Perilipin-2-null mice are protected against diet-induced obesity, adipose inflammation, and fatty liver disease.

The cytoplasmic lipid droplet (CLD) protein perilipin-2 (Plin2) is expressed in multiple nonadipose tissues, where it is thought to play a role in regulating their lipid storage properties. However, the extent to which Plin2 functions in nutrient utilization and metabolism, or how it influences the consequences of over-feeding, remains unclear. In this study, we demonstrate that the absence of Plin2 prevents high-fat diet(HFD)-induced obesity in male and female mice. This response is associated with increased formation of subcutaneous beige adipocyte cells with uncoupling protein 1 expression, and amelioration of inflammatory foci formation in white adipose tissue and steatosis in the liver. Experiments demonstrate that Plin2 loss results in reduced energy intake and increased physical activity in response to HFD feeding. Our study provides the first evidence that Plin2 contributes to HFD-induced obesity by modulating food intake, and that its absence prevents obesity-associated adipose tissue inflammatory foci and liver steatosis.

The mouse cochlea expresses a local hypothalamic-pituitary-adrenal equivalent signaling system and requires corticotropin-releasing factor receptor 1 to establish normal hair cell innervation and cochlear sensitivity.

Cells of the inner ear face constant metabolic and structural stress. Exposure to intense sound or certain drugs destroys cochlea hair cells, which in mammals do not regenerate. Thus, an endogenous stress response system may exist within the cochlea to protect it from everyday stressors. We recently described the existence of corticotropin-releasing factor (CRF) in the mouse cochlea. The CRF receptor type 1 (CRFR1) is considered the primary and canonical target of CRF signaling, and systemically it plays an essential role in coordinating the body-wide stress response via activation of the hypothalamic-pituitary-adrenal (HPA) axis. Here, we describe an essential role for CRFR1 in auditory system development and function, and offer the first description of a complete HPA equivalent signaling system resident within the cochlea. To reveal the role of CRFR1 activation in the cochlea, we have used mice carrying a null ablation of the CRFR1 gene. CRFR1(-/-) mice exhibited elevated auditory thresholds at all frequencies tested, indicating reduced sensitivity. Furthermore, our results suggest that CRFR1 has a developmental role affecting inner hair cell morphology and afferent and efferent synapse distribution. Given the role of HPA signaling in maintaining local homeostasis in other tissues, the presence of a cochlear HPA signaling system suggests important roles for CRFR1 activity in setting cochlear sensitivity, perhaps both neural and non-neural mechanisms. These data highlight the complex pleiotropic mechanisms modulated by CRFR1 signaling in the cochlea.

A corticotropin-releasing factor system expressed in the cochlea modulates hearing sensitivity and protects against noise-induced hearing loss.

Noise-induced hearing loss is a highly prevalent occupational injury, yet little is known concerning the signals controlling normal cochlear sensitivity and susceptibility to noise-induced trauma. While the corticotropin-releasing factor (CRF) system is involved in activation of the classic hypothalamic-pituitary-adrenal axis, it is also involved in local physiological responses to stress in many tissues, and is expressed in the inner ear. We demonstrate that mice lacking the CRF receptor CRFR2 exhibit a significantly lower auditory threshold than wild type mice, but this gain of function comes at the price of increased susceptibility to acoustic trauma. We further demonstrate that glutamatergic transmission, purinergic signaling, and activation of Akt (PKB) pathways within the cochlea are misregulated, which may underlie the enhanced sensitivity and trauma susceptibility observed in CRFR2(-/-) mice. Our data suggest that CRFR2 constitutively modulates hearing sensitivity under normal conditions, and thereby provides protection against noise-induced hearing loss.

Outpatient transition to extended-release injectable naltrexone for patients with opioid use disorder: A phase 3 randomized trial.

BACKGROUND: Injectable extended-release naltrexone (XR-NTX), approved to prevent relapse to opioid dependence, requires initial abstinence. This multisite outpatient clinical trial examined the efficacy and safety of low-dose oral naltrexone (NTX), combined with a brief buprenorphine (BUP) taper and standing ancillary medications, for detoxification and induction onto XR-NTX. METHODS: Patients (N = 378) were randomized, stratified by primary short-acting opioid-of-use, to one of three regimens: NTX + BUP; NTX + placebo BUP (PBO-B); placebo NTX (PBO-N) + PBO-B. Patients received 7 days of ascending NTX or placebo, concurrent with a 3-day BUP or placebo taper, and ancillary medications in an outpatient setting. Daily psychoeducational counseling was provided. On Day 8, patients passing a naloxone challenge received XR-NTX. RESULTS: Rates of transition to XR-NTX were comparable across groups: NTX/BUP (46.0%) vs. NTX/PBO-B (40.5%) vs. PBO-N/PBO-B (46.0%). Thus, the study did not meet its primary endpoint. Adverse events, reported by 32.5% of all patients, were mild to moderate in severity and consistent with opioid withdrawal. A first, second, and third XR-NTX injection was received by 44.4%, 29.9%, and 22.5% of patients, respectively. Compared with the PBO-N/PBO-B group, the NTX/BUP group demonstrated higher opioid abstinence during the transition and lower post-XR-NTX subjective opioid withdrawal scores. CONCLUSIONS: A 7-day detoxification protocol with NTX alone or NTX + BUP provided similar rates of induction to XR-NTX as placebo. For those inducted onto XR-NTX, management of opioid withdrawal symptoms prior to induction was achieved in a structured outpatient setting using a well-tolerated, fixed-dose ancillary medication regimen common to all three groups.

Mitogen-activated protein kinases and retinal ischemia.

PURPOSE: Mitogen-activated protein kinases (MAPKs), consisting of three major enzymes-extracellular signal-regulated kinase (ERK), p38, and c-jun N-terminal kinase (JNK)-couple cell-surface receptors to critical regulatory targets and gene transcription. We hypothesized that MAPKs are differentially expressed and have distinct functions after retinal ischemia. METHODS: Rats were subjected to retinal ischemia by elevation of intraocular pressure. Changes in MAPK expression were examined by Western blot of whole retinal homogenates and by immunohistochemistry of retinal cryosections. Phosphorylated (activated) ERK, p38, and JNK proteins were localized by fluorescent double labeling. The functional significance of activated MAPKs was assessed using pharmacological antagonists. Specific MAPK blockade was documented by kinase assay and immunohistochemistry for phosphorylated target proteins. The outcome after ischemia was examined with electroretinography (ERG), by measuring retinal cell layer thickness in paraffin-embedded sections, and by TUNEL staining on retinal cryosections. Data were analyzed using ANOVA and post hoc t-test, with P < 0.05 considered significant. RESULTS: Expression of phosphorylated JNK and p38 increased significantly after ischemia and followed a specific time course, beginning at 1 hour, and persisting up to 1 week later. JNK and p38 were expressed in the nuclei of ganglion and amacrine cells, the outer plexiform layer, the nerve fiber layer, and the axonal terminals of bipolar cells. Phosphorylated ERK was expressed in Müller cells, peaking at 1 to 6 hours after ischemia. Blocking activation of p38 or ERK significantly improved recovery of the ERG b-wave after ischemia, dramatically decreased thinning of the inner nuclear layers, and decreased the percentage of TUNEL-positive cells. CONCLUSIONS: The MAPKs each demonstrate a specific cellular distribution after ischemia, and ERK and p38 are linked to apoptosis. Blockade of p38 or ERK provides significant protection from ischemic damage, suggesting a novel therapeutic role for MAPK inhibition in neuroprotection.

The cochlea as an independent neuroendocrine organ: expression and possible roles of a local hypothalamic-pituitary-adrenal axis-equivalent signaling system.

A key property possessed by the mammalian cochlea is its ability to dynamically alter its own sensitivity. Because hair cells and ganglion cells are prone to damage following exposure to loud sound, extant mechanisms limiting cochlear damage include modulation involving both the mechanical (via outer hair cell motility) and neural signaling (via inner hair cell-ganglion cell synapses) steps of peripheral auditory processing. Feedback systems such as that embodied by the olivocochlear system can alter sensitivity, but respond only after stimulus encoding, allowing potentially damaging sounds to impact the inner ear before sensitivity is adjusted. Less well characterized are potential cellular signaling systems involved in protection against metabolic stress and resultant damage. Although pharmacological manipulation of the olivocochlear system may hold some promise for attenuating cochlear damage, targeting this system may still allow damage to occur that does not depend on a fully functional feedback loop for its mitigation. Thus, understanding endogenous cell signaling systems involved in cochlear protection may lead to new strategies and therapies for prevention of cochlear damage and consequent hearing loss. We have recently discovered a novel cochlear signaling system that is molecularly equivalent to the classic hypothalamic-pituitary-adrenal (HPA) axis. This cochlear HPA-equivalent system functions to balance auditory sensitivity and susceptibility to noise-induced hearing loss, and also protects against cellular metabolic insults resulting from exposures to ototoxic drugs. This system may represent a local cellular response system designed to mitigate damage arising from various types of insult.

The cochlear CRF signaling systems and their mechanisms of action in modulating cochlear sensitivity and protection against trauma.

A key requirement for encoding the auditory environment is the ability to dynamically alter cochlear sensitivity. However, merely attaining a steady state of maximal sensitivity is not a viable solution since the sensory cells and ganglion cells of the cochlea are prone to damage following exposure to loud sound. Most often, such damage is via initial metabolic insult that can lead to cellular death. Thus, establishing the highest sensitivity must be balanced with protection against cellular metabolic damage that can lead to loss of hair cells and ganglion cells, resulting in loss of frequency representation. While feedback mechanisms are known to exist in the cochlea that alter sensitivity, they respond only after stimulus encoding, allowing potentially damaging sounds to impact the inner ear at times coincident with increased sensitivity. Thus, questions remain concerning the endogenous signaling systems involved in dynamic modulation of cochlear sensitivity and protection against metabolic stress. Understanding endogenous signaling systems involved in cochlear protection may lead to new strategies and therapies for prevention of cochlear damage and consequent hearing loss. We have recently discovered a novel cochlear signaling system that is molecularly equivalent to the classic hypothalamic-pituitary-adrenal (HPA) axis. This cochlear HPA-equivalent system functions to balance auditory sensitivity and susceptibility to noise-induced hearing loss, and also protects against cellular metabolic insults resulting from exposures to ototoxic drugs. We review the anatomy, physiology, and cellular signaling of this system, and compare it to similar signaling in other organs/tissues of the body.