Ward Peterson - Academia.edu (original) (raw)
Papers by Ward Peterson
The presence of receptors for ATP has not been established in any native preparation of retinal n... more The presence of receptors for ATP has not been established in any native preparation of retinal neurons or glia. In the present study, we used conventional electrophysiological and [Ca 2ϩ ] in fluorescence imaging techniques to investigate the effects of ATP added to Ringer's solution perfusing the retinal-facing (apical) membrane of freshly isolated monolayers of bovine retinal pigment epithelium (RPE). ATP (or UTP) produced large, biphasic voltage and resistance changes with a K d of ϳ5 M for ATP and ϳ1 M for UTP. Electrical and pharmacological evidence indicates that the first and second phases of the response are attributable to an increase in basolateral membrane Cl conductance and a decrease in apical membrane K conductance, respectively. The ATP-induced responses were not affected by adenosine, but were reduced by the P 2 -purinoceptor blocker suramin. ATP also produced a large, transient increase in [Ca 2ϩ ] in that was blocked by cyclopiazonic acid, an inhibitor of endoplasmic reticulum Ca 2ϩ -ATPases. The calcium buffer BAPTA attenuated the voltage effects of ATP. We also found that apical DIDS significantly inhibited the ATP-evoked [Ca 2ϩ ] in and electrical responses, suggesting that DIDS blocked the purinoceptor. Measurements of fluid movement across the RPE using the capacitance probe technique demonstrated a significant increase in fluid absorption by apical UTP. These data indicate the presence of metabotropic P 2Y /P 2U -purinoceptors at the RPE apical membrane and implicate extracellular ATP in vivo as a retinal signaling molecule that could help regulate the hydration and chemical composition of the subretinal space.
To investigate the effects of INS37217, a synthetic P2Y 2 receptor agonist, on intracellular calc... more To investigate the effects of INS37217, a synthetic P2Y 2 receptor agonist, on intracellular calcium signaling, electrophysiology, and fluid transport in vitro and on experimentally induced retinal detachment in rat eyes in vivo.
Ciliary neurotrophic factor (CNTF) is pleiotrophic for central, peripheral, and sensory neurons. ... more Ciliary neurotrophic factor (CNTF) is pleiotrophic for central, peripheral, and sensory neurons. In the mature retina, CNTF treatment enhances survival of retinal ganglion and photoreceptor cells exposed to otherwise lethal perturbation. To understand its mechanism of action in vivo, the adult rat retina was used as a model to investigate CNTF-mediated activation of Janus kinase/signal transducer and activator of transcription (Jak-STAT) and ras-mitogen activated protein kinase (ras-MAPK). Intravitreal injection of Axokine, an analog of CNTF, phosphorylates STAT3 and MAPK and produces delayed upregulation of total STAT3 and STAT1 protein in rat retina. Activated STAT3 is predominantly localized in nuclei of retinal Mü ller (glial) cells, ganglion cells, and astrocytes, but not in photoreceptors. Although CNTF ␣-receptor (CNTFR␣) mRNA and protein are localized predominantly if not exclusively in retinal neurons, coincident CNTF-mediated STAT3 signaling was observed in both glia and neurons. CNTF-induced activation of Jak-STAT signaling prompted us to investigate STAT3 phosphorylation after a variety of stress-mediated, conditioning stimuli. We show that STAT3 is activated in the retina after exposure to subtoxic bright light, mechanical trauma, and systemic administration of the ␣ 2 -adrenergic agonist xylazine, all of which have been shown previously to condition photoreceptors to resist light-induced degeneration. These results demonstrate that CNTF directly stimulates Jak-STAT and ras-MAPK cascades in vivo and strongly suggest that STAT3 signaling is an underlying component of neural responsiveness to stress stimuli. The observation that CNTF activates STAT3 in ganglion cells, but not in photoreceptors, suggests that Jak-STAT signaling influences neuronal survival via both direct and indirect modes of action.
The presence of receptors for ATP has not been established in any native preparation of retinal n... more The presence of receptors for ATP has not been established in any native preparation of retinal neurons or glia. In the present study, we used conventional electrophysiological and [Ca 2ϩ ] in fluorescence imaging techniques to investigate the effects of ATP added to Ringer's solution perfusing the retinal-facing (apical) membrane of freshly isolated monolayers of bovine retinal pigment epithelium (RPE). ATP (or UTP) produced large, biphasic voltage and resistance changes with a K d of ϳ5 M for ATP and ϳ1 M for UTP. Electrical and pharmacological evidence indicates that the first and second phases of the response are attributable to an increase in basolateral membrane Cl conductance and a decrease in apical membrane K conductance, respectively. The ATP-induced responses were not affected by adenosine, but were reduced by the P 2 -purinoceptor blocker suramin. ATP also produced a large, transient increase in [Ca 2ϩ ] in that was blocked by cyclopiazonic acid, an inhibitor of endoplasmic reticulum Ca 2ϩ -ATPases. The calcium buffer BAPTA attenuated the voltage effects of ATP. We also found that apical DIDS significantly inhibited the ATP-evoked [Ca 2ϩ ] in and electrical responses, suggesting that DIDS blocked the purinoceptor. Measurements of fluid movement across the RPE using the capacitance probe technique demonstrated a significant increase in fluid absorption by apical UTP. These data indicate the presence of metabotropic P 2Y /P 2U -purinoceptors at the RPE apical membrane and implicate extracellular ATP in vivo as a retinal signaling molecule that could help regulate the hydration and chemical composition of the subretinal space.
To investigate the effects of INS37217, a synthetic P2Y 2 receptor agonist, on intracellular calc... more To investigate the effects of INS37217, a synthetic P2Y 2 receptor agonist, on intracellular calcium signaling, electrophysiology, and fluid transport in vitro and on experimentally induced retinal detachment in rat eyes in vivo.
Ciliary neurotrophic factor (CNTF) is pleiotrophic for central, peripheral, and sensory neurons. ... more Ciliary neurotrophic factor (CNTF) is pleiotrophic for central, peripheral, and sensory neurons. In the mature retina, CNTF treatment enhances survival of retinal ganglion and photoreceptor cells exposed to otherwise lethal perturbation. To understand its mechanism of action in vivo, the adult rat retina was used as a model to investigate CNTF-mediated activation of Janus kinase/signal transducer and activator of transcription (Jak-STAT) and ras-mitogen activated protein kinase (ras-MAPK). Intravitreal injection of Axokine, an analog of CNTF, phosphorylates STAT3 and MAPK and produces delayed upregulation of total STAT3 and STAT1 protein in rat retina. Activated STAT3 is predominantly localized in nuclei of retinal Mü ller (glial) cells, ganglion cells, and astrocytes, but not in photoreceptors. Although CNTF ␣-receptor (CNTFR␣) mRNA and protein are localized predominantly if not exclusively in retinal neurons, coincident CNTF-mediated STAT3 signaling was observed in both glia and neurons. CNTF-induced activation of Jak-STAT signaling prompted us to investigate STAT3 phosphorylation after a variety of stress-mediated, conditioning stimuli. We show that STAT3 is activated in the retina after exposure to subtoxic bright light, mechanical trauma, and systemic administration of the ␣ 2 -adrenergic agonist xylazine, all of which have been shown previously to condition photoreceptors to resist light-induced degeneration. These results demonstrate that CNTF directly stimulates Jak-STAT and ras-MAPK cascades in vivo and strongly suggest that STAT3 signaling is an underlying component of neural responsiveness to stress stimuli. The observation that CNTF activates STAT3 in ganglion cells, but not in photoreceptors, suggests that Jak-STAT signaling influences neuronal survival via both direct and indirect modes of action.