[Dermatologic toxicities of immune checkpoint inhibitors]

The development of immune checkpoint inhibitors (monoclonal antibodies targeting PD-1/PD-L1 or CTLA-4) represents a significant advance in the treatment of multiple cancers. Given their particular mechanism of action, which involves triggering CD4+/CD8+ T-cell activation and proliferation, they are associated with a specific safety profile. Their adverse events are primarily immune-related, and can affect practically all organs. In this context, dermatological toxicity is the most common, though it mostly remains mild to moderate and does not require discontinuation of treatment. More than a third of patients are faced with cutaneous adverse events, usually in the form of a maculopapular rash, pruritus or vitiligo (only in patients treated for melanoma). Much more specific dermatologic disorders, however, may occur such as lichenoid reactions, induced psoriasis, sarcoidosis, auto-immune diseases (bullous pemphigoid, dermatomyositis, alopecia areata), acne-like rash, xerostomia, etc. Rigorous dermatological evaluation is thus mandatory in the case of atypical, persistent/recurrent or severe lesions. In this article, we review the incidence and spectrum of dermatologic adverse events reported with immune checkpoint inhibitors. Finally, a management algorithm is proposed.

Activity-Regulated Cytoskeleton-Associated Protein Accumulates in the Nucleus in Response to Cocaine and Acts as a Brake on Chromatin Remodeling and Long-Term Behavioral Alterations

BACKGROUND

Addiction relies on persistent alterations of neuronal properties, which depends on gene regulation. Activity-regulated cytoskeleton-associated protein (Arc) is an immediate early gene that modulates neuronal plasticity underlying learning and memory. Its role in cocaine-induced neuronal and behavioral adaptations remains elusive.

METHODS

Acute cocaine-treated mice were used for quantitative reverse-transcriptase polymerase chain reaction, immunocytochemistry, and confocal imaging from striatum. Live imaging and transfection assays for Arc overexpression were performed from primary cultures. Molecular and behavioral adaptations to cocaine were studied from Arc-deficient mice and their wild-type littermates.

RESULTS

Arc messenger RNA and proteins are rapidly induced in the striatum after acute cocaine administration, via an extracellular-signal regulated kinase-dependent de novo protein synthesis. Although detected in dendrites, Arc accumulates in the nucleus in active zones of transcription, where it colocalizes with phospho-Ser10-histone H3, an important component of nucleosomal response. In vitro, Arc overexpression downregulates phospho-Ser10-histone H3 without modifying extracellular-signal regulated kinase phosphorylation in the nucleus. In vivo, Arc-deficient mice display decreased heterochromatin domains, a high RNA-polymerase II activity and enhanced c-Fos expression. These mice presented an exacerbated psychomotor sensitization and conditioned place preference induced by low doses of cocaine.

CONCLUSIONS

Cocaine induces the rapid induction of Arc and its nuclear accumulation in striatal neurons. Locally, it alters the nucleosomal response, and acts as a brake on chromatin remodeling and gene regulation. These original observations posit Arc as a major homeostatic modulator of molecular and behavioral responses to cocaine. Thus, modulating Arc levels may provide promising therapeutic approaches in drug addiction.

CYP46A1, the rate-limiting enzyme for cholesterol degradation, is neuroprotective in Huntington's disease

Huntington’s disease is an autosomal dominant neurodegenerative disease caused by abnormal polyglutamine expansion in huntingtin (Exp-HTT) leading to degeneration of striatal neurons. Altered brain cholesterol homeostasis has been implicated in Huntington’s disease, with increased accumulation of cholesterol in striatal neurons yet reduced levels of cholesterol metabolic precursors. To elucidate these two seemingly opposing dysregulations, we investigated the expression of cholesterol 24-hydroxylase (CYP46A1), the neuronal-specific and rate-limiting enzyme for cholesterol conversion to 24S-hydroxycholesterol (24S-OHC). CYP46A1 protein levels were decreased in the putamen, but not cerebral cortex samples, of post-mortem Huntington’s disease patients when compared to controls. Cyp46A1 mRNA and CYP46A1 protein levels were also decreased in the striatum of the R6/2 Huntington’s disease mouse model and in ST hdh Q111 cell lines. In vivo , in a wild-type context, knocking down CYP46A1 expression in the striatum, via an adeno-associated virus-mediated delivery of selective shCYP46A1, reproduced the Huntington’s disease phenotype, with spontaneous striatal neuron degeneration and motor deficits, as assessed by rotarod. In vitro , CYP46A1 restoration protected ST hdh Q111 and Exp-HTT-expressing striatal neurons in culture from cell death. In the R6/2 Huntington’s disease mouse model, adeno-associated virus-mediated delivery of CYP46A1 into the striatum decreased neuronal atrophy, decreased the number, intensity level and size of Exp-HTT aggregates and improved motor deficits, as assessed by rotarod and clasping behavioural tests. Adeno-associated virus-CYP46A1 infection in R6/2 mice also restored levels of cholesterol and lanosterol and increased levels of desmosterol. In vitro , lanosterol and desmosterol were found to protect striatal neurons expressing Exp-HTT from death. We conclude that restoring CYP46A1 activity in the striatum promises a new therapeutic approach in Huntington’s disease.

Psoriasis associated with idiopathic CD4+ T-cell lymphopenia: a regulatory T-cell defect?

Idiopathic CD4(+) lymphocytopenia (ICL) is a rare immunodeficiency syndrome of unknown origin for which the increased risks of opportunistic infections and of malignancies have been well established; however, skin dysimmune diseases, including psoriasis, have been scarcely reported up to now. We report herein the severe course of psoriasis in four patients with ICL, and show evidence for a defect in the skin recruitment of regulatory CD4(+) FoxP3(+) T cells. These data raise the apparent paradigm of the occurrence of a severe immunomediated disease together with a profound T-cell defect, a model that might also apply to other immune deficiencies associated with psoriasis.

Co-activation of VTA DA and GABA neurons mediates nicotine reinforcement

Smoking is the most important preventable cause of mortality and morbidity worldwide. This nicotine addiction is mediated through the nicotinic acetylcholine receptor (nAChR), expressed on most neurons, and also many other organs in the body. Even within the ventral tegmental area (VTA), the key brain area responsible for the reinforcing properties of all drugs of abuse, nicotine acts on several different cell types and afferents. Identifying the precise action of nicotine on this microcircuit, in vivo, is important to understand reinforcement, and finally to develop efficient smoking cessation treatments. We used a novel lentiviral system to re-express exclusively high-affinity nAChRs on either dopaminergic (DAergic) or γ-aminobutyric acid-releasing (GABAergic) neurons, or both, in the VTA. Using in vivo electrophysiology, we show that, contrary to widely accepted models, the activation of GABA neurons in the VTA plays a crucial role in the control of nicotine-elicited DAergic activity. Our results demonstrate that both positive and negative motivational values are transmitted through the dopamine (DA) neuron, but that the concerted activity of DA and GABA systems is necessary for the reinforcing actions of nicotine through burst firing of DA neurons. This work identifies the GABAergic interneuron as a potential target for smoking cessation drug development.

Reducing surgical margins in dermatofibrosarcoma protuberans using the pathological analysis technique 'vertical modified technique': a 5-year experience

BACKGROUND

For the treatment of dermatofibrosarcoma protuberans (DFSP), wide surgical excision has been recommended, with 3-5-cm margins, including the first underlying clear fascia. Since 2006, a technical improvement in pathological analysis called the vertical modified technique (VMT) has allowed us to reduce the surgical margin without increased oncological risk.

METHODS

Between 2006 and 2011, 66 cases of DFSP were analysed in our hospital, using VMT. We reviewed patient records, considering the initial margin, total margin, number of surgeries and outcomes. Functional and aesthetic consequences were assessed by the surgeon and by the patients.

RESULTS

Mean initial margin for the first resection was 18 mm (10-30 mm). First resection allowed complete resection of the tumour in 52 cases (78.8%). Mean total surgical margin was 21.3 mm (10-60 mm). There were no cases of local tumour recurrence at a median follow-up of 30 months. Reconstruction was performed using direct sutures in 53 cases (80.3%), split-thickness skin grafts in six cases (9.1%), full-thickness skin grafts in five cases (7.6%) and flaps in two patients (3%). For 90.9% of the patients, the aesthetic result was acceptable, whereas 84.8% patients were satisfied with the functional result.

CONCLUSION

VMT reduces surgical margins and allows for extensive analysis of margins. This technique represents a safe and reliable strategy in DFSP, without increasing the risk of recurrence. The outcomes of our study have confirmed the data from the literature regarding oncological safety.

Mitogen- and stress-activated protein kinase 1-induced neuroprotection in Huntington's disease: role on chromatin remodeling at the PGC-1-alpha promoter

Huntington's disease (HD) is a neurodegenerative disorder due to abnormal polyglutamine expansion in huntingtin protein (Exp-Htt). This expansion causes protein aggregation, leading to neuronal dysfunction and death. We have previously shown that mitogen- and stress-activated kinase (MSK-1), a nuclear protein kinase involved in chromatin remodeling through histone H3 phosphorylation, is deficient in the striatum of HD patients and model mice. Restoring MSK-1 expression in cultured striatal cells prevented neuronal dysfunction and death induced by Exp-Htt. Here we extend these observations in a rat model of HD based on striatal lentiviral expression of Exp-Htt (LV-Exp-HTT). MSK-1 overexpression attenuated Exp-Htt-induced down-regulation of DARPP-32 expression 4 and 10 weeks after infection and enhanced NeuN staining after 10 weeks. LV-MSK-1 induced constitutive hyperphosphorylation of H3 and cAMP-responsive element binding protein (CREB), indicating that MSK-1 has spontaneous catalytic activity. MSK-1 overexpression also upregulated peroxisome proliferator-activated receptor γ coactivator alpha (PGC-1α), a transcriptional co-activator involved in mitochondrial biogenesis. Chromatin immunoprecipitation indicated that transcriptional regulation of PGC-1α is directly linked to increased binding of MSK-1, along with H3 and CREB phosphorylation of the PGC-1α promoter. MSK-1 knock-out mice showed spontaneous striatal atrophy as they aged, as well as higher susceptibility to systemic administration of the mitochondrial neurotoxin 3-NP. These results indicate that MSK-1 activation is an important and key event in the signaling cascade that regulates PGC-1α expression. Strategies aimed at restoring MSK-1 expression in the striatum might offer a new therapeutic approach to HD.

Cyclic adenosine monophosphate-independent tyrosine phosphorylation of NR2B mediates cocaine-induced extracellular signal-regulated kinase activation

BACKGROUND

Activation of the extracellular signal-regulated kinase (ERK) in the striatum is crucial for long-term behavioral alterations induced by drugs of abuse. In response to cocaine, ERK phosphorylation (i.e., activation) is restricted to medium-sized spiny neurons expressing dopamine D1 receptor (D1R) and depends on a concomitant stimulation of D1R and glutamate N-methyl-D-aspartate receptor (NMDAR). However, the mechanisms responsible for this activation, especially the respective contribution of D1R and NMDAR, remain unknown.

METHODS

We studied striatal neurons in culture stimulated with D1R agonist and/or glutamate and wild-type or genetically modified mice treated with cocaine. Biochemical, immunohistochemical, and imaging studies were performed. Mice were also subjected to behavioral experiments.

RESULTS

Stimulation of D1R cannot activate ERK by itself but potentiates glutamate-mediated calcium influx through NMDAR that is responsible for ERK activation. Potentiation of NMDAR by D1R depends on a cyclic adenosine monophosphate-independent signaling pathway, which involves tyrosine phosphorylation of the NR2B subunit of NMDAR by Src family kinases. We also demonstrate that the D1R/Src family kinases/NR2B pathway is responsible for ERK activation by cocaine in vivo. Inhibition of this pathway abrogates cocaine-induced locomotor sensitization and conditioned place preference.

CONCLUSIONS

Our results show that potentiation of NR2B-containing NMDAR by D1R is necessary and sufficient to trigger cocaine-induced ERK activation. They highlight a new cyclic adenosine monophosphate-independent pathway responsible for the integration of dopamine and glutamate signals by the ERK cascade in the striatum and for long-term behavioral alterations induced by cocaine.

Haloperidol protects striatal neurons from dysfunction induced by mutated huntingtin in vivo

Huntington's disease (HD) results from an abnormal polyglutamine extension in the N-terminal region of the huntingtin protein. This mutation causes preferential degeneration of striatal projection neurons. We previously demonstrated, in vitro, that dopaminergic D2 receptor stimulation acted synergistically with mutated huntingtin (expHtt) to increase aggregate formation and striatal death. In the present work, we extend these observations to an in vivo system based on lentiviral-mediated expression of expHtt in the rat striatum. The early and chronic treatment with the D2 antagonist haloperidol decanoate protects striatal neurons from expHtt-induced dysfunction, as analyzed by DARPP-32 and NeuN stainings. Haloperidol treatment also reduces aggregates formation, an effect that is maintained over time. These findings indicate that D2 receptors activation contributes to the deleterious effects of expHtt on striatal function and may represent an interesting early target to alter the subsequent course of neuropathology in HD.

Glutamate induces histone H3 phosphorylation but not acetylation in striatal neurons: role of mitogen- and stress-activated kinase-1

Chromatin remodelling is thought to play a key role in gene regulation that underlies long-term synaptic plasticity and memory formation. The dynamic process of chromatin remodelling requires post-translational modifications of histones, a group of highly basic proteins that are tightly linked to DNA. In the present study, we investigated histone H3 modifications in response to glutamate stimulation leading to c-Fos and c-Jun induction in an in vitro model system of striatal neurons in culture. Intracellular signalling pathways implicated in these modifications were analysed. Histone H3 acetylation was strong in basal conditions and unmodified by glutamate treatment. By contrast, glutamate induced a strong phosphorylation of histone H3 that was inhibited by selective inhibitors of the extracellular signal-regulated kinase (ERK) and p38 mitogen-activated protein kinase (p38 MAPK) pathways, U0126 and SB203580, respectively. Blocking activation of mitogen- and stress-activated kinase 1 (MSK1), a kinase downstream ERK and p38 MAPK, by pharmacological approach or using striatal cells from MSK1 deficient mice, totally abolished H3 phosphorylation, as well as c-Fos and c-Jun induction. Chromatin immunoprecipitation assays confirmed increased levels of phosphorylated H3 at the c-jun promoter. Altogether, our data highlight the crucial role of MSK1 in the nucleosomal response necessary for gene induction in neuronal cells.

Unraveling a role for dopamine in Huntington's disease: the dual role of reactive oxygen species and D2 receptor stimulation

Huntington's disease (HD), an inherited neurodegenerative disorder, results from an abnormal polyglutamine extension in the N-terminal region of the huntingtin protein. This mutation leads to protein aggregation and neurotoxicity. Despite its widespread expression in the brain and body, mutated huntingtin causes selective degeneration of striatal projection neurons. In the present study, we investigate the role of dopamine (DA) in this preferential vulnerability. Using primary cultures of striatal neurons transiently expressing GFP-tagged-exon 1 of mutated huntingtin, we show that low doses of DA (100 microM) act synergistically with mutated huntingtin to activate the proapoptotic transcription factor c-Jun. Surprisingly, DA also increases aggregate formation of mutated huntingtin in all cellular compartments, including neurites, soma, and nuclei. DA-dependent potentiation of c-Jun activation was reversed by ascorbate, a reactive oxygen species (ROS) scavenger, and SP-600125, a selective inhibitor of the c-Jun N-terminal kinase (JNK) pathway. By contrast, DA effects on aggregate formation were reversed by a selective D2 receptor antagonist and reproduced by a D2 agonist. Similarly, striatal neurons from D2 knockout mice showed no effect of DA on aggregate formation. Blocking ROS production, JNK activation, or D2 receptor stimulation significantly reversed DA aggravation of mutated huntingtin-induced striatal death. The combined treatment with the ROS scavenger and D2 antagonist totally reversed DA's effects on mutated huntingtin-induced striatal death. Thus, the present results provide insights into the cellular mechanisms that govern striatal vulnerability in HD and strongly support a dual role of JNK activation and D2 receptor signaling in this process.

Regulation of extracellular signal-regulated kinase by homocysteine in hippocampus

In several neurological disorders including hyperhomocysteinemia, homocysteine (Hcy) accumulates in the brain, and acts as a potent neurotoxin. However, the molecular mechanisms induced by increased levels of Hcy in brain are not well understood. Here we show an activation of the extracellular signal-regulated kinases (ERK1 and ERK2) and the downstream nuclear targets Elk-1 and calcium/cAMP response element binding protein, in the hippocampus of cystathionine beta synthase deficient mice, a murine model of hyperhomocysteinemia. An ex vivo model of hippocampal slices allowed us to reproduce Hcy -induced ERK activation and to unravel the mechanisms responsible of this activation. Of interest, N-methyl-d-aspartate (NMDA), non-NMDA and metabotropic glutamate receptor antagonists all blocked Hcy -induced ERK activation. Moreover, the ERK activation was blocked in the presence of Na+-channel blocker tetrodotoxin, indicating the existence of a trans-synaptic activity in ERK activation by Hcy in hippocampal slices. The effects of Hcy on ERK cascade activation were also dependent on calcium influx, CaMK-II, PKC as well as PKA activation. Thus, altogether these data support a role of Hcy on ERK activation, via complex mechanisms, starting with a control of glutamate release, which in turn activates ionotropic and metabotropic receptor subtypes and produces increases in intracellular calcium levels.

Local endovascular treatment of aortic aneurysms. From operating theater to lab bench

Current treatment of aortic abdominal aneurysms by conventional surgery or endoprosthesis is flawed by high post-operative mortality and unpredictable durability of haemodynamic exclusion, respectively. We have developed endovascular approaches with cell and gene transfer, aimed at controlling further diameter expansion in an animal model of already-developed aneurysms in rats. Preliminary results suggest that both cell and gene endovascular therapy can be used to control expansion of aneurysms generated by inflammation and proteolytic destruction of the aortic wall.

Addictive and non-addictive drugs induce distinct and specific patterns of ERK activation in mouse brain

A major goal of research on addiction is to identify the molecular mechanisms of long-lasting behavioural alterations induced by drugs of abuse. Cocaine and delta-9-tetrahydrocannabinol (THC) activate extracellular signal-regulated kinase (ERK) in the striatum and blockade of the ERK pathway prevents establishment of conditioned place preference to these drugs. However, it is not known whether activation of ERK in the striatum is specific for these two drugs and/or this brain region. We studied the appearance of phospho-ERK immunoreactive neurons in CD-1 mouse brain following acute administration of drugs commonly abused by humans, cocaine, morphine, nicotine and THC, or of other psychoactive compounds including caffeine, scopolamine, antidepressants and antipsychotics. Each drug generated a distinct regional pattern of ERK activation. All drugs of abuse increased ERK phosphorylation in nucleus accumbens, lateral bed nucleus of the stria terminalis, central amygdala and deep layers of prefrontal cortex, through a dopamine D1 receptor-dependent mechanism. Although some non-addictive drugs moderately activated ERK in a few of these areas, they never induced this combined pattern of strong activation. Antidepressants and caffeine activated ERK in hippocampus and cerebral cortex. Typical antipsychotics mildly activated ERK in dorsal striatum and superficial prefrontal cortex, whereas clozapine had no effect in the striatum, but more widespread effects in cortex and amygdala. Our results outline a subset of structures in which ERK activation might specifically contribute to the long-term effects of drugs of abuse, and suggest mapping ERK activation in brain as a way to identify potential sites of action of psychoactive drugs.

[Development and repair of vessels from bone marrow stem cells in the adult: from biology to clinical practice]

In addition to its role in hematopoiesis, bone marrow appears to be a reservoir of stem cells that can differentiate into components of vessel wall. Upon stimulation by factors such as tissue ischemia, bone marrow stem cells can enter into circulating blood, and incorporate into areas of vascular development. Animal models suggest that bone marrow is a cellular source for tissue repair and/or regeneration. Data from humans, and clinical trials using bone marrow stem cells for the treatment of chronic ischemia in limbs and myocardium, support the view that stem cells may represent a new tool for the treatment of ischemia.