IL-4 increases GABAergic phenotype in rat retinal cell cultures: involvement of muscarinic receptors and protein kinase C.
Interleukin-4 (IL-4) is an anti-inflammatory cytokine. During injuries, infections and neurodegenerative diseases, high levels of this molecule are expressed in the brain. In the present work, we investigated the effect of IL-4 on GABAergic differentiation of retinal cells kept in vitro. We analyzed either the uptake of [3H]-gamma-aminobutyric acid (GABA) or the expression of glutamic acid decarboxylase (GAD-67) following IL-4 treatment. We have also investigated the pharmacological modulation of the [3H]-GABA uptake by cholinergic activation. Our results demonstrate that IL-4 increases the uptake of [3H]-GABA after 48 h in culture in a dose-dependent manner (0.5-100 U/ml). The maximal effect was obtained with 5 U/ml (75% increase). This effect was blocked by 1 mM of nipecotic acid, demonstrating the involvement of the GAT-1 subtype of GABA transporter. The IL-4 effect depends on M1 muscarinic activity, an increase in intracellular calcium levels, tyrosine kinase activity and protein kinase C (PKC) activity. Treatment with IL-4 for 48 h induced an increase of 90% in the number of GAD- and GABA-immunoreactive cells when compared with control cultures. Our results indicate that IL-4 modulates the GABAergic phenotype of retinal cells in culture. This result can suggest an important role for this cytokine either during the normal development of retinal circuitry or during neuroprotection after injuries.
Sholl-Franco
Alfred
A
Departamento de Neurobiologia, Programa de Neuroimunologia, Instituto de Biologia, Centro de Estudos Gerais, Universidade Federal Fluminense, CP# 100180, RJ 24001-970, RJ, Niterói, Brazil.
Marques
Patrícia M B
PM
Ferreira
Cecília M C
CM
de Araujo
Elizabeth G
EG
D000818:Animals; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005968:Glutamate Decarboxylase / Q000378:metabolism; D007150:Immunohistochemistry; D015847:Interleukin-4 / Q000378:metabolism* / Q000494:pharmacology; D018727:Muscarinic Antagonists / Q000494:pharmacology; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D010641:Phenotype; D011493:Protein Kinase C / Q000187:drug effects / Q000378:metabolism*; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D051381:Rats; D043643:Receptor, Muscarinic M1; D011976:Receptors, Muscarinic / Q000187:drug effects / Q000378:metabolism*; D012160:Retina / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism* / Q000494:pharmacology
D004791:Enzyme Inhibitors; D018727:Muscarinic Antagonists; D019384:Nucleic Acid Synthesis Inhibitors; D011500:Protein Synthesis Inhibitors; D043643:Receptor, Muscarinic M1; D011976:Receptors, Muscarinic; D015847:Interleukin-4; D005680:gamma-Aminobutyric Acid; D011493:Protein Kinase C; D005968:Glutamate Decarboxylase