Distinct Roles of Nrf1 and Nrf2 in Monitoring the Reductive Stress Response to Dithiothreitol (DTT).

Transcription factor Nrf2 (nuclear factor, erythroid 2-like 2, encoded by Nfe2l2) has been accepted as a key player in redox regulatory responses to oxidative or reductive stresses. However, relatively little is known about the potential role of Nrf1 (nuclear factor, erythroid 2-like 1, encoded by Nfe2l1) in the redox responses, particularly to reductive stress, although this 'fossil-like' factor is indispensable for cell homeostasis and organ integrity during the life process. Herein, we examine distinct roles of Nrf1 and Nrf2 in monitoring the defense response to 1,4-dithiothreitol (DTT, serving as a reductive stressor), concomitantly with unfolded protein response being induced by this chemical (also defined as an endoplasmic reticulum stressor). The results revealed that intracellular reactive oxygen species (ROS) were modestly increased in DTT-treated wild-type (WT) and Nrf1α-/- cell lines, but almost unaltered in Nrf2-/-ΔTA or caNrf2ΔN cell lines (with a genetic loss of transactivation or N-terminal Keap1-binding domains, respectively). This chemical treatment also enabled the rate of oxidized to reduced glutathione (i.e., GSSG to GSH) to be amplified in WT and Nrf2-/-ΔTA cells, but diminished in Nrf1α-/- cells, along with no changes in caNrf2ΔN cells. Consequently, Nrf1α-/-, but not Nrf2-/-ΔTA or caNrf2ΔN, cell viability was reinforced by DTT against its cytotoxicity, as accompanied by decreased apoptosis. Further experiments unraveled that Nrf1 and Nrf2 differentially, and also synergistically, regulated DTT-inducible expression of critical genes for defending against redox stress and endoplasmic reticulum stress. In addition, we also identified that Cys342 and Cys640 of Nrf1 (as redox-sensing sites within its N-glycodomain and DNA-binding domain, respectively) are required for its protein stability and transcription activity.

Nrf1D Is the First Candidate Secretory Transcription Factor in the Blood Plasma, Its Precursor Existing as a Unique Redox-Sensitive Transmembrane CNC-bZIP Protein in Hemopoietic and Somatic Tissues.

Among multiple distinct isoforms, Nrf1D is synthesized from a de novo translation of an alternatively-spliced transcript of Nrf1 mRNA, as accompanied by a naturally-occurring deletion of its stop codon-flanking 1466 nucleotides. This molecular event leads to the generation of a reading frameshift mutation, which results in a constitutive substitution of the intact Nrf1's C-terminal 72 amino acids (aa, covering the second half of the leucine zipper motif to C-terminal Neh3L domain) by an additional extended 80-aa stretch to generate a unique variant Nrf1D. The C-terminal extra 80-aa region of Nrf1D was herein identified to be folded into a redox-sensitive transmembrane domain, enabling it to be tightly integrated within the endoplasmic reticulum (ER) membranes. Notably, the salient feature of Nrf1D enables it to be distinguishable from prototypic Nrf1, such that Nrf1D is endowed with a lesser ability than wild-type Nrf1 to mediate target gene expression. Further evidence has also been presented revealing that both mRNA and protein levels of Nrf1D, together with other isoforms similar to those of Nrf1, were detected to varying extents in hemopoietic and somatic tissues. Surprisingly, we found the existence of Nrf1D-derived isoforms in blood plasma, implying that it is a candidate secretory transcription factor, albeit its precursor acts as an integral transmembrane-bound CNC-bZIP protein that entails dynamic topologies across membranes, before being unleashed from the ER to enter the blood.

Nrf1 is paved as a new strategic avenue to prevent and treat cancer, neurodegenerative and other diseases.

Transcription factor Nrf1 acts as a unique vital player in maintaining cellular homeostasis and organ integrity during normal development and growth throughout the life process. Loss-of-function of Nrf1 results in severe oxidative stress, genomic instability, embryonic lethality, developmental disorders, and adult diseases such as non-alcoholic steatohepatitis, hepatocellular carcinoma, diabetes and neurogenerative diseases. Thereby, Nrf1 is critically implicated in a variety of important physio-pathological processes by governing robust target genes in order to reinforce antioxidant, detoxification and cytoprotective responses to cellular stress. Notably, there also exists a proteasomal 'bounce-back' response mediated by Nrf1, insofar as to enhance the drug resistance to proteasomal inhibitors in clinical treatment of neuroblastoma, multiple myeloma and triple-negative breast cancers. Recently, several drugs or chemicals are found or re-found in new ways to block the proteasomal compensatory process through inhibiting the multistep processing of Nrf1. Conversely, activation of Nrf1 induced by some drugs or chemicals leads to cytoprotection from cell apoptosis and promotes cell viability. This is the start of constructive and meaningful studies, approaching to explore the mechanism(s) by which Nrf1 is activated to protect neurons and other cells from malignant and degenerative diseases. Overall, Nrf1 has appealed attentions as a new attractive therapeutic strategy for human diseases including cancers.

[Effectiveness of retrograde island neurocutaneous flap pedicled with lateral antebrachial cutaneous nerve in treatment of hand defect].

OBJECTIVE: To explore the effectiveness of retrograde island neurocutaneous flap pedicled with lateral antebrachial cutaneous nerve in the treatment of soft tissue defect of the hand. METHODS: Between October 2011 and December 2013, 17 cases of skin and soft tissue defects of the hands were treated. There were 8 males and 9 females, aged 23-62 years (mean, 44 years). Of them, defect was caused by trauma in 13 cases, by postoperative wound after degloving injury in 2 cases, and by resection of contracture of the first web in 2 cases; 13 cases of traumas had a disease duration of 2-6 hours (mean, 3.5 hours). The defect sites located at the back of the hand in 5 cases, at the radial side of the palm in 4 cases, at the first web in 2 cases, at the palmar side of the thumb in 4 cases, and at the radial dorsal side of the thumb in 2 cases. The bone, tendons, and other deep tissue were exposed in 15 cases. The defect size varied from 3 cm x 3 cm to 12 cm x 8 cm. The size of the flaps ranged from 3.6 cm x 3.6 cm to 13.2 cm x 8.8 cm. The lateral cutaneous nerve of the forearm was anastomosed with the cutaneous nerve of the recipient sites in 9 cases. The donor sites were repaired by free skin graft or were sutured directly. RESULTS: The other flaps survived, and obtained healing by first intention except 2 flaps which had partial necrosis with healing by second intention at 1 month after dressing change. The skin graft at donor site survived, and incisions healed by first intention. All patients were followed up 5-30 months (mean, 12 months). The flaps had good color and texture. Flap sensory recovery, of S2-S3+ was obtained; in 9 cases undergoing cutaneous nerve flap anastomosis, the sensation of the flaps recovered to S3-S3+ and was better than that of 8 cases that the nerves were disconnected (S2-S3). The patients achieved satisfactory recovery of hand function. Only 2 cases had extended limitation of the proximal interphalangeal joint. At last follow-up, according to the Chinese Medical Society of Hand Surgery function evaluation standards, the results were excellent in 15 cases and good in 2 cases. CONCLUSION: Retrograde island neurocutaneous flap pedicled with lateral antebrachial cutaneous nerve is an effective way to repair skin defects of the hand, with the advantages of reliable blood supply and simple surgical procedure.