN, 54 ± 4% of inhibition was obtained. These results allow to suggest that the antihyperalgesic activity of PCME is, at least in part, related to its capability to inhibit the hypersensitization induced by pro-inflammatory mediators, such as LPS, carrageenan and CFA, without interfering with locomotor activity or motor performance. Furthermore, compounds PC1, PC3 and PC4 inhibited the carrageenan-induced hyperalgesia with inhibition of 42 ± 6%, 48 ± 5% and 64 ± 4%, respectively. In summary, our data demonstrate that PCME has relevant antihyperalgesic activity and that the isolated PC1, PC3 and PC4 seem to be responsible, at least in part, for this important effect.

Epigenetic augmentation of the macrophage inflammatory protein 2/C-X-C chemokine receptor type 2 axis through histone H3 acetylation in injured peripheral nerves elicits neuropathic pain

Although there is growing evidence showing that the involvement of chemokines in the pathogenesis of neuropathic pain is associated with neuroinflammation, the details are unclear. We investigated the C-X-C chemokine ligand type 2 [macrophage inflammatory protein 2 (MIP-2)]/C-X-C chemokine receptor type 2 (CXCR2) axis and epigenetic regulation of these molecules in neuropathic pain after peripheral nerve injury. Expression of MIP-2 and CXCR2 were up-regulated and localized on accumulated neutrophils and macrophages in the injured sciatic nerve (SCN) after partial sciatic nerve ligation (PSL). Perineural injection of MIP-2-neutralizing antibody (anti-MIP-2) or the CXCR2 antagonist N-(2-bromophenyl)-N'-(2-hydroxy-4-nitrophenyl)urea (SB225002) prevented PSL-induced tactile allodynia and thermal hyperalgesia. Perineural injection of recombinant MIP-2 elicited neuropathic pain-like behaviors. Anti-MIP-2 suppressed neutrophil accumulation in the SCN after PSL. Neutrophil depletion by intraperitoneal injection of Ly6G antibody attenuated PSL-induced neuropathic pain. Both anti-MIP-2 and SB225002 suppressed up-regulation of inflammatory cytokines and chemokines in the injured SCN. In addition, acetylation of histone H3 [lysine (Lys9)-acetylated histone H3 (AcK9-H3)] on the promoter region of MIP-2 and CXCR2 was increased in the injured SCN after PSL. Expression of AcK9-H3 was observed in the nuclei of neutrophils and macrophages surrounding the epineurium. Administration of the histone acetyltransferase inhibitor anacardic acid suppressed the up-regulation of MIP-2 and CXCR2 in the SCN after PSL and resulted in the prevention of PSL-induced neuropathic pain. Taken together, these results show that augmentation of the MIP-2/CXCR2 axis by hyperacetylation of histone H3 on the promoter region of MIP-2 and CXCR2 located in the injured peripheral nerve elicits chronic neuroinflammation through neutrophil accumulation, leading to neuropathic pain.

CXCL5 mediates UVB irradiation-induced pain

Many persistent pain states (pain lasting for hours, days, or longer) are poorly treated because of the limitations of existing therapies. Analgesics such as nonsteroidal anti-inflammatory drugs and opioids often provide incomplete pain relief and prolonged use results in the development of severe side effects. Identification of the key mediators of various types of pain could improve such therapies. Here, we tested the hypothesis that hitherto unrecognized cytokines and chemokines might act as mediators in inflammatory pain. We used ultraviolet B (UVB) irradiation to induce persistent, abnormal sensitivity to pain in humans and rats. The expression of more than 90 different inflammatory mediators was measured in treated skin at the peak of UVB-induced hypersensitivity with custom-made polymerase chain reaction arrays. There was a significant positive correlation in the overall expression profiles between the two species. The expression of several genes [interleukin-1β (IL-1β), IL-6, and cyclooxygenase-2 (COX-2)], previously shown to contribute to pain hypersensitivity, was significantly increased after UVB exposure, and there was dysregulation of several chemokines (CCL2, CCL3, CCL4, CCL7, CCL11, CXCL1, CXCL2, CXCL4, CXCL7, and CXCL8). Among the genes measured, CXCL5 was induced to the greatest extent by UVB treatment in human skin; when injected into the skin of rats, CXCL5 recapitulated the mechanical hypersensitivity caused by UVB irradiation. This hypersensitivity was associated with the infiltration of neutrophils and macrophages into the dermis, and neutralizing the effects of CXCL5 attenuated the abnormal pain-like behavior. Our findings demonstrate that the chemokine CXCL5 is a peripheral mediator of UVB-induced inflammatory pain, likely in humans as well as rats.