Mice lacking Asic3 show reduced anxiety‐like behavior on the elevated plus maze and reduced aggression

Sensing external stimulation is crucial for central processing in the brain and subsequent behavioral expression. Although sensory alteration or deprivation may result in behavioral changes, most studies related to the control of behavior have focused on central mechanisms. Here we created a sensory deficit model of mice lacking acid‐sensing ion channel 3 (Asic3^?/?) to probe behavioral alterations. ASIC3 is predominately distributed in the peripheral nervous system. RT‐PCR and immunohistochemistry used to examine the expression of Asic3 in the mouse brain showed near‐background mRNA and protein levels of ASIC3 throughout the whole brain, except for the sensory mesencephalic trigeminal nucleus. Consistent with the expression results, Asic3 knockout had no effect on synaptic plasticity of the hippocampus and the behavioral tasks of motor function, learning and memory. In anxiety behavior tasks, Asic3^?/? mice spent more time in the open arms of an elevated plus maze than did their wild‐type littermates. Asic3^?/? mice also displayed less aggressiveness toward intruders but more stereotypic repetitive behaviors during resident–intruder testing than did wild‐type littermates. Therefore, loss of ASIC3 produced behavioral changes in anxiety and aggression in mice, which suggests that ASIC3‐dependent sensory activities might relate to the central process of emotion modulation.     

Behavioral flexibility in a mouse model for obsessive‐compulsive disorder: Impaired Pavlovian reversal learning in SAPAP3 mutants

Obsessive‐compulsive disorder (OCD) is characterized by obsessive thinking, compulsive behavior and anxiety, and is often accompanied by cognitive deficits. The neuropathology of OCD involves dysregulation of cortical‐striatal circuits. Similar to OCD patients, SAPAP3 knockout mice 3 (SAPAP3^?/?) exhibit compulsive behavior (grooming), anxiety and dysregulated cortical‐striatal function. However, it is unknown whether SAPAP3^?/? display cognitive deficits and how these different behavioral traits relate to one another. SAPAP3^?/? and wild‐type (WT) littermates were trained in a Pavlovian conditioning task pairing visual cues with the delivery of sucrose solution. After mice learned to discriminate between a reward‐predicting conditioned stimulus (CS+) and a non‐reward stimulus (CS?), contingencies were reversed (CS+ became CS? and vice versa). Additionally, we assessed grooming, anxiety and general activity. SAPAP3^?/? acquired Pavlovian approach behavior similarly to WT, albeit less vigorously and with a different strategy. However, unlike WT, SAPAP3^?/? were unable to adapt their behavior after contingency reversal, exemplified by a lack of re‐establishing CS+ approach behavior (sign tracking). Surprisingly, such behavioral inflexibility, decreased vigor, compulsive grooming and anxiety were unrelated. This study shows that SAPAP3^?/? are capable of Pavlovian learning, but lack flexibility to adapt associated conditioned approach behavior. Thus, SAPAP3^?/? not only display compulsive‐like behavior and anxiety, but also cognitive deficits, confirming and extending the validity of SAPAP3^?/? as a suitable model for the study of OCD. The observation that compulsive‐like behavior, anxiety and behavioral inflexibility were unrelated suggests a non‐causal relationship between these traits and may be of clinical relevance for the treatment of OCD.     

ASIC1A in neurons is critical for fear‐related behaviors

Acid‐sensing ion channels (ASICs) have been implicated in fear‐, addiction‐ and depression‐related behaviors in mice. While these effects have been attributed to ASIC1A in neurons, it has been reported that ASICs may also function in nonneuronal cells. To determine if ASIC1A in neurons is indeed required, we generated neuron‐specific knockout (KO) mice with floxed Asic1a alleles disrupted by Cre recombinase driven by the neuron‐specific synapsin I promoter (SynAsic1a KO mice). We confirmed that Cre expression occurred in neurons, but not all neurons, and not in nonneuronal cells including astrocytes. Consequent loss of ASIC1A in some but not all neurons was verified by western blotting, immunohistochemistry and electrophysiology. We found ASIC1A was disrupted in fear circuit neurons, and SynAsic1a KO mice exhibited prominent deficits in multiple fear‐related behaviors including Pavlovian fear conditioning to cue and context, predator odor‐evoked freezing and freezing responses to carbon dioxide inhalation. In contrast, in the nucleus accumbens ASIC1A expression was relatively normal in SynAsic1a KO mice, and consistent with this observation, cocaine conditioned place preference (CPP) was normal. Interestingly, depression‐related behavior in the forced swim test, which has been previously linked to ASIC1A in the amygdala, was also normal. Together, these data suggest neurons are an important site of ASIC1A action in fear‐related behaviors, whereas other behaviors likely depend on ASIC1A in other neurons or cell types not targeted in SynAsic1a KO mice. These findings highlight the need for further work to discern the roles of ASICs in specific cell types and brain sites.     

Impaired Reality Testing in Mice Lacking Phospholipase Cβ1: Observed by Persistent Representation-Mediated Taste Aversion

Hallucinations and delusions are the most prominent symptoms of schizophrenia and characterized by impaired reality testing. Representation-mediated taste aversion (RMTA) has been proposed as a potential behavioral assessment of reality testing and has been applied to a neurodevelopmental rat model of schizophrenia. However, the theory underlying this approach has not been generalized yet with any demonstration of impaired reality testing in other animal models of schizophrenia, such as genetically-modified mice. We devised a RMTA procedure for mice that combines a Pavlovian association protocol pairing odor conditioned stimulus (CS) with sugar reward unconditioned stimulus (US), and a conditioned taste aversion (CTA) method. In this RMTA paradigm, we compared performances of wild-type (PLCβ1^+/+) mice and phospholipase C β1 knock-out (PLCβ1^-/-) mice which are known as one of the genetic models for schizophrenia. With a minimal amount of initial odor-sugar associative training, both PLCβ1^+/+ and PLCβ1^-/- mice were able to form an aversion to the sugar reward when the odor CS predicting sugar was paired with nausea. With an extended initial training, however, only PLCβ1^-/- mice could form a RMTA. This persistent RMTA displayed by PLCβ1^-/- mice shows their inability to distinguish real sugar from the CS-evoked representation of sugar at a stage in associative learning where wild-type mice normally could differentiate the two. These results demonstrate an impaired reality testing first observed in a genetic mouse model of schizophrenia, and suggest that RMTA paradigm may, with general applicability, allow diverse biological approaches to impaired reality testing.     

Localization and behaviors in null mice suggest that ASIC1 and ASIC2 modulate responses to aversive stimuli

Acid‐sensing ion channels (ASICs) generate H⁺‐gated Na⁺ currents that contribute to neuronal function and animal behavior. Like ASIC1, ASIC2 subunits are expressed in the brain and multimerize with ASIC1 to influence acid‐evoked currents and facilitate ASIC1 localization to dendritic spines. To better understand how ASIC2 contributes to brain function, we localized the protein and tested the behavioral consequences of ASIC2 gene disruption. For comparison, we also localized ASIC1 and studied ASIC1^?/? mice. ASIC2 was prominently expressed in areas of high synaptic density, and with a few exceptions, ASIC1 and ASIC2 localization exhibited substantial overlap. Loss of ASIC1 or ASIC2 decreased freezing behavior in contextual and auditory cue fear conditioning assays, in response to predator odor and in response to CO₂ inhalation. In addition, loss of ASIC1 or ASIC2 increased activity in a forced swim assay. These data suggest that ASIC2, like ASIC1, plays a key role in determining the defensive response to aversive stimuli. They also raise the question of whether gene variations in both ASIC1 and ASIC2 might affect fear and panic in humans .     

Lifelong reduction in complex IV induces tissue‐specific metabolic effects but does not reduce lifespan or healthspan in mice

Loss of SURF1, a Complex IV assembly protein, was reported to increase lifespan in mice despite dramatically lower cytochrome oxidase (COX) activity. Consistent with this, our previous studies found advantageous changes in metabolism (reduced adiposity, increased insulin sensitivity, and mitochondrial biogenesis) in Surf1^?/? mice. The lack of deleterious phenotypes in Surf1^?/? mice is contrary to the hypothesis that mitochondrial dysfunction contributes to aging. We found only a modest (nonsignificant) extension of lifespan (7% median, 16% maximum) and no change in healthspan indices in Surf1^?/? vs. Surf1^+/+ mice despite substantial decreases in COX activity (22%–87% across tissues). Dietary restriction (DR) increased median lifespan in both Surf1^+/+ and Surf1^?/? mice (36% and 19%, respectively). We measured gene expression, metabolites, and targeted expression of key metabolic proteins in adipose tissue, liver, and brain in Surf1^+/+ and Surf1^?/? mice. Gene expression was differentially regulated in a tissue‐specific manner. Many proteins and metabolites are downregulated in Surf1^?/? adipose tissue and reversed by DR, while in brain, most metabolites that changed were elevated in Surf1^?/? mice. Finally, mitochondrial unfolded protein response (UPR^mt)‐associated proteins were not uniformly altered by age or genotype, suggesting the UPR^mt is not a key player in aging or in response to reduced COX activity. While the changes in gene expression and metabolism may represent compensatory responses to mitochondrial stress, the important outcome of this study is that lifespan and healthspan are not compromised in Surf1^?/? mice, suggesting that not all mitochondrial deficiencies are a critical determinant of lifespan.     

Nucleus accumbens neurons dynamically respond to appetitive and aversive associative learning

To survive, individuals must learn to associate cues in the environment with emotionally relevant outcomes. This association is partially mediated by the nucleus accumbens (NAc), a key brain region of the reward circuit that is mainly composed by GABAergic medium spiny neurons (MSNs), that express either dopamine receptor D1 or D2. Recent studies showed that both populations can drive reward and aversion, however, the activity of these neurons during appetitive and aversive Pavlovian conditioning remains to be determined. Here, we investigated the relevance of D1- and D2-neurons in associative learning, by measuring calcium transients with fiber photometry during appetitive and aversive Pavlovian tasks in mice. Sucrose was used as a positive valence unconditioned stimulus (US) and foot shock was used as a negative valence US. We show that during appetitive Pavlovian conditioning, D1- and D2-neurons exhibit a general increase in activity in response to the conditioned stimuli (CS). Interestingly, D1- and D2-neurons present distinct changes in activity after sucrose consumption that dynamically evolve throughout learning. During the aversive Pavlovian conditioning, D1- and D2-neurons present an increase in the activity in response to the CS and to the US (shock). Our data support a model in which D1- and D2-neurons are concurrently activated during appetitive and aversive conditioning.

     

Cell-Type-Specific Expression Pattern of Proton-Sensing Receptors and Channels in Pituitary Gland

In mammalian cells, extracellular protons act as orthosteric and allosteric ligands for multiple receptors and channels. The aim of this study is to identify proton sensors in the rat pituitary gland. qRT-PCR analysis indicated the expression of G-protein-coupled receptor 68 gene (Gpr68) and acid-sensing ion channel (ASIC) genes Asic1, Asic2, and Asic4 in anterior pituitary cells and Asic1 and Asic2 in immortalized GH3 pituitary cells. Asic1a and Asic2b were the dominant splice isoforms. Single anterior pituitary cell RNA sequencing and immunocytochemical analysis showed that nonexcitable folliculostellate cells express GPR68 gene and protein, whereas excitable secretory cells express ASIC genes and proteins. Asic1 was detected in all secretory cell types, Asic2 in gonadotrophs, thyrotrophs, and somatotrophs, and Asic4 in lactotrophs. Extracellular acidification activated two types of currents in a concentration-dependent manner: a fast-developing, desensitizing current with an estimated EC₅₀-value of pH 6.7 and a slow-developing, non-desensitizing current that required a higher proton concentration for activation. The desensitizing current was abolished by removal of bath sodium and application of amiloride, a blocker of ASIC channels, whereas the non-desensitizing current was amiloride insensitive and voltage dependent. Activation of both currents increased the excitability of secretory pituitary cells, consistent with their potential physiological relevance in control of voltage-gated calcium influx and calcium-dependent cellular functions.     

Exposure to cold: aversive Pavlovian conditioning in individual Drosophila melanogaster

Abstract. Temperature changes can be especially threatening for ectotherms, such as Drosophila melanogaster (Diptera: Drosophilidea Meigen, 1830 ), and in this study we tested whether flies can associate olfactory stimuli with a sudden drop in temperature. Such Pavlovian conditioning would allow them to make appropriate behavioural and/or physiological responses in the future. We found that exposing individual flies to one of two odours in the presence of a sudden drop in temperature resulted in Pavlovian conditioning with flies subsequently avoiding the odour paired with cold. The characteristics of Pavlovian conditioning in flies were comparable to those observed for mammalian species. Specifically, the strength of conditioning increased with increasing intensity of the cold and decreased as the time interval between the olfactory stimulus (CS) and cold (US) was lengthened. Finally, the order in which CS and US were presented affected the strength of conditioning. Learning was observed when the CS preceded US and when the US immediately preceded the CS, but not when the CS preceded the US by 30 s or more. These results provide further evidence for learning in individual flies, and confirm that Pavlovian conditioning is a general mechanism used by organisms to obtain information about their environment.     

Dual Benefit of Reduced Cx43 on Atherosclerosis in LDL Receptor-Deficient Mice

Paracrine cell-to-cell interactions are crucial events during atherogenesis, however, little is known on the role of gap junctional communication during this process. We recently demonstrated increased expression of Cx43 in intimal smooth muscle cells and in a subset of endothelial cells covering the shoulder of atherosclerotic plaques. The purpose of this study was to examine the role of Cx43 in the development of atherosclerosis in vivo. Atherosclerosis-susceptible LDL receptor-deficient (LDLR^?/?) mice were intercrossed with mice heterozygous for Cx43 (Cx43^+/?mice). Male mice with normal (Cx43^+/+LDLR^?/?) or reduced (Cx43^+/?LDLR^?/?) Cx43 level of 10 weeks old were fed a cholesterol-rich diet (1.25%) for 14 weeks. Both groups of mice showed similar increases in serum lipids and body weight. Interestingly, the progression of atherosclerosis was reduced by 50% (P < 0.01) in the thoraco-abdominal aorta and in the aortic roots of Cx43^+/?LDLR^?/?mice compared with Cx43^+/+LDLR^?/?littermate controls. In addition, atheroma in Cx43^+/?LDLR^?/?mice contained fewer inflammatory cells and exhibited thicker fibrous caps with more collagen and smooth muscle cells, important features associated, in human, with stable atherosclerotic lesions. Thus, reducing Cx43 expression in mice provides beneficial effects on both the progression and composition of the atherosclerotic lesions.     

A role for LFA‐1 in delaying T‐lymphocyte egress from lymph nodes

Lymphocytes use the integrin leukocyte function‐associated antigen‐1 (LFA‐1) to cross the vasculature into lymph nodes (LNs), but it has been uncertain whether their migration within LN is also LFA‐1 dependent. We show that LFA‐1 mediates prolonged LN residence as LFA‐1^?/? CD4 T cells have significantly decreased dwell times compared with LFA‐1^+/+ T cells, a distinction lost in hosts lacking the major LFA‐1 ligand ICAM‐1. Intra‐vital two‐photon microscopy revealed that LFA‐1^+/+ and LFA‐1^?/? T cells reacted differently when probing the ICAM‐1‐expressing lymphatic network. While LFA‐1^+/+ T cells returned to the LN parenchyma with greater frequency, LFA‐1^?/? T cells egressed promptly. This difference in exit behaviour was a feature of egress through all assessed lymphatic exit sites. We show that use of LFA‐1 as an adhesion receptor amplifies the number of T cells returning to the LN parenchyma that can lead to increased effectiveness of T‐cell response to antigen. Thus, we identify a novel function for LFA‐1 in guiding T cells at the critical point of LN egress when they either exit or return into the LN for further interactions.     

Caveolin-1 regulates the anti-atherogenic properties of macrophages

Atherosclerosis is a complex disease initiated by the vascular accumulation of lipoproteins in the sub-endothelial space, followed by the infiltration of monocytes into the arterial intima. Caveolin-1 (Cav-1) plays an essential role in the regulation of cellular cholesterol metabolism and of various signaling pathways. In order to study specifically the role of macrophage Cav-1 in atherosclerosis, we used Cav-1 ^?/? Apoe ^?/? mice and transplanted them with bone marrow (BM) cells obtained from Cav-1 ^+/+ Apoe ^?/? or Cav-1 ^?/? Apoe ^?/? mice and vice versa. We found that Cav-1 ^+/+ mice harboring Cav-1 ^?/? BM-derived macrophages developed significantly larger lesions than Cav-1 ^+/+ mice harboring Cav-1 ^+/+ BM-derived macrophages. Cav-1 ^?/? macrophages were more susceptible to apoptosis and more prone to induce inflammation. The present study provides clear evidence that the absence of Cav-1 in macrophage is pro-atherogenic, whereas its absence in endothelial cells protects against atherosclerotic lesion formation. These findings demonstrate the cell-specific role of Cav-1 during the development of this disease.     

ADAMTS5 deficiency in mice does not affect cardiac function

The aggrecanase ADAMTS5 (A Disintegrin and Metalloproteinase with ThromboSpondin type 1 motifs, member 5) and the cleavage of its substrate versican have been implicated in the development of heart valves. Furthermore, ADAMTS5 deficiency was shown to protect against diet‐induced obesity, a known risk factor for cardiovascular disease. Therefore, in this study, we investigated the potential role of ADAMTS5 in cardiac function using ADAMTS5‐deficient (Adamts5^?/?) mice and their wild‐type (Adamts5^+/+) counterparts exposed to a standard‐fat or a high‐fat diet (HFD). Eight‐weeks‐old Adamts5^?/? and Adamts5^+/+ mice were exposed to each diet for 15 weeks. Cardiac function and electrophysiology were analyzed by transthoracic echocardiogram and electrocardiogram at the end of the study. Cleavage of versican, as detected by the appearance of the DPEEAE neo‐epitope on western blotting with protein extracts, was defective in the heart of HFD‐treated Adamts5^?/? as compared with Adamts5^+/+ mice. ADAMTS5 deficiency led to statistically significant increases in diastolic posterior wall thickness (0.94 ± 0.023 vs. 0.82 ± 0.036 mm; P = 0.0056) and left ventricle volume (47 ± 4.5 vs. 31 ± 2.5 μL; P = 0.0043) in comparison to Adamts5^+/+ mice, but only in animals on a HFD. Cardiac function parameters such as ejection fraction, fractional shortening, and stroke volume were unaffected by ADAMTS5 deficiency or diet. Electrocardiogram analysis revealed no ADAMTS5‐specific changes in either diet group. Thus, in the absence of ADAMTS5, cleavage of versican in the cardiac extracellular matrix is impaired, but cardiac function, even upon exposure to a HFD, is not markedly affected.     

Structural abnormalities in the primary somatosensory cortex and a normal behavioral profile in Contactin-5 deficient mice

Contactin-5 (Cntn5) is an immunoglobulin cell adhesion molecule that is exclusively expressed in the central nervous system. In view of its association with neurodevelopmental disorders, particularly autism spectrum disorder (ASD), this study focused on Cntn5-positive areas in the forebrain and aimed to explore the morphological and behavioral phenotypes of the Cntn5 null mutant (Cntn5^?/?) mouse in relation to these areas and ASD symptomatology. A newly generated antibody enabled us to elaborately describe the spatial expression pattern of Cntn5 in P7 wild type (Cntn5^+/+) mice. The Cntn5 expression pattern included strong expression in the cerebral cortex, hippocampus and mammillary bodies in addition to described previously brain nuclei of the auditory pathway and the dorsal thalamus. Thinning of the primary somatosensory (S1) cortex was found in Cntn5^?/? mice and ascribed to a misplacement of Cntn5-ablated cells. This phenotype was accompanied by a reduction in the barrel/septa ratio of the S1 barrel field. The structure and morphology of the hippocampus was intact in Cntn5^?/? mice. A set of behavioral experiments including social, exploratory and repetitive behaviors showed that these were unaffected in Cntn5^?/? mice. Taken together, these data demonstrate a selective role of Cntn5 in development of the cerebral cortex without overt behavioral phenotypes.     

Different forms of glycine- and GABAA-receptor mediated inhibitory synaptic transmission in mouse superficial and deep dorsal horn neurons

Background

Inflammation-mediated hyperalgesia involves tissue acidosis and sensitization of nociceptors. Many studies have reported increased expression of acid-sensing ion channel 3 (ASIC3) in inflammation and enhanced ASIC3 channel activity with pro-inflammatory mediators. However, the role of ASIC3 in inflammation remains inconclusive because of conflicting results generated from studies of ASIC3 knockout (ASIC3 ^-/-) or dominant-negative mutant mice, which have shown normal, decreased or increased hyperalgesia during inflammation.

Results

Here, we tested whether ASIC3 plays an important role in inflammation of subcutaneous tissue of paw and muscle in ASIC3 ^-/- mice induced by complete Freund's adjuvant (CFA) or carrageenan by investigating behavioral and pathological responses, as well as the expression profile of ion channels. Compared with the ASIC3 ^+/+ controls, ASIC3 ^-/- mice showed normal thermal and mechanical hyperalgesia with acute (4-h) intraplantar CFA- or carrageenan-induced inflammation, but the hyperalgesic effects in the sub-acute phase (1–2 days) were milder in all paradigms except for thermal hyperalgesia with CFA-induced inflammation. Interestingly, carrageenan-induced primary hyperalgesia was accompanied by an ASIC3-dependent Nav1.9 up-regulation and increase of tetrodotoxin (TTX)-resistant sodium currents. CFA-inflamed muscle did not evoke hyperalgesia in ASIC3 ^-/- or ASIC3 ^+/+ mice, whereas carrageenan-induced inflammation in muscle abolished mechanical hyperalgesia in ASIC3 ^-/- mice, as previously described. However, ASIC3 ^-/- mice showed attenuated pathological features such as less CFA-induced granulomas and milder carrageenan-evoked vasculitis as compared with ASIC3 ^+/+ mice.

Conclusion

We provide a novel finding that ASIC3 participates in the maintenance of sub-acute-phase primary hyperalgesia in subcutaneous inflammation and mediates the process of granuloma formation and vasculitis in intramuscular inflammation.     

BMP2 rescues deficient cell migration in Tgfbr3−/− epicardial cells and requires Src kinase

During embryogenesis, the epicardium undergoes proliferation, migration, and differentiation into several cardiac cell types which contribute to the coronary vessels. The type III transforming growth factor-β receptor (TGFβR3) is required for epicardial cell invasion and development of coronary vasculature in vivo. Bone Morphogenic Protein-2 (BMP2) is a driver of epicardial cell migration. Utilizing a primary epicardial cell line derived from Tgfbr3^+/+ and Tgfbr3^?/? mouse embryos, we show that Tgfbr3^?/? epicardial cells are deficient in BMP2 mRNA expression. Tgfbr3^?/? epicardial cells are deficient in 2-dimensional migration relative to Tgfbr3^+/+ cells; BMP2 induces cellular migration to Tgfbr3^+/+ levels without affecting proliferation. We further demonstrate that Src kinase activity is required for BMP2 driven Tgfbr3^?/? migration. BMP2 also requires Src for filamentous actin polymerization in Tgfbr3^?/? epicardial cells. Taken together, our data identifies a novel pathway in epicardial cell migration required for development of the coronary vessels.     

Conditioning of stress in Nile tilapia

A Pavlovian conditioning paradigm was used to induce a connection between a conditioned stimulus, light (CS), associated with an unconditioned stimulus, confinement (US) in Nile tilapia Oreochromis niloticus , which resulted in a conditioned endocrine response (CR) to the CS alone manifested as an increase in plasma cortisol. Individual isolated Nile tilapia were submitted for 10 days to the conditioning treatment consisting of turning on a light (CS) for 1 min with subsequent 30 min confinement (US). On the 10th day of the experiment, plasma cortisol was not increased when fish were subjected to no handling at all, or only light, or even a daily stressor for the 9 days. On the other hand, at the 10th day cortisol was significantly increased only when light was presented either with or without pairing with the stressor. These results confirmed that the cue, light (CS), was not stressful in itself, but when given as the CS in the absence of the US post conditioning the hypothalamus–pituitary–interrenal axis was activated. Therefore, it was concluded that memory of a previous experience with a stressor can be recalled by a conditioned stimulus and induce stress, which is the first demonstration of a memory‐induced stress in fishes.     

“Ciliophagy”

Chronic obstructive pulmonary disease (COPD) involves aberrant airway inflammatory responses to cigarette smoke (CS) associated with respiratory epithelial cell cilia shortening and impaired mucociliary clearance (MCC). The underlying cellular and molecular mechanisms for CS-associated cilia shortening have remained incompletely understood. We have previously demonstrated increased autophagy in the lungs of COPD patients; however, whether or not this process is selective for specific autophagic targets in the lung was not elucidated. Based on observations that increased morphological and biochemical indicators of autophagy correlate with cilia shortening in our models, we posited that autophagy might regulate cilia length in response to CS in the lung. We demonstrate that CS-induced cilia shortening occurs through an autophagy-dependent mechanism mediated by the deacetylase HDAC6 (histone deacetylase 6). Autophagy-impaired (Becn1^+/?, map1lc3b^?/?, or Hdac6^-/Y) mice resist CS-induced cilia shortening. Furthermore, cilia components are identified as autophagic substrates during CS exposure. Assessment of airway cilia function using a 3D MCC assay demonstrates that Becn1^+/?, map1lc3b^?/?, and Hdac6^-/Y mice or mice injected with the HDAC6 inhibitor tubastatin A are protected from CS-associated mucociliary dysfunction. We concluded that an autophagy-dependent pathway regulates cilia length during CS exposure, which identifies new pathways and targets in COPD.     

Acid-sensing ion channel-1 contributes to axonal degeneration in autoimmune inflammation of the central nervous system

Multiple sclerosis is a neuroinflammatory disease associated with axonal degeneration. The neuronally expressed, proton-gated acid-sensing ion channel-1 (ASIC1) is permeable to Na+ and Ca2+, and excessive accumulation of these ions is associated with axonal degeneration. We tested the hypothesis that ASIC1 contributes to axonal degeneration in inflammatory lesions of the central nervous system (CNS). After induction of experimental autoimmune encephalomyelitis (EAE), Asic1-/- mice showed both a markedly reduced clinical deficit and reduced axonal degeneration compared to wild-type mice. Consistently with acidosis-mediated injury, pH measurements in the spinal cord of EAE mice showed tissue acidosis sufficient to open ASIC1. The acidosis-related protective effect of Asic1 disruption was also observed in nerve explants in vitro. Amiloride, a licensed and clinically safe blocker of ASICs, was equally neuroprotective in nerve explants and in EAE. Although ASICs are also expressed by immune cells, this expression is unlikely to explain the neuroprotective effect of Asic1 inactivation, as CNS inflammation was similar in wild-type and Asic1-/- mice. In addition, adoptive transfer of T cells from wild-type mice did not affect the protection mediated by Asic1 disruption. These results suggest that ASIC1 blockers could provide neuroprotection in multiple sclerosis.