MEK and ERK Kinase Inhibitors Increase Circulating Ceruloplasmin and Cause Green Serum in Rats

Abstract

Inhibition of the mitogen-activated protein kinase/extracellular signal-regulated (MAPK/ERK) pathway is an attractive therapeutic approach for human cancer therapy. In the course of evaluating structurally distinct small molecule inhibitors that target mitogen-activated protein kinase kinase (MEK) and ERK kinases in this pathway, we observed an unusual, dose-related increase in the incidence of green serum in preclinical safety studies in rats. Having ruled out changes in bilirubin metabolism, we demonstrated a 2- to 3-fold increase in serum ceruloplasmin levels, likely accounting for the observed green color. This was not associated with an increase in α-2-macroglobulin, the major acute phase protein in rats, indicating that ceruloplasmin levels increased independently of an inflammatory response. Elevated serum ceruloplasmin was also not correlated with changes in total hepatic copper, adverse clinical signs, or pathology findings indicative of copper toxicity, therefore discounting copper overload as the etiology. Both ERK and MEK inhibitors led to increased ceruloplasmin secretion in rat primary hepatocyte cultures in vitro, and this increase was associated with activation of the Forkhead box, class O1 (FOXO1) transcription factor. In conclusion, increased serum ceruloplasmin induced by MEK and ERK inhibition is due to increased synthesis by hepatocytes from FOXO1 activation and results in the nonadverse development of green serum in rats.

Poorly controlled diabetes during pregnancy and lactation activates the Foxo1 pathway and causes glucose intolerance in adult offspring

“…Thus, it is still unclear how maternal diabetes leads to the decreased phosphorylation of Foxo1 in the liver of STZ male offspring. Because additional factors that regulate the localisation and activity of Foxo1 were identified recently 35,42,43 , further studies of all regulatory factors, including the newly identified regulatory factors, are needed to clarify the molecular mechanism underlying the decreased phosphorylation and increased activity of Foxo1.…”

Targeted regulation of FoxO1 in chondrocytes prevents age‐related osteoarthritis via autophagy mechanism

“…That ERK cellular pathway is one of the critical signals of FoxO1 phosphorylation. The inhibition of ERK and MEK attenuate phosphorylation resulting in the activation of Foxo1 in rat hepatocytes 61 . Phosphorylation of FoxO1 is invalid in binding to ATG7 for autophagy initiation in mouse ovarian granulosa cells.…”

“…The inhibition of ERK and MEK attenuate phosphorylation resulting in the activation of Foxo1 in rat hepatocytes. 61 Phosphorylation of FoxO1 is invalid in binding to ATG7 for autophagy initiation in mouse ovarian granulosa cells. The FSH or melatonin induces both Akt‐mediated phosphorylation and Sirt1‐mediated deacetylation of FoxO1.…”

“…11 The impacts of FoxO1 phosphorylation on autophagy are significantly different in various pathways and cells. Phosphorylation induced by AKT, 59 ERK, 60 MEK 61 and AMPK is the essential PTMs of Foxo1 that trigger the alteration of subcellular localization. 62 Phosphorylated-Foxo1(p-FoxO1) is restricted in the cytoplasm and interacts with ubiquitin E3 ligases, evoking the degeneration of Foxo1.…”

Contemporary and Emerging Applications in Clinical Pathology

“…The contribution by Carter, Cregar, and Aulbach (2016) provides an updated and comprehensive assessment of normal bone marrow cytology in the nonhuman primate, further expanding the reference literature for nonclinical toxicity studies. Finally, we have a case example of the mechanistic workup and evidence-based risk assessment of an unusual clinical pathology finding—drug-induced green discoloration of the serum (Diaz et al 2016).…”