Critical Pathways in Heart Function: Bis(2-chloroethoxy)methane-Induced Heart Gene Transcript Change in F344 Rats

Abstract

Gene transcript changes after exposure to the heart toxin, bis(2-chloroethoxy)methane (CEM), were analyzed to elucidate mechanisms in cardiotoxicity and recovery. CEM was administered to 5-week-old male F344/N rats at 0, 200, 400, or 600 mg/kg by dermal exposure, 5 days per week, for a total of 12 doses by study day 16. Heart toxicity occurred after 2 days of dosing in all 3 regions of the heart (atrium, ventricle, interventricular septum) and was characterized by myofiber vacuolation, necrosis, mononuclear-cell infiltration, and atrial thrombosis. Ultrastructural analysis revealed that the primary site of damage was the mitochondrion. By day 5, even though dosing was continued, the toxic lesions in the heart began to resolve, and by study day 16, the heart appeared histologically normal. RNA was extracted from whole hearts after 2 or 5 days of CEM dosing. After a screen for transcript change by microarray analysis, dose-response trends for selected transcripts were analyzed by qRT-PCR. The selected transcripts code for proteins involved in energy production, control of calcium levels, and maintenance of heart function. The down-regulation of ATP subunit transcripts (Atp5j, ATP5k), which reside in the mitochondrial membranes, indicated a decrease in energy supply at day 2 and day 5. This was accompanied by down-regulation of transcripts involved in high-energy consumption processes such as membrane transport and ion channel transcripts (e.g., abc1a, kcnj12). The up-regulation of transcripts encoding for temperature regulation and calcium binding proteins (ucp1 and calb3) only at the 2 low exposure levels, suggest that these adaptive processes cannot occur in association with severe cardiotoxicity as seen in hearts at the high exposure level. Transcript expression changes occurred within 2 days of CEM exposure, and were dose-and time-dependent. The heart transcript changes suggest that CEM cardiotoxicity activates protective processes associated energy conservation and maintenance of heart function.

Occult Cardiotoxicity—Toxic Effects on Cardiac Ischemic Tolerance

“…CEM exerts cardiotoxic effect mainly through mitochondrial damage (Dunnick et al , 2006. Topical application of 400 and 600 mg/Kg/d cause time-and dose-dependent myocardial injury, expressed morphologically as perinuclear vacuolation .…”

Meta-Analysis of Large-Scale Toxicogenomic Data Finds Neuronal Regeneration Related Protein and Cathepsin D to Be Novel Biomarkers of Drug-Induced Toxicity

“…Among these methods, RF with 10-fold cross-validation achieved the best performance (82% correct classification); thus, it was selected as the final classifier. Next, we evaluated the performance of the 21-gene RF prediction model in 2,194 independent test samples in comparison to a model with an identical degree of complexity built using previously known organ-specific toxicity markers, which we compiled from various studies [ 5 , 9 , 22 – 25 ]. As shown in Table 2 , the accuracy of our 21-gene RF prediction model was slightly higher (62%) than the model built with previously known biomarkers (60.5%).…”

“…DEGs were identified in each comparison using a p -value cut-off of 0.0005. This p -value threshold was selected, because 44 known toxicity markers ( S4 Table ) [ 5 , 9 , 22 – 25 ] were most significantly enriched under this threshold and, at the same time, it provided a sufficiently large enough number of resultant DEGs for us to perform downstream analysis.…”

Distal Tumors Elicit Distinctive Gene Expression Changes in Mouse Brain, Different from Those Induced by Arthritis

“…We also validated the increased expression levels of thromboxane A2 receptor (Tbxa2r) an important lipid mediator generated during oxidative stress that was associated with olygodendrocytes myelination [28], contactin-2 (Cntn2), a gene involved in remodeling of synaptic connections [29] and oxytocin (Oxt) a pleiotrophic anorexigenic molecule known as a "satiety" and "fear" hormone also involved in remodeling of synaptic connections [30] ( Table 2). In addition, we also validated the down regulation of the mitochondrial ATP subunit transcript Atp5k [31], of the fibroblast activation protein, fap, an integral membrane serine protease associated with matrix remodeling [32], the DNA binding protein, kin [33] and Unc84a or SUN-1, an integral protein of the inner nuclear membrane [34]. We also validated the upregulated expression of Nad kinase (Nadk), the only known enzyme involved in the formation of NADP(+) from NAD(+) and ATP [35].…”