Neuropathic pain resolution by nerve barrier sealing and netrin-1

• Applicants: Privatdozentin Dr. Susanne Marlen Krug; Professorin Dr. Heike Lydia Rittner
• Subject Area: Anaesthesiology ; Anatomy and Physiology
• Term: from 2018 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 399489785

Barrier breakdown has been described in e.g. the intestinal barrier in inflammatory bowel diseases and the blood brain barrier (BBB) in malignancies, trauma, stroke or neuroinflammation. Long-term barrier restoration in the BBB via overexpression of the tight junction (TJ) protein claudin-1 seals the BBB and ameliorates experimental autoimmune encephalitis. However, barrier sealing for treatment is discussed controversially. In the peripheral nerve, neuropathy is accompanied by blood-nerve barrier (BNB) leakiness. Transient opening of the BNB for drug delivery for a few hours has no long-term pathophysiological sequelae. Resolving this dispute in peripheral nerve barriers, this project seeks evidence in molecular detail that barrier restoration heals neuropathy. Extending this hypothesis, we claim that pain resolution in neuropathy is a regulated process involving nerve barrier sealing. To this end, we want to accomplish three subprojects in a translational and mechanistic approach:(A) Barrier breakdown in defined compartments of the nerve in neuropathy. Barriers of the perineurium, the endoneurial vessels (together the BNB), and the autotypic junctions of the myelin nerve barrier (MNB) are formed by different TJ proteins. This subproject will solve, which of these barriers and specifically which TJ proteins are mainly affected in neuropathies in preclinical models and in patients with inflammatory neuropathy. (B) Netrin-1 for barrier sealing and neuropathic pain resolution. The axonal guidance protein netrin-1 acts as a regulator of TJs: full netrin-1 seals barriers, while truncated netrin-1 opens. Here, we want to define the role of netrin-1 in peripheral neuropathy. Netrin-1 fragments in early neuropathy could open nerve barriers and aggravate hyperalgesia/allodynia via certain netrin-1 receptors. Endogenous or exogenous full netrin-1 could reseal nerve barriers and provide a drug usable in clinic to promote pain resolution. (C) Mechanisms of netrin-1 in in vitro barrier sealing. In functional and molecular studies, we will define which TJ proteins are involved in barrier formation and regulation in nerve barrier models. Cell lines treated with neuropathy-relevant cytokines and netrin-1 will be characterized in detail with regard to their ion and macromolecule barrier. We will initially use well-established epithelial cell models which are responsive to netrin-1 treatment, and then will establish endothelial and Schwann cell models. The overall goals of this project are to provide a spatiotemporal signature of TJ proteins in neuropathies and to explore netrin-1 as a possible sealing mechanism for pain resolution in mechanistic detail. By using in vitro and in vivo animal models, cell cultures, and tissues from patients with chronic inflammatory demyelinating polyneuropathy we will gain detailed knowledge on netrin-1-dependent mechanisms which will result in new mechanistic and functional insights of pain and neuropathy.

• DFG Programme: Research Grants