Proteomic analysis of alternative protein tyrosine phosphorylation in 1,2-dichlorovinyl-cysteine-induced cytotoxicity in primary cultured rat renal proximal tubular cells

Urinary TCP1-eta: A Cortical Damage Marker for the Pathophysiological Diagnosis and Prognosis of Acute Kidney Injury

Acute kidney injury (AKI) is a serious syndrome with increasing incidence and health consequences, and high mortality rate among critically ill patients. Acute kidney injury lacks a unified definition, has ambiguous semantic boundaries, and relies on defective diagnosis. This, in part, is due to the absence of biomarkers substratifying AKI patients into pathophysiological categories based on which prognosis can be assigned and clinical treatment differentiated. For instance, AKI involving acute tubular necrosis (ATN) is expected to have a worse prognosis than prerenal, purely hemodynamic AKI. However, no biomarker has been unambiguously associated with tubular cell death or is able to provide etiological distinction. We used a cell-based system to identify TCP1-eta in the culture medium as a noninvasive marker of damaged renal tubular cells. In rat models of AKI, TCP1-eta was increased in the urine co-relating with renal cortical tubule damage. When kidneys from ATN rats were perfused in situ with Krebs-dextran solution, a portion of the urinary TCP1-eta protein content excreted into urine disappeared, and another portion remained within the urine. These results indicated that TCP1-eta was secreted by tubule cells and was not fully reabsorbed by the damaged tubules, both effects contributing to the increased urinary excretion. Urinary TCP1-eta is found in many etiologically heterogeneous AKI patients, and is statistically higher in patients partially recovered from severe AKI. In conclusion, urinary TCP1-eta poses a potential, substratifying biomarker of renal cortical damage associated with bad prognosis.

Contribution of proteomics to the study of the role of cytokeratins in disease and physiopathology

Cytokeratins (CKs), the most abundant group of cytoskeletal intermediate filaments, and proteomics are strongly connected. On the one hand, proteomics has been extremely useful to uncover new features and functions of CKs, on the other, the highly abundant CKs serve as an exceptional tool to test new technological developments in proteomics. As a result, proteomics has contributed to finding valuable associations of CKs with diseases as diverse as cancer, cystic fibrosis, steatohepatitis, viral and bacterial infection, keratoconus, vitreoretinopathy, preeclampsia or the chronic fatigue syndrome, as well as to characterizing their participation in a number of physiopathological processes, including drug resistance, response to toxicants, inflammation, stem cell differentiation, embryo development, and tissue repair. In some cases, like in cystic fibrosis, CKs have been described as potential therapeutic targets. The development of a specific field of proteomics where CKs become the main subject of research aims and hypotheses is suggested.

SnoN as a key regulator of the high glucose-induced epithelial-mesenchymal transition in cells of the proximal tubule

BACKGROUND/AIMS

Ski-related protein N (SnoN) suppression is essential to transforming growth factor-β1 induction and the epithelial-mesenchymal transition (EMT) in several cancer cells. The role of SnoN in diabetic nephropathy is unknown. We aimed to determine the role of SnoN in the EMT of proximal tubule cells (PTCs) maintained under high glucose conditions.

METHODS

Immunohistochemistry, immunocytochemistry, Western blotting, small interfering RNA gene silencing, viral transduction and RT-PCR were used to assess changes in SnoN, E-cadherin, cytokeratin-18, α-smooth muscle actin and fibronectin expression using an in vivo streptozotocin-induced rat diabetic nephropathy model, and PTCs exposed to high glucose (25 mmol/l).

RESULTS

High glucose induced EMT in vitro and in vivo. Exposure of PTCs to a high concentration of glucose suppressed SnoN expression in a time-dependent manner compared with normal glucose and high osmolarity-treated groups. SnoN gene silencing under high glucose conditions appears to enhance the transition of PTC phenotype. Conversely, ectopic expression of exogenous SnoN after transfection conferred tubular epithelial cell resistance to high glucose-induced EMT.

CONCLUSION

SnoN plays a negative role in high glucose-induced EMT in PTCs. The effect of SnoN downregulation in vivo and in vitro suggests that SnoN may be a potential therapeutic target.

The role of toxicoproteomics in assessing organ specific toxicity

Aims of this chapter on the role of toxicoproteomics in assessing organ-specific toxicity are to define the field of toxicoproteomics, describe its development among global technologies, and show potential uses in experimental toxicological research, preclinical testing and mechanistic biological research. Disciplines within proteomics deployed in preclinical research are described as Tier I analysis, involving global protein mapping and protein profiling for differential expression, and Tier II proteomic analysis, including global methods for description of function, structure, interactions and post-translational modification of proteins. Proteomic platforms used in toxicoproteomics research are briefly reviewed. Preclinical toxicoproteomic studies with model liver and kidney toxicants are critically assessed for their contributions toward understanding pathophysiology and in biomarker discovery. Toxicoproteomics research conducted in other organs and tissues are briefly discussed as well. The final section suggests several key developments involving new approaches and research focus areas for the field of toxicoproteomics as a new tool for toxicological pathology.