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Updated: Jul 20, 2026
Production and Detection of Reactive Oxygen Species (ROS) in Cancers
Published on: November 21, 2011
Modulation of the production of reactive oxygen species (ROS) by cAMP-elevating agents in granulocytes from diabetic
J A Nogueira-Machado1, F C Lima e Silva, E P Cunha
1Hospital Santa Casa de Belo Horizonte, Núcleo de Pesquisa e Pós, Graduação (NPPG), Brasil. nogueira.machado@pesquisador.cnpq.br
Background:
Granulocytes from healthy subjects and from patients suffering from diabetes mellitus present differences in reactivity to stimulation with cyclic nucleotide-elevating agents. The production of reactive oxygen species (ROS) is inhibited in cells from non-diabetic subjects following such stimulation, but activated through a PKA-independent signaling pathway in granulocytes from type 1 and type 2 diabetic patients. The aim of the present study was to understand better the changes in signaling mechanisms induced by the disease.
Methods:
ROS production in granulocytes from healthy subjects and from type 1 and type 2 diabetic patients was measured using a luminol-dependent chemiluminescence assay. Granulocytes were stimulated by the addition of the cAMP-elevating agent dibutyryl cAMP. In some experiments, granulocytes were pre-treated with an inhibitor of PKA or Akt/PKB prior to cAMP stimulation.
Results:
Intracellular elevation of cAMP induced a PKA-dependent and Akt/PKB-independent inhibition of ROS production in granulocytes from healthy subjects, but a significant activation in cells from both type 1 and type 2 diabetic patients. Most significantly, activation of ROS generation in cells from diabetic patients was shown to be Akt/PKB-dependent and PKA-independent.
Conclusions:
These results suggest that chronic hyperglycaemia could induce metabolic adaptation in cAMP-related signaling mechanisms. Epac (exchange protein directly activated by cAMP) is a novel cAMP receptor besides PKA involved in different signaling pathways. The cAMP-stimulated inverse ROS response in granulocytes from type 1 and type 2 diabetic patients may be due to a change in signaling pathways from cAMP/PKA to cAMP/Epac/Akt/PKB. These preliminary results require further studies in order to evaluate their consequences on innate immunity and pathogenesis of diabetes mellitus.
Insights
Diabetic granulocytes show altered reactive oxygen species (ROS) production due to changes in cyclic adenosine monophosphate (cAMP) signaling pathways. This suggests chronic hyperglycemia impacts innate immunity and diabetes pathogenesis.
Area of Science:
- Immunology
- Cell Signaling
- Metabolic Diseases
Background:
- Granulocytes from diabetic patients exhibit different reactivity to cyclic nucleotide-elevating agents compared to healthy individuals.
- Reactive oxygen species (ROS) production is inhibited in healthy cells but activated via a PKA-independent pathway in diabetic cells upon stimulation.
- Understanding these altered signaling mechanisms is crucial for comprehending disease-induced changes.
Purpose of the Study:
- To investigate the specific signaling pathway alterations in granulocytes from type 1 and type 2 diabetic patients.
- To elucidate the role of protein kinase A (PKA) and Akt/PKB in the differential ROS production.
Main Methods:
- Luminol-dependent chemiluminescence assay was used to measure ROS production in granulocytes.
- Cells from healthy and diabetic subjects were stimulated with dibutyryl cAMP, a cAMP-elevating agent.
- Inhibition of PKA or Akt/PKB was employed prior to cAMP stimulation to dissect signaling pathways.
Main Results:
- cAMP stimulation inhibited ROS production in healthy granulocytes via a PKA-dependent, Akt/PKB-independent pathway.
- Conversely, cAMP stimulation significantly activated ROS production in granulocytes from both type 1 and type 2 diabetic patients.
- This activation in diabetic cells was found to be Akt/PKB-dependent and PKA-independent.
Conclusions:
- Chronic hyperglycemia may induce metabolic adaptations in cAMP-related signaling pathways.
- The shift from cAMP/PKA to cAMP/Epac/Akt/PKB signaling may explain the inverse ROS response in diabetic granulocytes.
- Further research is needed to determine the implications for innate immunity and diabetes pathogenesis.
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