Background & Aims

Despite the diversity of drug classes for pain control, the treatment of chronic pain is still a challenge. Chronic pain represents a growing public health problem, often becoming debilitating, constant and resistant to therapies clinically available, and patients frequently report incomplete reversal of the painful condition or undesirable adverse effects of the medications. Then, studies to broaden the characterization of molecular mechanisms involved in pain processes, as well as the development of new therapies, including new analgesic drugs are essential. In this context, our group has focused on the development of a new analgesic molecule, named mini-Cro, with corresponds to a synthetic peptide of 6 aminoacids. Thus, the objective of this work was to characterize the analgesic effect of mini-Cro, to identify the signaling pathways involved in this effect, and to characterize some of its physicochemical aspects.

Methods

Male Wistar rats or mice were used (CEUA/3528010819). Acute pain was induced by carrageenan (200 µg/paw); neuropathic pain was induced by the chronic constriction of the sciatic nerve. Hypernociception was evaluated using electronic von Frey test. Thermal hyperalgesia was assessed using the acetone and the plantar tests. The Open Field method evaluated the exploratory and locomotor activities. The global gene expression analysis of the central nervous system was conducted using the GeneChip platform (Affymetrix mouse 1.0 ST bioarrays) and the data was analyzed using the Transcriptome Analysis Console (TAC, 4.0.1, ThermoFisher Scientific) and the Gene Ontology database. The alteration of Wnt/Ryk signaling on the spinal cord of animals was evaluated by Western blotting. Peptide stability was evaluated by HPLC under different conditions of pH and temperature.

Results

Our data show that mini-Cro induces analgesia in acute and chronic pain (100%) which lasts 96 or 24 h, respectively (n=6, p<0.05). Complete reversion of thermal hyperalgesia to heat and cold stimuli in animals with acute and/or chronic pain was also observed (n=6, p<0.05). The peptide does not induce change in general and locomotor activity nor the development of tolerance after repetitive administrations. The global gene analysis identified pathways involved in nociceptive processes that are negatively regulated by mini-CRO, including the PI3K-AKT pathway. By western blotting analysis, it was possible to confirm that mini-CRO inhibited the increase in the expression of the AKT protein induced by the neuropathic pain model in spinal cord of animals under surgery. In relation to its physicochemical properties, it was observed that the peptide is stable under different conditions of pH and temperature.

Conclusions

As a conclusion, our data indicate that mini-CRO is a potential drug candidate for the control of chronic pain conditions. In addition, we can suggest PI3K-AKT pathway as an important target for chronic pain control.

Financial support: Fapesp/CETICS 2013/07467-1, CAPES and Butantan Foundation

References

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Presenting Author

Gisele Picolo

Poster Authors

Gisele Picolo

MD, PhD

Butantan Institute

Lead Author

E-mail

Flavia Souza Ribeiro Lopes

MSc

Butantan Institute

Lead Author

E-mail

Ana Boaventura de Oliveira

Butantan Institute

Lead Author

E-mail

Louise Faggionato Kimura

PhD

Northwestern University

Lead Author

E-mail

Natalia Gabriele Hösch

Butantan Institute

Lead Author

E-mail

Fernanda Calheta Vieira Portaro

PhD

Butantan Institute

Lead Author

E-mail

Denis Servent

French Alternative Energies and Atomic Energy Commission

Lead Author

E-mail

Topics

  • Models: Chronic Pain - Neuropathic