4-Aminophenol (4-AP), D-
serine, and
cisplatin are established rodent nephrotoxins that damage proximal tubules within the renal cortex. Using high throughput 2D gel proteomics to profile
protein changes in the plasma of compound-treated animals, we identified several markers of kidney toxicity. Male F344 and Alpk rats were treated with increasing doses of 4-AP, D-
serine, or
cisplatin, and plasma samples were collected over time. Control groups received saline or nontoxic isomers,
L-serine, and
transplatin.
Plasma proteins that displayed dose- and temporal-dependent regulation in each study were further characterized by mass spectrometry to elucidate the
protein identity. Several
isoforms of the rat-specific
T-kininogen protein were identified in each study.
T-kininogen was elevated in the plasma of 4-AP-, D-
serine-, and
cisplatin-treated animals at early time points, returning to baseline levels 3 weeks
after treatment. The
protein was not elevated in the plasma of control animals or those treated with nontoxic compounds. We propose that
T-kininogen may be required to counteract apoptosis in proximal tubular cells in order to minimize tissue damage following a toxic insult. In addition,
T-kininogen may be required to stimulate localized
inflammation to aid tissue repair. We also identified several
isoforms of the
inter-alpha inhibitor H4P heavy chain in the 4-AP and D-
serine studies. In each case, the
protein expression levels in the blood samples paralleled the extent of kidney toxicity, highlighting the correlation between
protein alterations and clinical chemistry endpoints. A further set of
proteins correlating with kidney damage was found to be a component of the
complement cascade and other blood clotting factors, indicating a contribution of the immune system to the observed toxicity. These observations underscore the value of proteomics in identifying new
biomarkers and in the elucidation of mechanisms of toxicity.