Morphological and gene expression analysis in mouse primary cultured hepatocytes exposed to streptozotocin

The Effect of Nano-Epigallocatechin-Gallate on Oxidative Stress and Matrix Metalloproteinases in Experimental Diabetes Mellitus

Background: The antioxidant properties of epigallocatechin-gallate (EGCG), a green tea compound, have been already studied in various diseases. Improving the bioavailability of EGCG by nanoformulation may contribute to a more effective treatment of diabetes mellitus (DM) metabolic consequences and vascular complications. The aim of this study was to test the comparative effect of liposomal EGCG with EGCG solution in experimental DM induced by streptozotocin (STZ) in rats. Method: 28 Wistar-Bratislava rats were randomly divided into four groups (7 animals/group): group 1—control group, with intraperitoneal (i.p.) administration of 1 mL saline solution (C); group 2—STZ administration by i.p. route (60 mg/100 g body weight, bw) (STZ); group 3—STZ administration as before + i.p. administration of EGCG solution (EGCG), 2.5 mg/100 g b.w. as pretreatment; group 4—STZ administration as before + i.p. administration of liposomal EGCG, 2.5 mg/100 g b.w. (L-EGCG). The comparative effects of EGCG and L-EGCG were studied on: (i) oxidative stress parameters such as malondialdehyde (MDA), indirect nitric oxide (NOx) synthesis, and total oxidative status (TOS); (ii) antioxidant status assessed by total antioxidant capacity of plasma (TAC), thiols, and catalase; (iii) matrix-metalloproteinase-2 (MMP-2) and -9 (MMP-9). Results: L-EGCG has a better efficiency regarding the improvement of oxidative stress parameters (highly statistically significant with p-values < 0.001 for MDA, NOx, and TOS) and for antioxidant capacity of plasma (highly significant p < 0.001 for thiols and significant for catalase and TAC with p < 0.05). MMP-2 and -9 were also significantly reduced in the L-EGCG-treated group compared with the EGCG group (p < 0.001). Conclusions: the liposomal nanoformulation of EGCG may serve as an adjuvant therapy in DM due to its unique modulatory effect on oxidative stress/antioxidant biomarkers and MMP-2 and -9.

SPARC paucity alleviates superoxide-mediated oxidative stress, apoptosis, and autophagy in diabetogenic hepatocytes

Secreted protein acidic and rich in cysteine (SPARC) is known to play a previously unappreciated role in diabetes, but its precise mechanism in liver/hepatocyte pathology remains unknown. Inhibition of SPARC is critical in resolving candidate pathogenic events such as production of reactive oxygen species (ROS), which are broadly considered for their roles in diabetes, and is capable of protecting functional hepatocytes. Here, we provide in vitro and in vivo evidence demonstrating pathological correlations between SPARC and streptozotocin (STZ)-induced diabetic rat livers as well as cultured hepatocytes induced by diabetogenic stimuli. Under these conditions, transient SPARC silencing was carried out to investigate the role of SPARC in the pathogenesis of pro-diabetic hepatocyte damage and dysfunction. The constitutive expression of SPARC in hepatocytes was up-regulated under a diabetic environment. In addition, Nox4-dependent superoxide generation contributed to increased expression of SPARC, and this was inhibited by tiron and pharmacological or genetic inactivation of Nox4-containing NADPH oxidase. Remarkably, SPARC deficiency inhibited diabetic stimuli-induced elevation of superoxide production and resolved salient features of hepatocyte damage such as impaired cytoprotection, inflammation, apoptosis, and autophagy. At the same time, links between SPARC, integrin-β1, Nox4-derived superoxide, and JNK signaling provide a basis for these phenotypes. Taken together with the observations that SPARC deficiency had protective effects on hepatocytes via a favorable inhibition profile, functional knowledge of SPARC may offer a unique therapeutic approach to preserve hepatocellular fate decisions in diabetes.

Primary hepatocytes and their cultures in liver apoptosis research

Apoptosis not only plays a key role in physiological demise of defunct hepatocytes, but is also associated with a plethora of acute and chronic liver diseases as well as with hepatotoxicity. The present paper focuses on the modelling of this mode of programmed cell death in primary hepatocyte cultures. Particular attention is paid to the activation of spontaneous apoptosis during the isolation of hepatocytes from the liver, its progressive manifestation upon the subsequent establishment of cell cultures and simultaneously to strategies to counteract this deleterious process. In addition, currently applied approaches to experimentally induce controlled apoptosis in this in vitro setting for mechanistic research purposes and thereby its detection using relevant biomarkers are reviewed.

Characterization and validation of a streptozotocin-induced diabetes model in the vervet monkey

INTRODUCTION

Streptozotocin (STZ), preferentially toxic to pancreatic beta cells, is commonly used to model Type 1 diabetes mellitus (DM) in numerous species, including nonhuman primates.

METHODS

We induced DM in twenty vervet monkeys (Chlorocebus aethiops) by intravenous administration of either 45 (n=8, STZ-45) or 55 mg/kg STZ (n=12, STZ-55); ten control (CTL) monkeys received saline.

RESULTS

Overall there was 15% mortality, likely secondary to renal toxicity. Twice-daily insulin therapy was initiated to maintain comparable glycemic control, confirmed by comparable glycated hemoglobin levels. Exogenous insulin requirements increased rapidly for 4weeks; STZ-45 insulin doses stabilized thereafter while STZ-55 doses continued to increase through 16weeks. Glucose tolerance testing and arginine-stimulated insulin secretion confirmed 80-90% reduction in pancreatic beta cell function in both groups. Body weight was reduced in all STZ monkeys, with return to baseline only in STZ-45 at 16 wks. Elevated blood urea nitrogen (BUN) and creatinine were noted in the STZ-55 group. Alkaline phosphatase (ALKP) was also increased with STZ-55 (p < 0.05 vs. CTL) whereas STZ-45 ALKP elevation resolved by study end. Red cell parameters were reduced in all STZ monkeys, but more severely in the STZ-55 group.

DISCUSSION

We have demonstrated that a model of DM can be induced and maintained in vervets with a single dose of STZ. The lower dose of STZ (45 mg/kg) significantly improved the toxicity profile without altering efficacy in inducing DM. Finally, sufficient time following induction is recommended to allow transient renal, hepatic and hematologic parameters to resolve.

The hepatic transcriptome in human liver disease

The transcriptome is the mRNA transcript pool in a cell, organ or tissue with the liver transcriptome being amongst the most complex of any organ. Functional genomics methodologies are now being widely utilized to study transcriptomes including the hepatic transcriptome. This review outlines commonly used methods of transcriptome analysis, especially gene array analysis, focusing on publications utilizing these methods to understand human liver disease. Additionally, we have outlined the relationship between transcript and protein expressions as well as summarizing what is known about the variability of the transcriptome in non-diseased liver tissue. The approaches covered include gene array analysis, serial analysis of gene expression, subtractive hybridization and differential display. The discussion focuses on primate whole organ studies and in-vitro cell culture systems utilized. It is now clear that there are a vast number research opportunities for transcriptome analysis of human liver disease as we attempt to better understand both non-diseased and disease hepatic mRNA expression. We conclude that hepatic transcriptome analysis has already made significant contributions to the understanding of human liver pathobiology.