Role of the TRPC1 Channel in Hippocampal Long-Term Depression and in Spatial Memory Extinction.

Group I metabotropic glutamate receptors (mGluR) are involved in various forms of synaptic plasticity that are believed to underlie declarative memory. We previously showed that mGluR5 specifically activates channels containing TRPC1, an isoform of the canonical family of Transient Receptor Potential channels highly expressed in the CA1-3 regions of the hippocampus. Using a tamoxifen-inducible conditional knockout model, we show here that the acute deletion of the Trpc1 gene alters the extinction of spatial reference memory. mGluR-induced long-term depression, which is partially responsible for memory extinction, was impaired in these mice. Similar results were obtained in vitro and in vivo by inhibiting the channel by its most specific inhibitor, Pico145. Among the numerous known postsynaptic pathways activated by type I mGluR, we observed that the deletion of Trpc1 impaired the activation of ERK1/2 and the subsequent expression of Arc, an immediate early gene that plays a key role in AMPA receptors endocytosis and subsequent long-term depression.

Genetic deletion of soluble 5'-nucleotidase II reduces body weight gain and insulin resistance induced by a high-fat diet.

We previously investigated whether inhibition of AMP-metabolizing enzymes could enhance AMP-activated protein kinase (AMPK) activation in skeletal muscle for the treatment of type 2 diabetes. Soluble 5'-nucleotidase II (NT5C2) hydrolyzes IMP and its inhibition could potentially lead to a rise in AMP to activate AMPK. In the present study, we investigated effects of NT5C2 deletion in mice fed a normal-chow diet (NCD) or a high-fat diet (HFD). On a NCD, NT5C2 deletion did not result in any striking metabolic phenotype. On a HFD however, NT5C2 knockout (NT5C2-/-) mice displayed reduced body/fat weight gain, improved glucose tolerance, reduced plasma insulin, triglyceride and uric acid levels compared with wild-type (WT) mice. There was a tendency towards smaller and fewer adipocytes in epididymal fat from NT5C2-/- mice compared to WT mice, consistent with a reduction in triglyceride content. Differences in fat mass under HFD could not be explained by changes in mRNA expression profiles of epididymal fat from WT versus NT5C2-/- mice. However, rates of lipolysis tended to increase in epididymal fat pads from NT5C2-/- versus WT mice, which might explain reduced fat mass. In incubated skeletal muscles, insulin-stimulated glucose uptake and associated signalling were enhanced in NT5C2-/- versus WT mice on HFD, which might contribute towards improved glycemic control. In summary, NT5C2 deletion in mice protects against HFD-induced weight gain, adiposity, insulin resistance and associated hyperglycemia.

Defective adaptive thermogenesis contributes to metabolic syndrome and liver steatosis in obese mice.

Fatty liver diseases are complications of the metabolic syndrome associated with obesity, insulin resistance and low grade inflammation. Our aim was to uncover mechanisms contributing to hepatic complications in this setting. We used foz/foz mice prone to obesity, insulin resistance and progressive fibrosing non-alcoholic steatohepatitis (NASH). Foz/foz mice are hyperphagic but wild-type (WT)-matched calorie intake failed to protect against obesity, adipose inflammation and glucose intolerance. Obese foz/foz mice had similar physical activity level but reduced energy expenditure. Thermogenic adaptation to high-fat diet (HFD) or to cold exposure was severely impaired in foz/foz mice compared with HFD-fed WT littermates due to lower sympathetic tone in their brown adipose tissue (BAT). Intermittent cold exposure (ICE) restored BAT function and thereby improved glucose tolerance, decreased fat mass and liver steatosis. We conclude that failure of BAT adaptation drives the metabolic complications of obesity in foz/foz mice, including development of liver steatosis. Induction of endogenous BAT function had a significant therapeutic impact on obesity, glucose tolerance and liver complications and is a potential new avenue for therapy of non-alcoholic fatty liver disease (NAFLD).

TRPV4 is associated with central rather than nephrogenic osmoregulation.

TRPV4 is a polymodal cation channel expressed in osmosensitive neurons of the hypothalamus and in the mammalian nephron. The segmental distribution and role(s) of TRPV4 in osmoregulation remain debated. We investigated the renal distribution pattern of TRPV4 and the functional consequences of its disruption in mouse models. Using qPCR on microdissected segments, immunohistochemistry, and a LacZ reporter mouse, we found that TRPV4 is abundantly expressed in the proximal tubule, the late distal convoluted tubule, and throughout the connecting tubule and collecting duct, including principal and intercalated cells. TRPV4 was undetectable in the glomeruli and thick ascending limb and weakly abundant in the early distal convoluted tubule. Metabolic studies in Trpv4 (+/+) and Trpv4 (-/-) littermates revealed that the lack of TRPV4 did not influence activity, food and water intake, renal function, and urinary concentration at baseline. The mice showed a similar response to furosemide, water loading and deprivation, acid loading, and dietary NaCl restriction. However, Trpv4 (-/-) mice showed a significantly lower vasopressin synthesis and release after water deprivation, with a loss of the positive correlation between plasma osmolality and plasma vasopressin levels, and a delayed water intake upon acute administration of hypertonic saline. Specific activation of TRPV4 in primary cultures of proximal tubule cells increased albumin uptake, whereas no effect of TRPV4 deletion could be observed at baseline. These data reveal that, despite its abundant expression in tubular segments, TRPV4 does not play a major role in the kidney or is efficiently compensated when deleted. Instead, TRPV4 is critical for the release of vasopressin, the sensation of thirst, and the central osmoregulation.

Activation of phagocytic activity in astrocytes by reduced expression of the inflammasome component ASC and its implication in a mouse model of Alzheimer disease.

BACKGROUND: The proinflammatory cytokine interleukin-1ß (IL-1ß) is overexpressed in Alzheimer disease (AD) as a key regulator of neuroinflammation. Amyloid-ß (Aß) peptide triggers activation of inflammasomes, protein complexes responsible for IL-1ß maturation in microglial cells. Downregulation of NALP3 (NACHT, LRR, and PYD domains-containing protein 3) inflammasome has been shown to decrease amyloid load and rescue cognitive deficits in a mouse model of AD. Whereas activation of inflammasome in microglial cells has been described in AD, no data are currently available concerning activation of inflammasome in astrocytes, although they are involved in inflammatory response and phagocytosis. Here, by targeting the inflammasome adaptor protein ASC (apoptosis-associated speck-like protein containing a CARD domain), we investigated the influence of activation of the inflammasome on the phagocytic activity of astrocytes. METHODS: We used an ASC knockout mouse model, as ASC is a central protein in the inflammasome, acting as an adaptor and stabilizer of the complex and thus critical for its activation. Lipopolysaccharide (LPS)-primed primary cultures of astrocytes from newborn mice were utilized to evaluate Aß-induced inflammasome activation by measuring IL-1ß release by ECLIA (electro-chemiluminescence immunoassay). Phagocytosis efficiency was measured by incorporation of bioparticles, and the release of the chemokine CCL3 (C-C motif ligand 3) was measured by ECLIA. ASC mice were crossbred with 5xFAD (familial Alzheimer disease) mice and tested for spatial reference memory using the Morris water maze (MWM) at 7-8 months of age. Amyloid load and CCL3 were quantified by thioflavine S staining and quantitative real-time polymerase chain reaction (qRT-PCR), respectively. RESULTS: Cultured astrocytes primed with LPS and treated with Aß showed an ASC-dependent production of IL-1ß resulting from inflammasome activation mediated by Aß phagocytosis and cathepsin B enzymatic activity. ASC+/- astrocytes displayed a higher phagocytic activity as compared to ASC+/+ and ASC -/- cells, resulting from a higher release of the chemokine CCL3. A significant decrease in amyloid load was measured in the brain of 7-8-month-old 5xFAD mice carrying the ASC +/- genotype, correlated with an increase in CCL3 gene expression. In addition, the ASC +/- genotype rescued spatial reference memory deficits observed in 5xFAD mice. CONCLUSIONS: Our results demonstrate that Aß is able to activate astrocytic inflammasome. Downregulation of inflammasome activity increases phagocytosis in astrocytes due to the release of CCL3. This could explain why downregulation of inflammasome activity decreases amyloid load and rescues memory deficits in a mouse model of AD.

Osmosensation in TRPV2 dominant negative expressing skeletal muscle fibres.

Increased plasma osmolarity induces intracellular water depletion and cell shrinkage (CS) followed by activation of a regulatory volume increase (RVI). In skeletal muscle, the hyperosmotic shock-induced CS is accompanied by a small membrane depolarization responsible for a release of Ca(2+) from intracellular pools. Hyperosmotic shock also induces phosphorylation of STE20/SPS1-related proline/alanine-rich kinase (SPAK). TRPV2 dominant negative expressing fibres challenged with hyperosmotic shock present a slower membrane depolarization, a diminished Ca(2+) response, a smaller RVI response, a decrease in SPAK phosphorylation and defective muscle function. We suggest that hyperosmotic shock induces TRPV2 activation, which accelerates muscle cell depolarization and allows the subsequent Ca(2+) release from the sarcoplasmic reticulum, activation of the Na(+) -K(+) -Cl(-) cotransporter by SPAK, and the RVI response. Increased plasma osmolarity induces intracellular water depletion and cell shrinkage followed by activation of a regulatory volume increase (RVI). In skeletal muscle, this is accompanied by transverse tubule (TT) dilatation and by a membrane depolarization responsible for a release of Ca(2+) from intracellular pools. We observed that both hyperosmotic shock-induced Ca(2+) transients and RVI were inhibited by Gd(3+) , ruthenium red and GsMTx4 toxin, three inhibitors of mechanosensitive ion channels. The response was also completely absent in muscle fibres overexpressing a non-permeant, dominant negative (DN) mutant of the transient receptor potential, V2 isoform (TRPV2) ion channel, suggesting the involvement of TRPV2 or of a TRP isoform susceptible to heterotetramerization with TRPV2. The release of Ca(2+) induced by hyperosmotic shock was increased by cannabidiol, an activator of TRPV2, and decreased by tranilast, an inhibitor of TRPV2, suggesting a role for the TRPV2 channel itself. Hyperosmotic shock-induced membrane depolarization was impaired in TRPV2-DN fibres, suggesting that TRPV2 activation triggers the release of Ca(2+) from the sarcoplasmic reticulum by depolarizing TTs. RVI requires the sequential activation of STE20/SPS1-related proline/alanine-rich kinase (SPAK) and NKCC1, a Na(+) -K(+) -Cl(-) cotransporter, allowing ion entry and driving osmotic water flow. In fibres overexpressing TRPV2-DN as well as in fibres in which Ca(2+) transients were abolished by the Ca(2+) chelator BAPTA, the level of P-SPAK(Ser373) in response to hyperosmotic shock was reduced, suggesting a modulation of SPAK phosphorylation by intracellular Ca(2+) . We conclude that TRPV2 is involved in osmosensation in skeletal muscle fibres, acting in concert with P-SPAK-activated NKCC1.

Tauopathy contributes to synaptic and cognitive deficits in a murine model for Alzheimer's disease.

Tau alterations are now considered an executor of neuronal demise and cognitive dysfunction in Alzheimer's disease (AD). Mouse models combining amyloidosis and tauopathy and their parental counterparts are important tools to further investigate the interplay of abnormal amyloid-ß (Aß) and Tau species in pathogenesis, synaptic and neuronal dysfunction, and cognitive decline. Here, we crossed APP/PS1 mice with 5 early-onset familial AD mutations (5xFAD) and TauP301S (PS19) transgenic mice, denoted F(+)/T(+) mice, and phenotypically compared them to their respective parental strains, denoted F(+)/T(-) and F(-)/T(+) respectively, as controls. We found dramatically aggravated tauopathy (~10-fold) in F(+)/T(+) mice compared to the parental F(-)/T(+) mice. In contrast, amyloidosis was unaltered compared to the parental F(+)/T(-) mice. Tauopathy was invariably and very robustly aggravated in hippocampal and cortical brain regions. Most important, F(+)/T(+) displayed aggravated cognitive deficits in a hippocampus-dependent spatial navigation task, compared to the parental F(+)/T(-) strain, while parental F(-)/T(+) mice did not display cognitive impairment. Basal synaptic transmission was impaired in F(+)/T(+) mice compared to nontransgenic mice and the parental strains (≥40%). Finally, F(+)/T(+) mice displayed a significant hippocampal atrophy (~20%) compared to nontransgenic mice, in contrast to the parental strains. Our data indicate for the first time that pathological Aß species (or APP/PS1) induced changes in Tau contribute to cognitive deficits correlating with synaptic deficits and hippocampal atrophy in an AD model. Our data lend support to the amyloid cascade hypothesis with a role of pathological Aß species as initiator and pathological Tau species as executor.

Early ALS-type gait abnormalities in AMP-dependent protein kinase-deficient mice suggest a role for this metabolic sensor in early stages of the disease.

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by the selective loss of motoneurons. While the principal cause of the disease remains so far unknown, the onset and progression of the pathology are increasingly associated with alterations in the control of cell metabolism. On the basis of the well-known key roles of 5'-adenosine monophosphate-activated protein kinase (AMPK) in sensing and regulating the intracellular energy status, we hypothesized that mice with a genetic deletion of AMPK would develop locomotor abnormalities that bear similarity with those detected in the very early disease stage of mice carrying the ALS-associated mutated gene hSOD1(G93A). Using an automated gait analysis system (CatWalk), we here show that hSOD1(G93A) mice and age-matched mice lacking the neuronal and skeletal muscle predominant α2 catalytic subunit of AMPK showed an altered gait, clearly different from wild type control mice. Double mutant mice lacking AMPK α2 and carrying hSOD1(G93A) showed the same early gait abnormalities as hSOD1(G93A) mice over an age span of 8 to 16 weeks. Taken together, these data support the concept that altered AMPK function and associated bioenergetic abnormalities could constitute an important component in the early pathogenesis of ALS. Therapeutic interventions acting on metabolic pathways could prove beneficial on early locomotor deficits, which are sensitively detectable in rodent models using the CatWalk system.

Loss of Maged1 results in obesity, deficits of social interactions, impaired sexual behavior and severe alteration of mature oxytocin production in the hypothalamus.

MAGED1, NECDIN and MAGEL2 are members of the MAGE gene family. The latter two of these genes have been involved in Prader-Willi syndrome (PWS), which includes hyperphagia, repetitive and compulsive behaviors, and cognitive impairment. Here, we show that Maged1-deficient mice develop progressive obesity associated with hyperphagia and reduced motor activity. Loss of Maged1 also results in a complex behavioral syndrome that includes reduced social interactions and memory, deficient sexual behavior, as well as increased anxiety and self-grooming. Oxytocin (OT), which is produced in the hypothalamus, can act as a neurotransmitter that reduces anxiety, promotes social behaviors and regulates food intake. Growing evidences indicate that OT is involved in autism. We found that Maged1 mutants showed a severe reduction in the levels of mature OT, but not of its precursors, in the hypothalamus. Moreover, the administration of OT rescued the deficit in social memory of these mice. We conclude that Maged1 is required for OT processing or stability. A decrease in mature OT levels in Maged1 mutants affects social interactions and possibly other behavioral processes. Our observations suggest that, in human, MAGED1 could play a role in autism or cause a neurodevelopmental condition that is reminiscent of the PWS.

The Onecut transcription factor HNF-6 contributes to proper reorganization of Purkinje cells during postnatal cerebellum development.

The Onecut (OC) family of transcription factors comprises three members in mammals, namely HNF-6 (or OC-1), OC-2 and OC-3. During embryonic development, these transcriptional activators control cell differentiation in pancreas, in liver and in the nervous system. Adult Hnf6 mutant mice exhibit locomotion defects characterized by hindlimb muscle weakness, abnormal gait and defective balance and coordination. Indeed, HNF-6 is required in spinal motor neurons for proper formation of the hindlimb neuromuscular junctions, which likely explain muscle weakness observed in corresponding mutant animals. The goal of the present study was to determine the cause of the balance and coordination defects in Hnf6 mutant mice. Coordination and balance deficits were quantified by rotarod and runway tests. Hnf6 mutant animals showed an increase in the fall frequency from the beam and were unable to stay on the rotarod even at low speed, indicating a severe balance and coordination deficit. To identify the origin of this abnormality, we assessed whether the development of the main CNS structure involved in the control of balance and coordination, namely the cerebellum, was affected by the absence of HNF-6. Firstly, we observed that Hnf6 was expressed transiently during the first week after birth in the Purkinje cells of wild type newborn mice. Secondly, we showed that, in Hnf6-/- mice, the organization of Purkinje cells became abnormal during a second phase of their development. Indeed, Purkinje cells were produced normally but part of them failed to reorganize as a regular continuous monolayer at the interface between the molecular and the granular layer of the cerebellum. Thus, the Onecut factor HNF-6 contributes to the reorganization of Purkinje cells during a late phase of cerebellar development.

Administration of adiponectin receptor agonist AdipoRon relieves cancer cachexia by mitigating inflammation in tumour-bearing mice.

BACKGROUND: Cancer cachexia is a life-threatening, inflammation-driven wasting syndrome that remains untreatable. Adiponectin, the most abundant adipokine, plays an important role in several metabolic processes as well as in inflammation modulation. Our aim was to test whether administration of AdipoRon (AR), a synthetic agonist of the adiponectin receptors, prevents the development of cancer cachexia and its related muscle atrophy. METHODS: The effect of AR on cancer cachexia was investigated in two distinct murine models of colorectal cancer. First, 7-week-old CD2F1 male mice were subcutaneously injected with colon-26 carcinoma cells (C26) or vehicle (CT). Six days after injection, mice were treated for 5 days with AdipoRon (50 mg/kg/day; C26 + AR) or the corresponding vehicle (CT and C26). Additionally, a genetic model, the ApcMin/+ mouse, that develops spontaneously numerous intestinal polyps, was used. Eight-week-old male ApcMin/+ mice were treated with AdipoRon (50 mg/kg/day; Apc + AR) or the corresponding vehicle (Apc) over a period of 12 weeks, with C57BL/6J wild-type mice used as controls. In both models, several parameters were assessed in vivo: body weight, grip strength and serum parameters, as well as ex vivo: molecular changes in muscle, fat and liver. RESULTS: The protective effect of AR on cachexia development was observed in both cachectic C26 and ApcMin/+ mice. In these mice, AR administration led to a significant alleviation of body weight loss and muscle wasting, together with rescued muscle strength (P < 0.05 for all). In both models, AR had a strong anti-inflammatory effect, reflected by lower systemic interleukin-6 levels (-55% vs. C26, P < 0.001 and -80% vs. Apc mice, P < 0.05), reduced muscular inflammation as indicated by lower levels of Socs3, phospho-STAT3 and Serpina3n, an acute phase reactant (P < 0.05 for all). In addition, AR blunted circulating levels of corticosterone (-46% vs. C26 mice, P < 0.001 and -60% vs. Apc mice, P < 0.05), the predominant murine glucocorticoid known to induce muscle atrophy. Accordingly, key glucocorticoid-responsive factors implicated in atrophy programmes were-or tended to be-significantly blunted in skeletal muscle by AR. Finally, AR protected against lipid metabolism alterations observed in ApcMin/+ mice, as it mitigated the increase in circulating triglyceride levels (-38%, P < 0.05) by attenuating hepatic triglyceride synthesis and fatty acid uptake by the liver. CONCLUSIONS: Altogether, these results show that AdipoRon rescued the cachectic phenotype by alleviating body weight loss and muscle atrophy, along with restraining inflammation and hypercorticism in preclinical murine models. Therefore, AdipoRon could represent an innovative therapeutic strategy to counteract cancer cachexia.

Trpc1 ion channel modulates phosphatidylinositol 3-kinase/Akt pathway during myoblast differentiation and muscle regeneration.

We previously showed in vitro that calcium entry through Trpc1 ion channels regulates myoblast migration and differentiation. In the present work, we used primary cell cultures and isolated muscles from Trpc1(-/-) and Trpc1(+/+) murine model to investigate the role of Trpc1 in myoblast differentiation and in muscle regeneration. In these models, we studied regeneration consecutive to cardiotoxin-induced muscle injury and observed a significant hypotrophy and a delayed regeneration in Trpc1(-/-) muscles consisting in smaller fiber size and increased proportion of centrally nucleated fibers. This was accompanied by a decreased expression of myogenic factors such as MyoD, Myf5, and myogenin and of one of their targets, the developmental MHC (MHCd). Consequently, muscle tension was systematically lower in muscles from Trpc1(-/-) mice. Importantly, the PI3K/Akt/mTOR/p70S6K pathway, which plays a crucial role in muscle growth and regeneration, was down-regulated in regenerating Trpc1(-/-) muscles. Indeed, phosphorylation of both Akt and p70S6K proteins was decreased as well as the activation of PI3K, the main upstream regulator of the Akt. This effect was independent of insulin-like growth factor expression. Akt phosphorylation also was reduced in Trpc1(-/-) primary myoblasts and in control myoblasts differentiated in the absence of extracellular Ca(2+) or pretreated with EGTA-AM or wortmannin, suggesting that the entry of Ca(2+) through Trpc1 channels enhanced the activity of PI3K. Our results emphasize the involvement of Trpc1 channels in skeletal muscle development in vitro and in vivo, and identify a Ca(2+)-dependent activation of the PI3K/Akt/mTOR/p70S6K pathway during myoblast differentiation and muscle regeneration.

Hexafluorobenzene in comparison with perfluoro-15-crown-5-ether for repeated monitoring of oxygenation using 19F MRI in a mouse model.

Hexafluorobenzene (HFB) and perfluoro-15-crown-5-ether (15C5) were compared as fluorine reporter probes of tissue oxygenation using (19)F MRI for dynamic assessment of muscle oxygenation, with special focus on muscle tissue toxicity of the probes, and consecutive alteration of animal behavior. The latter were also compared in terms of sensitivity to changes in oxygenation as well as of signal-to-noise ratio for accurate pO(2) measurements. For that purpose, mouse muscles were imaged at 11.7 T, at 2- and 36-h after intramuscular injection of HFB or 15C5. Histological analysis of the muscle tissue revealed a lack of toxicity for 15C5 from 2 up to 36-h postinjection, whereas HFB induced tissue necrosis, blood clots and thrombosis as soon as 24-h postinjection. This muscle toxicity led to a limitation in mice mobility 24-h after injection of HFB as evidenced by behavioral testing (open-field, grip strength, and catwalk tests), which was not the case after 15C5 intramuscular injection. Finally, pO(2) measurements assessed 2-h postinjection showed consistent values with both probes, evidencing cross-validation of the (19)F MRI oximetry technique for acute measurements. However, the measurement at 36-h was hampered for HFB, which showed significant lower values of muscle pO(2), whereas 15C5 was able to reliably assess muscle pO(2) at 36-h postinjection.

Conditional deletion of KCC2 impairs synaptic plasticity and both spatial and nonspatial memory.

The postsynaptic inhibition through GABAA receptors (GABAAR) relies on two mechanisms, a shunting effect due to an increase in the postsynaptic membrane conductance and, in mature neurons, a hyperpolarization effect due to an entry of chloride into postsynaptic neurons. The second effect requires the action of the K+-Cl- cotransporter KCC2 which extrudes Cl- from the cell and maintains its cytosolic concentration very low. Neuronal chloride equilibrium seems to be dysregulated in several neurological and psychiatric conditions such as epilepsy, anxiety, schizophrenia, Down syndrome, or Alzheimer's disease. In the present study, we used the KCC2 Cre-lox knockdown system to investigate the role of KCC2 in synaptic plasticity and memory formation in adult mice. Tamoxifen-induced conditional deletion of KCC2 in glutamatergic neurons of the forebrain was performed at 3 months of age and resulted in spatial and nonspatial learning impairment. On brain slices, the stimulation of Schaffer collaterals by a theta burst induced long-term potentiation (LTP). The lack of KCC2 did not affect potentiation of field excitatory postsynaptic potentials (fEPSP) measured in the stratum radiatum (dendrites) but increased population spike (PS) amplitudes measured in the CA1 somatic layer, suggesting a reinforcement of the EPSP-PS potentiation, i.e., an increased ability of EPSPs to generate action potentials. At the cellular level, KCC2 deletion induced a positive shift in the reversal potential of GABAAR-driven Cl- currents (EGABA), suggesting an intracellular accumulation of chloride subsequent to the downregulation of KCC2. After treatment with bumetanide, an antagonist of the Na+-K+-Cl- cotransporter NKCC1, spatial memory impairment, chloride accumulation, and EPSP-PS potentiation were rescued in mice lacking KCC2. The presented results emphasize the importance of chloride equilibrium and GABA-inhibiting ability in synaptic plasticity and memory formation.

Multiparametric functional nuclear magnetic resonance imaging shows alterations associated with plasmid electrotransfer in mouse skeletal muscle.

BACKGROUND: In vivo gene electrotransfer is frequently used in preclinical gene therapy. Many studies have attempted to optimize protocols efficiency at the same time as reducing muscle damage. Most of them have reported histological evidence of muscle degeneration and completion of regeneration within 15 days. The functional consequences have rarely been addressed, which may reflect the lack of appropriate techniques. Yet, it is important to characterize the changes induced by the procedure itself because it may interfere with therapy. We used multiparametric functional (mpf)-nuclear magnetic resonance (NMR) imaging to evaluate mice hindlimb muscle after electrotransfer of an empty plasmid. METHODS: NMR experiments were performed in a 4T Bruker magnet. Arterial spin labeling imaging of perfusion and blood oxygenation level dependent contrast and (31) P spectroscopy of phosphocreatine kinetics and pH were simultaneously acquired from the mice hindlimb during 2 min of electrically stimulated exercise and recovery. RESULTS: After 15 days, hindlimb cross-sectional area decreased by 10% compared to control mice. Specific force-time integral and end-exercise pH were identical in both groups, whereas oxidative capacities increased. Perfusion values doubled, and oxygenation significantly decreased. Histology revealed: (i) degeneration/regeneration; (ii) a decrease in type IIb fibers and an increase in type I and IIa fibers; and (iii) increased capillary density. CONCLUSIONS: In this model, loss in muscle mass was accompanied by important alterations of perfusion and bioenergetics. Fifteen days after electrotransfer, this was correlated with fiber type shift, capillary bed remodeling and degeneration/regeneration. mpf-NMR provides new insights into the functional consequences of standard electrotransfer and represents a powerful tool for optimization and longitudinal assessment of preclinical gene therapy protocols.

Inhibitory synapse dysfunction and epileptic susceptibility associated with KIF2A deletion in cortical interneurons.

Malformation of cortical development (MCD) is a family of neurodevelopmental disorders, which usually manifest with intellectual disability and early-life epileptic seizures. Mutations in genes encoding microtubules (MT) and MT-associated proteins are one of the most frequent causes of MCD in humans. KIF2A is an atypical kinesin that depolymerizes MT in ATP-dependent manner and regulates MT dynamics. In humans, single de novo mutations in KIF2A are associated with MCD with epileptic seizures, posterior pachygyria, microcephaly, and partial agenesis of corpus callosum. In this study, we conditionally ablated KIF2A in forebrain inhibitory neurons and assessed its role in development and function of inhibitory cortical circuits. We report that adult mice with specific deletion of KIF2A in GABAergic interneurons display abnormal behavior and increased susceptibility to epilepsy. KIF2A is essential for tangential migration of cortical interneurons, their positioning in the cerebral cortex, and for formation of inhibitory synapses in vivo. Our results shed light on how KIF2A deregulation triggers functional alterations in neuronal circuitries and contributes to epilepsy.

Myosteatosis rather than sarcopenia associates with non-alcoholic steatohepatitis in non-alcoholic fatty liver disease preclinical models.

BACKGROUND: Non-alcoholic fatty liver (NAFL) disease (NAFLD) is the most common chronic liver disease in the world. While most subjects have 'inert' NAFL, a subset will progress to non-alcoholic steatohepatitis (NASH) and its life-threatening complications. A substantial body of literature supports that a low muscle mass, low strength, and/or muscle fatty infiltration (myosteatosis) are associated with NAFLD severity. Here, we evaluated the muscle compartment in NASH preclinical models to decipher the kinetics of muscle alterations in relation with liver disease progression. METHODS: We developed and validated a micro-computed tomography-based methodology to prospectively study skeletal muscle mass and density in muscle and liver (i.e. reflecting fatty infiltration) in a high-throughput and non-invasive manner in three preclinical NAFLD/NASH rodent models: fat aussie (FOZ) mice fed a high-fat diet (FOZ HF), wild-type (WT) mice fed a high-fat high-fructose diet (WT HFF), and WT mice fed a high-fat diet (WT HF). We compared them with WT mice fed a normal diet (WT ND) used as controls. RESULTS: -FOZ HF with fibrosing NASH had sarcopenia characterized by a reduced muscle strength when compared with WT HF and WT HFF with early NASH and WT ND controls (165.2 ± 5.2 g vs. 237.4 ± 11.7 g, 256 ± 5.7 g, and 242.9 ± 9.3 g, respectively, P 60; 0.001). Muscle mass or strength was not lower in FOZ HF, WT HF, and WT HFF with early NASH than in controls. Myosteatosis was present in FOZ HF with fibrosing NASH, but also in FOZ HF, WT HF, and WT HFF with early NASH (muscle density = 0.50 ± 0.02, 0.62 ± 0.02, 0.70 ± 0.05, and 0.75 ± 0.03, respectively, with P 60; 0.001 when compared with respective controls). Myosteatosis degree was strongly correlated with NAFLD activity score (r = -0.87, n = 67, P 60; 0.001). In multivariate analysis, the association between myosteatosis and NASH was independent from homeostatic model assessment of insulin resistance and visceral fat area (P 60; 0.05). Myosteatosis degree powerfully discriminated NASH from benign NAFL and normal liver (area under the receiver operating characteristic = 0.96, n = 67, P 60; 0.001). CONCLUSIONS: Taken together, our data support that there is no sarcopenia in obese mice with early NASH. In contrast, the severity of myosteatosis reflects on hepatocellular damage and inflammation during early NASH development. This observation prompts us to exploit myosteatosis as a novel non-invasive marker of NASH.

DIAPH3 deficiency links microtubules to mitotic errors, defective neurogenesis, and brain dysfunction.

Diaphanous (DIAPH) three (DIAPH3) is a member of the formin proteins that have the capacity to nucleate and elongate actin filaments and, therefore, to remodel the cytoskeleton. DIAPH3 is essential for cytokinesis as its dysfunction impairs the contractile ring and produces multinucleated cells. Here, we report that DIAPH3 localizes at the centrosome during mitosis and regulates the assembly and bipolarity of the mitotic spindle. DIAPH3-deficient cells display disorganized cytoskeleton and multipolar spindles. DIAPH3 deficiency disrupts the expression and/or stability of several proteins including the kinetochore-associated protein SPAG5. DIAPH3 and SPAG5 have similar expression patterns in the developing brain and overlapping subcellular localization during mitosis. Knockdown of SPAG5 phenocopies DIAPH3 deficiency, whereas its overexpression rescues the DIAHP3 knockdown phenotype. Conditional inactivation of Diaph3 in mouse cerebral cortex profoundly disrupts neurogenesis, depleting cortical progenitors and neurons, leading to cortical malformation and autistic-like behavior. Our data uncover the uncharacterized functions of DIAPH3 and provide evidence that this protein belongs to a molecular toolbox that links microtubule dynamics during mitosis to aneuploidy, cell death, fate determination defects, and cortical malformation.

Overexpression of wild-type human amyloid precursor protein alters GABAergic transmission.

The function of the amyloid precursor protein (APP) is not fully understood, but its cleavage product amyloid beta (Aß) together with neurofibrillary tangles constitute the hallmarks of Alzheimer's disease (AD). Yet, imbalance of excitatory and inhibitory neurotransmission accompanied by loss of synaptic functions, has been reported much earlier and independent of any detectable pathological markers. Recently, soluble APP fragments have been shown to bind to presynaptic GABAB receptors (GABABRs), subsequently decreasing the probability of neurotransmitter release. In this body of work, we were able to show that overexpression of wild-type human APP in mice (hAPPwt) causes early cognitive impairment, neuronal loss, and electrophysiological abnormalities in the absence of amyloid plaques and at very low levels of Aß. hAPPwt mice exhibited neuronal overexcitation that was evident in EEG and increased long-term potentiation (LTP). Overexpression of hAPPwt did not alter GABAergic/glutamatergic receptor components or GABA production ability. Nonetheless, we detected a decrease of GABA but not glutamate that could be linked to soluble APP fragments, acting on presynaptic GABABRs and subsequently reducing GABA release. By using a specific presynaptic GABABR antagonist, we were able to rescue hyperexcitation in hAPPwt animals. Our results provide evidence that APP plays a crucial role in regulating inhibitory neurotransmission.

In Vitro and In Vivo Characterization of MCT1 Inhibitor AZD3965 Confirms Preclinical Safety Compatible with Breast Cancer Treatment.

To survive and proliferate in solid tumors, cancer cells adapt and evolve rapidly in microenvironments where oxygen and substrate bioavailability fluctuates over time and space. This creates metabolic heterogeneity. Cancer cells can further cooperate metabolically, for example by swapping glycolytic end-product lactate for blood-borne glucose. This type of cooperation can be targeted therapeutically, since transmembrane lactate exchanges are facilitated by lactate-proton symporters of the monocarboxylate (MCT) family. Among new drugs, AZD3965 is a first-in-class selective MCT1 inhibitor currently tested in Phase I/II clinical trials for patients with different types of cancers. Because MCT1 can function bidirectionally, we tested here whether and how malignant and nonmalignant cells adapt their metabolism and MCT repertoire when AZD3965 inhibits either lactate import or export. Using breast-associated malignant and nonmalignant cell lines as models, we report that AZD3965 is not directly cytotoxic. In the presence of glucose and glutamine, oxidative cells can survive when lactate uptake is blocked, and proliferating cells compensate MCT1 inhibition by overexpressing MCT4, a specialized facilitator of lactate export. Phenotypic characterization of mice focusing on metabolism, muscle and brain physiology found partial and transient memory retention defect as sole consequence of MCT1 inhibition by AZD3965. We therefore conclude that AZD3965 is compatible with anticancer therapy.