Targeting CNG-Ca2+ channels: Evaluation of pharmacological and antisense oligonukleotide approaches for the treatment of retinitis pigmentosa.

• Applicant: Professor Dr. Francois Paquet-Durand
• Subject Area: Ophthalmology ; Molecular Biology and Physiology of Neurons and Glial Cells
• Term: from 2017 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 384355007

• Final Report Year: 2021

Final Report Abstract

Hereditary retinal degenerations (RD) are a major cause of blindness in the developed world. These diseases are at present untreatable, and the underlying neurodegenerative mechanisms are largely unknown, even though the genetic causes are often established. In different animal models for human RD photoreceptor cell death is known to be caused by elevated levels of cyclic guanosine monophosphate (cGMP). Furthermore, photoreceptor, cGMP-signalling is intricately linked to Ca2+ signalling via the activity of cGMP-gated Ca2+ cyclic-nucleotide-gated channels (CNGC). The project therefore investigated the potential of targeting CNGC and down-regulation of Ca2+-influx for therapeutic interventions aimed at preventing photoreceptor degeneration. A number of different inhibitors for CNGC and for voltage-gated-Ca2+ channels (VGCC) were tested. In particular, the registered drug L-cis-diltiazem clearly lowered Ca2+-influx and showed a strong selectivity for CNGC in rod photoreceptors over cone photoreceptors. Unexpectedly, CNGC inhibitors lowering intracellular Ca2+-levels, including L-cis-diltiazem, were not photoreceptor protective but in fact exhibited strong detrimental effects. The project therefore failed in its primary objective to identify CNGC targeting drugs that would prevent or delay photoreceptor degeneration. Nevertheless, the data generated changed our understanding of the importance of Ca2+ for photoreceptor cell death, notably by showing that Ca2+-influx via CNGC or VGCC is far less important for photoreceptor cell death than previously thought. Indeed, photoreceptor cell death now appears more likely to be triggered by too low intracellular Ca2+ levels. Moreover, project results indicated that the activation of Ca2+-dependent calpain-type proteases, often observed in dying photoreceptor cells, was in fact not due to activity of CNGC but instead indirectly mediated by activation of VGCC. The data also suggested a possible additional involvement of Ca2+-release activated channels (CRAC) in calpain activation. The data and ideas generated during the project have led to one follow-up project and several new grant applications. In particular, a BMBF-funded project aiming at validating different targets for the treatment of RD-type diseases was started in 2020 (TargetRD project).

Publications

• A retinal model of cerebral malaria. Sci Rep. 9(1):3470, 2019
  Paquet-Durand, François; Beck, Susanne C.; Das, Soumyaparna; Huber, Gesine; Schubert, Timm; Tanimoto, Naoyuki; Garcia-Garrido, Marina; Mühlfriedel, Regine; Bolz, Sylvia; Hoffmann, Wolfgang; Schraermeyer, Ulrich; Mordmüller, Benjamin & Seeliger, Mathias W.
  
• Entwicklung von cGMP-Analoga zur pharmakologischen Behandlung von neurodegenerativen Netzhauterkrankungen [Development of cGMP Analogues for the Pharmacological Treatment of Neurodegenerative Diseases of the Retina]. Klin Monbl Augenheilkd. 236(3):253-260, 2019
  Fischer, Dominik & Paquet-Durand, François
  
• The cGMP Pathway and Inherited Photoreceptor Degeneration: Targets, Compounds, and Biomarkers. Genes (Basel). 10(6):453, 2019
  Tolone, Arianna; Belhadj, Soumaya; Rentsch, Andreas; Schwede, Frank & Paquet-Durand, François
  
• Cellular mechanisms of hereditary photoreceptor degeneration - Focus on cGMP. Prog Retin Eye Res. 100772, 2019
  Power, Michael; Das, Soumyaparna; Schütze, Karin; Marigo, Valeria; Ekström, Per & Paquet-Durand, François
  
• Long-Term, Serum-Free Cultivation of Organotypic Mouse Retina Explants with Intact Retinal Pigment Epithelium. J Vis Exp. (165), 2020
  Belhadj, Soumaya; Tolone, Arianna; Christensen, Gustav; Das, Soumyaparna; Chen, Yiyi & Paquet-Durand, François
  
• Redefining the role of Ca2+-permeable channels in hereditary photoreceptor degeneration using the D- and L-cis enantiomers of diltiazem. Cell Death & Disease
  Das, Soumyaparna; Popp, Valerie; Power, Michael; Groeneveld, Kathrin; Melle, Christian; Rogerson, Luke; Achury, Marlly; Schwede, Frank; Strasser, Torsten; Euler, Thomas; Paquet-Durand, François & Nache, Vasilica
  
• Retina in a dish: Cell cultures, retinal explants and animal models for common diseases of the retina. Prog Retin Eye Res. 81:100880, 2021
  Schnichels, Sven; Paquet-Durand, François; Löscher, Marina; Tsai, Teresa; Hurst, José; Joachim, Stephanie C. & Klettner, Alexa
  
• The role of cGMP-signalling and calcium-signalling in photoreceptor cell death: perspectives for therapy development. Pflugers Arch. 473(9):1411-1421, 2021
  Das, Soumyaparna; Chen, Yiyi; Yan, Jie; Christensen, Gustav; Belhadj, Soumaya; Tolone, Arianna & Paquet-Durand, François