Cnicin promotes functional nerve regeneration.

BACKGROUND: The limited regenerative capacity of injured axons hinders functional recovery after nerve injury. Although no drugs are currently available in the clinic to accelerate axon regeneration, recent studies show the potential of vasohibin inhibition by parthenolide, produced in Tanacetum parthenium, to accelerate axon regeneration. However, due to its poor oral bioavailability, parthenolide is limited to parenteral administration. PURPOSE: This study investigates another sesquiterpene lactone, cnicin, produced in Cnicus benedictus for promoting axon regeneration. RESULTS: Cnicin is equally potent and effective in facilitating nerve regeneration as parthenolide. In culture, cnicin promotes axon growth of sensory and CNS neurons from various species, including humans. Neuronal overexpression of vasohibin increases the effective concentrations comparable to parthenolide, suggesting an interaction between cnicin and vasohibin. Remarkably, intravenous administration of cnicin significantly accelerates functional recovery after severe nerve injury in various species, including the anastomosis of severed nerves. Pharmacokinetic analysis of intravenously applied cnicin shows a blood half-life of 12.7 min and an oral bioavailability of 84.7 % in rats. Oral drug administration promotes axon regeneration and recovery after nerve injury in mice. CONCLUSION: These results highlight the potential of cnicin as a promising drug to treat axonal insults and improve recovery.

Small fibre integrity and axonal pathology in the rat model of experimental autoimmune neuritis.

Experimental autoimmune neuritis is a common animal model for acute human immune-mediated polyneuropathies. Although already established in 1955, a number of pathophysiological mechanisms remain unknown. In this study, we extensively characterize experimental autoimmune neuritis progression in Lewis rats, including new insights into the integrity of small nerve fibres, neuropathic pain and macrophage activation. Acute experimental autoimmune neuritis was induced with P253-78 peptide and consequently investigated using the gait analysis system CatWalk XT, electrophysiological and histopathological analyses, quantitative polymerase chain reaction (PCR), dorsal root ganglia outgrowth studies, as well as the von Frey hair and Hargreaves tests. For the longitudinal setup, rats were sacrificed at Day (d) 10 (onset), d15 (peak), d26 (recovery) and d29 (late recovery). We confirmed the classical T-cell and macrophage-driven inflammation and the primarily demyelinating nature of the experimental autoimmune neuritis. The dual role of macrophages in experimental autoimmune neuritis is implicated by the high number of remaining macrophages throughout disease progression. Furthermore, different subpopulations of macrophages based on Cx3-motif chemokine receptor 1 (Cx3cr1), platelet factor 4 (Pf4) and macrophage galactose-type lectin-1 (Mgl1) expressions were identified. In addition, modulation of the sensory system in experimental autoimmune neuritis was detected. An outgrowth of small fibres in the plantar skin at the onset and peak of the experimental autoimmune neuritis was evident parallel to the development of acute hyperalgesia mediated through transient receptor potential vanilloid 1 modulation. Our data depict experimental autoimmune neuritis as a primary demyelinating disease with implicated axonal damage, a small unmyelinated fibre impairment throughout the disease progression course, and underline the pivotal role of macrophages in the effector and during the recovery stage.

Targeting Vasohibins to Promote Axon Regeneration.

Treatments accelerating axon regeneration in the nervous system are still clinically unavailable. However, parthenolide promotes adult sensory neurons' axon growth in culture by inhibiting microtubule detyrosination. Here, we show that overexpression of vasohibins increases microtubule detyrosination in growth cones and compromises growth in culture and in vivo. Moreover, overexpression of these proteins increases the required parthenolide concentrations to promote axon regeneration. At the same time, the partial knockdown of endogenous vasohibins or their enhancer SVBP in neurons facilitates axon growth, verifying them as pharmacological targets for promoting axon growth. In vivo, repeated intravenous application of parthenolide or its prodrug di-methyl-amino-parthenolide (DMAPT) markedly facilitates the regeneration of sensory, motor, and sympathetic axons in injured murine and rat nerves, leading to acceleration of functional recovery. Moreover, orally applied DMAPT was similarly effective in promoting nerve regeneration. Thus, pharmacological inhibition of vasohibins facilitates axon regeneration in different species and nerves, making parthenolide and DMAPT the first promising drugs for curing nerve injury.