Inducible Early Gene Research Articles

Inhibition of Klf10 Attenuates Oxidative Stress-Induced Senescence of Chondrocytes via Modulating Mitophagy.

Osteoarthritis (OA) is the most prevalent degenerative joint disease in the elderly. Accumulation of evidence has suggested that chondrocyte senescence plays a significant role in OA development. Here, we show that Krüppel-like factor 10 (Klf10), also named TGFβ inducible early gene-1 (TIEG1), is involved in the pathology of chondrocyte senescence. Knocking down the Klf10 in chondrocytes attenuated the tert-butyl hydroperoxide (TBHP)-induced senescence, inhibited generation of reactive oxygen species (ROS), and maintained mitochondrial homeostasis by activating mitophagy. These findings suggested that knocking down Klf10 inhibited senescence-related changes in chondrocytes and improved cartilage homeostasis, indicating that Klf10 may be a therapeutic target for protecting cartilage against OA.

Serum and Soleus Metabolomics Signature of Klf10 Knockout Mice to Identify Potential Biomarkers

The transcription factor Krüppel-like factor 10 (Klf10), also known as Tieg1 for TGFβ (Inducible Early Gene-1) is known to control numerous genes in many cell types that are involved in various key biological processes (differentiation, proliferation, apoptosis, inflammation), including cell metabolism and human disease. In skeletal muscle, particularly in the soleus, deletion of the Klf10 gene (Klf10 KO) resulted in ultrastructure fiber disorganization and mitochondrial metabolism deficiencies, characterized by muscular hypertrophy. To determine the metabolic profile related to loss of Klf10 expression, we analyzed blood and soleus tissue using UHPLC-Mass Spectrometry. Metabolomics analyses on both serum and soleus revealed profound differences between wild-type (WT) and KO animals. Klf10 deficient mice exhibited alterations in metabolites associated with energetic metabolism. Additionally, chemical classes of aromatic and amino-acid compounds were disrupted, together with Krebs cycle intermediates, lipids and phospholipids. From variable importance in projection (VIP) analyses, the Warburg effect, citric acid cycle, gluconeogenesis and transfer of acetyl groups into mitochondria appeared to be possible pathways involved in the metabolic alterations observed in Klf10 KO mice. These studies have revealed essential roles for Klf10 in regulating multiple metabolic pathways whose alterations may underlie the observed skeletal muscle defects as well as other diseases.

Krüppel like factor 10 prevents intervertebral disc degeneration via TGF-β signaling pathway both in vitro and in vivo.

BackgroundKrüppel like factor 10 (KLF10), which is also known as TGF-β Inducible Early Gene-1 (TIEG1), plays a crucial role in regulating cell proliferation, cell apoptosis and inflammatory reaction in human carcinoma cells. Moreover, KLF10 knockout in mice leads to severe defects associated with muscle, skeleton and heart etc. However, the function of KLF10 in intervertebral disc degeneration (IVDD) has not been reported yet.MethodsThe relationship between KLF10 and IVDD were investigated in nucleus pulposus (NP) tissues from human and rats. The role of KLF10 in NP cells was explored via loss or gain of function experiments. IVDD rat models were constructed through needle puncture and the effects of KLF10 in IVDD model of rats were investigated via intradiscal injection of KLF10.ResultsWe first found that KLF10 was lowly expressed in degenerative NP tissues and the level of KLF10 showed negative correlation with the disc grades of IVDD patients. Loss or gain of function experiments demonstrated that KLF10 could inhibit apoptosis and enhance migration and proliferation of IL-1β induced NP cells. And KLF10 overexpression reduced extracellular matrix (ECM) degeneration and enhanced ECM synthesis, whereas knockdown of KLF10 resulted in adverse effects. These positive effects of KLF10 could be reversed by the inhibition of TGF-β signaling pathway. In vivo, KLF10 overexpression alleviated IVDD.ConclusionsThis is the first study to reveal that KLF10 was dysregulated in IVDD and overexpressed KLF10 could alleviate IVDD by regulating TGF-β signaling pathway both in vitro and in vivo, which were involved in prohibiting apoptosis, promoting proliferation and migration of NP cells.The translational potential of this article: Overexpression of KLF10 might be an effective therapeutic strategy in the treatment of IVDD.

Sclerostin antibody treatment rescues the osteopenic bone phenotype of TGFβ inducible early gene-1 knockout female mice.

Deletion of TGFβ inducible early gene-1 (TIEG) in mice results in an osteopenic phenotype that exists only in female animals. Molecular analyses on female TIEG knockout (KO) mouse bones identified increased expression of sclerostin, an effect that was confirmed at the protein level in serum. Sclerostin antibody (Scl-Ab) therapy has been shown to elicit bone beneficial effects in multiple animal model systems and human clinical trials. For these reasons, we hypothesized that Scl-Ab therapy would reverse the low bone mass phenotype of female TIEG KO mice. In this study, wildtype (WT) and TIEG KO female mice were randomized to either vehicle control (Veh, n = 12/group) or Scl-Ab therapy (10 mg/kg, 1×/wk, s.c.; n = 12/group) and treated for 6 weeks. Following treatment, bone imaging analyses revealed that Scl-Ab therapy significantly increased cancellous and cortical bone in the femur of both WT and TIEG KO mice. Similar effects also occurred in the vertebra of both WT and TIEG KO animals. Additionally, histomorphometric analyses revealed that Scl-Ab therapy resulted in increased osteoblast perimeter/bone perimeter in both WT and TIEG KO animals, with a concomitant increase in P1NP, a serum marker of bone formation. In contrast, osteoclast perimeter/bone perimeter and CTX-1 serum levels were unaffected by Scl-Ab therapy, irrespective of mouse genotype. Overall, our findings demonstrate that Scl-Ab therapy elicits potent bone-forming effects in both WT and TIEG KO mice and effectively increases bone mass in female TIEG KO mice.

KLF10 as a Tumor Suppressor Gene and Its TGF-β Signaling.

Krüppel-like factor 10 (KLF10), originally named TGF-β (Transforming growth factor beta) inducible early gene 1 (TIEG1), is a DNA-binding transcriptional regulator containing a triple C2H2 zinc finger domain. By binding to Sp1 (specificity protein 1) sites on the DNA and interactions with other regulatory transcription factors, KLF10 encourages and suppresses the expression of multiple genes in many cell types. Many studies have investigated its signaling cascade, but other than the TGF-β/Smad signaling pathway, these are still not clear. KLF10 plays a role in proliferation, differentiation as well as apoptosis, just like other members of the SP (specificity proteins)/KLF (Krüppel-like Factors). Recently, several studies reported that KLF10 KO (Knock out) is associated with defects in cell and organs such as osteopenia, abnormal tendon or cardiac hypertrophy. Since KLF10 was first discovered, several studies have defined its role in cancer as a tumor suppressor. KLF10 demonstrate anti-proliferative effects and induce apoptosis in various carcinoma cells including pancreatic cancer, leukemia, and osteoporosis. Collectively, these data indicate that KLF10 plays a significant role in various biological processes and diseases, but its role in cancer is still unclear. Therefore, this review was conducted to describe and discuss the role and function of KLF10 in diseases, including cancer, with a special emphasis on its signaling with TGF-β.

P.63 - TIEG1 is a novel regulator of muscle mitochondrial biogenesis

TGFβ inducible early gene-1 (TIEG1) is a member of KLF family that regulates gene expression in multiple cell and tissue types. Our first investigation in fast (EDL) and slow (soleus) twitch skeletal muscles provided new insights about the role of TIEG1 in the functional and structural properties. TIEG1 Knockout (KO) muscle showed a hyperplasia and hypertrophy of all fiber types along with an increase in glycolytic fibers and a decrease in oxidative fibers. Then we performed transmission electron microscopy (TEM), histochemical (SDH: succinate dehydrogenase, COX: cytochrome c oxidase, etc) and mitochondrial function assays on soleus and EDL of WT and TIEG1 KO mice. In mutant tissues, TEM revealed muscle disorganization, shorter sarcomeres, disappearance of I bands, decreased mitochondria mass and changes in mitochondrial shape. Histochemical analysis demonstrated a total absence of SDH staining and a decrease of COX in TIEG1 KO soleus muscle. These phenomena were also observed, but to a lesser degree, in TIEG1 KO EDL muscle likely due to its glycolytic profile. Mitochondrial biogenesis downregulation in mutants was confirmed in soleus muscle by decrease in the complex I, COX and citrate synthase activities while only complex I (the main controller step of the electron flux through electron-transport chain) was inhibited in TIEG1 KO EDL muscle. These data demonstrate that TIEG1 deficiency alters mitochondrial properties in a muscle-type specific manner. Furthermore, when TIEG1 KO mice were subjected to treadmill exercise, they tired more quickly than WT controls. These characteristics resemble human diseases associated with exercise intolerance. Therefore, TIEG1 KO mice are a useful model system to study the cellular and molecular mechanisms controlling mitochondrial function and muscle metabolism which pertains to multiple muscle related diseases and disorders.

TIEG1 modulates β-catenin sub-cellular localization and enhances Wnt signaling in bone.

We have previously demonstrated that TGFβ Inducible Early Gene-1 (TIEG1), also known as KLF10, plays important roles in mediating skeletal development and homeostasis in mice. TIEG1 has also been identified in clinical studies as one of a handful of genes whose altered expression levels or allelic variations are associated with decreased bone mass and osteoporosis in humans. Here, we provide evidence for the first time that TIEG1 is involved in regulating the canonical Wnt signaling pathway in bone through multiple mechanisms of action. Decreased Wnt signaling in the absence of TIEG1 expression is shown to be in part due to impaired β-catenin nuclear localization resulting from alterations in the activity of AKT and GSK-3β. We also provide evidence that TIEG1 interacts with, and serves as a transcriptional co-activator for, Lef1 and β-catenin. Changes in Wnt signaling in the setting of altered TIEG1 expression and/or activity may in part explain the observed osteopenic phenotype of TIEG1 KO mice as well as the known links between TIEG1 expression levels/allelic variations and patients with osteoporosis.

Impact of TIEG1 on the structural properties of fast- and slow-twitch skeletal muscle.

Transforming growth factor-beta (TGF-β)-inducible early gene-1 (TIEG1) is a transcription factor that is highly expressed in skeletal muscle. The purpose of this study was to characterize the structural properties of both fast-twitch (EDL) and slow-twitch (soleus) muscles in the hindlimb of TIEG1-deficient (TIEG1-/- ) mice. Ten slow and 10 fast muscles were analyzed from TIEG1-/- and wild-type (WT) mice using MRI texture (MRI-TA) and histological analyses. MRI-TA could discriminate between WT slow and fast muscles. Deletion of the TIEG1 gene led to changes in the texture profile within both muscle types. Specifically, muscle isolated from TIEG1-/- mice displayed hypertrophy, hyperplasia, and a modification of fiber area distribution. We demonstrated that TIEG1 plays an important role in the structural properties of skeletal muscle. This study further implicates important roles for TIEG1 in the development of skeletal muscle and suggests that defects in TIEG1 expression and/or function may be associated with muscle disease. Muscle Nerve 55: 410-416, 2017.

Impact of TIEG1 Deletion on the Passive Mechanical Properties of Fast and Slow Twitch Skeletal Muscles in Female Mice.

As transforming growth factor (TGF)-β inducible early gene-1 is highly expressed in skeletal muscle, the effect of TIEG1 gene deletion on the passive mechanical properties of slow and fast twitch muscle fibers was analyzed. Twenty five muscle fibers were harvested from soleus (Sol) and extensor digitorum longus (EDL) muscles from TIEG1-/- (N = 5) and control (N = 5) mice. Mechanical tests were performed on fibers and the dynamic and static stresses were measured. A viscoelastic Hill model of 3rd order was used to fit the experimental relaxation test data. In parallel, immunohistochemical analyses were performed on three serial transverse sections to detect the myosin isoforms within the slow and fast muscles. The percentage and the mean cross sectional area of each fiber type were calculated. These tests revealed a significant increase in the mechanical stress properties for the TIEG1-/- Sol fibers while a significant decrease appeared for the TIEG1-/- EDL fibers. Hill model tracked the shape of the experimental relaxation curve for both genotypes and both fiber types. Immunohistochemical results showed hypertrophy of all fiber types for TIEG1-/- muscles with an increase in the percentage of glycolytic fibers (IIX, and IIB) and a decrease of oxidative fibers (I, and IIA). This study has provided new insights into the role of TIEG1, known as KLF10, in the functional (SoltypeI: more resistant, EDLtypeIIB: less resistant) and morphological (glycolytic hypertrophy) properties of fast and slow twitch skeletal muscles. Further investigation at the cellular level will better reveal the role of the TIEG1 gene in skeletal muscle tissue.

TGF-beta-induced early gene-1 overexpression promotes oxidative stress protection and actin cytoskeleton rearrangement in human skin fibroblasts

BackgroundTransforming growth factor beta inducible early gene-1 (TIEG-1), a member of the Krüppel-like factor, was identified as a primary response gene for TGF-β. The role of TIEG-1 in skin repair has been mainly addressed in vivo on TIEG-1 null mice model and the mechanism remains unexplored. MethodsWe investigated the modulation of TIEG-1 expression in normal human skin fibroblasts by either down-expressing or overexpressing the gene. We evaluated reactive oxygen species production and the cell viability of treated cells. The effect of TIEG-1 overexpression was monitored by wound healing assay and immunofluorescence staining of actin fibers organization and alpha-smooth muscle actin (α-SMA). Western blots were carried out to identify the level of expression or phosphorylation of key proteins such as cofilin, Rho GTPases, and p38 mitogen-activated protein kinase (p38 MAPK). ResultsTIEG-1 down-regulation had a deleterious effect on the cell viability. It was significantly reduced (65±5%) and exposure to ultraviolet further increased this effect (47±3%). By contrast, cells overexpressing TIEG-1 had a reduced reactive oxygen species production (75%) compared to control and mock-transfected cells. This overexpression also resulted in formation of actin stress fibers and increased α-SMA expression and an enhanced wound healing feature. RhoB GTPase was upregulated and phosphorylation of cofilin and p38 MAPK was observed. ConclusionTIEG-1 overexpression in normal human skin fibroblasts results in improved resistance to oxidative stress, myofibroblast-like conversion that involved RhoB signaling pathway with cofilin and p38 MAPK proteins activation. General significanceThis study enlightens the role of TIEG-1 role in skin biology.

Impact of exogenous stress on TGF‐β inducible early gene 1 in human skin cells

Keywords: oxidative stress; skin ageing; skin photoexposure; TGF-β; TGF-β inducible early gene-1

TIEG1 Inhibits Angiotensin II-induced Cardiomyocyte Hypertrophy by Inhibiting Transcription Factor GATA4.

The transforming growth factor (TGF-β)-inducible early gene (TIEG1), a member of the Sp1/Krüppel-like family of transcription factors, plays an important role in regulating cell growth, differentiation, and apoptosis in many human diseases, including breast cancer, osteoporosis, and atherosclerosis. However, little is known about the role of TIEG1 in the heart. In this study, we investigated the role of TIEG1 in angiotensin II (Ang II)-induced cardiomyocyte hypertrophy and its underlying mechanism. Our results showed that TIEG1 expression was downregulated in Ang II-induced hypertrophic cardiomyocytes. Gene silencing of TIEG1 by RNA interference upregulated cellular surface area and ANF and BNP messenger RNA levels, whereas TIEG1 overexpression inhibited the expression of those genes. Mechanistically, TIEG1 could inhibit the expression and transcriptional activity of transcription factor GATA4 in cardiomyocytes, which was recognized as an important factor mediating cardiac gene transcription. In summary, our data disclose a novel role of TIEG1 as an inhibitor in Ang II-induced hypertrophic cardiomyocytes through GATA4 signal pathway.

Investigation of the roles of interleukin 6 and transforming growth factor β signaling in Th17/Treg imbalance of Hashimoto's thyroiditis

Objective To investigate the role of interleukin(IL)-6/transforming growth factor β(TGF-β)signaling in T helper cell 17(Th17)/regulatory T cells(Treg)imbalance of Hashimoto's thyroiditis(HT). Methods Thirty-eight patients with HT and thirty-two healthy controls were studied. Plasma concentration of IL-6 and TGF-β was measured by enzyme-linked immunosorbent assay. Expression levels of retinoid related orphan receptor γt(RORγt), forkhead box P3(FOXP3), Smad3, Smad4, transforming growth factor β inducible early response gene 1(TIEG1), itchy E3 ubiquitin protein ligase(Itch), suppressor of cytokine signaling 1(SOCS1), and SOCS3 mRNA were determined by realtime PCR. The proportions of CD4+ IL-17A+ T cells(Th17), CD4+ CD25+ FOXP3+ regulatory T cells(Treg)and mean fluorescence intensity for transforming growth factor β receptor type Ⅱ(TGF-βRⅡ)and phosphated signal transducer and activator of transcription 3(pSTAT3)protein in CD4+ T cells were analyzed by flow cytometry. Quantitative methylation specific PCR was used to evaluate methylation status of CpG islands in SOCS1 exon2, and three potential bind sites for signal transducer and activator of transcription 3(STAT3)in 5'-untraslated region(5'-UTR)of SOCS3 in CD4+ T cells. In-vitro culture of CD4+ T cells isolated from healthy donors was used to identify the effects of IL-6/TGF-β signaling on differentiation of Th17/Treg and methylation status of SOCS1 and SOCS3 genes after being stimulated for 72 hours. Results (1)In patients with HT, the proportion of Th17 cells and expression levels of RORγt mRNA were significantly elevated(P 0.05). (4)Compared with blank controls, Treg increased remarkably while Th17 and the ration of Th17/Treg decreased significantly after TGF-β stimulation for 72 h(P 0.05). Conclusions Aberrant IL-6/TGF-β signaling may be one of the important factors that contribute to imbalance of Th17/Treg in HT. (Chin J Endocrinol Metab, 2015, 31: 320-326) Key words: Interleukin 6; STAT3; Hashimoto's thyroiditis; Th17; Regulatory T cells

Effect of TIEG1 on apoptosis and expression of Bcl-2/Bax and Pten in leukemic cell lines.

We examined the effect of transforming growth factor-b inducible early gene-1 (TIEG1) on the apoptosis of leukemic cell lines and expression of B-cell lymphoma 2 (Bcl-2) and phosphatase and tensin homolog (Pten). Four leukemic cell lines (HL-60, U937, Raji, and K562) were treated with 0, 1, 5, 10, and 20 ng/mL TIEG1, respectively. The cell growth inhibitory ratio was assessed using the MTT assay. An inhibitory curve was drawn, and half-maximal inhibitory concentration was calculated. Additionally, 1640 culture medium containing 10 ng/mL TIEG1 was used to culture leukemic cell lines for 0, 6, 12, 24, and 48 h. The apoptosis of each cell line at different time points was detected by flow cytometry. Total RNA was extracted before reverse transcription-polymerase chain reaction. The products of this reaction were analyzed by electrophoresis, and the expression of Bcl-2/Bcl-2-associated X protein (Bax) and Pten were detected. After treatment with TIEG1, proliferation of the 4 leukemic cell lines was inhibited both time- and dose-dependently. During apoptosis induction, the expression of Bcl-2 was decreased and the expressions of Bax and Pten were increased in the 4 leukemic cell lines induced by TIEG1 (P < 0.05). TIEG1 can inhibit the proliferation of leukemic cells and induce their apoptosis in a time- and dose-dependent manner. A close relationship exists between Bcl-2/Bax and Pten expression and cell apoptosis induced by TIEG1.

Effect of Dexamethasone, LPS, or INFγ on the production of TNFα, IL-12, IL-6, IL-10, CXCL8, CXCL10, and CLC3, by bovine macrophages infected in vitro with Mycobacterium avium paratuberculosis.

Effect of Dexamethasone, LPS, or INFγ on the production of TNFα, IL-12, IL-6, IL-10, CXCL8, CXCL10, and CLC3, by bovine macrophages infected in vitro with Mycobacterium avium paratuberculosis.

TGFβ2 regulates hypothalamic Trh expression through the TGFβ inducible early gene-1 (TIEG1) during fetal development

The hypothalamus regulates the homeostasis of the organism by controlling hormone secretion from the pituitary. The molecular mechanisms that regulate the differentiation of the hypothalamic thyrotropin-releasing hormone (TRH) phenotype are poorly understood. We have previously shown that Klf10 or TGFβ inducible early gene-1 (TIEG1) is enriched in fetal hypothalamic TRH neurons. Here, we show that expression of TGFβ isoforms (1-3) and both TGFβ receptors (TβRI and II) occurs in the hypothalamus concomitantly with the establishment of TRH neurons during late embryonic development. TGFβ2 induces Trh expression via a TIEG1 dependent mechanism. TIEG1 regulates Trh expression through an evolutionary conserved GC rich sequence on the Trh promoter. Finally, in mice deficient in TIEG1, Trh expression is lower than in wild type animals at embryonic day 17. These results indicate that TGFβ signaling, through the upregulation of TIEG1, plays an important role in the establishment of Trh expression in the embryonic hypothalamus.

Progression of diet induced nonalcoholic steatohepatitis is accompanied by increased expression of Kruppel-like-factor 10 in mice.

BackgroundKruppel-like-factor (KLF) 10 is identified as transforming growth factor (TGF) β inducible early gene and is reported to suppress lipogenic genes. Although previous studies report that TGFβ plays an important role in progression of nonalcoholic steatohepatitis (NASH) by regulating liver fibrosis, the association of KLF10 and NASH has never been explored. Thus we evaluated expressions and changes of KLF10 in diet induced NASH and in NASH which was alleviated by ursodeoxycholic acid (UDCA). We also assessed KLF10 in quiescent and activated hepatic stellate cells (HSCs).MethodsC57BL/6 mice were given high fat, sucrose diet (HFSD) at least for 12 weeks up to 48 weeks and sacrificed at 12, 24 and 48 weeks thereafter. In other groups, either standard diet (SD) or HFSD was given for 24 weeks at which point mice fed with HFSD were divided into two groups, and were given either UDCA in combination with HFSD or vehicle with HFSD. Mice under SD were given vehicle. HSCs were isolated from C57BL/6 mice in order to evaluated KLF10 expression in activated HSCs.ResultsThe mice were found to acquire liver steatosis and inflammation starting from week 12 of HFSD feeding, although significant liver fibrosis was noticed by week 24. Increased TGFβ and collagen α1(I) (Col1α(I)) expression was also apparent from week 24. However, expression of KLF10 mRNA started to increase from week 12, earlier than TGFβ gene. Up-regulation of KLF10 was accompanied by suppressed carbohydrate response element-binding protein (ChREBP) that is known to be protective against insulin resistance. The mice fed with HFSD and UDCA had decreased Colα(I) mRNA that was coincided with reduced TGFβ and KLF10 expression. Expression of ChREBP was also recovered by UDCA administration. Enhanced KLF10 was noticed in activated HSCs when quiescent cell showed minimal expression.ConclusionsOur study demonstrated that KLF10 expression was significantly increased in diet induced NASH and collagen producing activated HSCs. We also noticed that this up-regulation of KLF10 was accompanied by increased TGFβ signaling genes and suppressed ChREBP expression. These observations suggest possible association of KLF10 and NASH progression.

TGFβ Inducible Early Gene-1 Plays an Important Role in Mediating Estrogen Signaling in the Skeleton

TGFβ Inducible Early Gene-1 (TIEG1) knockout (KO) mice display a sex-specific osteopenic phenotype characterized by low bone mineral density, bone mineral content, and overall loss of bone strength in female mice. We, therefore, speculated that loss of TIEG1 expression would impair the actions of estrogen on bone in female mice. To test this hypothesis, we employed an ovariectomy (OVX) and estrogen replacement model system to comprehensively analyze the role of TIEG1 in mediating estrogen signaling in bone at the tissue, cell, and biochemical level. Dual-energy X-ray absorptiometry (DXA), peripheral quantitative computed tomography (pQCT), and micro-CT analyses revealed that loss of TIEG1 expression diminished the effects of estrogen throughout the skeleton and within multiple bone compartments. Estrogen exposure also led to reductions in bone formation rates and mineralizing perimeter in wild-type mice with little to no effects on these parameters in TIEG1 KO mice. Osteoclast perimeter per bone perimeter and resorptive activity as determined by serum levels of CTX-1 were differentially regulated after estrogen treatment in TIEG1 KO mice compared with wild-type littermates. No significant differences were detected in serum levels of P1NP between wild-type and TIEG1 KO mice. Taken together, these data implicate an important role for TIEG1 in mediating estrogen signaling throughout the mouse skeleton and suggest that defects in this pathway are likely to contribute to the sex-specific osteopenic phenotype observed in female TIEG1 KO mice.

Effects of withdrawal from repeated amphetamine exposure in peri-puberty on neuroplasticity-related genes in mice

Although extensive evidence demonstrates that repeated administration of amphetamine (AMPH) induces behavioral and neurochemical sensitization, the influence of the developmental timing of AMPH administration is unknown. This is an important issue to address because it could help clarify the influence of early drug exposure on neuronal plasticity and the involvement of dopaminergic sensitization in the etiopathology of neuropsychiatric disorders.Thus, we decided to investigate the molecular alterations induced by the administration of AMPH during adolescence, when repeated exposure to the psychostimulant may interfere with developmental neuroplasticity. We investigated the expression of the neurotrophin brain-derived neurotrophic factor (BDNF) and of two inducible-early genes (arc and cfos) that bridge neuronal activity with long-lasting functional alterations. We found that peri-pubertal treatment with AMPH induces long-lasting changes in the expression of bdnf and of activity-regulated genes in the hippocampus and in the prefrontal/frontal cortex, and leads to alterations of their short-term modulation in response to a subsequent acute AMPH challenge. These data suggest that AMPH exposure in peri-puberty may negatively affect the maturation of brain structures, such as the prefrontal cortex, which facilitate the development of dopamine sensitization and may contribute to dopamine-dependent behavioral dysfunctions and molecular alterations in adulthood.

Gene expression profiling as functional readout of rodent models for psychiatric disorders

Gene expression changes are well documented in depression and schizophrenia and might contribute to the pathologic phenotype associated with these disorders. On this basis, the investigation of transcriptional changes is extensively employed at the preclinical level in order to identify and characterize genes causally related to a pathologic condition. Key information can be achieved with respect to functional alterations in selected brain structures and to anatomical networks and systems that are altered in mental disorders. Furthermore, such analyses are used to investigate the impact of pharmacologic intervention in mechanisms that are significantly impaired in the disease or that might contribute to their therapeutic effectiveness. In this review, we will primarily discuss target approach analyses as a valuable instrument to address key questions in experimental work. We will focus on a few paradigmatic examples, such as the modulation of the neurotrophin brain-derived neurotrophic factor and the regulation of inducible early genes and the functional implication of such analyses. We will also briefly discuss genome-wide approaches that aim at identifying, in an unbiased manner, all the genes differentially affected under a given experimental setting.