Neuroprotective effects of a ligand of translocator protein-18kDa (Ro5-4864) in experimental diabetic neuropathy

doi:10.1016/j.neuroscience.2009.08.005

Neuroscience

Volume 164, Issue 2, 1 December 2009, Pages 520-529

https://doi.org/10.1016/j.neuroscience.2009.08.005 Get rights and content

Abstract

Peripheral neuropathy represents an important complication of diabetes involving a spectrum of structural, functional and biochemical alterations in peripheral nerves. Recent observations obtained in our laboratory have shown that the levels of neuroactive steroids present in the sciatic nerve of rat raised diabetic by a single injection of streptozotocin (STZ) are reduced and that, in the same experimental model, treatment with neuroactive steroids, such as progesterone, testosterone and their derivatives show neuroprotective effects. On this basis, an interesting therapeutic strategy could be to increase the levels of neuroactive steroids directly in the nervous system. With this perspective, ligands of translocator protein-18 kDa (TSPO) may represent an interesting option. TSPO is mainly present in the mitochondrial outer membrane, where it promotes the translocation of cholesterol to the inner mitochondrial membrane, and, as demonstrated in other cellular systems, it allows the transformation of cholesterol into pregnenolone and the increase of steroid levels. In the diabetic model of STZ rat, we have here assessed whether treatment with Ro5-4864 (i.e., a ligand of TSPO) could increase the low levels of neuroactive steroids in sciatic nerve and consequently to be protective in this experimental model. Data obtained by liquid chromatography–tandem mass spectrometry show that treatment with Ro5-4864 was able to significantly stimulate the low levels of pregnenolone, progesterone and dihydrotestosterone observed in the sciatic nerves of diabetic rats. The treatment with Ro5-4864 also counteracted the impairment of NCV and thermal threshold, restored skin innervation density and P0 mRNA levels, and improved Na⁺,K⁺-ATPase activity. In conclusion, data here reported show for the first time that a TSPO ligand, such as Ro5-4864, is effective in reducing the severity of diabetic neuropathy through a local increase of neuroactive steroid levels.

Section snippets

Materials

5-pregnen-3β-ol-20-one (pregnenolone; PREG), PROG, 5α-pregnane-3, 20-dione (dihydroprogesterone; DHP), 3α-hydroxy-5α-pregnen-20-one (THP), 3β-hydroxy-5α-pregnen-20-one (isopregnanolone), T, 5α-androstane-17β-ol-3-one (dihydrotestosterone; DHT), 3α-diol, were purchased from Sigma Aldrich. 17,21,21,21-D₄-PREG (D4-PREG) was kindly synthesized by Dr. P. Ferraboschi (Department of Medical Chemistry, Biochemistry and Biotechnology, University of Milano, Milano, Italy); 2,2,4,6,6–17α,21,21,21-D₉-PROG

Results

We have here tested an experimental protocol of treatment previously utilized in case of neuroactive steroids and demonstrated to be protective in STZ rat (Leonelli et al 2007, Roglio et al 2007). Thus, animals received 16 treatments of Ro5-4864 and injections were administered every 2 days (experimental protocol 1). We have compared the effect of this experimental protocol with another one in which we have decreased the frequency of treatment. Thus, animals were injected once a week and

Discussion

Our recent results suggested that neuroactive steroids, such as PROG, T and their derivatives, might be considered as promising therapeutic strategy for diabetic neuropathy. The results of the present work demonstrate for the first time that stimulating TSPO with its ligand Ro5-4864 an increase of PREG (i.e. the first steroid synthesized from cholesterol) associated to an increase of its first derivative, PROG, and of a T metabolite, such as DHT, occurred directly in the sciatic nerve of STZ

Conclusion

Our findings indicate that Ro5-4864, a ligand of TSPO, is able to increase the low levels of neuroactive steroids, such as PREG, PROG and DHT, present in the sciatic nerve of STZ-induced diabetic neuropathy. Ro5-4864 also exerts neuroprotective actions against the pathological changes induced by experimental diabetes in peripheral nerves. These neuroprotective effects are most likely mediated by PREG, PROG, T and DHT, rather than by other neuroactive steroids, such as DHP, previously shown to

Acknowledgments

The financial support of PRIN (20074SPYCM_002) and PUR from Università degli Studi di Milano, Italy, to Roberto C. Melcangi is gratefully acknowledged.

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Cellular NeuroscienceResearch PaperNeuroprotective effects of a ligand of translocator protein-18kDa (Ro5-4864) in experimental diabetic neuropathy

Abstract

Section snippets

Materials

Results

Discussion

Conclusion

Acknowledgments

Life Sci

Biochem Pharmacol

Brain Res

Int Rev Neurobiol

Neurochem Int

Neurochem Int

Metabolism

Anal Biochem

Pharmacol Ther

Exp Cell Res

Steroids

Neurosci Lett

Brain Res

Neurobiol Dis

Neuroscience

Mech Ageing Dev

J Biol Chem

Mol Cell Neurosci

J Neurol Sci

Steroids

J Biol Chem

Neuroscience

Brain Res Rev

Neurobiol Dis

Pharmacol Ther

Neurosci Lett

Prog Neurobiol

Brain Res

Pharmacol Ther

Eur J Pharmacol

Cellular Neuroscience
Research Paper
Neuroprotective effects of a ligand of translocator protein-18kDa (Ro5-4864) in experimental diabetic neuropathy