Biomedical subjects

Andrew D Kraft

Publications and source records attributed to Andrew D Kraft.

4 recordsLinked to original sources

PubMed2006

Neuronal sensitivity to kainic acid is dependent on the Nrf2-mediated actions of the antioxidant response element.

The transcription factor, nuclear factor E2 (erythroid-derived 2)-related factor 2 (Nrf2), is essential for the induction of a battery of phase II detoxification genes through the antioxidant response element (ARE) that lies in their promoter region. Genes driven by the ARE are up-regulated in response to various stressors of the cellular environment. These genetic changes to the cellular reducing potential may reflect an intrinsic damage response to harmful toxicants. Analysis of transgenic reporter mice following kainate injection revealed selective ARE activation within the damaged hippocampus. Further, 2 x 2 microarray analyses comparing Nrf2 knockout versus wild-type hippocampi unmasked gene changes associated with ion movement and myelination, in addition to alterations to detoxification-related genes. Nrf2 knockout mice were more sensitive to kainate toxicity, as evidenced by elevated seizure severity, seizure duration, hippocampal neuron damage and mortality. Knockout mice injected with kainate displayed altered glial fibrillary acidic protein immunoreactivity and increased microglial infiltration. The wild-type to knockout damage differential was not dependent on the peripheral metabolism of the excitotoxin, was well correlated with increased seizure susceptibility, and was therefore not necessarily the neuroprotective effects of Nrf2. These results combine to support a role for Nrf2 in the neural cell defense response of the adult brain.

Animals↗

PubMed2005

Nrf2, a multi-organ protector?

NF-E2-related factor 2 (Nrf2) is a basic leucine zipper transcription factor that binds to the promoter sequence "antioxidant responsive element (ARE)" leading to coordinated up-regulation of ARE-driven detoxification and antioxidant genes. Since the expression of a wide array of antioxidant and detoxification genes are positively regulated by the ARE sequence, Nrf2 may serve as a master regulator of the ARE-driven cellular defense system against oxidative stress. In support of this, numerous studies have shown that Nrf2 protects many cell types and organ systems from a broad spectrum of toxic insults and disease pathogenesis. This Nrf2-conferred, multi-organ protection phenomenon raises an interesting question about how a single protein can protect many different organs from various toxic insults. A possible molecular mechanism explaining this phenomenon is that Nrf2 protects many different cell types by coordinately up-regulating classic ARE-driven genes as well as cell type-specific target genes that are required for the defense system of each cell type in its unique environment. This hypothesis is supported by microarray data indicating the protective role of Nrf2 is conveyed through both known ARE-driven genes and novel cell type-specific genes. The widespread nature of Nrf2 may have an important therapeutic potential, allowing prevention of carcinogenesis and neurodegenerative diseases.

Animals↗

PubMed2004

Nuclear factor E2-related factor 2-dependent antioxidant response element activation by tert-butylhydroquinone and sulforaphane occurring preferentially in astrocytes conditions neurons against oxidative insult.

Binding of the transcription factor nuclear factor E2-related factor 2 (Nrf2) to the antioxidant response element (ARE) in neural cells results in the induction of a battery of genes that can coordinate a protective response against a variety of oxidative stressors. In this study, tert-butylhydroquinone (tBHQ) and sulforaphane were used as activators of this pathway. Consistent with previous studies, treatment of primary cortical cultures from ARE reporter mice revealed selective promoter activity in astrocytes. This activation protected neurons from hydrogen peroxide and nonexcitotoxic glutamate toxicity. tBHQ treatment of cultures from Nrf2 knock-out animals resulted in neither ARE activation nor neuroprotection. By reintroducing Nrf2 via infection with a replication-deficient adenovirus (ad), both the genetic response and neuroprotection were rescued. Conversely, infection with adenovirus encoding dominant-negative (DN) Nrf2 (ad-DN-Nrf2) or pretreatment with the selective phosphatidylinositol-3 kinase inhibitor LY294002 inhibited the tBHQ-mediated promoter response and corresponding neuroprotection. Interestingly, the adenoviral infection showed a high selectivity for astrocytes over neurons. In an attempt to reveal some of the cell type-specific changes resulting from ARE activation, cultures were infected with adenovirus encoding green fluorescent protein (GFP) (ad-GFP) or ad-DN-Nrf2 (containing GFP) before tBHQ treatment. A glia-enriched population of GFP-infected cells was then isolated from a population of uninfected neurons using cell-sorting technology. Microarray analysis was used to evaluate potential glial versus neuron-specific contributions to the neuroprotective effects of ARE activation and Nrf2 dependence. Strikingly, the change in neuronal gene expression after tBHQ treatment was dependent on Nrf2 activity in the astrocytes. This suggests that Nrf2-dependent genetic changes alter neuron-glia interactions resulting in neuroprotection.

Adenoviridae↗

PubMed2003

Coordinate regulation of glutathione biosynthesis and release by Nrf2-expressing glia potently protects neurons from oxidative stress.

Astrocytes have a higher antioxidant potential in comparison to neurons. Pathways associated with this selective advantage include the transcriptional regulation of antioxidant enzymes via the action of the Cap'n'Collar transcription factor Nrf2 at the antioxidant response element (ARE). Here we show that Nrf2 overexpression can reengineer neurons to express this glial pathway and enhance antioxidant gene expression. However, Nrf2-mediated protection from oxidative stress is conferred primarily by glia in mixed cultures. The antioxidant properties of Nrf2-overexpressing glia are more pronounced than those of neurons, and a relatively small number of these glia (< 1% of total cell number added) could protect fully cocultured naive neurons from oxidative glutamate toxicity associated with glutathione (GSH) depletion. Microarray and biochemical analyses indicate a coordinated upregulation of enzymes involved in GSH biosynthesis (xCT cystine antiporter, gamma-glutamylcysteine synthetase, and GSH synthase), use (glutathione S-transferase and glutathione reductase), and export (multidrug resistance protein 1) with Nrf2 overexpression, leading to an increase in both media and intracellular GSH. Selective inhibition of glial GSH synthesis and the supplementation of media GSH indicated that an Nrf2-dependent increase in glial GSH synthesis was both necessary and sufficient for the protection of neurons, respectively. Neuroprotection was not limited to overexpression of Nrf2, because activation of endogenous glial Nrf2 by the small molecule ARE inducer, tert-butylhydroquinone, also protected against oxidative glutamate toxicity.

Adenoviridae↗