Sustained delivery of insulin-loaded block copolymers: Potential implications on renal ischemia/reperfusion injury in diabetes mellitus

Short-Term Preconditioning with Insulin and Glucose Efficiently Protected the Kidney Against Ischemia-Reperfusion Injury via the P-AKT-Bax-Caspase-3 Signaling Pathway in Mice

Objective

Insulin attaches insulin receptor to activate the PI3-kinase/Akt signaling to maintain glucose homeostasis and inhibit apoptosis. This study determined whether preconditioning with insulin and glucose protects the kidney against ischemia-reperfusion injury (IRI).

Methods

Kidney IRI was performed in C57BL/6 mice by clamping the renal vessels for 30 min, followed by reperfusion for 24 h. A total subcutaneous 0.1 unit of insulin along with 10% glucose in drinking water was treated on the mice for 24 h before kidney IRI. The kidney function and injuries were investigated through the determination of BUN and Cr in blood plasma, as well as the apoptosis and the expression of P-AKT, BAX, and caspase-3 in the kidneys. The role of P-AKT in insulin-treated IRI kidneys was tested using an AKT inhibitor. The effects of the preconditional duration of insulin and glucose on IRI kidneys were investigated by expanding the treatment duration to 1, 3, and 6 days.

Results

Preconditioning with insulin and glucose protected the kidney against IRI as manifested by a decrease in creatinine and BUN and a reduction of kidney tubular injury. The protection effect was mediated by P-AKT-BAX-caspase-3 signaling pathway resulting in suppression of apoptotic cell death. An AKT inhibitor partially reversed the protective effects of preconditional insulin. The preconditional duration for 1, 3, and 6 days had no differences in improving kidney functions and pathology.

Conclusion

A short-term preconditioning with insulin and glucose protected the kidney from IRI through the activation of p-AKT and subsequent reduction of BAX-caspase-3-induced apoptosis. The short-term precondition provides a practicable strategy for protecting the kidney against predictable IRI, such as kidney transplant and major surgical operations with high risk of hypotension.

Superparamagnetic Nanocrystals Clustered Using Poly(ethylene glycol)-Crosslinked Amphiphilic Copolymers for the Diagnosis of Liver Cancer

Superparamagnetic iron oxide (SPIO) nanocrystals have been extensively studied as theranostic nanoparticles to increase transverse (T2) relaxivity and enhance contrast in magnetic resonance imaging (MRI). To improve the blood circulation time and enhance the diagnostic sensitivity of MRI contrast agents, we developed an amphiphilic copolymer, PCPZL, to effectively encapsulate SPIO nanocrystals. PCPZL was synthesized by crosslinking a polyethylene glycol (PEG)-based homobifunctional linker with a hydrophobic star-like poly(ε-benzyloxycarbonyl-L-lysine) segment. Consequently, it could self-assemble into shell-crosslinked micelles with enhanced colloidal stability in bloodstream circulation. Notably, PCPZL could effectively load SPIO nanocrystals with a high loading capacity of 66.0 ± 0.9%, forming SPIO nanoclusters with a diameter of approximately 100 nm, a high cluster density, and an impressive T2 relaxivity value 5.5 times higher than that of Resovist®. In vivo MRI measurements highlighted the rapid accumulation and contrast effects of SPIO-loaded PCPZL micelles in the livers of both healthy mice and nude mice with an orthotopic hepatocellular carcinoma tumor model. Moreover, the magnetic micelles remarkably enhanced the relative MRI signal difference between the tumor and normal liver tissues. Overall, our findings demonstrate that PCPZL significantly improves the stability and magnetic properties of SPIO nanocrystals, making SPIO-loaded PCPZL micelles promising MRI contrast agents for diagnosing liver diseases and cancers.

Membrane-disruptive peptides/peptidomimetics-based therapeutics: Promising systems to combat bacteria and cancer in the drug-resistant era

Membrane-disruptive peptides/peptidomimetics (MDPs) are antimicrobials or anticarcinogens that present a general killing mechanism through the physical disruption of cell membranes, in contrast to conventional chemotherapeutic drugs, which act on precise targets such as DNA or specific enzymes. Owing to their rapid action, broad-spectrum activity, and mechanisms of action that potentially hinder the development of resistance, MDPs have been increasingly considered as future therapeutics in the drug-resistant era. Recently, growing experimental evidence has demonstrated that MDPs can also be utilized as adjuvants to enhance the therapeutic effects of other agents. In this review, we evaluate the literature around the broad-spectrum antimicrobial properties and anticancer activity of MDPs, and summarize the current development and mechanisms of MDPs alone or in combination with other agents. Notably, this review highlights recent advances in the design of various MDP-based drug delivery systems that can improve the therapeutic effect of MDPs, minimize side effects, and promote the co-delivery of multiple chemotherapeutics, for more efficient antimicrobial and anticancer therapy.

Poly(α-l-lysine)-based nanomaterials for versatile biomedical applications: Current advances and perspectives

Poly(α-l-lysine) (PLL) is a class of water-soluble, cationic biopolymer composed of α-l-lysine structural units. The previous decade witnessed tremendous progress in the synthesis and biomedical applications of PLL and its composites. PLL-based polymers and copolymers, till date, have been extensively explored in the contexts such as antibacterial agents, gene/drug/protein delivery systems, bio-sensing, bio-imaging, and tissue engineering. This review aims to summarize the recent advances in PLL-based nanomaterials in these biomedical fields over the last decade. The review first describes the synthesis of PLL and its derivatives, followed by the main text of their recent biomedical applications and translational studies. Finally, the challenges and perspectives of PLL-based nanomaterials in biomedical fields are addressed.

Simvastatin Alleviates Intestinal Ischemia/Reperfusion Injury by Modulating Omi/HtrA2 Signaling Pathways

PURPOSE

The objective of this research was to survey the therapeutic action of simvastatin (Sim) on intestinal ischemia/reperfusion injury (II/RI) by modulating Omi/HtrA2 signaling pathways.

METHODS

Sprague Dawley rats were pretreated with 40 mg/kg Sim and then subjected to 1 hour of ischemia and 3 hours of reperfusion. The blood and intestinal tissues were collected, pathologic injury was observed, the contents of serum tumor necrosis factor-α and interleukin-6 (IL-6) were estimated, and superoxide dismutase, methane dicarboxylic aldehyde, and cysteinyl aspartate specific proteinase-3 (caspase-3) levels, as well as the expressions of Omi/HtrA2 and caspase-3, were measured in the intestinal tissues.

RESULTS

Sim preconditioning mitigated the damnification of intestinal tissues by decreasing oxidative stress, inflammatory damage, and apoptosis and downregulating the expression of Omi/HtrA2 compared to the ischemia/reperfusion group, while Sim+Ucf-101 significantly augmented this effect.

CONCLUSION

These results suggest that Sim may alleviate intestinal ischemia/reperfusion injury by modulating Omi/HtrA2 signaling pathways.

Phycocyanin/PEG-b-(PG-g-PEI) attenuated hepatic ischemia/reperfusion-induced pancreatic islet injury and enlarged islet functionality

Background

Hepatic ischemia/reperfusion-induced pancreatic islet injury (HI/RIPII) was an important pathophysiological phenomenon in clinics. In the present study, we observed the effects of phycocyanin on HI/RIPII. However, the half-life of phycocyanin was extremely short and limited its use in vivo.

Materials and methods

In order to overcome this shortcoming, poly(ethylene glycol)-b-(poly(l-glutamic acid)-g-polyethylenimine) (PEG-b-(PG-g-PEI)) was synthesized and estimated as a nanocarrier for lengthening delivery of phycocyanin through the abdominal subcutaneous injection in rats. Phycocyanin (isoelectric point=4.3) was encapsulated with PEG-b-(PG-g-PEI) via electrostatic interactions at pH 7.4.

Results

In vitro phycocyanin was fast and efficiently encapsulated and showing efficient loading and sustained release. In vivo the anti-HI/RIPII function of phycocyanin/PEG-b-(PG-g-PEI) complex was surveyed in rats using free phycocyanin as the controls, and the results showed that phycocyanin/PEG-b-(PG-g-PEI) complex reduced HI/RIPII property and enlarged islet functionality.

Conclusion

These results suggested that PEG-b-(PG-g-PEI) might be treated as a potential phycocyanin nanocarrier.

Effects of Dexmedetomidine on Renal Ischaemia Reperfusion Injury in Streptozotocin-Induced Diabetic Rats

Objective

The aim of this study was to investigate the effects of dexmedetomidine before and after ischaemia in diabetic rat kidney ischaemia reperfusion (IR) injury in the experimental diabetic rat model.

Methods

Data belonging to 35 rats weighing between 250 and 300 g were analysed. Diabetes mellitus (DM) was induced using streptozotocin. Groups had bilateral renal vasculature clamped for 45 min ischaemia before clamps were removed, and 4 hours reperfusion was applied. Rats were divided into five groups: Group I or nondiabetic sham group (n=7), Group II or diabetic sham group (n=7), Group III or diabetic IR group (n=7), Group IV or diabetic IR+prophylactic Dex P (before ischaemia) (n=7) and Group V or diabetic IR+therapeutic Dex T (following reperfusion) (n=7). Dexmedetomidine was administered at a dose of 100 μg kg^-1 intraperitoneally. Histomorphological and biochemical methods were used to assess the blood and tissue samples.

Results

The proximal tubule injury score in the control sham group was significantly lower than in other groups. The proximal tubule and total cell damage scores of the diabetic IR group were significantly higher than the diabetic IR+Dex T group, and no significant difference was detected in the diabetic IR+Dex P group. The biochemical parameters of the IR group were significantly increased compared to Groups I and II; however, there was no significant reduction in these parameters in the groups administered dexmedetomidine.

Conclusion

Although administration of dexmedetomidine after ischaemia in the diabetic rat renal IR model was found to be more effective on the histopathological injury scores compared to preischaemic administration, this study has not shown that dexmedetomidine provides effective and complete protection in DM.

Lumbrokinase/paclitaxel nanoparticle complex: potential therapeutic applications in bladder cancer

Background

Lumbrokinase (LK) is an enzyme complex with antithrombotic, antioxidant, antitumor, and immunomodulatory effects. It has been extensively studied and used in clinical anti-tumor therapy. However, its half-life is short, its bioavailability is low, and its toxicity and side effects are great, which greatly limit its clinical application. Therefore, LK is often combined with other drugs (such as immune agents, hormones, or Chinese herbal medicine) to reduce its dosage and side effects and to improve its anti-tumor effects.

Methods and results

Here, we described an LK/paclitaxel (PTX) nanocarrier based on poly(ethylene glycol)-b-(poly(ethylenediamine l-glutamate)-g-poly(ε-benzyoxycarbonyl-l-lysine)-r-poly(l-lysine)) (PEG-b-(PELG-g-(PZLL-r-PLL))). In the present study, LK and PTX were loaded by electrostatic and/or hydrophobic effects under mild conditions, thereby increasing the half-life and bioavailability of the drugs via the sustained release and enhancement of tumor site enrichment by the LK/PTX/PEG-b-(PELG-g-(PZLL-r-PLL)) complex through passive targeting. In this study, using bladder cancer cells (J82 cells) and rat bladder cancer model as the object, the structure of the nanocarrier, the relationship between drugs composition and antitumor properties were systematically studied.

Conclusion

We propose that the block copolymer PEG-b-(PELG-g-(PZLL-r-PLL)) may function as a potent nanocarrier for augmenting anti-bladder cancer pharmacotherapy, with unprecedented clinical benefits.

Endogenous ornithine decarboxylase/polyamine system mediated the antagonist role of insulin/PEG-CMCS preconditioning against heart ischemia/reperfusion injury in diabetes mellitus

INTRODUCTION

Insulin has shown antioxidation and cytoprotective effects to decrease heart ischemia/reperfusion injury (HI/RI) in diabetes mellitus (DM), but the role of insulin/poly(ethylene glycol)-carboxymethyl chitosan (PEG-CMCS) on HI/RI in DM is not known. This research explored whether insulin/PEG-CMCS revealed a protective effect on HI/RI in DM through ornithine decarboxylase (ODC)/polyamine systems.

MATERIALS AND METHODS

Diabetes was induced via streptozotocin (STZ) in Sprague Dawley (SD) rats, which suffered from HI via blocking the left circumflex artery for 45 minutes, followed by 2 hours of reperfusion. α-Difluoromethylornithine-ethylglyoxal bis (guanylhydrazone) (DFMO-EGBG) and insulin/PEG-CMCS were administered to diabetic rats to explore their roles on severity of HI/RI.

RESULTS

Insulin could be fleetly and efficiently loaded via the nanocarrier PEG-CMCS at pH =6, showing efficient loading and stable release. In addition, insulin/PEG-CMCS showed significant hypoglycemic activity in diabetic rats. On the other hand, ischemia/reperfusion obviously augmented the contents of creatine kinase (CK), lactic dehydrogenase (LDH), putrescine (Pu), myocardial infarct size, and NF-κB and spermidine/spermine N'-acetyltransferase (SSAT) expressions and decreased the levels of spermine (Sp), polyamine pools (PAs), heart rate (HR), coronary blood flow (CF), left ventricular developed pressure (LVDP), and ODC expression, compared with Sham. Administration of insulin and insulin/PEG-CMCS both reduced the contents of CK, LDH, Pu, myocardial infarct size, and NF-κB and SSAT expressions and increased the levels of Sp, PAs, HR, CF, LVDP, and ODC expression, while insulin/PEG-CMCS significantly indicated the protective results, and DFMO-EGBG showed the opposite effects.

CONCLUSION

The research showed that insulin/PEG-CMCS could play a protective effect on HR/RI in diabetic rats via its antioxidative, antiapoptotic, and anti-inflammatory roles and modulating ODC/polyamine systems.

In vitro/vivo drug release and anti-diabetic cardiomyopathy properties of curcumin/PBLG-PEG-PBLG nanoparticles

Background

The objective of this study was to survey the therapeutic function of curcumin-encapsulated poly(gamma-benzyl l-glutamate)-poly(ethylene glycol)-poly(gammabenzyl l-glutamate) (PBLG-PEG-PBLG) (P) on diabetic cardiomyopathy (DCM) via cross regulation effect of calcium-sensing receptor (CaSR) and endogenous cystathionine-γ-lyase (CSE)/hydrogen sulfide (H₂S).

Methods

Diabetic rats were preconditioned with 20 mg/kg curcumin or curcumin/P complex continuously for 8 weeks. The blood and myocardiums were collected, the level of serum H₂S was observed, and the [Ca²⁺]_i content was measured in myocardial cells, and hematoxylin-eosin, CaSR, CSE, and calmodulin (CaM) expression were detected.

Results

Both curcumin and curcumin/P pretreatment alleviated pathological morphological damage of myocardium, increased H₂S and [Ca²⁺]_i levels, and upregulated the expression of CaSR, CSE, and CaM as compared to DCM group, while curcumin/P remarkably augmented this effect.

Conclusion

PBLG-PEG-PBLG could improve water-solubility and bioactivity of curcumin and curcumin/PBLG-PEG-PBLG significantly alleviated diabetic cardiomyopathy.

Role of Calcium Sensing Receptor in Streptozotocin-Induced Diabetic Rats Exposed to Renal Ischemia Reperfusion Injury

BACKGROUND/AIMS

Renal ischemia/reperfusion (I/R) injury (RI/RI) is a common complication of diabetes, and it may be involved in altering intracellular calcium concentrations at its onset, which can result in inflammation, abnormal lipid metabolism, the production of reactive oxygen species (ROS), and nitroso-redox imbalance. The calcium-sensing receptor (CaSR) is a G-protein coupled receptor, however, the functional involvement of CaSR in diabetic RI/ RI remains unclear. The present study was intended to investigate the role of CaSR on RI/RI in diabetes mellitus (DM).

METHODS

The bilateral renal arteries and veins of streptozotocin (STZ)-induced diabetic rats were subjected to 45-min ischemia followed by 2-h reperfusion with or without R-568 (agonist of CaSR) and NPS-2143 (antagonist of CaSR) at the beginning of I/R procedure. DM without renal I/R rats served as control group. The expressions of CaSR, calmodulin (CaM), and p47phox in the renal tissue were analyzed by qRT-PCR and Western blot. The renal pathomorphology, renal function, oxidative stress, inflammatory response, and calcium disorder were evaluated by detection of a series of indices by hematoxylin-eosin (HE) staining, transmission electron microscope (TEM), commercial kits, enzyme-linked immunosorbent assay (ELISA), and spectrophotofluorometry, respectively.

RESULTS

Results showed that the expressions of CaSR, CaM, and p47phox in I/R group were significantly up-regulated as compared with those in DM group, which were accompanied by renal tissue injury, increased calcium, oxidative stress, inflammation, and nitroso-redox imbalance.

CONCLUSION

These results suggest that activation of CaSR is involved in the induction of damage of renal tubular epithelial cell during diabetic RI/RI, resulting in lipid peroxidation, inflammatory response, nitroso-redox imbalance, and apoptosis.