Fibroblast-derived PI16 sustains inflammatory pain via regulation of CD206+ myeloid cells

Originally identified in fibroblasts, Protease Inhibitor (PI)16 was recently shown to be crucial for the development of neuropathic pain via effects on blood-nerve barrier permeability and leukocyte infiltration, though its impact on inflammatory pain has not been established. Using the complete Freund's Adjuvant inflammatory pain model, we show that Pi16-/- mice are protected against sustained inflammatory pain. Accordingly, intrathecal delivery of a PI16 neutralizing antibody in wild-type mice prevented sustained CFA pain. In contrast to neuropathic pain models, we did not observe any changes in blood-nerve barrier permeability due to PI16 deletion. Instead, Pi16-/- mice display reduced macrophage density in the CFA-injected hindpaw. Furthermore, there was a significant bias toward CD206hi (anti-inflammatory) macrophages in the hindpaw and associated dorsal root ganglia. Following CFA, intrathecal depletion of CD206+ macrophages using mannosylated clodronate liposomes promoted sustained pain in Pi16-/- mice. Similarly, an IL-10 neutralizing antibody also promoted sustained CFA pain in the Pi16-/ when administered intrathecally. Collectively, our results point to fibroblast-derived PI16 mediating substantial differences in macrophage phenotype in the pain neuroaxis under conditions of inflammation. The co-expression of PI16 alongside fibroblast markers in human DRG raise the likelihood that a similar mechanism operates in human inflammatory pain states. Collectively, our findings may have implications for targeting fibroblast-immune cell crosstalk for the treatment of chronic pain.

Intranasally Administered MSC-Derived Extracellular Vesicles Reverse Cisplatin-Induced Cognitive Impairment

Neurotoxic side effects of chemotherapy include deficits in attention, memory, and executive functioning. Currently, there are no FDA-approved therapies. In mice, cisplatin causes long-term cognitive deficits, white matter damage, mitochondrial dysfunction, and loss of synaptic integrity. We hypothesized that MSC-derived small extracellular vesicles (sEVs) could restore cisplatin-induced cognitive impairments and brain damage. Animals were injected with cisplatin intraperitoneally and treated with MSC-derived sEVs intranasally 48 and 96 h after the last cisplatin injection. The puzzle box test (PBT) and the novel object place recognition test (NOPRT) were used to determine cognitive deficits. Synaptosomal mitochondrial morphology was analyzed by transmission electron microscopy. Immunohistochemistry using antibodies against synaptophysin and PSD95 was applied to assess synaptic loss. Black-Gold II staining was used to quantify white matter integrity. Our data show that sEVs enter the brain in 30 min and reverse the cisplatin-induced deficits in executive functioning and working and spatial memory. Abnormalities in mitochondrial morphology, loss of white matter, and synaptic integrity in the hippocampus were restored as well. Transcriptomic analysis revealed upregulation of regenerative functions after treatment with sEVs, pointing to a possible role of axonal guidance signaling, netrin signaling, and Wnt/Ca²⁺ signaling in recovery. Our data suggest that intranasal sEV treatment could become a novel therapeutic approach for the treatment of chemobrain.

Discovery of IACS-52825, a Potent and Selective DLK Inhibitor for Treatment of Chemotherapy-Induced Peripheral Neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN) is a major unmet medical need with limited treatment options. Despite different mechanisms of action, diverse chemotherapeutics can cause CIPN through a converged pathway─an active axon degeneration program that engages the dual leucine zipper kinase (DLK). DLK is a neuronally enriched kinase upstream in the MAPK-JNK cascade, and while it is dormant under physiological conditions, DLK mediates a core mechanism for neuronal injury response under stress conditions, making it an attractive target for treatment of neuronal injury and neurodegenerative diseases. We have developed potent, selective, brain penetrant DLK inhibitors with excellent PK and activity in mouse models of CIPN. Lead compound IACS-52825 (22) showed strongly effective reversal of mechanical allodynia in a mouse model of CIPN and was advanced into preclinical development.

Tonic Meningeal Interleukin-10 Upregulates Delta Opioid Receptor to Prevent Relapse to Pain

Chronic pain often alternates between transient remission and relapse of severe pain. While most research on chronic pain has focused on mechanisms maintaining pain, there is a critical unmet need to understand what prevents pain from re-emerging in those who recover from acute pain. We found that interleukin (IL)-10, a pain resolving cytokine, is persistently produced by resident macrophages in the spinal meninges during remission from pain. IL-10 upregulated expression and analgesic activity of δ-opioid receptor (δOR) in the dorsal root ganglion. Genetic or pharmacological inhibition of IL-10 signaling or δOR triggered relapse to pain in both sexes. These data challenge the widespread assumption that remission of pain is simply a return to the naïve state before pain was induced. Instead, our findings strongly suggest a novel concept that: remission is a state of lasting pain vulnerability that results from a long-lasting neuroimmune interactions in the nociceptive system.

Resolution of cisplatin-induced fatigue does not require endogenous interleukin-10 in male mice

Based on previous results showing a pivotal role of endogenous interleukin-10 (IL-10) in the recovery from cisplatin-induced peripheral neuropathy, the present experiments were carried out to determine whether this cytokine plays any role in the recovery from cisplatin-induced fatigue in male mice. Fatigue was measured by decreased voluntary wheel running in mice trained to run in a wheel in response to cisplatin. Mice were treated with a monoclonal neutralizing antibody (IL-10na) administered intranasally during the recovery period to neutralize endogenous IL-10. In the first experiment, mice were treated with cisplatin (2.83 mg/kg/day) for five days and IL-10na (12 μg/day for three days) five days later. In the second experiment, they were treated with cisplatin (2.3 mg/kg/day for 5 days twice at a five-day interval) and IL10na (12 μg/day for three days) immediately after the last injection of cisplatin. In both experiments, cisplatin decreased body weight and reduced voluntary wheel running. However, IL-10na did not impair recovery from these effects. These results show that the recovery from the cisplatin-induced decrease in wheel running does not require endogenous IL-10 in contrast to the recovery from cisplatin-induced peripheral neuropathy.

Employment and family income in psychological and immune outcomes during bereavement

Spousal bereavement is one of the most stressful experiences in adulthood. In a sample of 183 widow(er)s, bereaved about three months prior, we examined the intersection of employment, family income, and health outcomes (proinflammatory marker production, perceived stress, and grief symptoms). Bereaved employees had higher levels of monocyte-stimulated interleukin-6, tumor necrosis factor-α, chemokine ligands 4, and perceived stress than bereaved retirees. We also found an interaction such that family income was positively associated with perceived stress and grief symptoms for employed window(er)s, but not for retirees. These findings align with the reserve capacity model, which states that people at higher levels of socioeconomic status have more psychosocial resources to address psychosocial stressors. Employment likely served as an added psychological and inflammatory burden for all bereaved workers, except those with the highest incomes.

Nasal administration of mesenchymal stem cells prevents accelerated age-related tauopathy after chemotherapy in mice

BACKGROUND

There is increasing concern that cancer and cancer treatment accelerate aging and the associated cognitive decline. We showed recently that treatment of 9-month-old male mice with cisplatin causes cognitive deficits that are associated with formation of tau deposits in the hippocampus. Here we explored the capacity of mesenchymal stem cells (MSC) given via the nose to prevent age-related brain tau deposits. Moreover, we more closely examined the cellular distribution of this hallmark of accelerated brain aging in response to treatment of 9-month-old female and male mice with cisplatin.

RESULTS

We show that cisplatin induces tau deposits in the entorhinal cortex and hippocampus in both sexes. The tau deposits colocalize with syndecan-2. Astrocytes surrounding tau deposits have increased glial fibrillary acidic protein glial fibrillary acidic protein (GFAP) expression. Most of the cisplatin-induced tau deposits were located in microtubule associated protein-2 (MAP-2)⁺ neurons that were surrounded by aquaporin 4⁺ (AQP4)⁺ neuron-facing membrane domains of astrocytes. In addition, some tau deposits were detected in the perinuclear region of GFAP⁺ astrocytes and in CD31⁺ endothelial cells. There were no morphological signs of activation of ionized calcium binding adaptor molecule-1⁺ (Iba-1)⁺ microglia and no increases in brain cytokine production. Nasal administration of MSC at 48 and 96 hours after cisplatin prevented formation of tau deposits and normalized syndecan-2 and GFAP expression. Behaviorally, cisplatin-induced tau cluster formation was associated with reduced executive functioning and working/spatial memory and nasal administration of MSC at 48 and 96 hours after cisplatin prevented these cognitive deficits. Notably, delayed MSC administration (1 month after cisplatin) also prevented tau cluster formation and cognitive deficits, in both sexes.

CONCLUSION

In summary, nasal administration of MSC to older mice at 2 days or 1 month after completion of cisplatin treatment prevents the accelerated development of tau deposits in entorhinal cortex and hippocampus and the associated cognitive deficits. Since MSC are already in clinical use for many other clinical indications, developing nasal MSC administration for treatment of accelerated brain aging and cognitive deficits in cancer survivors should be feasible and would greatly improve their quality of life.

Complex I inhibitor of oxidative phosphorylation in advanced solid tumors and acute myeloid leukemia: phase I trials

Although targeting oxidative phosphorylation (OXPHOS) is a rational anticancer strategy, clinical benefit with OXPHOS inhibitors has yet to be achieved. Here we advanced IACS-010759, a highly potent and selective small-molecule complex I inhibitor, into two dose-escalation phase I trials in patients with relapsed/refractory acute myeloid leukemia (NCT02882321, n = 17) and advanced solid tumors (NCT03291938, n = 23). The primary endpoints were safety, tolerability, maximum tolerated dose and recommended phase 2 dose (RP2D) of IACS-010759. The PK, PD, and preliminary antitumor activities of IACS-010759 in patients were also evaluated as secondary endpoints in both clinical trials. IACS-010759 had a narrow therapeutic index with emergent dose-limiting toxicities, including elevated blood lactate and neurotoxicity, which obstructed efforts to maintain target exposure. Consequently no RP2D was established, only modest target inhibition and limited antitumor activity were observed at tolerated doses, and both trials were discontinued. Reverse translational studies in mice demonstrated that IACS-010759 induced behavioral and physiological changes indicative of peripheral neuropathy, which were minimized with the coadministration of a histone deacetylase 6 inhibitor. Additional studies are needed to elucidate the association between OXPHOS inhibition and neurotoxicity, and caution is warranted in the continued development of complex I inhibitors as antitumor agents.

Chronic restraint stress impairs voluntary wheel running but has no effect on food-motivated behavior in mice

Chronic restraint stress is known to cause significant alterations of mitochondrial biology. However, its effects on effort-based behavior and the sensitivity of these effects to treatments that restore mitochondrial function have not been assessed. Based on the hypothesis that the behavioral consequences of this stressor should be more severe for an energy demanding activity than for an energy procuring activity, we compared the effects of chronic restraint stress on the performance of male mice trained to use a running wheel or to nose poke for a food reward in an operant conditioning cage. In accordance with our hypothesis, we observed that exposure of mice to 2-hour daily restraint sessions for 14 to 16 days during the light phase of the cycle reliably decreased voluntary wheel running but had no effect on working for food in a fixed ratio 10 schedule of food reinforcement or in a progressive ratio schedule of food reinforcement. This dissociation between the two types of behavioral activities could reflect an adaptive response to the constraint imposed by chronic restraint stress on mitochondria function and its negative consequences on energy metabolism. To determine whether it is the case, we administered mesenchymal stem cells intranasally to chronically restrained mice to repair the putative mitochondrial dysfunction induced by chronic restraint stress. This intervention had no effect on wheel running deficits. Assessment of mitochondrial gene expression in the brain of mice submitted to chronic restraint stress revealed an increase in the expression of genes involved in mitochondrial biology that showed habituation with repetition of daily sessions of restraint stress. These original findings can be interpreted to indicate that chronic restraint stress induces behavioral and mitochondrial adjustments that contribute to metabolic adaptation to this stressor and maintain metabolic flexibility.

HDAC6 Inhibition Reverses Cisplatin-Induced Mechanical Hypersensitivity via Tonic Delta Opioid Receptor Signaling

Peripheral neuropathic pain induced by the chemotherapeutic cisplatin can persist for months to years after treatment. Histone deacetylase 6 (HDAC6) inhibitors have therapeutic potential for cisplatin-induced neuropathic pain since they persistently reverse mechanical hypersensitivity and spontaneous pain in rodent models. Here, we investigated the mechanisms underlying reversal of mechanical hypersensitivity in male and female mice by a 2 week treatment with an HDAC6 inhibitor, administered 3 d after the last dose of cisplatin. Mechanical hypersensitivity in animals of both sexes treated with the HDAC6 inhibitor was temporarily reinstated by a single injection of the neutral opioid receptor antagonist 6β-naltrexol or the peripherally restricted opioid receptor antagonist naloxone methiodide. These results suggest that tonic peripheral opioid ligand-receptor signaling mediates reversal of cisplatin-induced mechanical hypersensitivity after treatment with an HDAC6 inhibitor. Pointing to a specific role for δ opioid receptors (DORs), Oprd1 expression was decreased in DRG neurons following cisplatin administration, but normalized after treatment with an HDAC6 inhibitor. Mechanical hypersensitivity was temporarily reinstated in both sexes by a single injection of the DOR antagonist naltrindole. Consistently, HDAC6 inhibition failed to reverse cisplatin-induced hypersensitivity when DORs were genetically deleted from advillin+ neurons. Mechanical hypersensitivity was also temporarily reinstated in both sexes by a single injection of a neutralizing antibody against the DOR ligand met-enkephalin. In conclusion, we reveal that treatment with an HDAC6 inhibitor induces tonic enkephalin-DOR signaling in peripheral sensory neurons to suppress mechanical hypersensitivity.SIGNIFICANCE STATEMENT Over one-fourth of cancer survivors suffer from intractable painful chemotherapy-induced peripheral neuropathy (CIPN), which can last for months to years after treatment ends. HDAC6 inhibition is a novel strategy to reverse CIPN without negatively interfering with tumor growth, but the mechanisms responsible for persistent reversal are not well understood. We built on evidence that the endogenous opioid system contributes to the spontaneous, apparent resolution of pain caused by nerve damage or inflammation, referred to as latent sensitization. We show that blocking the δ opioid receptor or its ligand enkephalin unmasks CIPN in mice treated with an HDAC6 inhibitor (latent sensitization). Our work provides insight into the mechanisms by which treatment with an HDAC6 inhibitor apparently reverses CIPN.

Associations between fatigue and cellular metabolism in breast cancer patients: A longitudinal study

PURPOSE

Fatigue is frequently experienced during treatment for cancer and persists for months to years after treatment completion in a subset of patients. The underlying mechanisms remain poorly understood. We postulated that reduced cellular energy metabolism may underlie fatigue in cancer patients and survivors and tested this hypothesis in a sample of patients newly diagnosed with early-stage breast cancer (n = 49) followed for approximately 1 year from before the start of neoadjuvant chemotherapy (NACT) till after treatment completion.

METHODS

Patient-reported fatigue was assessed with the Checklist Individual Strength, and blood samples were obtained before, during, and shortly after NACT. A final assessment was completed after surgery and radiation therapy, 4-6 months after NACT. At each study time point, mitochondrial oxygen consumption and glycolytic activity were measured in peripheral blood mononuclear cells (PBMC). Associations of these measures of PBMC energy metabolism with fatigue were assessed in multilevel models.

RESULTS

Before NACT, higher mitochondrial oxygen consumption and glycolytic activity were associated with higher fatigue, whereas after completion of all primary treatment, these assessments were associated with lower fatigue.

CONCLUSION

These findings suggest that lower cellular energy metabolism after treatment may be a novel target for interventions aimed at preventing or reducing persistent fatigue. Earlier studies investigated the use of supplements for maintaining mitochondrial health during treatment, with mixed results; when proven to be safe, such interventions may be more effective after treatment and in individuals with reduced mitochondrial oxygen consumption rates.

Targeting the Meningeal Compartment to Resolve Chemobrain and Neuropathy via Nasal Delivery of Functionalized Mitochondria

Cognitive deficits (chemobrain) and peripheral neuropathy occur in ∼75% of patients treated for cancer with chemotherapy and persist long-term in >30% of survivors. Without preventive or curative interventions and with increasing survivorship rates, the population debilitated by these neurotoxicities is rising. Platinum-based chemotherapeutics, including cisplatin, induce neuronal mitochondrial defects leading to chemobrain and neuropathic pain. This study investigates the capacity of nasally administered mesenchymal stem cell-derived mitochondria coated with dextran-triphenylphosphonium polymer (coated mitochondria) to reverse these neurotoxicities. Nasally administered coated mitochondria are rapidly detectable in macrophages in the brain meninges but do not reach the brain parenchyma. The coated mitochondria change expression of >2400 genes regulating immune, neuronal, endocrine and vascular pathways in the meninges of mice treated with cisplatin. Nasal administration of coated mitochondria reverses cisplatin-induced cognitive deficits and resolves neuropathic pain at a >55-times lower dose compared to uncoated mitochondria. Reversal of these neuropathologies is associated with resolution of cisplatin-induced deficits in myelination, synaptosomal mitochondrial integrity and neurogenesis. These findings demonstrate that nasally administered coated mitochondria promote resolution of chemobrain and peripheral neuropathy, thereby identifying a novel facile strategy for clinical application of mitochondrial donation and treating central and peripheral nervous system pathologies by targeting the brain meninges.

CD8+ T cell-derived IL-13 increases macrophage IL-10 to resolve neuropathic pain

Understanding the endogenous mechanisms regulating resolution of pain may identify novel targets for treatment of chronic pain. Resolution of chemotherapy-induced peripheral neuropathy (CIPN) after treatment completion depends on CD8⁺ T cells and on IL-10 produced by other cells. Using Rag2^–/– mice lacking T and B cells and adoptive transfer of Il13^–/– CD8⁺ T cells, we showed that CD8⁺ T cells producing IL-13 were required for resolution of CIPN. Intrathecal administration of anti–IL-13 delayed resolution of CIPN and reduced IL-10 production by dorsal root ganglion macrophages. Depleting local CD206⁺ macrophages also delayed resolution of CIPN. In vitro, TIM3⁺CD8⁺ T cells cultured with cisplatin, apoptotic cells, or phosphatidylserine liposomes produced IL-13, which induced IL-10 in macrophages. In vivo, resolution of CIPN was delayed by intrathecal administration of anti-TIM3. Resolution was also delayed in Rag2^–/– mice reconstituted with Havcr2 (TIM3)^–/– CD8⁺ T cells. Our data indicated that cell damage induced by cisplatin activated TIM3 on CD8⁺ T cells, leading to increased IL-13 production, which in turn induced macrophage IL-10 production and resolution of CIPN. Development of exogenous activators of the IL-13/IL-10 pain resolution pathway may provide a way to treat the underlying cause of chronic pain.

An HDAC6 inhibitor reverses chemotherapy-induced mechanical hypersensitivity via an IL-10 and macrophage dependent pathway

Chemotherapy-induced peripheral neuropathy (CIPN) impacts a growing number of cancer survivors and treatment options are limited. Histone deacetylase 6 (HDAC6) inhibitors are attractive candidates because they reverse established CIPN and may enhance anti-tumor effects of chemotherapy. Before considering clinical application of HDAC6 inhibitors, the mechanisms underlying reversal of CIPN need to be identified. We showed previously that deletion of Hdac6 from sensory neurons did not prevent cisplatin-induced mechanical hypersensitivity, while global deletion of Hdac6 was protective, indicating involvement of HDAC6 in other cell types. Here we show that local depletion of MRC1 (CD206)-positive macrophages without affecting microglia by intrathecal administration of mannosylated clodronate liposomes reduced the capacity of an HDAC6 inhibitor to reverse cisplatin-induced mechanical hypersensitivity. The HDAC6 inhibitor increased spinal cord Il10 mRNA and this was M2-macrophage dependent. Intrathecal administration of anti-IL-10 antibody or genetic deletion of Il10 prevented resolution of mechanical hypersensitivity. Genetic deletion of the IL-10 receptor from Advillin+ neurons prevented resolution of mechanical hypersensitivity in mice treated with the HDAC6 inhibitor. These findings indicate that treatment with an HDAC6 inhibitor increases macrophage-derived IL-10 signaling to IL-10 receptors on Advillin+ sensory neurons to resolve mechanical hypersensitivity. Cisplatin decreases mitochondrial function in sensory axons, and HDAC6 inhibition can promote axonal transport of healthy mitochondria. Indeed, the HDAC6 inhibitor normalized cisplatin-induced tibial nerve mitochondrial deficits. However, this was independent of macrophages and IL-10 signaling. In conclusion, our findings indicate that administration of an HDAC6 inhibitor reverses cisplatin-induced mechanical hypersensitivity through two complementary pathways: macrophage HDAC6 inhibition to promote IL-10 production and IL-10 signaling to DRG neurons, and neuronal HDAC6 inhibition to restore axonal mitochondrial health.

HDAC6 inhibition reverses long-term doxorubicin-induced cognitive dysfunction by restoring microglia homeostasis and synaptic integrity

Breast cancer is the most common female malignancy in both the developed and developing world. Doxorubicin is one of the most commonly used chemotherapies for breast cancer. Unfortunately, up to 60% of survivors report long-term chemotherapy-induced cognitive dysfunction (CICD) characterized by deficits in working memory, processing speed and executive function. Currently, no therapeutic standard for treating CICD exists. Here, we hypothesized that treatment with a blood-brain barrier permeable histone deacetylase 6 (HDAC6) inhibitor can successfully reverse long-term doxorubicin-induced cognitive dysfunction. Methods: The puzzle box test and novel object/place recognition test were used to assess cognitive function following a therapeutic doxorubicin dosing schedule in female mice. Mitochondrial function and morphology in neuronal synaptosomes were evaluated using the Seahorse XF24 extracellular flux analyzer and transmission electron microscopy, respectively. Hippocampal postsynaptic integrity was evaluated using immunofluorescence. Hippocampal microglia phenotype was determined using advanced imaging techniques and single-nucleus RNA sequencing. Results: A 14-day treatment with a blood-brain barrier permeable HDAC6 inhibitor successfully reversed long-term CICD in the domains of executive function, working and spatial memory. No significant changes in mitochondrial function or morphology in neuronal synaptosomes were detected. Long-term CICD was associated with a decreased expression of postsynaptic PSD95 in the hippocampus. These changes were associated with decreased microglial ramification and alterations in the microglia transcriptome that suggest a stage 1 disease-associated microglia (DAM) phenotype. HDAC6 inhibition completely reversed these doxorubicin-induced alterations, indicating a restoration of microglial homeostasis. Conclusion: Our results show that decreased postsynaptic integrity and a neurodegenerative microglia phenotype closely resembling stage 1 DAM microglia contribute to long-term CICD. Moreover, HDAC6 inhibition shows promise as an efficacious pharmaceutical intervention to alleviate CICD and improve quality of life of breast cancer survivors.

Childhood maltreatment, subjective social status, and health disparities in bereavement

BACKGROUND

Spousal bereavement can lead to adverse health outcomes; however, not all widow(er)s experience the same degree of health problems. Thus, it is important to understand the contribution of disparities (e.g., childhood maltreatment and subjective social status) that may underlie adverse health outcomes that arise following bereavement.

METHODS

We collected data from 130 spousally bereaved individuals at 3-time points (3 months post-loss, 4 months post-loss, and 6 months post-loss). Using mixed models, we assessed the interaction of childhood maltreatment, subjective social status, and time to predict changes in proinflammatory cytokine production, depressive symptoms, grief symptoms.

RESULTS

We found a significant interaction between childhood maltreatment, subjective social status, and time predicting proinflammatory cytokine production (beta > -0.01, p = 0.048), depressive symptoms (beta = 0.008, p = .010), and grief symptoms (beta = 0.001 p = .001).

CONCLUSION

This study highlights the role of disparities related to childhood maltreatment and subjective social status on adverse health outcomes following spousal bereavement.

Immune regulation of pain: Friend and foe

[Figure: see text].

Associations of meaning of illness with psychosocial, clinical, and immunological characteristics in patients with Leptomeningeal metastasis

Background

Leptomeningeal metastasis (LM) creates symptoms related to both the disease within the nervous system and treatment toxicities. Biologic processes, such as inflammation and behavioral processes, such as the meaning ascribed to illness (Meaning of Illness: MoI), can impact physical and psychosocial symptoms. The aim of this study was to understand the relationships among MoI, physical and psychosocial symptoms, and inflammation in patients with LM.

Methods

Thirty enrolled participants completed the MD Anderson Symptom Inventory-Brain Tumor with spine experimental symptoms added. Meaning of illness, quality of life (QoL), and depression were captured by validated instruments. Interleukin (IL)-6 and tumor necrosis factor (TNF)-α in serum and cerebrospinal fluid (CSF) were measured by ELISA. Correlations were performed to assess relationships among the variables.

Results

Participants were primarily white (73%), female (63%). Median age was 54 years (34–83). Breast (50%) and lung (20%) were most common diagnosis. Higher MoI scores were associated with better QoL (p < .01) and fewer depressive symptoms (p < .01). All CSF samples contained IL-6 and all but one sample had elevated IL-6. Higher levels of IL-6 in the CSF were associated with greater symptom burden (p < .01) and interference of symptoms in daily life (p = .02) but not MoI.

Conclusions

MoI was associated with QoL and depression. High levels of IL-6 in the CSF were associated with more severe symptoms. This study provides the groundwork for future research, including interventional studies to improve QoL in patients with LM.

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Ascribing positive meaning to illness is associated with higher reported QoL in patients with LM.

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High IL-6 in the CSF was associated with increased symptom burden but not depressive symptoms.

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Fostering meaning in patients with LM may help mood, reduce inflammation, and improve symptoms.

Inhibition of dual leucine zipper kinase prevents chemotherapy-induced peripheral neuropathy and cognitive impairments

ABSTRACT

Chemotherapy-induced peripheral neuropathy (CIPN) and chemotherapy-induced cognitive impairments (CICI) are common, often severe neurotoxic side effects of cancer treatment that greatly reduce quality of life of cancer patients and survivors. Currently, there are no Food and Drug Administration-approved agents for the prevention or curative treatment of CIPN or CICI. The dual leucine zipper kinase (DLK) is a key mediator of axonal degeneration that is localized to axons and coordinates the neuronal response to injury. We developed a novel brain-penetrant DLK inhibitor, IACS'8287, which demonstrates potent and highly selective inhibition of DLK in vitro and in vivo. Coadministration of IACS'8287 with the platinum derivative cisplatin prevents mechanical allodynia, loss of intraepidermal nerve fibers in the hind paws, cognitive deficits, and impairments in brain connectivity in mice, all without interfering with the antitumor activity of cisplatin. The protective effects of IACS'8287 are associated with preservation of mitochondrial function in dorsal root ganglion neurons and in brain synaptosomes. In addition, RNA sequencing analysis of dorsal root ganglia reveals modulation of genes involved in neuronal activity and markers for immune cell infiltration by DLK inhibition. These data indicate that CIPN and CICI require DLK signaling in mice, and DLK inhibitors could become an attractive treatment in the clinic when coadministered with cisplatin, and potentially other chemotherapeutic agents, to prevent neurotoxicities as a result of cancer treatment.

TTI-101: A competitive inhibitor of STAT3 that spares oxidative phosphorylation and reverses mechanical allodynia in mouse models of neuropathic pain

Signal Transducer and Activator of Transcription (STAT) 3 emerged rapidly as a high-value target for treatment of cancer. However, small-molecule STAT3 inhibitors have been slow to enter the clinic due, in part, to serious adverse events (SAE), including lactic acidosis and peripheral neuropathy, which have been attributed to inhibition of STAT3's mitochondrial function. Our group developed TTI-101, a competitive inhibitor of STAT3 that targets the receptor pY705-peptide binding site within the Src homology 2 (SH2) domain to block its recruitment and activation. TTI-101 has shown target engagement, no toxicity, and evidence of clinical benefit in a Phase I study in patients with solid tumors. Here we report that TTI-101 did not affect mitochondrial function, nor did it cause STAT3 aggregation, chemically modify STAT3 or cause neuropathic pain. Instead, TTI-101 unexpectedly suppressed neuropathic pain induced by chemotherapy or in a spared nerve injury model. Thus, in addition to its direct anti-tumor effect, TTI-101 may be of benefit when administered to cancer patients at risk of developing chemotherapy-induced peripheral neuropathy (CIPN).

Inflammation and future depressive symptoms among recently bereaved spouses

Major depressive disorder (MDD) is an important contributor to the total disease burden because of its high comorbidity with chronic illnesses. Many people with high levels of depressive symptoms exhibit elevated systemic inflammation, but inflammation is not a necessary determinant of depression onset. Among those who recently experienced the death of a spouse, we investigated whether (a) inflammation assessed early in bereavement predicted future depressive symptoms and whether (b) inflammation predicted change in depressive symptoms from baseline to follow-up. Ninety-nine spousally bereaved individuals (M=68.61, SD=10.70) from a larger study were evaluated at baseline (3 months post-death) and follow-up (6 months post-death). Subjects received a venous blood draw and completed the Center for Epidemiologic Studies Depression Scale (CES-D). Stimulated T-cell derived cytokines (IL-6, TNF-α, and IFN-γ) were assessed individually and as a pro-inflammatory composite index. After controlling for confounding factors (i.e., age, sex, body mass index, race, ethnicity, anti-inflammatory medication, days since spousal death, smoking status, comorbidities), individuals with higher levels of IL-6, TNF-α, and IFN-γ at baseline exhibited more depressive symptoms (composite index, p = .05) and an increased probability of experiencing clinical levels of depression (CES-D score ≥16) (composite index, p = .04). Inflammatory levels were not predictive of change in depressive symptoms or in clinical depression status from baseline to follow-up. Among individuals who did not experience clinical levels of depression at baseline, baseline inflammatory levels predicted clinical levels of depression 3 months later (p = .03). This study provides support for an inflammatory mechanism underlying depression following bereavement. It suggests that one's inflammatory profile following a significant social stressor in older adulthood can be prognostic of depression risk months later. These findings add to our understanding of the physiological and mental health risks experienced by the bereaved population and provide insight into identifying vulnerable widow(er)s at risk for maladaptive grief coping.

T Cells as Guardians of Pain Resolution

Despite successful research efforts aimed at understanding pain mechanisms, there is still no adequate treatment for many patients suffering from chronic pain. The contribution of neuroinflammation to chronic pain is widely acknowledged. Here, we summarize findings indicating that T cells play a key role in the suppression of pain. An active contribution of the immune system to resolution of pain may explain why immunosuppressive drugs are often not sufficient to control pain. This would also imply that dysregulation of certain immune functions promote transition to chronic pain. Conversely, stimulating the endogenous immune-mediated resolution pathways may provide a potent approach to treat chronic pain.

Autoimmune regulation of chronic pain

Chronic pain is an unpleasant and debilitating condition that is often poorly managed by existing therapeutics. Reciprocal interactions between the nervous system and the immune system have been recognized as playing an essential role in the initiation and maintenance of pain. In this review, we discuss how neuroimmune signaling can contribute to peripheral and central sensitization and promote chronic pain through various autoimmune mechanisms. These pathogenic autoimmune mechanisms involve the production and release of autoreactive antibodies from B cells. Autoantibodies-ie, antibodies that recognize self-antigens-have been identified as potential molecules that can modulate the function of nociceptive neurons and thereby induce persistent pain. Autoantibodies can influence neuronal excitability by activating the complement pathway; by directly signaling at sensory neurons expressing Fc gamma receptors, the receptors for the Fc fragment of immunoglobulin G immune complexes; or by binding and disrupting ion channels expressed by nociceptors. Using examples primarily from rheumatoid arthritis, complex regional pain syndrome, and channelopathies from potassium channel complex autoimmunity, we suggest that autoantibody signaling at the central nervous system has therapeutic implications for designing novel disease-modifying treatments for chronic pain.

Nasal administration of mesenchymal stem cells reverses chemotherapy-induced peripheral neuropathy in mice

Chemotherapy-induced peripheral neuropathy (CIPN) is one of the most frequently reported adverse effects of cancer treatment. CIPN often persists long after treatment completion and has detrimental effects on patient's quality of life. There are no efficacious FDA-approved drugs for CIPN. We recently demonstrated that nasal administration of mesenchymal stem cells (MSC) reverses the cognitive deficits induced by cisplatin in mice. Here we show that nasal administration of MSC after cisplatin- or paclitaxel treatment- completely reverses signs of established CIPN, including mechanical allodynia, spontaneous pain, and loss of intraepidermal nerve fibers (IENF) in the paw. The resolution of CIPN is associated with normalization of the cisplatin-induced decrease in mitochondrial bioenergetics in DRG neurons. Nasally administered MSC enter rapidly the meninges of the brain, spinal cord and peripheral lymph nodes to promote IL-10 production by macrophages. MSC-mediated resolution of mechanical allodynia, recovery of IENFs and restoration of DRG mitochondrial function critically depends on IL-10 production. MSC from IL-10 knockout animals are not capable of reversing the symptoms of CIPN. Moreover, WT MSC do not reverse CIPN in mice lacking IL-10 receptors on peripheral sensory neurons. In conclusion, only two nasal administrations of MSC fully reverse CIPN and the associated mitochondrial abnormalities via an IL-10 dependent pathway. Since MSC are already applied clinically, we propose that nasal MSC treatment could become a powerful treatment for the large group of patients suffering from neurotoxicities of cancer treatment.

Nasal administration of mitochondria reverses chemotherapy-induced cognitive deficits

Up to seventy-five percent of patients treated for cancer suffer from cognitive deficits which can persist for months to decades, severely impairing quality of life. Although the number of cancer survivors is increasing tremendously, no efficacious interventions exist. Cisplatin, most commonly employed for solid tumors, leads to cognitive impairment including deficits in memory and executive functioning. We recently proposed deficient neuronal mitochondrial function as its underlying mechanism. We hypothesized nasal administration of mitochondria isolated from human mesenchymal stem cells to mice, can reverse cisplatin-induced cognitive deficits. Methods: Puzzle box, novel object place recognition and Y-maze tests were used to assess the cognitive function of mice. Immunofluorescence and high-resolution confocal microscopy were employed to trace the nasally delivered mitochondria and evaluate their effect on synaptic loss. Black Gold II immunostaining was used to determine myelin integrity. Transmission electron microscopy helped determine mitochondrial and membrane integrity of brain synaptosomes. RNA-sequencing was performed to analyse the hippocampal transcriptome. Results: Two nasal administrations of mitochondria isolated from human mesenchymal stem cells to mice, restored executive functioning, working and spatial memory. Confocal imaging revealed nasally delivered mitochondria rapidly arrived in the meninges where they were readily internalized by macrophages. The administered mitochondria also accessed the rostral migratory stream and various other brain regions including the hippocampus where they colocalized with GFAP+ cells. The restoration of cognitive function was associated with structural repair of myelin in the cingulate cortex and synaptic loss in the hippocampus. Nasal mitochondrial donation also reversed the underlying synaptosomal mitochondrial defects. Moreover, transcriptome analysis by RNA-sequencing showed reversal of cisplatin-induced changes in the expression of about seven hundred genes in the hippocampus. Pathway analysis identified Nrf2-mediated response as the top canonical pathway. Conclusion: Our results provide key evidence on the therapeutic potential of isolated mitochondria - restoring both brain structure and function, their capability to enter brain meninges and parenchyma upon nasal delivery and undergo rapid cellular internalization and alter the hippocampal transcriptome. Our data identify nasal administration of mitochondria as an effective strategy for reversing chemotherapy-induced cognitive deficits and restoring brain health, providing promise for the growing population of both adult and pediatric cancer survivors.

GRK2 levels in myeloid cells modulate adipose-liver crosstalk in high fat diet-induced obesity

Macrophages are key effector cells in obesity-associated inflammation. G protein-coupled receptor kinase 2 (GRK2) is highly expressed in different immune cell types. Using LysM-GRK2^+/- mice, we uncover that a reduction of GRK2 levels in myeloid cells prevents the development of glucose intolerance and hyperglycemia after a high fat diet (HFD) through modulation of the macrophage pro-inflammatory profile. Low levels of myeloid GRK2 confer protection against hepatic insulin resistance, steatosis and inflammation. In adipose tissue, pro-inflammatory cytokines are reduced and insulin signaling is preserved. Macrophages from LysM-GRK2^+/- mice secrete less pro-inflammatory cytokines when stimulated with lipopolysaccharide (LPS) and their conditioned media has a reduced pathological influence in cultured adipocytes or naïve bone marrow-derived macrophages. Our data indicate that reducing GRK2 levels in myeloid cells, by attenuating pro-inflammatory features of macrophages, has a relevant impact in adipose-liver crosstalk, thus preventing high fat diet-induced metabolic alterations.

Bexarotene normalizes chemotherapy-induced myelin decompaction and reverses cognitive and sensorimotor deficits in mice

Frequently reported neurotoxic sequelae of cancer treatment include cognitive deficits and sensorimotor abnormalities that have long-lasting negative effects on the quality of life of an increasing number of cancer survivors. The underlying mechanisms are not fully understood and there is no effective treatment. We show here that cisplatin treatment of mice not only caused cognitive dysfunction but also impaired sensorimotor function. These functional deficits are associated with reduced myelin density and complexity in the cingulate and sensorimotor cortex. At the ultrastructural level, myelin abnormalities were characterized by decompaction. We used this model to examine the effect of bexarotene, an agonist of the RXR-family of nuclear receptors. Administration of only five daily doses of bexarotene after completion of cisplatin treatment was sufficient to normalize myelin density and fiber coherency and to restore myelin compaction in cingulate and sensorimotor cortex. Functionally, bexarotene normalized performance of cisplatin-treated mice in tests for cognitive and sensorimotor function. RNAseq analysis identified the TR/RXR pathway as one of the top canonical pathways activated by administration of bexarotene to cisplatin-treated mice. Bexarotene also activated neuregulin and netrin pathways that are implicated in myelin formation/maintenance, synaptic function and axonal guidance. In conclusion, short term treatment with bexarotene is sufficient to reverse the adverse effects of cisplatin on white matter structure, cognitive function, and sensorimotor performance. These encouraging findings warrant further studies into potential clinical translation and the underlying mechanisms of bexarotene for chemobrain.

A central role for apathy in the effectiveness of interventions for cancer-related fatigue

OBJECTIVE

Cancer-related fatigue (CRF) affects a substantial number of cancer patients and survivors. Recommendations for CRF treatments are largely based on results of randomized controlled trials. The interpretability of such results is limited to patients eligible and willing to participate in these trials. We aimed to address this limitation in a retrospective study of patients seen at a CRF clinic in a comprehensive cancer center. The objectives were to (a) determine the effectiveness of clinician-initiated interventions for CRF and identify their mediators and (b) describe the frequency and effectiveness of patient-initiated physical activity (PA) behavior for alleviating CRF and identify determinants of this PA.

METHODS

Data (patient-reported somatic and mood symptoms; clinical data; clinician-documented changes in medication and behavior) from n = 213 patients collected as part of the clinic's standard of care at initial clinical consult and follow-up 4 to 11 weeks later were included. Effects of clinician-initiated interventions and patient-initiated PA on change in fatigue were analyzed using linear models.

RESULTS

Of all clinician-initiated interventions, only psychostimulant start was recorded frequent enough for further investigation and was associated with reduced fatigue; this association was mediated by a reduction in apathy. PA was also associated with reduced fatigue severity. PA initiation/increase after consult was associated with lower apathy at consult.

CONCLUSIONS

These results demonstrate a major role for patient apathy in the effectiveness and initiation of CRF-targeting interventions. Behavioral therapies focusing on reduction in apathy should be considered as initial treatment of CRF in those with substantial apathy.

Astrocytes rescue neuronal health after cisplatin treatment through mitochondrial transfer

Neurodegenerative disorders, including chemotherapy-induced cognitive impairment, are associated with neuronal mitochondrial dysfunction. Cisplatin, a commonly used chemotherapeutic, induces neuronal mitochondrial dysfunction in vivo and in vitro. Astrocytes are key players in supporting neuronal development, synaptogenesis, axonal growth, metabolism and, potentially mitochondrial health. We tested the hypothesis that astrocytes transfer healthy mitochondria to neurons after cisplatin treatment to restore neuronal health.We used an in vitro system in which astrocytes containing mito-mCherry-labeled mitochondria were co-cultured with primary cortical neurons damaged by cisplatin. Culture of primary cortical neurons with cisplatin reduced neuronal survival and depolarized neuronal mitochondrial membrane potential. Cisplatin induced abnormalities in neuronal calcium dynamics that were characterized by increased resting calcium levels, reduced calcium responses to stimulation with KCl, and slower calcium clearance. The same dose of cisplatin that caused neuronal damage did not affect astrocyte survival or astrocytic mitochondrial respiration. Co-culture of cisplatin-treated neurons with astrocytes increased neuronal survival, restored neuronal mitochondrial membrane potential, and normalized neuronal calcium dynamics especially in neurons that had received mitochondria from astrocytes which underlines the importance of mitochondrial transfer. These beneficial effects of astrocytes were associated with transfer of mitochondria from astrocytes to cisplatin-treated neurons. We show that siRNA-mediated knockdown of the Rho-GTPase Miro-1 in astrocytes reduced mitochondrial transfer from astrocytes to neurons and prevented the normalization of neuronal calcium dynamics.In conclusion, we showed that transfer of mitochondria from astrocytes to neurons rescues neurons from the damage induced by cisplatin treatment. Astrocytes are far more resistant to cisplatin than cortical neurons. We propose that transfer of functional mitochondria from astrocytes to neurons is an important repair mechanism to protect the vulnerable cortical neurons against the toxic effects of cisplatin.

CD3+ T cells are critical for the resolution of comorbid inflammatory pain and depression-like behavior

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T cells are necessary for resolution of CFA-induced mechanical allodynia and spontaneous pain.

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T cells are required for the resolution of inflammation-induced depression-like behavior.

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T cells did not contribute to onset or severity of indicators of pain and depression-like behavior.

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T cells did not affect cytokine expression in the paw, spinal cord and brain.

Background

Chronic pain and depression often co-occur. The mechanisms underlying this comorbidity are incompletely understood. Here, we investigated the role of CD3⁺ T cells in an inflammatory model of comorbid persistent mechanical allodynia, spontaneous pain, and depression-like behavior in mice.

Methods

C57Bl/6 wt and Rag2^−/− mice were compared in their response to intraplantar administration of complete Freund’s adjuvant (CFA). Mechanical allodynia, spontaneous pain and depression-like behavior were assessed by von Frey, conditioned place preference and forced swim test respectively.

Results

Resolution of mechanical allodynia, spontaneous pain, and depression-like behavior was markedly delayed in Rag2^−/− mice that are devoid of adaptive immune cells. Reconstitution of Rag2^−/− mice with CD3⁺ T cells from WT mice before CFA injection normalized the resolution of indicators of pain and depression-like behavior. T cells did not contribute to onset or severity of indicators of pain and depression-like behavior. The lack of T cells did not affect cytokine expression in the paw, spinal cord and brain, indicating that the delayed resolution was not resulting from prolonged (neuro)inflammation.

Conclusions

Our findings show that T cells are critical for the natural resolution of mechanical allodynia, spontaneous pain, and depression-like behavior after an inflammatory challenge. Dysregulation of this T cell-mediated resolution pathway could contribute to the comorbidity of chronic pain and depression.

Significance

Chronic pain and depression are frequently associated with signs of inflammation. However, general immunosuppression is not sufficient to resolve comorbid pain and depression. Here we demonstrate that T cells are required for resolution of comorbid persistent mechanical allodynia, spontaneous pain, and depression in a model of peripheral inflammation, indicating the immune system can contribute to both onset and resolution of these comorbidities. Enhancing pro-resolution effects of T cells may have a major impact to treat patients with comorbid persistent pain and depression.

Alleviation of paclitaxel-induced mechanical hypersensitivity and hyperalgesic priming with AMPK activators in male and female mice

AMP-activated protein kinase (AMPK) is an energy-sensing kinase that has emerged as a novel therapeutic target for pain due to its ability to inhibit mechanistic target of rapamycin (mTOR) and mitogen activated protein kinase (MAPK) signaling, two signaling pathways that are linked to pain promotion after injury as well as the development of hyperalgesic priming. MAPK and mTOR signaling are also implicated in chemotherapy induced peripheral neuropathy (CIPN). We conducted a series of experiments to gain further insight into how AMPK activators might best be used to treat pain in both sexes in the setting of CIPN from paclitaxel. We also assessed whether hyperalgesic priming emerges from paclitaxel treatment and if this can be prevented by AMPK targeting. AMPK can be pharmacologically activated indirectly through regulation of upstream kinases like liver kinase B1 (LKB1) or directly using positive allosteric modulators. We used the indirect AMPK activators metformin and narciclasine, both of which have been shown to reduce pain in preclinical models but with much different potencies and different efficacies depending on the sex of the animal. We used the direct AMPK activator MK8722 because it is the most potent and specific such activator described to date. Here, the AMPK activators were used in 2 different treatment paradigms. First the drugs were given concurrently with paclitaxel to test whether they prevent mechanical hypersensitivity. Second the AMPK activators were given after the completion of paclitaxel treatment to test whether they reverse established mechanical hypersensitivity. Consistent with our previously published findings with metformin, narciclasine (1 mg/kg) produced an anti-hyperalgesic effect, preventing paclitaxel-induced neuropathy in outbred mice of both sexes. In contrast to metformin, narciclasine also reversed mechanical hypersensitivity in established CIPN. Both metformin (200 mg/kg) and narciclasine prevented the development of hyperalgesic priming induced by paclitaxel treatment. MK8722 (30 mg/kg) had no effect on mechanical hypersensitivity caused by paclitaxel in either the prevention or reversal treatment paradigms. However, MK8722 did attenuate hyperalgesic priming in male and female mice. We conclude that paclitaxel induces robust hyperalgesic priming that is prevented by AMPK targeting and that narciclasine is a particularly attractive candidate for further development as a CIPN treatment.

T Cells as an Emerging Target for Chronic Pain Therapy

The immune system is critically involved in the development and maintenance of chronic pain. However, T cells, one of the main regulators of the immune response, have only recently become a focus of investigations on chronic pain pathophysiology. Emerging clinical data suggest that patients with chronic pain have a different phenotypic profile of circulating T cells compared to controls. At the preclinical level, findings on the function of T cells are mixed and differ between nerve injury, chemotherapy, and inflammatory models of persistent pain. Depending on the type of injury, the subset of T cells and the sex of the animal, T cells may contribute to the onset and/or the resolution of pain, underlining T cells as a major player in the transition from acute to chronic pain. Specific T cell subsets release mediators such as cytokines and endogenous opioid peptides that can promote, suppress, or even resolve pain. Inhibiting the pain-promoting functions of T cells and/or enhancing the beneficial effects of pro-resolution T cells may offer new disease-modifying strategies for the treatment of chronic pain, a critical need in view of the current opioid crisis.

Chemotherapy accelerates age-related development of tauopathy and results in loss of synaptic integrity and cognitive impairment

Cancer and its treatment are associated with neurotoxic side effects, including cognitive dysfunction, altered functional connectivity in the brain and structural abnormalities in white matter. There is evidence that cancer and its treatment can accelerate aging. Tau is a microtubule associated protein that contributes to microtubule stability thereby playing a key role in neuronal function. Clustering of tau is commonly observed in the aged brain and is related to cognitive decline. We hypothesized that chemotherapy-induced cognitive impairment is associated with accelerated development of tau clustering in the brain as a sign of accelerated aging. We show for the first time that treatment of adult (7-8 month-old) male C57BL/6 mice with cisplatin results in reduced cognitive function and a marked increase in the number of large endogenous tau clusters in the hippocampus when assessed 4 months later. In contrast, we detected only few small tau clusters in the hippocampus of age-matched 11-12 month-old control mice. Astrocyte GFAP expression was increased in close vicinity to the tau clusters in cisplatin-treated mice. We did not detect changes in the microglial marker Iba-1 in the brain of mice treated with cisplatin. The accelerated formation of Tau-1 clusters in cisplatin-treated mice was associated with a decrease in the levels of the post-synaptic marker PSD95 and of the presynaptic marker synaptophysin in the hippocampus. We demonstrate here for the first time that chemotherapy markedly accelerates development of signs of tauopathy and loss of synaptic integrity in the hippocampus. These findings provide a mechanistic link between chemotherapy cognitive decline and accelerated aging in cancer survivors.

Motivational changes that develop in a mouse model of inflammation-induced depression are independent of indoleamine 2,3 dioxygenase

Despite years of research, our understanding of the mechanisms by which inflammation induces depression is still limited. As clinical data points to a strong association between depression and motivational alterations, we sought to (1) characterize the motivational changes that are associated with inflammation in mice, and (2) determine if they depend on inflammation-induced activation of indoleamine 2,3 dioxygenase-1 (IDO1). Lipopolysaccharide (LPS)-treated or spared nerve injured (SNI) wild type (WT) and Ido1^-/- mice underwent behavioral tests of antidepressant activity (e.g., forced swim test) and motivated behavior, including assessment of (1) reward expectancy using a food-related anticipatory activity task, (2) willingness to work for reward using a progressive ratio schedule of food reinforcement, (3) effort allocation using a concurrent choice task, and (4) ability to associate environmental cues with reward using conditioned place preference. LPS- and SNI-induced deficits in behavioral tests of antidepressant activity in WT but not Ido1^-/- mice. Further, LPS decreased food related-anticipatory activity, reduced performance in the progressive ratio task, and shifted effort toward the preferred reward in the concurrent choice task. These effects were observed in both WT and Ido1^-/- mice. Finally, SNI mice developed a conditioned place preference based on relief from pain in an IDO1-independent manner. These findings demonstrate that the motivational effects of inflammation do not require IDO1. Further, they indicate that the motivational component of inflammation-induced depression is mechanistically distinct from that measured by behavioral tests of antidepressant activity.

Mitochondrial transfer from mesenchymal stem cells to neural stem cells protects against the neurotoxic effects of cisplatin

Mesenchymal stem cells (MSCs) transfer healthy mitochondria to damaged acceptor cells via actin-based intercellular structures. In this study, we tested the hypothesis that MSCs transfer mitochondria to neural stem cells (NSCs) to protect NSCs against the neurotoxic effects of cisplatin treatment. Our results show that MSCs donate mitochondria to NSCs damaged in vitro by cisplatin. Transfer of healthy MSC-derived mitochondria decreases cisplatin-induced NSC death. Moreover, mitochondrial transfer from MSCs to NSCs reverses the cisplatin-induced decrease in mitochondrial membrane potential. Blocking the formation of actin-based intercellular structures inhibited the transfer of mitochondria to NSCs and abrogated the positive effects of MSCs on NSC survival. Conversely, overexpression of the mitochondrial motor protein Rho-GTPase 1 (Miro1) in MSCs increased mitochondrial transfer and further improved survival of cisplatin-treated NSCs.

In vivo, MSC administration prevented the loss of DCX+ neural progenitor cells in the subventricular zone and hippocampal dentate gyrus which occurs as a result of cisplatin treatment. We propose mitochondrial transfer as one of the mechanisms via which MSCs exert their therapeutic regenerative effects after cisplatin treatment.

Resolution of inflammation-induced depression requires T lymphocytes and endogenous brain interleukin-10 signaling

In humans, depression is often associated with low-grade inflammation, activation of the tryptophan/kynurenine pathway, and mild lymphopenia. Preclinical research confirms that inflammation induces depression-like behavior through activation of the tryptophan/kynurenine pathway. However, the mechanisms governing recovery from depression are unknown. Understanding the pathways leading to resolution of depression will likely lead to identification of novel targets for treatment. We investigated the contribution of T lymphocytes to the resolution of lipopolysaccharide-induced depression-like behavior. Duration of depression-like behavior was markedly prolonged in mice without mature T or B lymphocytes (Rag1^-/- mice). This prolonged depression-like behavior was associated with persistent upregulation of the tryptophan-metabolizing enzyme indoleamine-2,3-dioxygenase (Ido)1 in the prefrontal cortex (PFC). Reconstitution of Rag1^-/- mice with T lymphocytes normalized resolution of depression-like behavior and expression of Ido1 in the PFC. During resolution of inflammation-induced depression-like behavior, T lymphocytes accumulated in the meninges and were required for induction of interleukin (IL)-10 in the meninges and the PFC. Inhibition of IL-10 signaling by nasal administration of neutralizing anti-IL-10 antibody to WT mice led to persistent upregulation of Ido1 in the PFC and prolonged depression-like behavior. Conversely, nasal administration of recombinant IL-10 in Rag1^-/- mice normalized Ido1 expression and resolution of depression-like behavior. In conclusion, the present data show for the first time that resolution of inflammation-induced depression is an active process requiring T lymphocytes acting via an IL-10-dependent pathway to decrease Ido1 expression in the brain. We propose that targeting the T lymphocyte/IL-10 resolution pathway could represent a novel approach to promote recovery from major depressive disorder.

An effort expenditure perspective on cancer-related fatigue

While fatigue is the most common and debilitating side effect of cancer and cancer treatment it is still poorly understood, partly because it is usually characterized by patient-reported outcomes. As patient-reports are inherently subjective, behavioral correlates of the symptom of fatigue are needed to increase our understanding of the symptom. We focused on motivational effort expenditure as a crucial behavior in cancer-related fatigue, using a validated computerized task contrasting high effort/high reward and low effort/low reward choices under different probabilities of success. Effort expenditure-choices were analyzed in 47 cancer patients differing by their status; current evidence for disease (n = 17) or post-treatment survivors with no evidence for disease (n = 30). In addition, patient-reported fatigue, negative and positive affect, and biomarkers of inflammation were assessed. Patient-reported general and motivational fatigue, negative affect, and plasma concentrations of pro-inflammatory biomarkers were related to higher effort expenditure while positive affect was associated with lower effort expenditure. As all four measures interacted with patient status, exploratory models were computed for patients and survivors separately. These analyses indicated that the effects of fatigue and negative affect were predominantly seen in survivors. In patients still under or shortly post treatment, general fatigue, but not motivational fatigue, was associated with lower effort expenditure but only in the most favorable reward condition. Negative affect did not have an effect. Thus, the effects observed seemed primarily driven by cancer survivors in whom both fatigue and negative affect were associated with higher effort expenditure. These findings are tentatively interpreted to suggest that a tendency to invest more effort despite feelings of fatigue is a vulnerability for developing chronic fatigue. Inflammation and negative affect might contribute to fatigue in some survivors through this effort investment pathway.

Pharmacological inhibition of HDAC6 reverses cognitive impairment and tau pathology as a result of cisplatin treatment

Chemotherapy-induced cognitive impairment (CICI) is a commonly reported neurotoxic side effect of chemotherapy, occurring in up to 75% cancer patients. CICI manifests as decrements in working memory, executive functioning, attention, and processing speed, and greatly interferes with patients’ daily performance and quality of life. Currently no treatment for CICI has been approved by the US Food and Drug Administration. We show here that treatment with a brain-penetrating histone deacetylase 6 (HDAC6) inhibitor for two weeks was sufficient to fully reverse cisplatin-induced cognitive impairments in male mice, as demonstrated in the Y-maze test of spontaneous alternation, the novel object/place recognition test, and the puzzle box test. Normalization of cognitive impairment was associated with reversal of cisplatin-induced synaptosomal mitochondrial deficits and restoration of synaptic integrity. Mechanistically, cisplatin induced deacetylation of the microtubule protein α-tubulin and hyperphosphorylation of the microtubule-associated protein tau. These cisplatin-induced changes were reversed by HDAC6 inhibition. Our data suggest that inhibition of HDAC6 restores microtubule stability and reverses tau phosphorylation, leading to normalization of synaptosomal mitochondrial function and synaptic integrity and thereby to reversal of CICI. Remarkably, our results indicate that short-term daily treatment with the HDAC6 inhibitor was sufficient to achieve prolonged reversal of established behavioral, structural and functional deficits induced by cisplatin. Because the beneficial effects of HDAC6 inhibitors as add-ons to cancer treatment have been demonstrated in clinical trials, selective targeting of HDAC6 with brain-penetrating inhibitors appears a promising therapeutic approach for reversing chemotherapy-induced neurotoxicity while enhancing tumor control.

FOXP1 Promotes Embryonic Neural Stem Cell Differentiation by Repressing Jagged1 Expression

Mutations in FOXP1 have been linked to neurodevelopmental disorders including intellectual disability and autism; however, the underlying molecular mechanisms remain ill-defined. Here, we demonstrate with RNA and chromatin immunoprecipitation sequencing that FOXP1 directly regulates genes controlling neurogenesis. We show that FOXP1 is expressed in embryonic neural stem cells (NSCs), and modulation of FOXP1 expression affects both neuron and astrocyte differentiation. Using a murine model of cortical development, FOXP1-knockdown in utero was found to reduce NSC differentiation and migration during corticogenesis. Furthermore, transplantation of FOXP1-knockdown NSCs in neonatal mice after hypoxia-ischemia challenge demonstrated that FOXP1 is also required for neuronal differentiation and functionality in vivo. FOXP1 was found to repress the expression of Notch pathway genes including the Notch-ligand Jagged1, resulting in inhibition of Notch signaling. Finally, blockade of Jagged1 in FOXP1-knockdown NSCs rescued neuronal differentiation in vitro. Together, these data support a role for FOXP1 in regulating embryonic NSC differentiation by modulating Notch signaling.

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FOXP1 promotes astrocyte and neuronal differentiation of NSCs in vitro

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FOXP1 promotes neuronal differentiation of NSCs in vivo

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FOXP1 transcriptionally regulates pro-neural genes and represses Notch pathway genes

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FOXP1 promotes neuronal differentiation by limiting Jagged1 expression

Low GRK2 Underlies Hyperalgesic Priming by Glial Cell-Derived Neurotrophic Factor

Background: We recently identified the balance between the level of G protein coupled receptor kinase 2 (GRK2) and Epac1 in nociceptors as a key factor in the transition from acute to chronic pain that occurs in mice 'primed' by an inflammatory stimulus. Here, we examined the contribution of GRK2 and Epac-signaling to growth factor-induced hyperalgesic priming. Methods: Mice were primed by intraplantar injection with glial cell-derived neurotrophic factor (GDNF). Mechanical allodynia in response to PGE₂ was followed over time in primed and non-primed animals. GRK2 protein levels in dorsal root ganglion (DRG) neurons were quantified by immunohistochemistry. The effect of herpes simplex virus (HSV)-GRK2 amplicons to restore GRK2 levels or of an Epac inhibitor on PGE₂ allodynia in primed mice was examined. Results: Glial cell-derived neurotrophic factor-induced hyperalgesia disappeared within 12 days. The hyperalgesic response to a subsequent intraplantar injection of PGE₂ was prolonged from <24 h in control mice to more than 72 h in GDNF-primed mice. In male and female primed mice, PGE₂ hyperalgesia was inhibited by oral administration of the Epac inhibitor ESI-09, while the drug had no effect in control mice. Mice primed with GDNF had reduced levels of GRK2 in IB4(+) small DRG neurons, but normal GRK2 levels in IB4(-) DRG neurons. Intraplantar administration of HSV-GRK2 amplicons to increase GRK2 protein levels prevented the prolongation of PGE₂-induced hyperalgesia in GDNF-primed mice. Conclusion: Low GRK2 in nociceptors is critical to develop a primed state in response to GDNF and leads to engagement of Epac signaling and transition to chronic PGE₂-induced hyperalgesia. Increasing GRK2 protein or inhibiting Epac signaling may represent new avenues for preventing transition to a chronic pain state.

The High Costs of Low-Grade Inflammation: Persistent Fatigue as a Consequence of Reduced Cellular-Energy Availability and Non-adaptive Energy Expenditure

Chronic or persistent fatigue is a common, debilitating symptom of several diseases. Persistent fatigue has been associated with low-grade inflammation in several models of fatigue, including cancer-related fatigue and chronic fatigue syndrome. However, it is unclear how low-grade inflammation leads to the experience of fatigue. We here propose a model of an imbalance in energy availability and energy expenditure as a consequence of low-grade inflammation. In this narrative review, we discuss how chronic low-grade inflammation can lead to reduced cellular-energy availability. Low-grade inflammation induces a metabolic switch from energy-efficient oxidative phosphorylation to fast-acting, but less efficient, aerobic glycolytic energy production; increases reactive oxygen species; and reduces insulin sensitivity. These effects result in reduced glucose availability and, thereby, reduced cellular energy. In addition, emerging evidence suggests that chronic low-grade inflammation is associated with increased willingness to exert effort under specific circumstances. Circadian-rhythm changes and sleep disturbances might mediate the effects of inflammation on cellular-energy availability and non-adaptive energy expenditure. In the second part of the review, we present evidence for these metabolic pathways in models of persistent fatigue, focusing on chronic fatigue syndrome and cancer-related fatigue. Most evidence for reduced cellular-energy availability in relation to fatigue comes from studies on chronic fatigue syndrome. While the mechanistic evidence from the cancer-related fatigue literature is still limited, the sparse results point to reduced cellular-energy availability as well. There is also mounting evidence that behavioral-energy expenditure exceeds the reduced cellular-energy availability in patients with persistent fatigue. This suggests that an inability to adjust energy expenditure to available resources might be one mechanism underlying persistent fatigue.

Associations of inflammation with symptom burden in patients with acute myeloid leukemia

The aim of the study was to assess the association inflammation with symptom burden in patients with acute myeloid leukemia (AML), assessed before and during remission induction chemotherapy (IC). Patients with AML (n = 95) were followed from baseline (before IC) to the third week of IC for severity of self-reported somatic symptoms (assessed with the MD Anderson Symptom Inventory) and plasma levels of 13 inflammation-related biomarkers (n = 64). A composite symptom burden severity score was computed as the average score of the six most severe somatic symptoms i.e., fatigue, disturbed sleep, drowsiness, dry mouth, lack of appetite, and pain. Results from cross-sectional analyses showed that inflammation was weakly associated with symptom burden before IC (multiple regression model, explained variance = 10%) but this association grew stronger during IC (week 3 explained variance = 35%). About half of the sample showed a change over time in symptom severity. These changes were not reflected in similar changes over time in inflammatory markers, suggesting that it is the absolute concentration of a given inflammatory marker at a given time point rather than its relative change over time that is of importance. In conclusion, inflammation was strongly associated with symptom burden only during IC, possibly because expression of cytokines only then becomes relevant for regulation of symptom burden. While the current study does not allow for determination of causality, the results suggest that AML patients might benefit from anti-inflammatory interventions during treatment to alleviate somatic symptom experience.

Beyond symptomatic relief for chemotherapy-induced peripheral neuropathy: Targeting the source

Chemotherapy-induced peripheral neuropathy (CIPN) is a serious adverse side effect of many chemotherapeutic agents, affecting >60% of patients with cancer. Moreover, CIPN persists long into survivorship in approximately 20% to 30% of these patients. To the authors' knowledge, no drugs have been approved to date by the US Food and Drug Administration to effectively manage chemotherapy-induced neuropathic pain. The majority of the drugs tested for the management of CIPN aim at symptom relief, including pain and paresthesia, yet are not very efficacious. The authors propose that there is a need to acquire a more thorough understanding of the etiology of CIPN so that effective, mechanism-based, disease-modifying interventions can be developed. It is important to note that such interventions should not interfere with the antitumor effects of chemotherapy. Mitochondria are rod-shaped cellular organelles that represent the powerhouses of the cell, in that they convert oxygen and nutrients into the cellular energy "currency" adenosine triphosphate. In addition, mitochondria regulate cell death. Neuronal mitochondrial dysfunction and the associated nitro-oxidative stress represent crucial final common pathways of CIPN. Herein, the authors discuss the potential to prevent or reverse CIPN by protecting mitochondria and/or inhibiting nitro-oxidative stress with novel potential drugs, including the mitochondrial protectant pifithrin-μ, histone deacetylase 6 inhibitors, metformin, antioxidants, peroxynitrite decomposition catalysts, and anti-inflammatory mediators including interleukin 10. This review hopefully will contribute toward bridging the gap between preclinical research and the development of realistic novel therapeutic strategies to prevent or reverse the devastating neurotoxic effects of chemotherapy on the (peripheral) nervous system. Cancer 2018;124:2289-98. © 2018 American Cancer Society.

Identification of FAM173B as a protein methyltransferase promoting chronic pain

Chronic pain is a debilitating problem, and insights in the neurobiology of chronic pain are needed for the development of novel pain therapies. A genome-wide association study implicated the 5p15.2 region in chronic widespread pain. This region includes the coding region for FAM173B, a functionally uncharacterized protein. We demonstrate here that FAM173B is a mitochondrial lysine methyltransferase that promotes chronic pain. Knockdown and sensory neuron overexpression strategies showed that FAM173B is involved in persistent inflammatory and neuropathic pain via a pathway dependent on its methyltransferase activity. FAM173B methyltransferase activity in sensory neurons hyperpolarized mitochondria and promoted macrophage/microglia activation through a reactive oxygen species–dependent pathway. In summary, we uncover a role for methyltransferase activity of FAM173B in the neurobiology of pain. These results also highlight FAM173B methyltransferase activity as a potential therapeutic target to treat debilitating chronic pain conditions.

Pain is an evolutionarily conserved physiological phenomenon necessary for survival. Yet, pain can become pathological when it occurs independently of noxious stimuli. The molecular mechanisms of pathological pain are still poorly understood, limiting the development of highly needed novel analgesics. Recently, genetic variations in the genomic region encoding FAM173B—a functionally uncharacterized protein—have been linked to chronic pain in humans. In this study, we identify the role and function of FAM173B in the development of pathological pain. We used genetic, biochemical, and behavioral approaches in mice to show that FAM173B is a mitochondrial lysine methyltransferase—a protein that transfers methyl group to donor proteins. By genetically silencing or overexpressing FAM173B in sensory neurons, we showed that FAM173B methyltransferase activity promotes the development of chronic pain. In addition, we discovered that FAM173B methyltransferase activity in the mitochondria of sensory neurons promotes chronic pain via a pathway that depends on the production of reactive oxygen species and on the engagement of spinal cord microglia—engulfing cells of the central nervous system. These data point to an essential role of FAM173B in the regulation of pathological pain.

Intranasal Stem Cell Treatment as a Novel Therapy for Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) represents a major health problem in Western society due to high mortality and morbidity, and the relative young age of patients. Currently, efficacious therapeutic options are very limited. Mesenchymal stem cell (MSC) administration has been shown to improve functional outcome and lesion size in experimental models of stroke and neonatal hypoxic-ischemic brain injury. Here, we studied the therapeutic potential of intranasally administered bone marrow-derived MSCs relatively late postinsult using a rat endovascular puncture model for SAH. Six days after induction of SAH, rats were treated with MSCs or vehicle through nasal administration. Intranasal MSC treatment significantly improved sensorimotor and mechanosensory function at 21 days after SAH. Gray and white matter loss was significantly reduced by MSC treatment and the number of NeuN⁺ neurons around the lesion increased due to MSC treatment. Moreover, intranasal MSC administration led to a sharp decrease in SAH-induced activation of astrocytes and microglia/macrophages in the lesioned hemisphere, especially of M2-like (CD206⁺) microglia/macrophages. Interestingly, MSC administration also decreased SAH-induced depression-like behavior in association with a restoration of tyrosine hydroxylase expression in the substantia nigra and striatum. We show here for the first time that intranasal MSC administration reverses the devastating consequences of SAH, including regeneration of the cerebral lesion, functional recovery, and treatment of comorbid depression-like behavior.

Upregulation of neuronal kynurenine 3-monooxygenase mediates depression-like behavior in a mouse model of neuropathic pain

Pain and depression often co-occur, but the underlying mechanisms have not been elucidated. Here, we used the spared nerve injury (SNI) model in mice to induce both neuropathic pain and depression-like behavior. We investigated whether brain interleukin (IL)-1 signaling and activity of kynurenine 3-monoxygenase (KMO), a key enzyme for metabolism of kynurenine into the neurotoxic NMDA receptor agonist quinolinic acid, are necessary for comorbid neuropathic pain and depression-like behavior. SNI mice showed increased expression levels of Il1b and Kmo mRNA in the contralateral side of the brain. The SNI-induced increase of Kmo mRNA was associated with increased KMO protein and elevated quinolinic acid and reduced kynurenic acid in the contralateral hippocampus. The increase in KMO-protein in response to SNI mostly took place in hippocampal NeuN-positive neurons rather than microglia. Inhibition of brain IL-1 signaling by intracerebroventricular administration of IL-1 receptor antagonist after SNI prevented the increase in Kmo mRNA and depression-like behavior measured by forced swim test. However, inhibition of brain IL-1 signaling has no effect on mechanical allodynia. In addition, intracerebroventricular administration of the KMO inhibitor Ro 61-8048 abrogated depression-like behavior without affecting mechanical allodynia after SNI. We show for the first time that the development of depression-like behavior in the SNI model requires brain IL-1 signaling and activation of neuronal KMO, while pain is independent of this pathway. Inhibition of KMO may represent a promising target for treating depression.

Combined fetal inflammation and postnatal hypoxia causes myelin deficits and autism-like behavior in a rat model of diffuse white matter injury

Diffuse white matter injury (WMI) is a serious problem in extremely preterm infants, and is associated with adverse neurodevelopmental outcome, including cognitive impairments and an increased risk of autism-spectrum disorders. Important risk factors include fetal or perinatal inflammatory insults and fluctuating cerebral oxygenation. However, the exact mechanisms underlying diffuse WMI are not fully understood and no treatment options are currently available. The use of clinically relevant animal models is crucial to advance knowledge on the pathophysiology of diffuse WMI, allowing the definition of novel therapeutic targets. In the present study, we developed a multiple-hit animal model of diffuse WMI by combining fetal inflammation and postnatal hypoxia in rats. We characterized the effects on white matter development and functional outcome by immunohistochemistry, MRI and behavioral paradigms. Combined fetal inflammation and postnatal hypoxia resulted in delayed cortical myelination, microglia activation and astrogliosis at P18, together with long-term changes in oligodendrocyte maturation as observed in 10 week old animals. Furthermore, rats with WMI showed impaired motor performance, increased anxiety and signs of autism-like behavior, i.e. reduced social play behavior and increased repetitive grooming. In conclusion, the combination of fetal inflammation and postnatal hypoxia in rats induces a pattern of brain injury and functional impairments that closely resembles the clinical situation of diffuse WMI. This animal model provides the opportunity to elucidate pathophysiological mechanisms underlying WMI, and can be used to develop novel treatment options for diffuse WMI in preterm infants.

Mechanisms of Neurotoxic Symptoms as a Result of Breast Cancer and Its Treatment: Considerations on the Contribution of Stress, Inflammation, and Cellular Bioenergetics

PURPOSE OF REVIEW

Breast cancer and its treatment are associated with a range of neurotoxic symptoms, such as fatigue, cognitive impairment, and pain. Although these symptoms generally subside after treatment completion, they become chronic in a significant subset of patients. We here summarize recent findings on neuroinflammation, stress, and mitochondrial dysfunction as mechanistic pathways leading to neurotoxic symptom experience in breast cancer patients and survivors.

RECENT FINDINGS

Neuroinflammation related to stress or cancer treatment and stress resulting from diagnosis, treatment, or (cancer-related) worrying are important predictors of a neurotoxic symptom experience, both during and after treatment for breast cancer. Both inflammation and stress hormones, as well as cancer treatment, can induce mitochondrial dysfunction resulting in reduced cellular energy.

SUMMARY

We propose reduced cellular energy (mitochondrial dysfunction) induced by inflammation, oxygen radical production, and stress as a result of cancer and/or cancer treatment as a final mechanism underlying neurotoxic symptoms.