Apolipoprotein A-IV Inhibits AgRP/NPY Neurons and Activates Pro-Opiomelanocortin Neurons in the Arcuate Nucleus.

BACKGROUND/AIMS: Apolipoprotein A-IV (apoA-IV) in the brain potently suppresses food intake. However, the mechanisms underlying its anorexigenic effects remain to be identified. METHODS: We first examined the effects of apoA-IV on cellular activities in hypothalamic neurons that co-express agouti-related peptide (AgRP) and neuropeptide Y (NPY) and in neurons that express pro-opiomelanocortin (POMC). We then compared anorexigenic effects of apoA-IV in wild-type mice and in mutant mice lacking melanocortin 4 receptors (MC4Rs; the receptors of AgRP and the POMC gene product). Finally, we examined expression of apoA-IV in mouse hypothalamus and quantified its protein levels at fed versus fasted states. RESULTS: We demonstrate that apoA-IV inhibited the firing rate of AgRP/NPY neurons. The decreased firing was associated with hyperpolarized membrane potential and decreased miniature excitatory postsynaptic current. We further used c-fos immunoreactivity to show that intracerebroventricular (i.c.v.) injections of apoA-IV abolished the fasting-induced activation of AgRP/NPY neurons in mice. Further, we found that apoA-IV depolarized POMC neurons and increased their firing rate. In addition, genetic deletion of MC4Rs blocked anorexigenic effects of i.c.v. apoA-IV. Finally, we detected endogenous apoA-IV in multiple neural populations in the mouse hypothalamus, including AgRP/NPY neurons, and food deprivation suppressed hypothalamic apoA-IV protein levels. CONCLUSION: Our findings support a model where central apoA-IV inhibits AgRP/NPY neurons and activates POMC neurons to activate MC4Rs, which in turn suppresses food intake.

Spinal IFN-γ-induced protein-10 (CXCL10) mediates metastatic breast cancer-induced bone pain by activation of microglia in rat models.

Cancer-induced bone pain (CIBP) is a common clinical problem in breast cancer patients with bone metastasis. Recent studies shows chemokines are novel targets for treatment of CIBP. In this study, we intra-tibial inoculated with Walker 256 rat mammary gland carcinoma cells into rat bone to established metastatic breast cancer. Then we measured the expression of CXCL10 in the spinal cord of metastatic bone cancer rats, investigated the role of CXCL10 in the development of CIBP, and the underlying mechanism. Results revealed that after intra-tibial inoculation with Walker 256 cells, rats showed up-regulation of CXCL10 and its receptor CXCR3 in the spinal cord. Interestingly, intrathecally injection of recombinant CXCL10 protein induced mechanical allodynia in naïve rats. Blocking the function of CXCL10/CXCR3 pathway via anti-CXCL10 antibody or CXCR3 antagonist prevented the development of CIBP and microglial activation. Moreover, CXCL10-induced mechanical allodynia was rescued by minocycline treatment during the late-stage of CIBP, days 10-14. The regulation of CXCL10 expression involved microglial activation in a manner of autocrine positive feedback. These results suggest that CXCL10 may be a necessary algogenic molecule, especially in the development of CIBP. Its function was partly mediated via spinal microglial activation. This study provides a novel insight into the biological function of chemokine CXCL10 in the molecular mechanism underlying cancer pain. It also provides new target for clinical treatment of metastatic breast cancer-induced bone pain in future.

Visualizing estrogen receptor-α-expressing neurons using a new ERα-ZsGreen reporter mouse line.

BACKGROUND: A variety of biological functions of estrogens, including regulation of energy metabolism, are mediated by neurons expressing estrogen receptor-α (ERα) in the brain. However, complex intracellular processes in these ERα-expressing neurons are difficult to unravel, due to the lack of strategy to visualize ERα-expressing neurons, especially in unfixed brain tissues. RESULTS AND CONCLUSIONS: Here we generated a novel ERα-ZsGreen reporter mouse line in which expression of a green fluorescent reporter protein, ZsGreen, is driven by a 241kb ERα gene promoter. We validated that ZsGreen is highly colocalized with endogenous ERα in the brain. Native ZsGreen signals were visualized in unfixed brain tissue, and were used to assist single cell collection and electrophysiological recordings. Finally, we demonstrated that this ERα-ZsGreen mouse allele can be used in combination with other genetic reporter alleles to allow experiments in highly selective neural populations.

PI3K in the ventromedial hypothalamic nucleus mediates estrogenic actions on energy expenditure in female mice.

Estrogens act in the ventromedial hypothalamic nucleus (VMH) to regulate body weight homeostasis. However, the molecular mechanisms underlying these estrogenic effects are unknown. We show that activation of estrogen receptor-α (ERα) stimulates neural firing of VMH neurons expressing ERα, and these effects are blocked with intracellular application of a pharmacological inhibitor of the phosphatidyl inositol 3-kinase (PI3K). Further, we demonstrated that mice with genetic inhibition of PI3K activity in VMH neurons showed a sexual dimorphic obese phenotype, with only female mutants being affected. In addition, inhibition of VMH PI3K activity blocked effects of 17ß-estradiol to stimulate energy expenditure, but did not affect estrogen-induced anorexia. Collectively, our results indicate that PI3K activity in VMH neurons plays a physiologically relevant role in mediating estrogenic actions on energy expenditure in females.

SRC-1 Regulates Blood Pressure and Aortic Stiffness in Female Mice.

Framingham Heart Study suggests that dysfunction of steroid receptor coactivator-1 may be involved in the development of hypertension. However, there is no functional evidence linking steroid receptor coactivator-1 to the regulation of blood pressure. We used immunohistochemistry to map the expression of steroid receptor coactivator-1 protein in mouse brain, especially in regions implicated in the regulation of blood pressure. Steroid receptor coactivator-1 protein was found in central amygdala, medial amygdala, supraoptic nucleus, arcuate nucleus, ventromedial, dorsomedial, paraventricular hypothalamus, and nucleus of the solitary tract. To determine the effects of steroid receptor coactivator-1 protein on cardiovascular system we measured blood pressures, blood flow velocities, echocardiographic parameters, and aortic input impedance in female steroid receptor coactivator-1 knockout mice and their wild type littermates. Steroid receptor coactivator-1 knockout mice had higher blood pressures and increased aortic stiffness when compared to female wild type littermates. Additionally, the hearts of steroid receptor coactivator-1 knockout mice seem to consume higher energy as evidenced by increased impedance and higher heart rate pressure product when compared to female wild type littermates. Our results demonstrate that steroid receptor coactivator-1 may be functionally involved in the regulation of blood pressure and aortic stiffness through the regulation of sympathetic activation in various neuronal populations.

Estrogen Receptor-α in the Medial Amygdala Prevents Stress-Induced Elevations in Blood Pressure in Females.

Psychological stress contributes to the development of hypertension in humans. The ovarian hormone, estrogen, has been shown to prevent stress-induced pressor responses in females by unknown mechanisms. Here, we showed that the antihypertensive effects of estrogen during stress were blunted in female mice lacking estrogen receptor-α in the brain medial amygdala. Deletion of estrogen receptor-α in medial amygdala neurons also resulted in increased excitability of these neurons, associated with elevated ionotropic glutamate receptor expression. We further demonstrated that selective activation of medial amygdala neurons mimicked effects of stress to increase blood pressure in mice. Together, our results support a model where estrogen acts on estrogen receptor-α expressed by medial amygdala neurons to prevent stress-induced activation of these neurons, and therefore prevents pressor responses to stress.

Meta-chlorophenylpiperazine enhances leptin sensitivity in diet-induced obese mice.

BACKGROUND AND PURPOSE: Most forms of human obesity are characterized by impaired leptin sensitivity and, therefore, the effectiveness of anti-obesity leptin therapy in these leptin-resistant obese patients is marginal. Hence, the development of strategies to increase leptin sensitivity is of high priority in the field of obesity research. EXPERIMENTAL APPROACH: We first examined the effects of co-administration of leptin and meta-chlorophenylpiperazine (mCPP), an agonist of 5-HT2C and 5-HT1B receptors, on energy balance in leptin-resistant diet-induced obese (DIO) mice. We further assessed leptin-induced phosphorylation of the STAT-3 (pSTAT3) in various brain regions of DIO mice pretreated with mCPP or in mice genetically lacking 5-HT2C receptors. RESULTS: Co-administration of mCPP with leptin had an additive effect on reducing body weight in DIO mice. Furthermore, mCPP pretreatment in DIO mice enhanced leptin-induced pSTAT3 in the arcuate nucleus, the ventromedial hypothalamic nucleus, and the ventral premammillary nucleus. Finally, deletion of 5-HT2C receptors significantly blunted leptin-induced pSTAT3 in these same hypothalamic regions. CONCLUSIONS AND IMPLICATIONS: Our study provides evidence that drugs, which activate 5-HT2C receptors, could function as leptin sensitizers and be used in combination with leptin to provide additional weight loss in DIO.

The ERα-PI3K Cascade in Proopiomelanocortin Progenitor Neurons Regulates Feeding and Glucose Balance in Female Mice.

Estrogens act upon estrogen receptor (ER)α to inhibit feeding and improve glucose homeostasis in female animals. However, the intracellular signals that mediate these estrogenic actions remain unknown. Here, we report that anorexigenic effects of estrogens are blunted in female mice that lack ERα specifically in proopiomelanocortin (POMC) progenitor neurons. These mutant mice also develop insulin resistance and are insensitive to the glucose-regulatory effects of estrogens. Moreover, we showed that propyl pyrazole triol (an ERα agonist) stimulates the phosphatidyl inositol 3-kinase (PI3K) pathway specifically in POMC progenitor neurons, and that blockade of PI3K attenuates propyl pyrazole triol-induced activation of POMC neurons. Finally, we show that effects of estrogens to inhibit food intake and to improve insulin sensitivity are significantly attenuated in female mice with PI3K genetically inhibited in POMC progenitor neurons. Together, our results indicate that an ERα-PI3K cascade in POMC progenitor neurons mediates estrogenic actions to suppress food intake and improve insulin sensitivity.

Estrogen receptor-α in medial amygdala neurons regulates body weight.

Estrogen receptor-α (ERα) activity in the brain prevents obesity in both males and females. However, the ERα-expressing neural populations that regulate body weight remain to be fully elucidated. Here we showed that single-minded-1 (SIM1) neurons in the medial amygdala (MeA) express abundant levels of ERα. Specific deletion of the gene encoding ERα (Esr1) from SIM1 neurons, which are mostly within the MeA, caused hypoactivity and obesity in both male and female mice fed with regular chow, increased susceptibility to diet-induced obesity (DIO) in males but not in females, and blunted the body weight-lowering effects of a glucagon-like peptide-1-estrogen (GLP-1-estrogen) conjugate. Furthermore, selective adeno-associated virus-mediated deletion of Esr1 in the MeA of adult male mice produced a rapid body weight gain that was associated with remarkable reductions in physical activity but did not alter food intake. Conversely, overexpression of ERα in the MeA markedly reduced the severity of DIO in male mice. Finally, an ERα agonist depolarized MeA SIM1 neurons and increased their firing rate, and designer receptors exclusively activated by designer drug-mediated (DREADD-mediated) activation of these neurons increased physical activity in mice. Collectively, our results support a model where ERα signals activate MeA neurons to stimulate physical activity, which in turn prevents body weight gain.

Applications for radio-frequency identification technology in the perioperative setting.

We implemented a two-year project to develop a security-gated management system for the perioperative setting using radio-frequency identification (RFID) technology to enhance the management efficiency of the OR. We installed RFID readers beside the entrances to the OR and changing areas to receive and process signals from the RFID tags that we sewed into surgical scrub attire and shoes. The system also required integrating automatic access control panels, computerized lockers, light-emitting diode (LED) information screens, wireless networks, and an information system. By doing this, we are able to control the flow of personnel and materials more effectively, reduce OR costs, optimize the registration and attire-changing process for personnel, and improve management efficiency. We also anticipate this system will improve patient safety by reducing the risk of surgical site infection. Application of security-gated management systems is an important and effective way to help ensure a clean, convenient, and safe management process to manage costs in the perioperative area and promote patient safety.

Protocadherin20 promotes excitatory synaptogenesis in dorsal horn and contributes to bone cancer pain.

The majority of patients with metastatic bone disease experience moderate to severe pain. Bone cancer pain is usually progressive as the disease advances, and is very difficult to treat due to the poor understanding of the underlying mechanisms. Recent studies demonstrated that synaptic plasticity induces spinal cord sensitization and contributes to bone cancer pain. However, whether the synaptic plasticity is due to modifications of existing synapses or the formation of new synaptic connections is still unknown. Here we showed that a carcinoma implantation into a rats' tibia induced a significant increase in the number of excitability synapses in the dorsal horn, which contributes to the development of bone cancer pain. Previous studies identified that non-clustered protocadherins play significant roles in neuronal development and other implications in neurological disorders. In the present study, we showed that Protocadherin20 was significantly increased in the dorsal horn of cancer-bearing rats, while knockdown of Protocadherin20 with RNAi lentivirus reversed bone cancer-induced pain behaviors and decreased excitatory synaptogenesis in ipsilateral dorsal horn. In an in vitro study, we showed that knockdown of Protocadherin20 inhibited neurite outgrowth and excitatory synapse formation of dorsal neurons. These findings indicate that Protocadherin20 is required for the development of bone cancer pain probably by promoting the excitability synaptogenesis.