SETDB1-mediated FosB regulation via ERK2 is associated with an increase in cell invasiveness during anticancer drug treatment of A549 human lung cancer cells

We have determined a functional link to the inverse expression of SETDB1 and FosB following anticancer drug treatment. Doxorubicin treatment caused decreased SETDB1 expression and FosB overexpression both at the mRNA and protein levels. The decreased HMTase activity of SETDB1 coincided with altered occupancy across the promoter region of the FosB gene. SETDB1 overexpression decreased the luciferase reporter activity containing the FosB promoter region, but siSETDB1 increased the luciferase reporter activity, suggesting that SETDB1 directly and negatively regulated FosB expression. In addition, MEK inhibitor (PD98059) blocked the SETDB1 regulation of the FosB promoter activity via ERK2 activation during doxorubicin treatment. A microscopic analysis reveals that FosB expression was observed in living cells in spite of doxorubicin treatment. Ectopic FosB/ΔFosB expression increased the number of colonies and the migration of A549 cells compared to that in control. These results suggest that the ERK2-SETDB1-FosB signaling pathway might have an anti-therapeutic regulatory mechanism that increases the transformation and migration activity of cancer cells during anticancer drug treatment.     

ΔFosB in the nucleus accumbens is critical for reinforcing effects of sexual reward

Sexual behavior in male rats is rewarding and reinforcing. However, little is known about the specific cellular and molecular mechanisms mediating sexual reward or the reinforcing effects of reward on subsequent expression of sexual behavior. This study tests the hypothesis that ΔFosB, the stably expressed truncated form of FosB, plays a critical role in the reinforcement of sexual behavior and experience‐induced facilitation of sexual motivation and performance. Sexual experience was shown to cause ΔFosB accumulation in several limbic brain regions including the nucleus accumbens (NAc), medial prefrontal cortex, ventral tegmental area and caudate putamen but not the medial preoptic nucleus. Next, the induction of c‐Fos, a downstream (repressed) target of ΔFosB, was measured in sexually experienced and naïve animals. The number of mating‐induced c‐Fos‐immunoreactive cells was significantly decreased in sexually experienced animals compared with sexually naïve controls. Finally, ΔFosB levels and its activity in the NAc were manipulated using viral‐mediated gene transfer to study its potential role in mediating sexual experience and experience‐induced facilitation of sexual performance. Animals with ΔFosB overexpression displayed enhanced facilitation of sexual performance with sexual experience relative to controls. In contrast, the expression of ΔJunD, a dominant negative binding partner of ΔFosB, attenuated sexual experience‐induced facilitation of sexual performance and stunted long‐term maintenance of facilitation compared to green fluorescence protein and ΔFosB overexpressing groups. Together, these findings support a critical role for ΔFosB expression in the NAc for the reinforcing effects of sexual behavior and sexual experience‐induced facilitation of sexual performance.     

Repeated 6-Hz Corneal Stimulation Progressively Increases FosB/ΔFosB Levels in the Lateral Amygdala and Induces Seizure Generalization to the Hippocampus

Exposure to repetitive seizures is known to promote convulsions which depend on specific patterns of network activity. We aimed at evaluating the changes in seizure phenotype and neuronal network activation caused by a modified 6-Hz corneal stimulation model of psychomotor seizures. Mice received up to 4 sessions of 6-Hz corneal stimulation with fixed current amplitude of 32 mA and inter-stimulation interval of 72 h. Video-electroencephalography showed that evoked seizures were characterized by a motor component and a non-motor component. Seizures always appeared in frontal cortex, but only at the fourth stimulation they involved the hippocampus, suggesting the establishment of an epileptogenic process. Duration of seizure non-motor component progressively decreased after the second session, whereas convulsive seizures remained unchanged. In addition, a more severe seizure phenotype, consisting of tonic-clonic generalized convulsions, was predominant after the second session. Immunohistochemistry and double immunofluorescence experiments revealed a significant increase in neuronal activity occurring in the lateral amygdala after the fourth session, most likely due to activity of principal cells. These findings indicate a predominant role of amygdala in promoting progressively more severe convulsions as well as the late recruitment of the hippocampus in the seizure spread. We propose that the repeated 6-Hz corneal stimulation model may be used to investigate some mechanisms of epileptogenesis and to test putative antiepileptogenic drugs.     

Constitutive expression of FosB and its short form, FosB/SF, induces malignant cell transformation in rat-1A cells

We have established Rat-1A cell lines constitutively expressing c-Fos and the two products of the fosB gene, FosB and its short form, FosB/SF. The expressed proteins in the different stable transfectants have been characterized by immunofluorescence and immunoprecipitation analysis. Our results demonstrate that constitutive expression of FosB, like the constitutive expression of c-Fos and, to a lesser extent, FosB/SF, results in cells that grow to increased saturation densities and have the ability to grow in an anchorage-independent manner. Most important is the finding that expression of these proteins augments the tumorigenic potential of Rat-1A cells. These results show that both forms of FosB have a stimulatory effect on cell proliferation.     

脑深部电刺激自身给药大鼠伏隔核区△FosB的表达

目的:对吗啡依赖大鼠实施双侧伏隔核脑深部电刺激(NAc-DBS),分析NAc区△FosB的表达变化,为NAc-DBS治疗药物依赖提供分子生物学证据.方法:18只大鼠随机分为三组,包括DBS组(n=6,实施颈静脉插管和电板植入手术,吗啡给药,DBS),Sham组(n=6,实施颈静脉插管和电极植入手术,吗啡给药),Control组(n=6,实施颈静脉插管和电极植入手术,给予生理盐水),观察DBS组大鼠在高频电烈激期(160 Hz,1 h/d,7d)的觅药行为变化,然后进行取脑,切片,免疫组化染色,观察伏隔核区△FosB的表达.结果:成瘾大鼠在高频电刺激期,觅药行为明显减少;免疫组化染色后观察到DBS组大鼠NAc区△FosB的表达相对于Sham和Control组明显减少.结论:双侧NAc-DBS抑制吗啡成瘾大鼠的觅药行为以及NAc区△FosB的表达,证实△FosB可能是慢性成瘾转换机制的关键分子的观点.     

Recurrent hypoglycemia alters hypothalamic expression of the regulatory proteins FosB and synaptophysin

A limiting factor to the clinical management of diabetes is iatrogenic hypoglycemia. With multiple hypoglycemic episodes, the collective neuroendocrine response that restores euglycemia is impaired. In our animal model of recurrent hypoglycemia (RH), neuroendocrine deficits are accompanied by a decrease in medial hypothalamic activation. Here we tested the hypothesis that the medial hypothalamus may exhibit unique changes in the expression of regulatory proteins in response to RH. We report that expression of the immediate early gene FosB is increased in medial hypothalamic nuclei, anterior hypothalamus, and posterior paraventricular nucleus of the thalamus (THPVN) of the thalamus following RH. We identified the hypothalamic PVN, a key autonomic output site, among the regions expressing FosB. To identify the subtype(s) of neuronal populations that express FosB, we screened candidate neuropeptides of the PVN for coexpression using dual fluorescence immunohistochemistry. Among the neuropeptides analyzed [including oxytocin, vasopressin, thyrotropin-releasing hormone, and corticotropin-releasing factor (CRF)], FosB was only identified in CRF-positive neurons. Inhibitory gamma-aminobutyric acid-positive processes appear to impinge on these FosB-expressing neurons. Finally, we observed a significant decrease in the presynaptic marker synaptophysin within the PVN of RH-treated vs. saline-treated rats, suggesting that rapid alterations of synaptic morphology may occur in association with RH. Collectively, these data suggest that RH stress triggers cellular changes that support synaptic plasticity, in specific neuroanatomical sites, which may contribute to the development of hypoglycemia-associated autonomic failure.     

Long-Term Expression of Fos-Related Antigen and Transient Expression of ΔFosB Associated with Seizures in the Rat Hippocampus and Striatum

Abstract: Systemic administration of kainic acid (KA), an analogue of glutamic acid, causes limbic seizures and pathophysiological changes in adult rats that are very similar to human temporal lobe epilepsy. One of the earliest changes in gene expression after treatment with KA is the induction of immediate-early genes. The fos and jun families are frequently studied immediate-early genes that are induced by KA. Several groups, including ours, have recently reported that a 35-kDa Fos-related antigen (FRA) is induced for a protracted time by various stimuli. It has been suggested that this FRA is ΔFosB, which has a molecular mass of ∼35 kDa. The present study characterizes the long-term expression of FRA and ΔFosB after systemic treatment with KA. Immunocytochemistry and western blot analysis using an antibody that cross-reacts with all known FRAs showed that a 35-kDa FRA was induced at high levels in both the hippocampus and striatum for up to 1 month by KA. A semi-quantitative PCR analysis showed that ΔFosB was induced by KA, but its expression lasted for only 6 h. This result was also verified by northern blot analysis. These results suggested that the 35-kDa FRA with long-term elevated levels seen with western blot analysis and immunocytochemistry is a new species of the FRA and not ΔFosB. The long-term expression of FRA in both the hippocampus and striatum may be associated with the pathophysiological changes after KA administration.