Slowing Hearing Loss in Diabetics and Hyperglycemics

Our Neuronal-Glial Markers are used in a variety of applications. Here our P0 or P-Zero antibody is used to show myelination levels in the cochlear ganglion. Demyelination is caused by hyperglycemia and type 2 diabetes and results in hearing loss and eventually deafness. Here's the related publication and highlights: Silvia Murillo-Cuesta, Guadalupe Camarero, Águeda González-Rodríguez, Lourdes Rodríguez-de la Rosa, Deborah J Burks, Carlos Avendaño,Ángela M Valverde and Isabel Varela-Nieto1. Insulin Receptor Substrate 2 (IRS2)-Deficient Mice Show Sensorineural Hearing Loss That Is Delayed by Concomitant Protein Tyrosine Phosphatase 1B (PTP1B) Loss of Function. Online address: http://www.molmed.org. doi: 10.2119/molmed.2011.00328
Highlights: The authors objective was to study the hearing function and cochlear morphology of Irs2-null mice and the impact of PTP1B deficiency. They have studied the auditory brainstem responses and the cochlear morphology of systemic Irs2–/–Ptpn1+/+, Irs2+/+Ptpn1–/– and Irs2–/–Ptpn1–/– mice at different postnatal ages. The results indicated that Irs2–/–Ptpn1+/+ mice present a profound congenital sensorineural deafness before the onset of diabetes and altered cochlear morphology with hypoinnervation of the cochlear ganglion and aberrant stria vascularis, compared with wild-type mice. Simultaneous PTP1B deficiency in Irs2–/–Ptpn1–/– mice delays the onset of deafness.

Images:  Cochlear ganglion and nerve fibers. (A–C) Cresyl violet staining of midmodiolar methacrylate sections of the cochlear ganglion at the cochlear basal turn in Irs2+/+Ptpn1+/+ (A), Irs2–/–Ptpn1+/+ (B) and Irs2–/–Ptpn1–/–mice (C) at postnatal wk 11. A slight reduction in the cellular density was more evident in both mutants (B, C) compared with wild-type (A). (D–F) Myelin P0 immunostaining of the cochlear ganglion shows less intense labeling in Irs2–/–Ptpn1+/+ (E) and Irs2–/–Ptpn1–/– (F) mice than in control mice (D). (G–I) Accordingly, myelin P0 immunostaining of nerve fibers projecting from the cochlear ganglion to the sensory cells is less intense in Irs2–/–Ptpn1+/+ and Irs2–/–Ptpn1–/– (arrows in H and I) than in wild-type mice (G). (J–L) Similarly, a weaker neurofilament 200-kDa immunostaining is observed in Irs2+/+Ptpn1–/– (K, white arrow) and Irs2–/–Ptpn1–/– (L, white arrow) mice compared with wild-type mice (J). Scale bars: A–I, 50 μm; J–L, 75 μm.

The results presented in this study demonstrate for the first time a unique tissue-specific role of IRS2 in cochlear development and hearing function; therefore, the Irs2–/– mouse could be a novel model for the in vivo study of hearing loss associated with altered glucose metabolism. The data also suggest that modulation of PTP1B activity could be a pharmacological target of interest for the sensory syndromes associated with diabetes.

Opioid Addiction During Pregnancy-Implications for Neuro-development

I would like to thank Dr. Carmen Sato-Bigbee, Virginia Commonwealth University School of Medicine, for kindly sharing this important study. The publication also references use of our Mu Opioid and Nociceptin/Orphanin FQ Receptor Antibodies: Andrew C. Eschenroeder, Allison A. Vestal-Laborde, Emilse S. Sanchez, Susan E. Robinson, Carmen Sato-Bigbee. Oligodendrocyte responses to buprenorphine uncover novel and opposing roles of μ-opioid- and nociceptin/orphanin FQ receptors in cell development: Implications for drug addiction treatment during pregnancy. Glia Volume 60, Issue 1, pages 125–136, January 2012.

Highlights: Oligodendrocytes are responsible for making myelin in the CNS. The authors have shown We have shown previously that rat brain myelination is significantly altered by buprenorphine, an opioid analogue currently used in clinical trials for managing pregnant opioid addicts. In this study, perinatal exposure to low levels of this drug induced accelerated and increased expression of myelin basic proteins (MBPs), cellular and myelin components that are markers of mature oligodendrocytes. In contrast, supra-therapeutic drug doses delayed MBP brain expression and resulted in a decreased number of myelinated axons. We have now found that this biphasic-dose response to buprenorphine can be attributed to the participation of both the l-opioid receptor (MOR) and the nociceptin/orphanin FQ receptor (NOP receptor) in the oligodendrocytes. This is the first study showing the potential role of the NOP receptor in myelination.

High levels of opiate exposure could negatively disrupt the normal interplay between these two systems altering the developmental pattern of brain myelination. Understanding this pathway, could help researchers find ways to favorably modulate myelination and protect neuro-development of fetuses exposed to high levels of opiates during pregnancy.

Related Data:

Direct treatment of immature oligodendrocytes with buprenorphine alters MBP expression in a dose-specific manner. Cells isolated from 9-day-old rat brains were incubated for 4 days in CDM with or without 0.25, 0.5, 1.0, and 3.0 lM buprenorphine. MBP levels were determined by western blotting using b-actin levels as loading controls. Figures correspond to representative experiments. Results in the bar graph are expressed as percentage of controls (0 lM buprenorphine) 6 SEM from five experiments and correspond to the combined scanning of the four major MBP isoforms. **P <0.005 and ***P<0.0001.

Pre-oligodendrocytes express both MOR and the NOP receptor. Cells isolated from 9-day-old rat brain were allowed to fully attachon the culture plates by overnight incubation and stained by double
immunocytochemistry with O4 (green) together with anti-MOR or anti-NOP receptor antibodies (red). Scale bar: 20 lm. The western blot shows MOR and NOP receptor expression in two different samples of developing oligodendrocytes directly isolated from 9-day-old rat brains.

I will be posting future studies investigating the molecular mechanisms by which buprenorphine and methadone affect myelination and neuron-glial interactions. These should provide deeper understanding into these developmental processes and new and better strategies for the managing of both pregnant addicts and drug addiction in adolescence.