Different Susceptibility to the Parkinson's Toxin MPTP in Mice Lacking the Redox Master Regulator Nrf2 or Its Target Gene Heme Oxygenase-1

This is an open-access article distributed under the terms of the Creative Commons Attribution License.-- et al.[Background]: The transcription factor Nrf2 (NF-E2-related factor 2) and its target gene products, including heme oxygenase-1 (HO-1), elicit an antioxidant response that may have therapeutic value for Parkinson's disease (PD). However, HO-1 protein levels are increased in dopaminergic neurons of Parkinson's disease (PD) patients, suggesting its participation in free-iron deposition, oxidative stress and neurotoxicity. Before targeting Nrf2 for PD therapy it is imperative to determine if HO-1 is neurotoxic or neuroprotective in the basal ganglia. [Methodology]: We addressed this question by comparing neuronal damage and gliosis in Nrf2- or HO-1-knockout mice submitted to intraperitoneal injection of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) for five consecutive days. Nrf2- knockout mice showed exacerbated gliosis and dopaminergic nigrostriatal degeneration, as determined by immunohistochemical staining of tyrosine hydroxylase in striatum (STR) and substantia nigra (SN) and by HPLC determination of striatal dopamine and 3,4-dihydroxyphenylacetic acid (DOPAC). On the other hand, the severity of gliosis and dopaminergic degeneration in HO-1-null mice was neither increased nor reduced. Regarding free-iron deposition, both Nrf2- and HO-1-deficient mice exhibited similar number of deposits as determined by Perl's staining, therefore indicating that these proteins do not contribute significantly to iron accumulation or clearance in MPTP-induced Parkinsonism. [Conclusions]: These results suggest that HO-1 does not protect or enhance the sensitivity to neuronal death in Parkinson's disease and that pharmacological or genetic intervention on Nrf2 may provide a neuroprotective benefit as add on therapy with current symptomatic protocols.This work was supported by grant SAF2007-62646 from the Spanish Ministry of Science and Innovation. The Faculty of Biochemistry, Biophysics and Biotechnology of the Jagiellonian University is a beneficiary of the structural funds from the European Union (grant No: POIG.02.01.00-12-064/08 and 02.02.00-00- 014/08). N.I. is recipient of a FPU fellowship of Universidad Autónoma of Madrid.Peer reviewe

Heme Oxygenase-1 Accelerates Cutaneous Wound Healing in Mice

Heme oxygenase-1 (HO-1), a cytoprotective, pro-angiogenic and anti-inflammatory enzyme, is strongly induced in injured tissues. Our aim was to clarify its role in cutaneous wound healing. In wild type mice, maximal expression of HO-1 in the skin was observed on the 2nd and 3rd days after wounding. Inhibition of HO-1 by tin protoporphyrin-IX resulted in retardation of wound closure. Healing was also delayed in HO-1 deficient mice, where lack of HO-1 could lead to complete suppression of reepithelialization and to formation of extensive skin lesions, accompanied by impaired neovascularization. Experiments performed in transgenic mice bearing HO-1 under control of keratin 14 promoter showed that increased level of HO-1 in keratinocytes is enough to improve the neovascularization and hasten the closure of wounds. Importantly, induction of HO-1 in wounded skin was relatively weak and delayed in diabetic (db/db) mice, in which also angiogenesis and wound closure were impaired. In such animals local delivery of HO-1 transgene using adenoviral vectors accelerated the wound healing and increased the vascularization. In summary, induction of HO-1 is necessary for efficient wound closure and neovascularization. Impaired wound healing in diabetic mice may be associated with delayed HO-1 upregulation and can be improved by HO-1 gene transfer

Jozkowicz A. Haem oxygenase-1: non-canonical roles in physiology and pathology. Clin Sci (Lond

A B S T R A C T HO-1 (haem oxygenase-1) is a ubiquitously expressed inducible enzyme degrading haem to CO, biliverdin and Fe 2 + . Its activation reduces oxidative stress in cells and inhibits inflammation, both due to removal of haem and because of the biological activity of HO-1 products. CO may act similarly to NO, activating soluble guanylate cyclase and elevating cGMP production. It inhibits platelet aggregation, reduces leucocyte adhesion, decreases apoptosis and lowers the production of some pro-inflammatory cytokines. Biliverdin is converted into bilirubin by biliverdin reductase, and both compounds are potent antioxidants, free radical scavengers and inhibitors of the complement cascade. Iron ions can be potentially toxic, increasing the generation of hydroxyl radicals, but simultaneous induction of ferritin and activation of the Fe-ATPase iron transporter protects cells from oxidative stress. Importantly, basal and induced expression of HO-1 is very variable in the human population because of the highly polymorphic (GT)n fragment in the promoter, which may have clinical relevance. The recognized roles of HO-1 are far beyond cytoprotection. The enzyme is important in the regulation of cell proliferation, differentiation and apoptosis. Its activity improves neovascularization, attenuates inflammation and modulates the immune response, thereby influencing carcinogenesis, wound healing, transplant survival and the progression of cardiovascular diseases. Recent results indicate that HO-1 may also act through the regulation of microRNAs, which suggests a much broader involvement of HO-1 in the modulation of cell functions and offers a potential explanation for some well-known activities whose mechanism has hitherto been unclear. A CLOSER LOOK AT HO-1 (HAEM OXYGENASE-1) Enzymes serve a wide variety of functions in living organisms, and very often their role is much broader than only substrate catabolism. The example of such an enzyme, influencing numerous molecular processes, is HO-1. This evolutionarily conserved protein [1] degrades toxic haem, yielding three biologically active products: CO, biliverdin and Fe 2 + [2] (Scheme 1). Multiple data have indicated the products of HO-1 activity and the protein itself [3] to be involved in the maintenance of cell homoeostasis and regulation of cell metabolism as well as to play a role in pathological processe

Overlooked and valuable facts to know in the NRF2/KEAP1 field

NRF2 (nuclear factor erythroid 2-related factor 2) is a critical regulator of the cellular stress response. It is a transcription factor that controls the expression of hundreds of genes. We will soon celebrate the thirtieth anniversary of its discovery [1]. Over the years, NRF2 and its repressor KEAP1 have become the subject of intensive research, ranging from the detailed molecular mechanisms of their activity to clinical perspectives and generating over a dozen thousand publications. This review intends to draw the attention of researchers to essential issues in the NRF2/KEAP1 field, highlighting the overlooked facts and clarifying potential misconceptions.This research was funded by the Spanish Ministry of Economy and Competitiveness (MINECO) (grants PID2019-110061RB-I00, and PDC2021-121421-I00) and The Autonomous Community of Madrid (grant B2017/BMD-3827). FLM enjoyed FPI contract of MINECO (FPI-2017). The National Science Centre supported this work with grants Sonata Bis No. 2016/22/E/NZ3/00405 (AGP), Opus No. 2021/43/B/NZ4/02130 (AGP), and Sonata No. 2018/31/D/NZ4/00077 (APP). AK is supported by L'Oreal for Women in Science and START Scholarship from Foundation for Polish Science. CP and CS are supported by Diabetes UK award 20/0006178

MPTP induces a similar deposition of ferric iron in Nrf2^−/− and HO-1^−/− mice.

<p>Iron precipitates were detected by DAB-enhanced Perls reaction followed by Nissl counterstaining. <i>A,</i> simplified scheme of a coronal section of midbrain showing the location of mouse dorsal and ventral substantia nigra on the left (SNc and SNr, respectively). The rectangle on the right side indicates the region shown in panels <i>D, E, F and G</i>). <i>B</i> and <i>C</i>, high magnification pictures of the boundary between SNc and SNr from wild type mice submitted to saline or MPTP treatments, respectively. Yellow arrowheads point some large Perls-negative cells with pale nuclei and dark nucleoli typical of dopaminergic neurons. Green arrowheads point small Perls-positive cells with picnotic nuclei typical of microglia. The red arrowhead points a Perls-positive microglial cell that has been drawn in the inset to show microgrial extensions. The large panels show representative fields of both SNc and SNr (location indicated in the rectangle of <i>A</i> panel), from saline-treated wild type mice (<i>D</i>), MPTP-treated wild type mice (<i>E</i>), MPTP-treated Nrf2^−/− mice (<i>F</i>), and MPTP-treated HO-1^−/− mice (<i>G</i>).</p

DA and DOPAC levels in STR of MPTP-treated Nrf2^−/− and HO-1^−/− and wild type littermate mice.

<p>Animals received one daily i.p. injection of saline or MPTP (30 mg/kg) for five consecutive days and striatal DA and DOPAC levels were determined by HPLC. <i>A and B,</i> the reduction in DA and DOPAC is more pronounced in MPTP-treated Nrf2^−/− mice than in MPTP-treated wild type littermates. <i>C and D,</i> the reduction in DA and DOPAC is similar between MPTP-treated HO-1^−/− mice and their wild type littermates. Values represent the mean ± SD from five samples. Two-way ANOVA followed by Bonferroni's test was applied to determine the significance of biochemical differences among groups. Asterisks denote significant differences between treatments with <i>P</i><0.05.</p