Biomedical subjects

Renato Rozental

Publications and source records attributed to Renato Rozental.

4 recordsLinked to original sources

PubMed2005

Blockade of gap junctions in vivo provides neuroprotection after perinatal global ischemia.

BACKGROUND AND PURPOSE: We investigated the contribution of gap junctions to brain damage and delayed neuronal death produced by oxygen-glucose deprivation (OGD). METHODS: Histopathology, molecular biology, and electrophysiological and fluorescence cell death assays in slice cultures after OGD and in developing rats after intrauterine hypoxia-ischemia (HI). RESULTS: OGD persistently increased gap junction coupling and strongly activated the apoptosis marker caspase-3 in slice cultures. The gap junction blocker carbenoxolone applied to hippocampal slice cultures before, during, or 60 minutes after OGD markedly reduced delayed neuronal death. Administration of carbenoxolone to ischemic pups immediately after intrauterine HI prevented caspase-3 activation and dramatically reduced long-term neuronal damage. CONCLUSIONS: Gap junction blockade may be a useful therapeutic tool to minimize brain damage produced by perinatal and early postnatal HI.

Animals↗

PubMed2005

Alterations in metabolism and gap junction expression may determine the role of astrocytes as "good samaritans" or executioners.

Our knowledge of astroglia and their physiological and pathophysiological role(s) in the central nervous system (CNS) has grown during the past decade, revealing a complex picture. It is becoming increasingly clear that glia play a significant role in the homeostasis and function of the CNS and that neurons should no longer be considered the only cell type that responds, both rapidly and slowly, to electrochemical activity. We discuss recent advances in the field with an emphasis on the impact of hypoxia and ischemia on astrocytic metabolism and the functional relationship between glucose metabolism and gap junctions in astrocytes. We also address the controversy over whether astrocytic gap junctions mediate protection or killing of neurons during or after hypoxic or ischemic insults.

Astrocytes↗

PubMed2003

Gap junctions mediate bystander cell death in developing retina.

During development of the retina, programmed cell death helps to establish the final size and distribution of various cell classes in distinct layers of the tissue. Here we show that dying cells in the developing ganglion and inner nuclear layers are clustered spatially and that gap junction inhibitors decrease the clustering of dying cells. To confirm the role of gap junctions in cell death, we induced targeted cell death via intracellular cytochrome c (Cc) and examined the induced cells and their neighbors for apoptotic morphology or caspase-3 cleavage. These studies indicate that bystander killing extends to coupled cells. Quantitative studies of bystander killing were performed by scrape-loading retinas with Cc in the presence of rhodamine dextran (RD; to identify Cc-loaded cells) and by counting pyknotic cells in cryosections. Although only 1.5% of control scrape-loaded cells (RD alone) showed apoptotic morphology, 97% of Cc scrape-loaded cells were pyknotic. Moreover, bystander killing extended to neighboring cells, not labeled with RD, and was reduced significantly by the gap junction inhibitors octanol and carbenoxolone. We hypothesize that dying cells in the retina generate a gap junction-permeant apoptotic signal that mediates bystander killing. This novel finding of naturally occurring bystander cell death may have important implications in the histogenesis and pathology of the nervous system.

Animals↗

PubMed2002

Prospects for rational development of pharmacological gap junction channel blockers.

Connexin-null mice and human genetic gap junction diseases illustrate the important roles that gap junction channels play under normal conditions, and the neuro- and cardioprotective effects of gap junction blocking agents demonstrate that closure of these channels may be beneficial in certain pathological situations. This overview summarizes studies in which gap junction modifying reagents have been characterized, highlighting examples of agents for which selectivity for gap junction subtypes has been demonstrated. In addition, strategies for targeting connexin domains through peptide inhibitors are outlined, which may ultimately provide agents that are not only connexin-selective in their actions, but also affect only a subset of a gap junction channel's gating responses.

Animals↗