Increased toxicity of amylin (Islet Amyloid Polypeptide) in beta cells induced by photochemical internalization

Singh Rinku; Ingrid Hals; Anders Høgset; Valdemar Grill; Odrun A Gederaas

doi:10.1016/j.pdpdt.2018.06.017

Increased toxicity of amylin (Islet Amyloid Polypeptide) in beta cells induced by photochemical internalization

Photodiagnosis Photodyn Ther. 2018 Sep:23:218-220. doi: 10.1016/j.pdpdt.2018.06.017. Epub 2018 Jun 21.

Authors

Singh Rinku¹, Ingrid Hals¹, Anders Høgset², Valdemar Grill¹, Odrun A Gederaas³

Affiliations

¹ Department of Clinical and Molecular Medicine, Faculty of Medicine and Health Sciences, Norwegian University of Science and Technology (NTNU), N-7006, Trondheim, Norway.
² PCI Biotech AS, Ullernchauséen 64, 0379, Oslo, Norway.
³ Department of Clinical and Molecular Medicine, Faculty of Medicine and Health Sciences, Norwegian University of Science and Technology (NTNU), N-7006, Trondheim, Norway; Department of Chemistry, Faculty of Natural Science, Norwegian University of Science and Technology (NTNU), N-7489, Trondheim, Norway. Electronic address: odrun.gederaas@ntnu.no.

PMID: 29936141
DOI: 10.1016/j.pdpdt.2018.06.017

Abstract

Background: Amylin and oligomers formed from amylin are implicated in demise of beta cells in type 2 diabetes. However, whether putative toxicity is exerted intra or extracellularly is unclear. Use of photochemical internalization (PCI) technique may give clues for impact of intracellular toxicity.

Aim: (a) To optimize the concentration and exposure set up of the photosensitizing compound meso-disulfonated tetraphenyl chlorin TPCS_2a (Amphinex^®) for use in insulin producing beta cells and (b) to utilize the photosensitizing technique to probe for intracellular effects in beta cells by amylin.

Materials and methods: The titration of TPCS_2a and blue light exposure was evaluated by MTT assay. The insulin producing INS-1 832/13 beta cells were incubated with the photosensitizing agent TPCS_2a prior to exposure of amylin. Viability and function were further evaluated by standard biochemical techniques.

Results: A protocol was developed for use in INS-1 832/13 cells in which the optimal concentration of TPCS_2a was found to be 4ng/ml. Using this protocol human amylin (10 μM, 8 h) in combination with TPCS_2a (4 ng/ml, 18 h) and blue light exposure (60 s) exerted toxic effects above those by TPCS_2a and illumination alone as measured by MTT (15 ± 3.6%, n = 6, p < 0.007) for effect of amylin exposure. On the other hand, rat amylin (which does not form oligomers) had no effect. Insulin secretion was non-significantly reduced by the combination of human amylin with TPCS_2a and illumination compared to TPCS_2a and illumination alone. Cellular insulin content was not affected, nor were measured parameters of apoptosis and necrosis.

Conclusion: PCI technology could be a useful tool to induce endosomal rupture in clonal beta cells. The present results using PCI are compatible with intracellular negative effects following exposure to amylin.

Keywords: Amylin; Islet amyloid polypeptide (IAPP); Photochemical internalization (PCI); Type 2 diabetes; meso-tetraphenylchlorin disulfonate (TPCS(2a)).

MeSH terms

Animals
Cell Survival
Diabetes Mellitus, Type 2
Dose-Response Relationship, Drug
Insulin / biosynthesis
Insulin-Secreting Cells / drug effects*
Islet Amyloid Polypeptide / pharmacology*
Photochemotherapy / methods*
Photosensitizing Agents / pharmacology*
Porphyrins / pharmacology*
Rats

Substances

Insulin
Islet Amyloid Polypeptide
Photosensitizing Agents
Porphyrins
meso-tetraphenyl chlorin disulphonate