Neonatal ventral hippocampus lesion leads to reductions in nerve growth factor inducible-B mRNA in the prefrontal cortex and increased amphetamine response in the nucleus accumbens and dorsal striatum

Converging evidence in schizophrenia suggests prefrontal cortical neuronal deficits that correlate with exaggerated subcortical dopamine (DA) functions: Excitotoxic lesion of the ventral hippocampus (VH) in neonatal rats is widely considered a putative animal model of schizophrenia as they lead to characteristic post-pubertal emergence of behavioral and cognitive abnormalities suggesting a developmental change in the neural circuits comprising the prefrontal cortex (PFC) and subcortical DA. Nerve growth factor inducible-B (NGFI-B, also known as Nur77), an orphan nuclear receptor and transcriptional regulator, is constitutively expressed in the target structures of DA pathways. It acts as an immediate early gene with rapid modulation of its mRNA expression by stress, DA and antipsychotic drugs. The present study assessed the effects of neonatal VH (nVH) lesion and amphetamine treatment on the expression of NGFI-B mRNA in pre- and post-pubertal rats. Sprague-Dawley rat pups received bilateral injection of ibotenic acid or phosphate buffered saline in VH at postnatal (PD) 7. At PD35 and PD56, groups of sham and lesioned animals were administered with D-amphetamine (1.5 mg/kg) or saline and killed 20 min later. In situ hybridization analyses showed that the basal level of NGFI-B mRNA in saline-treated lesioned rats was significantly reduced in the medial PFC (mPFC) and cingulate cortex (CC) only at post-pubertal (PD56) age. No significant difference in NGFI-B mRNA levels was seen in the dorsal striatum or nucleus accumbens (NAcc). Amphetamine treatment increased the expression of NGFI-B mRNA in the mPFC, CC, striatum and NAcc in both control and lesioned animals of both ages. Interestingly, however, striatal and NAcc regions of lesioned rats showed a significantly greater effect of amphetamine at PD56. The data suggest that nVH lesions lead to delayed changes in PFC gene expression along with functional DAergic hyperactivity in subcortical regions.

Impact of antipsychotic drug administration on the expression of nuclear receptors in the neocortex and striatum of the rat brain

We have recently shown that the expression of the nerve growth factor-inducible gene B (NGFI-B, or Nur77), a transcription factor belonging to the large ligand-activated nuclear receptor family, is modulated by antipsychotic drugs in the rat forebrain. In the present work, we have investigated the impact of antipsychotic drugs on a series of transcription factors also belonging to the nuclear receptor family. The receptors investigated include retinoid X receptor (RXR), thyroid hormone receptor (TR), retinoic acid receptor (RAR), RAR-related orphan receptor (RZR) and Rev-erb receptor isoforms in addition to the NGFI-B transcript. We have used in situ hybridization to monitor their mRNA levels after acute and chronic antipsychotic drug administration. RZRbeta and NGFI-B mRNA levels are down-regulated after chronic haloperidol or clozapine treatment in the primary somatosensory cortex. The TRbeta1 isoform mainly expressed in the cingulate cortex is modulated only after chronic clozapine treatment, whereas TRalpha isoform mRNAs are modulated by both antipsychotics in the cingulate cortex and nucleus accumbens shell; two brain areas associated with limbic functions. The RXRgamma1 isoform, mostly expressed in the dorsolateral portion of the striatum is modestly affected by antipsychotics. Modulation of the expression of transcription factors belonging to the ligand-activated nuclear receptor family by antipsychotics represents an additional molecular event in the mechanism of action of these drugs. We suggest that modification of the pattern of transcription factor expression may play a role in long-term cellular responses to these drugs.

Expression of cathepsin D, stromelysin-3, and urokinase by reactive stromal cells on breast carcinoma prognosis

BACKGROUND

Current literature suggests that several proteases act in a cascade to mediate remodeling of the extracellular matrix and favor cancer progression. Others and the authors of this study recently identified cathepsin D, stromelysin-3, and urokinase plasminogen activator (uPA) expression by reactive stromal cells as significant factors of poor prognosis in breast carcinoma. The authors evaluated the joint effect of protease expression on cancer aggressiveness.

METHODS

Protease expression was analyzed by immunohistochemistry (cathepsin D) and in situ hybridization (stromelysin-3 and uPA) on formalin fixed paraffin embedded specimens from 557 breast carcinomas without distant metastasis at diagnosis and with an average of 10 years of follow-up.

RESULTS

Of the 557 breast carcinomas, 80 (14.3%) expressed all 3 proteases, and 134 (24%) expressed none of them. An adjusted Cox model revealed significantly worse distant metastasis free survival (DMFS) with expression of all three proteases (P < 0.0001). The DMFS of patients whose tumor lacked at least one of the three proteases was similar to that of patients without any protease expression, irrespective of the type or number of proteases missing.

CONCLUSIONS

This study suggests that proteases expressed by reactive stromal cells are interdependent and that a breach in the protease pathway may impair breast carcinoma progression.

Isolation and characterization of the monkey UDP-glucuronosyltransferase cDNA clone monUGT1A01 active on bilirubin and estrogens

Although enzymes that catalyze the formation of steroids are well known, less information is available about the enzymes involved in the metabolism of these hormones. Steroid glucuronidation, by UDP-glucuronosyltransferase enzymes, is one mechanism by which steroid hormones can be metabolized and eliminated from a tissue. Previous results suggest that the monkey represents the most appropriate animal model for studying the physiologic relevance of steroid glucuronidating enzymes. The monkey UGT1A01 cDNA clone was isolated by RT-PCR amplification of the liver RNA. The cDNA contains an open reading frame of 1599 bp encoding a protein of 533 residues. The primary structure of monkey UGT1A01 is 95% identical to human UGT1A1. To compare monkey and human UGT1A1 enzymes, both cDNA clones were transfected into HK293 cells and stable cell lines expressing each UGT1A1 protein were established. Western blot analysis of the monUGT1A01-HK293 and hUGT1A1-HK293 cell lines using a anti-UGT1A polyclonal antibody (RC-71) revealed expression of exogenous 55 kDa UGT1 proteins. The transferase activities of monkey and human UGT1A1 proteins were tested with over 60 compounds and were demonstrated to be active on the same compounds. For endogenous compounds only bilirubin and C18 steroids were glucuronidated by these enzymes. Using microsome preparation (from HK293 cell expressing monkey UGT1A01), the apparent K(m) values were 13, 5 and 6 microM for the conjugation of estradiol, 2-hydroxyestradiol and 2-hydroxyestrone, respectively, and were very similar to the values obtained with human UGT1A1. Specific RT-PCR analysis demonstrated the expression of monkey and human UGT1A1 transcripts in several tissues including liver, kidney, intestine, prostate, testis and ovary suggesting a contribution of this isoenzyme to estrogen metabolism in the cynomolgus monkey as in human.

Contrasting patterns and cellular specificity of transcriptional regulation of the nuclear receptor nerve growth factor-inducible B by haloperidol and clozapine in the rat forebrain

This study was designed to investigate the possible involvement of members of the nuclear receptor family of transcription factors in the effects of antipsychotic drugs used in the treatment of schizophrenia. We have identified, using RT-PCR screening, an important modulation of nerve growth factor-inducible B (NGFI-B) mRNA levels by typical and atypical neuroleptics in the rat forebrain. NGFI-B, a member of the nuclear receptor family, can be observed in target structures of dopaminergic pathways. Using in situ hybridization, we also demonstrate that typical and atypical antipsychotics induced contrasting patterns of expression of NGFI-B after both acute and chronic administration. An acute treatment with clozapine or haloperidol induces high NGFI-B mRNA levels in the prefrontal and cingulate cortices and in the nucleus accumbens shell. However, haloperidol, but not clozapine, dramatically increases NGFI-B expression in the dorsolateral striatum. In contrast, chronic treatment with clozapine reduces NGFI-B expression below basal levels in the rat forebrain, whereas haloperidol still induces high NGFI-B mRNA levels in the dorsolateral striatum. Finally, using a double in situ hybridization technique, we show that acute administration of both neuroleptics increases NGFI-B expression in neurotensin-containing neurons in the nucleus accumbens shell, whereas the effects of haloperidol in the dorsolateral striatum are mainly observed in enkephalin-containing neurons. These results are the first demonstration that members of the nuclear receptor family of transcription factors could play an important role in the effects of antipsychotic drugs.

Distribution of uridine diphosphate-glucuronosyltransferase (UGT) expression and activity in cynomolgus monkey tissues: evidence for differential expression of steroid-conjugating UGT enzymes in steroid target tissues

Based on the similarity of pathways and enzymes involved in steroid metabolism, simians represent a relevant animal model to study steroid elimination by glucuronidation. In this study the tissue distribution of UDP-glucuronosyltransferase (UGT) transcripts, proteins, and enzymatic activities were examined in 24 different cynomolgus monkey tissues. RT-PCR and Western blot analysis on total RNA and microsomal proteins demonstrated the presence of UGT1A and UGT2B transcripts and proteins in a wide range of tissues including steroid target tissues. Glucuronidation activity on eugenol, 5alpha-androstane-3alpha,17beta-diol, androsterone, and 4-hydroxyestradiol was measured using tissue homogenates and radiolabeled [14C]UDP-glucuronic acid. All tissues contained conjugation activity on these substrates, but glucuronidation rates were significantly lower in steroid target tissues than in liver, kidney, or gut. However, the ratio of steroid glucuronidation vs. eugenol glucuronidation was higher in steroid target tissues, suggesting a differential expression of steroid-conjugating enzymes in these tissues. Taken together, these results clearly demonstrate the presence of steroid glucuronidation enzymes in extrahepatic steroid target tissues and support the hypothesis that steroid glucuronidation is an important intracrine pathway involved in termination of steroid signaling.

The monkey and human uridine diphosphate-glucuronosyltransferase UGT1A9, expressed in steroid target tissues, are estrogen-conjugating enzymes

Considering the physiologic importance of the steroid response, which is regulated in part by steroid levels in a given tissue, relatively little is known about steroid glucuronidation, which is widely accepted as a major pathway involved in the catabolism and elimination of steroid hormones from the human body. In a previous study, it was ascertained that the monkey may be the most appropriate model in which to examine the role of steroid glucuronidation. Northern blot analysis of simian RNA, hybridized with human UGT complementary DNA (cDNA) probes demonstrate the similarity of the transcripts. The simian UGT1A09 cDNA isolated from a liver library is 2396 bp and contains an open reading frame encoding 530 amino acids. The predicted primary structure is most homologous to the human UGT1A9 (hUGT1A9) enzyme, which share 93% identity. Stable transfection of the monkey UGT1A09 (monUGT1A09) cDNA into HK293 cells, expresses a microsomal protein with an apparent molecular mass of 55 kDa. Of the more than 30 endogenous substrates tested, both proteins show the highest activity on 4-hydroxyestradiol and 4-hydroxyestrone, followed by 2-hydroxyestradiol and estradiol. RT-PCR analysis demonstrate that UGT1A9 transcript is expressed in several tissues, which include the prostate, testis, breast, ovary, and skin of the monkey and humans. The expression of UGT1A9 in extrahepatic estrogen-responsive tissues, and its high activity on estrogens is consistent with this enzyme having a role in estrogen metabolism.

Structural requirements and mechanism of the pressor activity of Leu-Val-Val-hemorphin-7, a fragment of hemoglobin beta-chain in rats

A rat blood pressure assay was used to perform a structure-activity relationship study (SAR) of Leu-Val-Val-hemorphin-7 (LVV-H7), a fragment of hemoglobin (Hb) beta-chain, elucidate the mechanisms of its cardiovascular effects, and test its potential involvement in the pressor activity of diaspirin crosslinked Hb (DCLHb), a recently developed Hb-based oxygen carrier. The SAR study revealed that the C-terminal-Arg-Phe-amino acid sequence of LVV-H7 contained the main determinants of the pressor activity of this peptide. Drug interaction studies using various inhibitory drugs (e.g., phentolamine, clonidine, etc.) and LVV-H7 showed that the pressor effect and tachycardia elicited by LVV-H7 involved the activation of the sympathetic nervous system (SNS). Additional studies using phenytoin (sodium channel blocker), [Tic7]H7(5-7)-NH2 (putative antagonist of receptors for LVV-H7) and H7(5-7)-NH2, an amidated C-terminal fragment of LVV-H7, suggested that LVV-H7 activated the SNS by interacting with specific receptors functionally coupled with phenytoin-sensitive sodium channels. The pressor effect and tachycardia caused by LVV-H7 were potentiated by captopril, suggesting that the angiotensin converting enzyme may contribute to the inactivation of LVV-H7 in rats. The pressor activity of DCLHb, in contrast to that elicited by LVV-H7, was not affected by animal pretreatment with LVV-H7 fragments shown to inhibit the pressor effect of LVV-H7. We conclude that: 1) LVV-H7 is unlikely to mediate the pressor activity of DCLHb in rats; 2) the pressor and tachycardic activities of LVV-H7 are mediated by the SNS; 3) the C-terminal-Arg-Phe-amino acid sequence of LVV-H7 contains the chemical groups responsible for the pressor effect of this peptide in rats; 4) LVV-H7 and FMRF amide-related peptides may share the same mechanism of pressor activity in rats.

Secretion of endogenous and exogenous proteins from polarized MDCK cell monolayers

Confluent monolayers of MDCK (Madin-Darby canine kidney) cells provide a widely used system to study the biogenesis of epithelial cell polarity. We now report that these cells are also capable of the vectorial constitutive secretion of a major endogenous product, a glycoprotein of 81 kDa, which is released into the medium from the apical surface within 30 min of its synthesis. This release represents a bona fide exocytotic secretory process and is not the result of proteolytic cleavage of a plasma membrane-associated precursor since, in cells treated with chloroquine, a protein indistinguishable from the mature secretory product accumulated intracellularly. In contrast to the vectorial secretion of the endogenous product, a variety of exogenous exocrine and endocrine proteins synthesized in MDCK cells transfected with the corresponding genes were secreted from both the apical and basolateral surfaces. These included proteins such as rat growth hormone, chicken oviduct lysozyme, bovine gastric prochymosin, and rat salivary gland alpha 2u-globulin, which in their cells of origin are secreted via a regulated pathway, as well as the liver form of the alpha 2u-globulin and the immunoglobulin kappa chain, which are normally released constitutively. These results demonstrate the existence of secretory pathways that lead to both surfaces of MDCK cells and are accessible to the foreign secretory products. They are consistent with the operation of a sorting mechanism in which the polarized secretion of the endogenous product is effected through the recognition of signals that prevent its random distribution within the fluid phase in the cellular endomembrane system.