Attenuated Expression of Episodic Growth Hormone-Induced CYP2C11 in Female Rats Associated with Suboptimal Activation of the Jak2/Stat5B and Other Modulating Signaling Pathways

Abstract

ABSTRACT:Inherent sex differences in various parameters of growth, musculoskeletal function, metabolism, and cytochrome P450 (P450)-dependent drug metabolism have been reported in rats and humans administered typical intermittent/episodic growth hormone (GH) replacement therapy. Having infused and monitored the identical physiologic masculine (episodic) growth hormone profile to both hypophysectomized male and female rats, we observed that induction levels of hepatic CYP2C11 were 35 to 40% lower in females. Associated with the reduced expression of the P450 isoform in the episodic GH-treated females were dramatically lower activation levels of Janus kinase (Jak2), signal transducers and activators of transcription (Stat5A and 5B) as well as 50% less binding of Stat5B to the CYP2C11 promoter. Because the Jak2/ Stat5B signaling pathway mediates the effects of the masculine GH profile on its target cells, we conclude that the lower induction level of CYP2C11 in females exposed to the masculine GH profile is probably due, at least in part, to the suboptimum activation of the Jak2/Stat5B pathway. In addition to the reduced activation of the Jak2/Stat5B pathway, we observed lower activational levels of mitogen-activated protein kinase (p44/p42) and, indirectly, nuclear factor-B in the episodic GH-treated females that may be involved in attenuating the activity of the Jak2/Stat5B pathway diminishing CYP2C11 expression levels.

Exploring endocrine GH pattern in mice using rank plot analysis and random blood samples

“…Peripheral GHR and GHR-dependent Jak2/Stat5 signaling pathways are activated within minutes after GH peaks in the circulation (Tannenbaum et al 2001, Verma et al 2005, Dhir et al 2007. We showed previously that in wild-type mice, Jak2 activation in the liver is completed 2 min after GH injection into the portal vein (Kappeler et al 2008).…”

Growth hormone: a newly identified developmental organizer

“…That is, the masculine “episodic” GH profile induces expression of the male-specific CYP isoforms, whereas the feminine “continuous” GH profile induces expression of the female-specific CYP isoforms. In this regard, we previously reported that adult male rats and men cannot be induced (regardless of GH treatment) to express the normal female profile of hepatic CYPs (Dhir et al, 2006; Pampori and Shapiro, 1999; Thangavel et al, 2004; Thangavel and Shapiro, 2008; Thangavel et al, 2011) nor can adult female rats or women be induced to fully express the masculine CYP profile (Dhir et al, 2006; Thangavel et al, 2006; Thangavel and Shapiro, 2007; Dhir et al, 2007). The response of each of the dozen or so sex-dependent rat CYP isoforms to GH regulation has been described (Thangavel and Shapiro, 2008; Banerjee et al, 2014; Das et al, 2013a).…”

Inherent Sexually Dimorphic Expression of Hepatic CYP2C12 Correlated with Repressed Activation of Growth Hormone-Regulated Signal Transduction in Male Rats

“…With the use of a standard protocol (Dhir et al, 2007;Thangavel and Shapiro, 2007) for those proteins identified by immunoblotting (IB) alone, 50 to 75 g of whole cell extract was resolved on 10% SDS-polyacrylamide gel electrophoresis columns and transferred electrophoretically onto a Immuno-Blot polyvinylidene difluoride membrane (BioRad) with a Bio-Rad transfer unit. The membranes were then blocked and incubated with antibodies against phospho-Erk1 and -Erk2 (phospho-p42/p44 MAPK) (Cell Signaling Technology Inc., Beverly, MA), HNF-4␣, HNF-6 (Santa Cruz Biotechnology, Inc., Santa Cruz, CA), rat growth hormone receptor [full-length (GHR L ) and short-form (GHR S ); a gift from Dr. G. Peter Frick, University of Massachusetts Medical School, Worcester, MA), or CYP2C12 (a gift from Dr. Marika Rönnholm, Huddinge University Hospital, Huddinge, Sweden).…”

“…1 The suboptimal response of hepatic P450s in females to the masculine GH profile can be explained by the muted response of the signal transduction pathways activated by the episodic GH profile. That is, activation of the Jak2/ Stat5B signaling pathway normally mediating the cellular action (e.g., CYP2C11 induction) of episodic GH is highly suppressed in females (Dhir et al, 2007) as a likely result of an inherent overexpression of Cis, a member of the suppressors of the cytokine signaling family that normally down-regulate the Jak2/Stat5B pathway . In the present study, we have investigated the molecular basis for both the normal and suboptimum induction of femalespecific CYP2C12 in female and male hepatocytes, respectively, exposed to the continuous GH regime.…”