People with type 1 diabetes (T1D) must administer insulin exogenously due to the destruction of their pancreatic β-cells. Endogenous insulin is stored in β-cell granules along with C-peptide, a 31 amino acid peptide that is secreted from these granules in amounts equal to insulin. Exogenous co-administration of C-peptide with insulin has proven to reduce diabetes-associated complications in animals and humans. The exact mechanism of C-peptide's beneficial effects after secretion from the β-cell granules is not completely understood, thus hindering its development as an exogenously administered hormone. Monitoring tissue-to-tissue communication using a 3D-printed microfluidic device revealed that zinc and C-peptide are being delivered to erythrocytes by albumin. Upon delivery, erythrocyte-derived ATP increased by >50%, as did endothelium-derived NO, which was measured downstream in the 3D-printed device. Our results suggest that hormone replacement therapy in diabetes may be improved by exogenous administration of a C-peptide ensemble that includes zinc and albumin.

Our previous research has shown that α-(N)-heterocyclic thiosemicarbazone (TSC) metal complexes inhibit human topoisomerase IIα (TopoIIα), while the ligands without metals do not. To find out the structural elements of TSC that are important for inhibiting TopoIIα, we have synthesized two series of α-(N)-heterocyclic TSCs with various substrate ring segments, side chain substitutions, and metal ions, and we have examined their activities in TopoIIα-mediated plasmid DNA relaxation and cleavage assays. Our goal is to explore the structure–activity relationship of α-(N)-heterocyclic TSCs and their effect on TopoIIα. Our data suggest that, similar to Cu­(II)-TSCs, Pd­(II)-TSC complexes inhibit plasmid DNA relaxation mediated by TopoIIα. In TopoIIα-mediated plasmid DNA cleavage assays, the Cu­(II)-TSC complexes induce higher levels of DNA cleavage than their Pd­(II) counterparts. The Cu­(II)-TSC complexes with methyl, ethyl, and tert-butyl substitutions are slightly more effective than those with benzyl and phenyl groups. The α-(N)-heterocyclic ring substrates of the TSCs, including benzoylpyridine, acetylpyridine, and acetylthiazole, do not exhibit a significant difference in TopoIIα-mediated DNA cleavage. Our data suggest that the metal ion of TSC complexes plays a predominant role in inhibition of TopoIIα, the side chain substitution of the terminal nitrogen plays a secondary role, while the substrate ring segment has the least effect. Our molecular modeling data support the biochemical data, which together provide a mechanism by which Cu­(II)-TSC complexes stabilize TopoIIα-mediated cleavage complexes.

C-peptide does not affect NO production in bPAECs directly but can impact NO production through an erythrocyte-mediated mechanism. Furthermore, in the absence of Zn(2+), C-peptide does not stimulate this NO production directly or indirectly. These results suggest that C-peptide, in the presence of Zn(2+), may be a determinant in purinergic receptor signalling via its ability to stimulate the release of ATP from erythrocytes.

■ AbstractInspired by previous reports, our group has recently demonstrated that C-peptide exerts beneficial effects upon interactions with red blood cells (RBCs). These effects can be measured in RBCs obtained from animal models of both type 1 diabetes and type 2 diabetes, though to different extents. To date, the key metrics that have been measured involving C-peptide and RBCs include an increase in glucose uptake by these cells and a subsequent increase in adenosine triphosphate (ATP) release. Importantly, to date, our group has only been able to elicit these beneficial effects when the C-peptide is prepared in the presence of Zn 2+ . The C-peptide-induced release of ATP is of interest when considering that ATP is a purinergic signaling molecule known to stimulate the production of nitric oxide (NO) in the endothelium and in platelets. This NO production has been shown to participate in smooth muscle relaxation and subsequent vessel dilation. Furthermore, NO is a well-established platelet inhibitor. The objective of this review is to provide information pertaining to C-peptide activity on RBCs. Special attention is paid to the necessity of Zn 2+ activation, and the origin of that activation in vivo. Finally, a mechanism is proposed that explains how C-peptide is exerting its effects on other cells in the bloodstream, particularly on endothelial cells and platelets, via its ability to stimulate the release of ATP from RBCs.

The focus of this research is on the study of a series of copper (II) benzoylpyridine thiosemicarbazone complexes. Of the six benzoylpyridine thiosemicarbazone ligands used in this study, two are reported for the first time; 2-benzoylpyridine tert-butyl thiosemicarbazone (BZP-tBTSC), and 2-benzoylpyridine benzyl thiosemicarbazone (BZP-BzTSC). Once characterized by NMR, melting point, and MS, these mono-anionic tridentate ligands were then reacted with Cu 2+ to form the new square planar metal complexes [Cu(BZP-tBTSC)Cl] and [Cu(BZP-BzTSC)Cl]. All of the copper complexes display marked inhibition of human topoisomerase IIα. The [Cu(BZP-tBTSC)Cl] complex shows marked activity against human breast cancer cell lines.