Neuromuscular ultrasound for taxane peripheral neuropathy in breast cancer.

BACKGROUND: Our study aim was to evaluate neuromuscular ultrasound (NMUS) for the assessment of taxane chemotherapy-induced peripheral neuropathy (CIPN), the dose-limiting toxicity of this agent. METHODS: This cross-sectional study of breast cancer patients with taxane CIPN measured nerve cross-sectional area (CSA) by NMUS and compared with healthy historical controls. Correlations were determined between CSA and symptom scale, nerve conduction studies, and intraepidermal nerve fiber density (IENFD). RESULTS: A total of 20 participants reported moderate CIPN symptoms at a median of 3.8 months following the last taxane dose. Sural nerve CSA was 1.2 mm2 smaller than healthy controls (P ≤ .01). Older age and time since taxane were associated with smaller sural nerve CSA. For each 1 mm2 decrease in sural nerve CSA, distal IENFD decreased by 2.1 nerve/mm (R2 0.30; P = .04). CONCLUSIONS: These data support a sensory predominant taxane neuropathy or neuronopathy and warrant future research on longitudinal NMUS assessment of CIPN.

Mitogen activated protein kinase phosphatase-1 prevents the development of tactile sensitivity in a rodent model of neuropathic pain.

BACKGROUND: Neuropathic pain due to nerve injury is one of the most difficult types of pain to treat. Following peripheral nerve injury, neuronal and glial plastic changes contribute to central sensitization and perpetuation of mechanical hypersensitivity in rodents. The mitogen activated protein kinase (MAPK) family is pivotal in this spinal cord plasticity. MAPK phosphatases (MKPs) limit inflammatory processes by dephosphorylating MAPKs. For example, MKP-1 preferentially dephosphorylates p-p38. Since spinal p-p38 is pivotal for the development of chronic hypersensitivity in rodent models of pain, and p-p38 inhibitors have shown clinical potential in acute and chronic pain patients, we hypothesize that induction of spinal MKP-1 will prevent the development of peripheral nerve-injury-induced hypersensitivity and p-p38 overexpression. RESULTS: We cloned rat spinal cord MKP-1 and optimize MKP-1 cDNA in vitro using transfections to BV-2 cells. We observed that in vitro overexpression of MKP-1 blocked lipopolysaccharide-induced phosphorylation of p38 (and other MAPKs) as well as release of pro-algesic effectors (i.e., cytokines, chemokines, nitric oxide). Using this cDNA MKP-1 and a non-viral, in vivo nanoparticle transfection approach, we found that spinal cord overexpression of MKP-1 prevented development of peripheral nerve-injury-induced tactile hypersensitivity and reduced pro-inflammatory cytokines and chemokines and the phosphorylated form of p38. CONCLUSIONS: Our results indicate that MKP-1, the natural regulator of p-p38, mediates resolution of the spinal cord pro-inflammatory milieu induced by peripheral nerve injury, resulting in prevention of chronic mechanical hypersensitivity. We propose that MKP-1 is a potential therapeutic target for pain treatment or prevention.

Cannabinoid receptor type 2 activation induces a microglial anti-inflammatory phenotype and reduces migration via MKP induction and ERK dephosphorylation.

BACKGROUND: Cannabinoid receptor type 2 (CBR2) inhibits microglial reactivity through a molecular mechanism yet to be elucidated. We hypothesized that CBR2 activation induces an anti-inflammatory phenotype in microglia by inhibiting extracellular signal-regulated kinase (ERK) pathway, via mitogen-activated protein kinase-phosphatase (MKP) induction. MKPs regulate mitogen activated protein kinases, but their role in the modulation of microglial phenotype is not fully understood. RESULTS: JWH015 (a CBR2 agonist) increased MKP-1 and MKP-3 expression, which in turn reduced p-ERK1/2 in LPS-stimulated primary microglia. These effects resulted in a significant reduction of tumor necrosis factor-alpha (TNF) expression and microglial migration. We confirmed the causative link of these findings by using MKP inhibitors. We found that the selective inhibition of MKP-1 by Ro-31-8220 and PSI2106, did not affect p-ERK expression in LPS+JWH015-treated microglia. However, the inhibition of both MKP-1 and MKP-3 by triptolide induced an increase in p-ERK expression and in microglial migration using LPS+JWH015-treated microglia. CONCLUSION: Our results uncover a cellular microglial pathway triggered by CBR2 activation. These data suggest that the reduction of pro-inflammatory factors and microglial migration via MKP-3 induction is part of the mechanism of action of CBR2 agonists. These findings may have clinical implications for further drug development.

Cytokine production capabilities of human primary monocyte-derived macrophages from patients with diabetes mellitus type 2 with and without diabetic peripheral neuropathy.

INTRODUCTION: Monocytes from patients with diabetes mellitus type 2 (DM2) are dysfunctional, persistently primed, and prone to a proinflammatory phenotype. This may alter the phenotype of their differentiation to macrophages and result in diabetic peripheral neuropathy (DPN), nerve damage, nerve sensitization, and chronic pain. We have previously demonstrated that CD163 is a molecule that promotes an anti-inflammatory cellular phenotype in human primary macrophages, but this has not been proven in macrophages from patients with DM2 or DPN. Thus, we hypothesize that macrophages from patients with DM2 or DPN display an altered proinflammatory functional phenotype related to cytokine production and that the induction of CD163 expression will promote a more homeostatic phenotype by reducing their proinflammatory responsiveness. PATIENTS AND METHODS: We tested these hypotheses in vitro using blood monocyte-derived macrophages from healthy subjects and patients with DM2 with and without DPN. Cells were incubated in the presence or the absence of 5 µg/mL of lipopolysaccharide (LPS). The concentrations of interleukin-10, interleukin-6, tumor necrosis factor-alpha (TNF-α), TGF-ß, and monocyte chemoattractant protein-1 (MCP-1) were measured using ELISA assays. Macrophages were transfected with an empty vector plasmid or a plasmid containing the CD163 gene using mannosylated polyethylenimine nanoparticles. RESULTS: Our results show that nonstimulated DM2 or DPN macrophages have a constitutive primed proinflammatory state and display a deficient production of proinflammatory cytokines upon a proinflammatory challenge when compared to healthy macrophages. CD163 induction produced an anti-inflammatory phenotype in the healthy control group, and this effect was partial in DM2 or DPN macrophages. CONCLUSION: Our results suggest that diabetic macrophages adopt a complex phenotype that is only partially reversed by CD163 induction. Future experiments are focused on elucidating this differential responsiveness between healthy and diabetic macrophages.

Neuroimmune interactions and pain: focus on glial-modulating targets.

Chronic pain is the most difficult type of pain to treat. Previously, the development of analgesics has focused on neuronal targets; however, current analgesics are only modestly effective, have significant side effects and do not provide universal efficacy. New strategies are needed for the development of more effective analgesics. Glial cells have integral roles in CNS homeostasis, and chronic pain etiology and progression. In this review, the role of glia in neuropathic pain and opioid administration is described, as well as the potential superior efficacy and wider therapeutic indices provided by drugs that modulate specific glial function via novel targets.

Propentofylline, a CNS glial modulator does not decrease pain in post-herpetic neuralgia patients: in vitro evidence for differential responses in human and rodent microglia and macrophages.

There is a growing body of preclinical evidence for the potential involvement of glial cells in neuropathic pain conditions. Several glial-targeted agents are in development for the treatment of pain conditions. Here we report the failure of a glial modulating agent, propentofylline, to decrease pain reported in association with post-herpetic neuralgia. We offer new evidence to help explain why propentofylline failed in patients by describing in vitro functional differences between rodent and human microglia and macrophages. We directly compared the proinflammatory response induced by lipopolysaccharide (LPS) with or without propentofylline using rat postnatal microglia, rat peritoneal macrophages, human fetal microglia, human peripheral macrophages and human immortalized THP-1 cells. We measured tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1ß) and nitrite release (as an indicator of nitric oxide (NO)) as downstream indicators. We found that LPS treatment did not induce nitrite in human microglia, macrophages or THP-1 cells; however LPS treatment did induce nitrite release in rat microglia and macrophages. Following LPS exposure, propentofylline blocked TNF-α release in rodent microglia with all the doses tested (1-100 µM), and dose-dependently decreased TNF-α release in rodent macrophages. Propentofylline partially decreased TNF-α (35%) at 100 µM in human microglia, macrophages and THP-1 macrophages. Propentofylline blocked nitrite release from LPS stimulated rat microglia and inhibited nitrite in LPS-stimulated rat macrophages. IL-1ß was decreased in LPS-stimulated human microglia following propentofylline at 100 µM. Overall, human microglia were less responsive to LPS stimulation and propentofylline treatment than the other cell types. Our data demonstrate significant functional differences between cell types and species following propentofylline treatment and LPS stimulation. These results may help explain the differential behavioral effects of propentofylline observed between rodent models of pain and the human clinical trial.

Propentofylline decreases tumor growth in a rodent model of glioblastoma multiforme by a direct mechanism on microglia.

Glioblastoma multiforme (GBM) is the most common and aggressive primary brain cancer, with a median survival of less than 2 years after diagnosis. The tumor microenvironment plays a critical role in tumor invasion and progression. Microglia and infiltrating macrophages are the most abundant immune cells in the tumor. In the present study, we demonstrate that systemic propentofylline (PPF), an atypical methylxanthine with central nervous system (CNS) glial modulating and anti-inflammatory actions, significantly decreased tumor growth in a CNS-1 rat model of GBM by targeting microglia and not tumor cells. Rats received tumor injections of 1 × 10(5) CNS-1 cells in the right striatum with daily intraperitonial injections of PPF (50 mg/kg) or saline beginning the day of tumor injection. PPF did not cause apoptosis or decrease proliferation of CNS-1 tumor cells. Furthermore, we demonstrate, using in vitro methods, that PPF decreased microglial migration toward CNS-1 tumor cells and decreased MMP-9 expression. The effects of PPF were shown to be specific to microglia and not peripheral macrophages. These results support a differential functional role of resident microglia and infiltrating macrophages in the brain tumor environment. Our data highlight microglia as a crucial target for future therapeutic development and present PPF as a possible drug for treatment of human GBM.

Proinflammatory cytokines mediating burn-injury pain.

Thermal burns induce pain at the site of injury, mechanical hyperalgesia, associated with a complex time-dependent inflammatory response. To determine the contribution of inflammatory mediators to burn injury-induced mechanical hyperalgesia, we measured dynamic changes in the levels of three potent hyperalgesic cytokines, interleukin IL-1 beta, IL-6, and tumor necrosis factor-alpha (TNFalpha), in skin of the rat, following a partial-thickness burn injury. Only IL-6 demonstrated a sustained increase ipsilateral but not contralateral to the burn, correlating with the prolonged ipsilateral mechanical hyperalgesia. Spinal intrathecal injection of oligodeoxynucleotides antisense for gp130, a receptor subunit shared by members of the IL-6 family of cytokines, attenuated both burn- and intradermal IL-6-induced hyperalgesia, as did intradermal injection of anti-IL-6 function blocking antibodies. These studies suggest that IL-6 is an important mediator of burn-injury pain.