KCa3.1 channel mediates inflammatory signaling of pancreatic β cells and progression of type 2 diabetes mellitus

Exploring dual effects of dinutuximab beta on cell death and proliferation of insulinoma

Insulinoma INS-1 cells are pancreatic beta cell tumors. Dinutuximab beta (DB) is a monoclonal antibody used in the treatment of neuroblastoma. The aim of this study is to investigate the effects of DB on pancreatic beta cell tumors at the molecular level. DB (Qarziba®) was available from EUSA Pharma. Streptozotocin (STZ) was used induce to cell cytotoxicity. DB was applied to the cells before or after the STZ application. KCND3, KCNN4, KCNK1, and PTHrP gene expression levels were analyzed by q-RT-PCR, and protein levels were analyzed by Western blotting. Analysis of glucose-stimulated insulin secretion was performed. Ca+2 and CA19-9 levels were determined by the ELISA kit. PERK, CHOP, HSP90, p-c-Jun, p-Atf2, and p-Elk1 protein levels were analyzed by simple WES. Decreased KCND3, KCNK1, and PTHrP protein levels and increased KCND3, KCNN4, KCNK1, and PTHrP gene expression levels were observed with DB applied after STZ application. Cell dysfunction was detected with DB applied before and after STZ application. Ca19-9 and Ca+2 levels were increased with DB applied after STZ application. PERK, CHOP, and p-Elk1 levels decreased, while HSP90 levels increased with DB applied after STZ application. CHOP, p-Akt-2, and p-c-Jun levels increased in the DB group. As a result, INS-1 cells go to cell death via the ERK signaling pathway without ER stress and release insulin with the decrease of K+ channels and an increase in Ca+2 levels with DB applied after STZ application. Moreover, the cells proliferate via JNK signaling with DB application. DB holds promise for the treatment of insulinoma. The study should be supported by in vivo studies.

Pancreatic KCa3.1 channels in health and disease

Ion channels play an important role for regulation of the exocrine and the endocrine pancreas. This review focuses on the Ca²⁺-regulated K⁺ channel K_Ca3.1, encoded by the KCNN4 gene, which is present in both parts of the pancreas. In the islets of Langerhans, K_Ca3.1 channels are involved in the regulation of membrane potential oscillations characterizing nutrient-stimulated islet activity. Channel upregulation is induced by gluco- or lipotoxic conditions and might contribute to micro-inflammation and impaired insulin release in type 2 diabetes mellitus as well as to diabetes-associated renal and vascular complications. In the exocrine pancreas K_Ca3.1 channels are expressed in acinar and ductal cells. They are thought to play a role for anion secretion during digestion but their physiological role has not been fully elucidated yet. Pancreatic carcinoma, especially pancreatic ductal adenocarcinoma (PDAC), is associated with drastic overexpression of K_Ca3.1. For pharmacological targeting of K_Ca3.1 channels, we are discussing the possible benefits K_Ca3.1 channel inhibitors might provide in the context of diabetes mellitus and pancreatic cancer, respectively. We are also giving a perspective for the use of a fluorescently labeled derivative of the K_Ca3.1 blocker senicapoc as a tool to monitor channel distribution in pancreatic tissue. In summary, modulating K_Ca3.1 channel activity is a useful strategy for exo-and endocrine pancreatic disease but further studies are needed to evaluate its clinical suitability.

Cadmium exposure suppresses insulin secretion through mtROS-mediated mitochondrial dysfunction and inflammatory response in pancreatic beta cells

BACKGROUND

Cadmium (Cd) exposure is a worldwide environmental threat to the public health and participates in the pathogenesis of multiple diseases. Epidemiologic research have established a direct relation between Cd exposure and diabetes development in humans. Although pancreatic β-cell dysfunction has been considered as the major culprit in the pathogenesis of diabetes, there is a paucity of studies to elucidate the molecular mechanism of Cd toxicity on β-cells.

METHODS

To unveil the toxic effect and its underlying mechanism of Cd exposure on β-cells, we used an in vitro MIN6 cell model of environment-relevant Cd exposure to elucidate the crucial role of mtROS-mediated mitochondrial dysfunction and inflammatory response in suppression of pancreatic β-cell insulin secretion.

RESULTS

We uncovered that Cd treatment suppresses cell viability and induces insulin secretion dysfunction in a dose-dependent manner. Moreover, Cd exposure elicits the inflammatory response, as indicated by increased IL-1β, IL-6 and TNF-α expressions. Significant elevations of intracellular ROS and mitochondrial ROS levels were detected as early as 3 h after Cd treatment. In mitochondrial function analysis, we demonstrated that Cd treatment induced mitochondrial dysfunction and disorder of mitochondrial fission indicated by the significant decline in ATP production, the marked depolarization of mitochondrial membrane potential, the decrease in mtDNA copy numbers, the suppressions of mitochondrial transcription factor A (Tfam) and mitochondrial fission-related gene Drp1 expressions. Pretreatment with TEMPO, a specific mitochondrial ROS (mtROS) scavenger, efficiently antagonizes Cd cytotoxicity, which is indicated by attenuating Cd-induced mitochondrial dysfunction, suppressing IL-1β, IL-6 and TNF-α expressions, ameliorating insulin production dysfunction and preserving cell viability in MIN6 cells.

CONCLUSION

Our study demonstrates that Cd exposure induces an inflammatory response through mtROS-mediated mitochondrial dysfunction. Antagonism of mtROS production might be an effective strategy to prevent pancreatic toxicity from environment-relevant Cd exposure.

Mechanisms of Rhizoma Coptidis against type 2 diabetes mellitus explored by network pharmacology combined with molecular docking and experimental validation

This study systematically explored the underlying mechanism of Rhizoma Coptidis against type 2 diabetes mellitus (T2DM) by using network pharmacology and molecular docking and experimental validation. We retrieved and screened active compounds of Rhizoma Coptidis and corresponding T2DM-related targets across multiple databases. PPI networks of the genes were constructed using STRING, and the core targets were screened via topological analysis. GO and KEGG enrichment analyses were performed by using DAVID. Finally, molecular docking and experimental studies were performed after bioinformatic analysis for verification. There were 14 active compounds and 19 core targets of Rhizoma Coptidis-T2DM, of which quercetin was identified as the main compound and IL6, VEGFA and TNF were the most significant core targets. GO and KEGG enrichment analyses showed that Rhizoma Coptidis ameliorated T2DM by regulating multiple biological processes and pathways. Docking studies indicated that IL6, VEGFA and TNF could stably bind with all active compounds of Rhizoma Coptidis. The results of our experiments revealed that Rhizoma Coptidis could inhibit the expression of IL6 and TNFα and enhance islet cell viability. This study suggests anti-inflammatory therapeutic effects of Rhizoma Coptidis on T2DM, thereby providing a scientific basis and new insight for further research on the antidiabetic effect of Rhizoma Coptidis.