Nuclear heme oxygenase-1 (HO-1) modulates subcellular distribution and activation of Nrf2, impacting metabolic and anti-oxidant defenses

An 8-aminoquinoline-naphthyl copper complex causes apoptotic cell death by modulating the expression of apoptotic regulatory proteins in breast cancer cells

Breast cancer is one of the most common cancers globally and a leading cause of cancer-related deaths among women. Despite the combination of chemotherapy with targeted therapy, including monoclonal antibodies and kinase inhibitors, drug resistance and treatment failure remain a common occurrence. Copper, complexed to various organic ligands, has gained attention as potential chemotherapeutic agents due to its perceived decreased toxicity to normal cells. The cytotoxic efficacy and the mechanism of cell death of an 8-aminoquinoline-naphthyl copper complex (Cu8AqN) in MCF-7 and MDA-MB-231 breast cancer cell lines was investigated. The complex inhibited the growth of MCF-7 and MDA-MB-231 cells with IC50 values of 2.54 ± 0.69 μM and 3.31 ± 0.06 μM, respectively. Nuclear fragmentation, annexin V binding, and increased caspase-3/7 activity indicated apoptotic cell death. The loss of mitochondrial membrane potential, an increase in caspase-9 activity, the absence of active caspase-8 and a decrease of tumour necrosis factor receptor 1(TNFR1) expression supported activation of the intrinsic apoptotic pathway. Increased ROS formation and increased expression of haem oxygenase-1 (HMOX-1) indicated activation of cellular stress pathways. Expression of p21 protein in the nuclei was increased indicating cell cycle arrest, whilst the expression of inhibitor of apoptosis proteins (IAPs); cIAP1, XIAP and survivin were decreased, creating a pro-apoptotic environment. Phosphorylated p53 species; phospho-p53(S15), phospho-p53(S46), and phospho-p53(S392) accumulated in MCF-7 cells indicating the potential of Cu8AqN to restore p53 function in the cells. In combination, the data indicates that Cu8AqN is a useful lead molecule worthy of further exploration as a potential anti-cancer drug.

The crosstalk between oxidative stress and DNA damage induces neural stem cell senescence by HO-1/PARP1 non-canonical pathway

Neural stem cells play a crucial role in maintaining brain homeostasis. Neural stem cells senescence can lead to the decline of nerve repair and regeneration, causing brain aging and neurodegenerative diseases. However, the mechanism underlying neural stem cells senescence remains poorly understood. In this study, we report a novel HO-1/PARP1 non-canonical pathway highlighting how oxidative stress triggers the DNA damage response, ultimately leading to premature cellular senescence in neural stem cells. HO-1 acts as a sensor for oxidative stress, while PARP1 functions as a sensor for DNA damage. The simultaneous expression and molecular interaction of these two sensors can initiate a crosstalk of oxidative stress and DNA damage response processes, leading to the vicious cycle. The persistent activation of this pathway contributes to the senescence of neural stem cells, which in turn plays a crucial role in the progression of neurodegenerative diseases. Consequently, targeting this novel signaling pathway holds promise for the development of innovative therapeutic strategies and targets aimed at mitigating neural stem cells senescence-related disorders.

Design and Synthesis of Novel Antioxidant 2-Substituted-5,7,8-Trimethyl-1,4-Benzoxazine Hybrids: Effects on Young and Senescent Fibroblasts

The exponential growth of the aged population worldwide is followed by an increase in the prevalence of age-related disorders. Oxidative stress plays central role in damage accumulation during ageing and cell senescence. Thus, a major target of today's anti-ageing research has been focused on antioxidants counteracting senescence. In the current work, six novel 5,7,8-trimethyl-1,4-benzoxazine/catechol or resorcinol hybrids were synthesized connected through a methoxymethyl-1,2,3-triazolyl or a 1,2,3-triazoly linker. The compounds were evaluated for their antioxidant capacity in a cell-free system and for their ability to reduce intracellular ROS levels in human skin fibroblasts, both young (early-passage) and senescent. The most efficient compounds were further tested in these cells for their ability to induce the expression of the gene heme oxygenase-1 (ho-1), known to regulate redox homeostasis, and cellular glutathione (GSH) levels. Overall, the two catechol derivatives were found to be more potent than the resorcinol analogues. Furthermore, these two derivatives were shown to act coordinately as radical scavengers, ROS inhibitors, ho-1 gene expression inducers, and GSH enhancers. Interestingly, one of the two catechol derivatives was also found to enhance human skin fibroblast viability. The properties of the synthesized compounds support their potential use in cosmetic applications, especially in products targeting skin ageing.

Mechanism of Prunella vulgaris L. and luteolin in restoring Tfh/Tfr balance and alleviating oxidative stress in Graves' disease

BACKGROUND

The pathophysiology of Graves' disease (GD) involves imbalances between follicular helper T (Tfh) and follicular regulatory T (Tfr) cells, as well as oxidative stress (OS). Prunella vulgaris L. (Xia Ku Cao, XKC) and its primary bioactive compound, luteolin, are recognized for their potential in treating GD. Yet, the mechanism accounting for the immune-modulatory and antioxidant effects of XKC remains elusive.

PURPOSE

This study aims to evaluate the pharmacological effects and elucidate the underlying mechanism of XKC and luteolin in a GD mouse model induced by recombinant adenovirus of TSH receptor A subunit (Ad-hTSHR-289).

METHODS

High-Performance Liquid Chromatography-Quadrupole Time-of-Flight Mass Spectrometry (HPLC-QTOF MS) was used to detect the constituents of XKC. The GD model was established through inducing female BALB/c mice with three intramuscular injections of Ad-TSHR-289. Thyroid function, autoantibody and OS parameters were measured by ELISA. Changes of Tfh cells and Tfr cells were detected by flow cytometry. RT-qPCR, Western Blotting, immunohistochemistry were used to explore the related molecular mechanisms.

RESULTS

A total of 37 chemical components from XKC were identified by HPLC-QTOF MS, represented by flavonoids, steroids, terpenoids, and luteolin. XKC and luteolin reduced T4, TRAb levels and facilitated the recovery from thyroid damage in GD mice. Meanwhile, XKC and luteolin effectively alleviated OS by decreasing the levels of MDA, NOX2, 4-HNE, 8-OHdG, while increasing GSH level. Flow cytometry showed that XKC and luteolin restored the abnormal proportions of Tfh/Tfr and Tfh/Treg, and the mRNA levels of IL-21, Bcl-6 and Foxp3 in GD mice. In addition, XKC and luteolin inhibited PI3K, Akt, p-PI3K and p-Akt, but activated Nrf2 and HO-1.

CONCLUSION

XKC and luteolin could inhibit the development of GD in vivo by rebalancing Tfh/Tfr cells and alleviating OS. This therapeutic mechanism may involve the Nrf2/HO-1 and PI3K/Akt signaling pathways. Luteolin is the main efficacy material basis of XKC in countering GD. For the first time, we revealed the mechanism of XKC and luteolin in the treatment of GD from the perspective of autoimmune and OS.

Celastrol enhances the viability of random-pattern skin flaps by regulating autophagy through the AMPK-mTOR-TFEB axis

In reconstructive and plastic surgery, random-pattern skin flaps (RPSF) are often used to correct defects. However, their clinical usefulness is limited due to their susceptibility to necrosis, especially on the distal side of the RPSF. This study validates the protective effect of celastrol (CEL) on flap viability and explores in terms of underlying mechanisms of action. The viability of different groups of RPSF was evaluated by survival zone analysis, laser doppler blood flow, and histological analysis. The effects of CEL on flap angiogenesis, apoptosis, oxidative stress, and autophagy were evaluated by Western blot, immunohistochemistry, and immunofluorescence assays. Finally, its mechanistic aspects were explored by autophagy inhibitor and Adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) inhibitor. On the seventh day after surgery, the survival area size, blood supply, and microvessel count of RPSF were augmented following the administration of CEL. Additionally, CEL stimulated angiogenesis, suppressed apoptosis, and lowered oxidative stress levels immediately after elevated autophagy in ischemic regions; These effects can be reversed using the autophagy inhibitor chloroquine (CQ). Specifically, CQ has been observed to counteract the protective impact of CEL on the RPSF. Moreover, it has also been discovered that CEL triggers the AMPK-mTOR-TFEB axis activation in the area affected by ischemia. In CEL-treated skin flaps, AMPK inhibitors were demonstrated to suppress the AMPK-mTOR-TFEB axis and reduce autophagy levels. This investigation suggests that CEL benefits the survival of RPSF by augmenting angiogenesis and impeding oxidative stress and apoptosis. The results are credited to increased autophagy, made possible by the AMPK-mTOR-TFEB axis activation.

Malaria parasites require a divergent heme oxygenase for apicoplast gene expression and biogenesis

Malaria parasites have evolved unusual metabolic adaptations that specialize them for growth within heme-rich human erythrocytes. During blood-stage infection, Plasmodium falciparum parasites internalize and digest abundant host hemoglobin within the digestive vacuole. This massive catabolic process generates copious free heme, most of which is biomineralized into inert hemozoin. Parasites also express a divergent heme oxygenase (HO)-like protein (PfHO) that lacks key active-site residues and has lost canonical HO activity. The cellular role of this unusual protein that underpins its retention by parasites has been unknown. To unravel PfHO function, we first determined a 2.8 Å-resolution X-ray structure that revealed a highly α-helical fold indicative of distant HO homology. Localization studies unveiled PfHO targeting to the apicoplast organelle, where it is imported and undergoes N-terminal processing but retains most of the electropositive transit peptide. We observed that conditional knockdown of PfHO was lethal to parasites, which died from defective apicoplast biogenesis and impaired isoprenoid-precursor synthesis. Complementation and molecular-interaction studies revealed an essential role for the electropositive N-terminus of PfHO, which selectively associates with the apicoplast genome and enzymes involved in nucleic acid metabolism and gene expression. PfHO knockdown resulted in a specific deficiency in levels of apicoplast-encoded RNA but not DNA. These studies reveal an essential function for PfHO in apicoplast maintenance and suggest that Plasmodium repurposed the conserved HO scaffold from its canonical heme-degrading function in the ancestral chloroplast to fulfill a critical adaptive role in organelle gene expression.

Novel Acetamide-Based HO-1 Inhibitor Counteracts Glioblastoma Progression by Interfering with the Hypoxic-Angiogenic Pathway

Glioblastoma multiforme (GBM) represents the deadliest tumor among brain cancers. It is a solid tumor characterized by uncontrolled cell proliferation generating the hypoxic niches in the cancer core. By inducing the transcription of hypoxic inducible factor (HIF), hypoxia triggers many signaling cascades responsible for cancer progression and aggressiveness, including enhanced expression of vascular endothelial growth factor (VEGF) or antioxidant enzymes, such as heme oxygenase-1 (HO-1). The present work aimed to investigate the link between HO-1 expression and the hypoxic microenvironment of GBM by culturing two human glioblastoma cell lines (U87MG and A172) in the presence of a hypoxic mimetic agent, deferoxamine (DFX). By targeting hypoxia-induced HO-1, we have tested the effect of a novel acetamide-based HO-1 inhibitor (VP18/58) on GBM progression. Results have demonstrated that hypoxic conditions induced upregulation and nuclear expression of HO-1 in a cell-dependent manner related to malignant phenotype. Moreover, our data demonstrated that the HO-1 inhibitor counteracted GBM progression by modulating the HIFα/HO-1/VEGF signaling cascade in cancer cells bearing more malignant phenotypes.

Anoikis-related gene signatures predict prognosis of lung adenocarcinoma patients and reveal immune infiltration

Background

Lung adenocarcinoma (LUAD), a type of lung cancer, is one of the most aggressive and deadly malignancies worldwide. Malignant tumor cells exhibit strong anti-anoikis properties to achieve distant metastasis through the circulatory system. However, more research is needed to understand how anoikis is involved in the progression, metastasis and especially the prognosis of LUAD.

Methods

We obtained anoikis-related genes (ARGs) from two websites, Harmonizome and Genecards, and integrated them to select and model the genes associated with LUAD prognosis. In addition, we investigated differences in the immune cell microenvironment and pathways of enrichment analysis between subtypes. We finally constructed a nomogram based on ARGs and used decision curve analysis (DCA) to demonstrate that this model could help clinicians make clinical decisions.

Results

Sixty-four differentially expressed genes (DEGs) were found to be associated with survival, and of these, six were chosen to build a prognostic model. The time-dependent receiver operating characteristic (ROC) curves showed that the model had a satisfactory predictive ability. Enrichment analysis and immune microenvironment analysis revealed that the immune status and drug sensitivity of populations at high and low risk were different. We integrated the clinicopathological features of LUAD with the risk score to build the nomogram. The nomogram was shown to be a good predictor of short- and long-term survival in LUAD patients through DCA analysis.

Conclusions

This new model based on six ARGs and nomograms in our study could help patients with LUAD develop personalized treatment plans.

Tectorigenin inhibits oxidative stress by activating the Keap1/Nrf2/HO-1 signaling pathway in Th2-mediated allergic asthmatic mice

Asthma is a chronic obstructive airway condition and one of the most common non-communicable illnesses worldwide. Tectorigenin (Tec) is an isoflavonoid found in plants that possesses significant antioxidative and anti-inflammatory abilities. Nevertheless, the antioxidative properties of Tec have not yet been documented in allergic asthma. In this study, we created an asthmatic BALB/c mouse model induced by ovalbumin (OVA) and used it to assess the efficacy of Tec as a possible therapy agent. Tec decreased the serum OVA-specific immunoglobulin (Ig) E and IgG1 secretion levels. The total number of cells and the distribution of inflammatory cells decreased significantly in bronchoalveolar lavage fluid (BALF), with weakened inflammatory reaction in pulmonary tissues. Additionally, Tec regulated the T helper 1(Th1)/Th2 balance by increasing the expression of Th1- related factors (interleukin (IL)-12 and T-bet) and decreasing the expression of Th2-related factors (IL-4, IL-5, IL-13, and GATA binding protein 3. In addition, the pro-inflammatory cytokines such as IL-6, tumor necrosis factor-alpha, and IL-1β were also inhibited by Tec. Tec also dramatically increased antioxidant (catalase and superoxide dismutase) concentrations while lowering the intensity of the indicators of oxidative stress such as reactive oxygen species and malondialdehyde in BALF. Finally, Tec effectively activated the Keap1/Nrf2/HO-1 signaling pathway and prevented the epithelial-mesenchymal transition. The results of the current study show that Tec may be useful in relieving the inflammatory and oxidative stress responses associated with asthma.

The Neuroprotective Effect of Sophocarpine against Glutamate-Induced HT22 Cell Cytotoxicity

Neuronal cell death and dysfunction of the central nervous system can be caused by oxidative stress, which is associated with the development of neurodegenerative diseases. Sophocarpine, an alkaloid compound derived from Sophora moorcroftiana (Benth.) Baker seeds, has a wide range of medicinal value. This study sought to determine how sophocarpine exerts neuroprotective effects by inhibited oxidative stress and apoptosis in mouse hippocampus neuronal (HT22) cells. 20mM glutamate-induced HT22 cells were used to develop an in vitro model of oxidative stress damage. The Cell Counting Kit-8 (CCK-8) assay was used to assess cell viability. According to the instructions on the kits to detect reactive oxygen species (ROS) levels and oxidative stress indicators. HT22 cells were examined using immunofluorescence and Western Blotting to detect Nuclear Factor Erythroid 2-related Factor 2 (Nrf2) expression. The expression of proteins and messenger RNA (mRNA) for heme oxygenase-1 (HO-1) was examined by Western Blotting and Quantitative real time polymerase chain reaction (qRT-PCR). Mitochondrial membrane potential (MMP) and Cell apoptosis were used by 5, 5', 6, 6'-Tetrachloro-1, 1', 3, 3'-tetraethyl-imidacarbocyanine iodide (JC- 1) kit and Terminal Deoxynucleotidyl Transferase-mediated dUTP Nick-End Labeling (TUNEL) apoptosis assay kit, respectively. Finally, the expression of pro-apoptotic proteins was detected by Western Blotting. The result demonstrated that sophocarpine (1.25 μM-10 μM) can significantly inhibit glutamate-induced cytotoxicity and ROS generation, improve the activity of antioxidant enzymes. Sophocarpine increased the expression of HO-1 protein and mRNA and the nuclear translocation of Nrf2 to play a cytoprotective role; however, cells were transfected with small interfering RNA targeting HO-1 (si-HO-1) reversed the above effects of sophocarpine. In addition, sophocarpine significantly inhibited glutamate induced mitochondrial depolarization and further inhibited cell apoptosis by reducing the expression level of caspase-related proteins.

Association between Nfr2, HO-1, NF-kB Expression, Plasma ADMA, and Oxidative Stress in Metabolic Syndrome

Endothelial dysfunction is one of the major factors in the pathogenesis of metabolic syndrome (MetS), and its molecular mechanisms are not completely understood. The present study aimed to examine the connection between nuclear factor2-related factor2 (Nrf2), nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), heme oxygenase 1 (HO-1), and plasma asymmetric dimethylarginine (ADMA) and malondialdehyde (MDA) in people with MetS. Participants in the study were as follows: with MetS (n = 30) and without MetS (Control) (n = 14). Expression of Nrf2, NF-kB, and HO-1 was measured in peripheral blood mononuclear cells (PBMCs). Plasma ADMA was determined using the ELISA technique and MDA via the thiobarbituric acid method. Our study showed that mRNA of NF-kB, Nrf2, and HO-1 levels in PBMCs in the MetS group were significantly higher than in the controls by 53%, 130%, and 185% (p < 0.05), respectively. Similarly, elevated levels of MDA (by 78%, p < 0.001) and ADMA (by 18.7%, p < 0.001) were established in the MetS group. Our findings show the importance of transcription factor Nrf2, playing an integral role in the protection of the endothelium, and of NF-κB, a transcription factor mediating the inflammatory response in MetS. Knowledge of complex cellular-molecular mechanisms would allow the use of biomarkers such as Nrf2, NF-kB, HO-1, and ADMA for the assessment of endothelial dysfunction in clinical practice.

Heme Oxygenase-1 and Its Role in Colorectal Cancer

Heme oxygenase-1 (HO-1) is an enzyme located at the endoplasmic reticulum, which is responsible for the degradation of cellular heme into ferrous iron, carbon monoxide and biliverdin-IXa. In addition to this main function, the enzyme is involved in many other homeostatic, toxic and cancer-related mechanisms. In this review, we first summarize the importance of HO-1 in physiology and pathophysiology with a focus on the digestive system. We then detail its structure and function, followed by a section on the regulatory mechanisms that control HO-1 expression and activity. Moreover, HO-2 as important further HO isoform is discussed, highlighting the similarities and differences with regard to HO-1. Subsequently, we describe the direct and indirect cytoprotective functions of HO-1 and its breakdown products carbon monoxide and biliverdin-IXa, but also highlight possible pro-inflammatory effects. Finally, we address the role of HO-1 in cancer with a particular focus on colorectal cancer. Here, relevant pathways and mechanisms are presented, through which HO-1 impacts tumor induction and tumor progression. These include oxidative stress and DNA damage, ferroptosis, cell cycle progression and apoptosis as well as migration, proliferation, and epithelial-mesenchymal transition.

Phycocyanin as a nature-inspired antidiabetic agent: A systematic review

BACKGROUND

Nutraceuticals have been important for more than two decades for their safety, efficacy, and outstanding effects. Diabetes is a major metabolic syndrome, which may be improved using nutritional pharmaceuticals. Some microalgae species, such as spirulina, stand out by providing biomass with exceptional nutritional properties. Spirulina has a wide range of pharmacological effects, mostly related to phycocyanin. Phycocyanin is a protein compound with antidiabetic properties, known as a nutraceutical.

OBJECTIVE

This review delves into phycocyanin applications in diabetes and its complications and ascertains the mechanisms involved.

METHODS

Scopus, PubMed, Cochrane Library, Web of Science, and ProQuest databases were systematically reviewed (up to April 30, 2023), in which only animal and cellular studies were found.

RESULTS

According to animal studies, the administration of phycocyanin affected biochemical parameters (primary outcome) related to diabetes. These results showed an increase in fasting insulin serum and a decrease in fasting blood glucose, glycosylated serum protein, and glycosylated hemoglobin. In cellular studies, though, phycocyanin prevented methylglyoxal and human islet amyloid polypeptide-induced dysfunction in β-cells and induced apoptosis through different molecular pathways (secondary outcome), including activation of Nrf2, PI3K/Akt, and suppression of JNK and p38. Also, phycocyanin exerted its antidiabetic effect by affecting the pathways regulating hepatic glucose metabolism.

CONCLUSIONS

Thus, based on the available information and literature, targeting these pathways by phycocyanin may unleash an array of benefits, including positive outcomes of the antidiabetic effects of phycocyanin as a nutraceutical.

OTHER

This systematic review was registered in the International Prospective Register of Systematic Reviews (PROSPERO) at the National Institute of Health. The registration number is CRD42022307522.

Cellular protection from H2O2 toxicity by Fv-Hsp70: protection via catalase and gamma-glutamyl-cysteine synthase

Heat shock proteins (HSPs), especially Hsp70 (HSPA1), have been associated with cellular protection from various cellular stresses including heat, hypoxia-ischemia, neurodegeneration, toxins, and trauma. Endogenous HSPs are often synthesized in direct response to these stresses but in many situations are inadequate in protecting cells. The present study addresses the transduction of Hsp70 into cells providing protection from acute oxidative stress by H2O2. The recombinant Fv-Hsp70 protein and two mutant Fv-Hsp70 proteins minus the ATPase domain and minus the ATPase and terminal lid domains were tested at 0.5 and 1.0 μM concentrations after two different concentrations of H2O2 treatment. All three recombinant proteins protected SH-SY5Y cells from acute H2O2 toxicity. This data indicated that the protein binding domain was responsible for cellular protection. In addition, experiments pretreating cells with inhibitors of antioxidant proteins catalase and gamma-glutamylcysteine synthase (GGCS) before H2O2 resulted in cell death despite treatment with Fv-Hsp70, implying that both enzymes were protected from acute oxidative stress after treatment with Fv-Hsp70. This study demonstrates that Fv-Hsp70 is protective in our experiments primarily by the protein-binding domain. The Hsp70 terminal lid domain was also not necessary for protection.

Phaeanthus vietnamensis Ban Ameliorates Lower Airway Inflammation in Experimental Asthmatic Mouse Model via Nrf2/HO-1 and MAPK Signaling Pathway

Asthma is a chronic airway inflammatory disease listed as one of the top global health problems. Phaeanthus vietnamensis BÂN is a well-known medicinal plant in Vietnam with its anti-oxidant, anti-microbial, anti-inflammatory potential, and gastro-protective properties. However, there is no study about P. vietnamensis extract (PVE) on asthma disease. Here, an OVA-induced asthma mouse model was established to evaluate the anti-inflammatory and anti-asthmatic effects and possible mechanisms of PVE. BALB/c mice were sensitized by injecting 50 μg OVA into the peritoneal and challenged by nebulization with 5% OVA. Mice were orally administered various doses of PVE once daily (50, 100, 200 mg/kg) or dexamethasone (Dex; 2.5 mg/kg) or Saline 1 h before the OVA challenge. The cell infiltrated in the bronchoalveolar lavage fluid (BALF) was analyzed; levels of OVA-specific immunoglobulins in serum, cytokines, and transcription factors in the BALF were measured, and lung histopathology was evaluated. PVE, especially PVE 200mg/kg dose, could improve asthma exacerbation by balancing the Th1/Th2 ratio, reducing inflammatory cells in BALF, depressing serum anti-specific OVA IgE, anti-specific OVA IgG1, histamine levels, and retrieving lung histology. Moreover, the PVE treatment group significantly increased the expressions of antioxidant enzymes Nrf2 and HO-1 in the lung tissue and the level of those antioxidant enzymes in the BALF, decreasing the oxidative stress marker MDA level in the BALF, leading to the relieving the activation of MAPK signaling in asthmatic condition. The present study demonstrated that Phaeanthus vietnamensis BÂN, traditionally used in Vietnam as a medicinal plant, may be used as an efficacious agent for treating asthmatic disease.

Cytoprotective Role of Heme Oxygenase-1 in Cancer Chemoresistance: Focus on Antioxidant, Antiapoptotic, and Pro-Autophagy Properties

Chemoresistance remains the foremost challenge in cancer therapy. Targeting reactive oxygen species (ROS) manipulation is a promising strategy in cancer treatment since tumor cells present high levels of intracellular ROS, which makes them more vulnerable to further ROS elevation than normal cells. Nevertheless, dynamic redox evolution and adaptation of tumor cells are capable of counteracting therapy-induced oxidative stress, which leads to chemoresistance. Hence, exploring the cytoprotective mechanisms of tumor cells is urgently needed to overcome chemoresistance. Heme oxygenase-1 (HO-1), a rate-limiting enzyme of heme degradation, acts as a crucial antioxidant defense and cytoprotective molecule in response to cellular stress. Recently, emerging evidence indicated that ROS detoxification and oxidative stress tolerance owing to the antioxidant function of HO-1 contribute to chemoresistance in various cancers. Enhanced HO-1 expression or enzymatic activity was revealed to promote apoptosis resistance and activate protective autophagy, which also involved in the development of chemoresistance. Moreover, inhibition of HO-1 in multiple cancers was identified to reversing chemoresistance or improving chemosensitivity. Here, we summarize the most recent advances regarding the antioxidant, antiapoptotic, and pro-autophagy properties of HO-1 in mediating chemoresistance, highlighting HO-1 as a novel target for overcoming chemoresistance and improving the prognosis of cancer patients.

Exposure to a static magnetic field attenuates hepatic damage and function abnormality in obese and diabetic mice

Static magnetic fields (SMFs) exhibit significant effect on health care. However, the effect of SMF on hepatic metabolism and function in obesity and diabetes are still unknown. Liver is not only the main site for glucolipid metabolism but also the core part for iron metabolism regulation. Dysregulations of iron metabolism and redox status are risk factors for the development of hepatic injury and affect glucolipid metabolism in obesity and diabetes. Mice of HFD-induced obesity and HFD/streptozocin-induced diabetes were exposed to a moderate-intensity SMF (0.4-0.7 T, direction: upward, 4 h/day, 8 weeks). Results showed that SMF attenuated hepatic damage by decreasing inflammation and fibrosis in obese and diabetic mice. SMF had no effects on improving glucose/insulin tolerance but regulated proteins (GLUT1 and GLUT4) and genes (G6pc, Pdk4, Gys2 and Pkl) participating in glucose metabolism with phosphorylation of Akt/AMPK/GSK3β. SMF also reduced lipid droplets accumulation through decreasing Plin2 and Plin5 and regulated lipid metabolism with elevated hepatic expressions of PPARγ and C/EBPα in obese mice. In addition, SMF decreased hepatic iron deposition with lower FTH1 expression and modulated systematic iron homeostasis via BMP6-mediated regulation of hepcidin. Moreover, SMF balanced hepatic redox status with regulation on mitochondrial function and MAPKs/Nrf2/HO-1 pathway. Finally, we found that SMF activated hepatic autophagy and enhanced lipophagy by upregulating PNPLA2 expression in obese and diabetic mice. Our results demonstrated that SMF significantly ameliorated the development of hepatic injury in obese and diabetic mice by inhibiting inflammatory level, improving glycolipid metabolism, regulating iron metabolism, balancing redox level and activating autophagy.

Modulation of Nrf2/HO-1 by Natural Compounds in Lung Cancer

Oxidative stresses (OSs) are considered a pivotal factor in creating various pathophysiological conditions. Cells have been able to move forward by modulating numerous signaling pathways to moderate the defects of these stresses during their evolution. The company of Kelch-like ECH-associated protein 1 (Keap1) as a molecular sensing element of the oxidative and electrophilic stress and nuclear factor erythroid 2 (NF-E2)-related factor 2 (Nrf2) as a master transcriptional regulator of the antioxidant response makes a master cytoprotective antioxidant pathway known as the Keap1/Nrf2 pathway. This pathway is considered a dual-edged sword with beneficial features for both normal and cancer cells by regulating the gene expression of the array of endogenous antioxidant enzymes. Heme oxygenase-1 (HO-1), a critical enzyme in toxic heme removal, is one of the clear state indicators for the duality of this pathway. Therefore, Nrf2/HO-1 axis targeting is known as a novel strategy for cancer treatment. In this review, the molecular mechanism of action of natural antioxidants on lung cancer cells has been investigated by relying on the Nrf2/HO-1 axis.

The dual role of heme oxygenase in regulating apoptosis in the nervous system of Drosophila melanogaster

Accumulating evidence from mammalian studies suggests the dual-faced character of heme oxygenase (HO) in oxidative stress-dependent neurodegeneration. The present study aimed to investigate both neuroprotective and neurotoxic effects of heme oxygenase after the ho gene chronic overexpression or silencing in neurons of Drosophila melanogaster. Our results showed early deaths and behavioral defects after pan-neuronal ho overexpression, while survival and climbing in a strain with pan-neuronal ho silencing were similar over time with its parental controls. We also found that HO can be pro-apoptotic or anti-apoptotic under different conditions. In young (7-day-old) flies, both the cell death activator gene (hid) expression and the initiator caspase Dronc activity increased in heads of flies when ho expression was changed. In addition, various expression levels of ho produced cell-specific degeneration. Dopaminergic (DA) neurons and retina photoreceptors are particularly vulnerable to changes in ho expression. In older (30-day-old) flies, we did not detect any further increase in hid expression or enhanced degeneration, however, we still observed high activity of the initiator caspase. In addition, we used curcumin to further show the involvement of neuronal HO in the regulation of apoptosis. Under normal conditions, curcumin induced both the expression of ho and hid, which was reversed after exposure to high-temperature stress and when supplemented in flies with ho silencing. These results indicate that neuronal HO regulates apoptosis and this process depends on ho expression level, age of flies, and cell type.

Molecular Characterization of Spodoptera frugiperda Heme Oxygenase and Its Involvement in Susceptibility to Chlorantraniliprole

The mammalian heme oxygenase (HO) plays an important role in cytoprotection against oxidative-stress-induced cell damage; however, functional characterization of insect HO is still limited. In this study, cDNA encoding a HO, named SfHO, was cloned from Spodoptera frugiperda. Analysis of the transcription level and enzymatic activity showed that exposure of the LC₃₀ concentration of chlorantraniliprole to the third instar larvae significantly upregulated both the mRNA level and enzymatic activity of SfHO at 24 h after treatment. Further injection of the HO activator, hemin, into the third instar larvae led to the upregulation of SfHO as well as decreased susceptibility of S. frugiperda to chlorantraniliprole. Consistently, overexpression of SfHO increased the Sf9 cell viability under chlorantraniliprole treatment. Strikingly, both RNAi and the dual-luciferase reporter assay in Sf9 cells revealed that, unlike mammalian HO that is regulated by the transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2), SfHO was not subject to the regulation by cap 'n' collar isoform C (CncC), the Nrf2 homologue in insects. These data provide insights into the function and regulatory mechanism of insect HOs and had applied implications for the control of S. frugiperda.

Cystic Fibrosis Transmembrane Conductance Regulator Attenuates Oxidative Stress-Induced Injury in Diabetic Retinopathy Rats

PURPOSE

To investigate the effects of cystic fibrosis transmembrane conductance regulator (CFTR) on oxidative stress-induced injury of diabetic retinopathy (DR) rats.

METHODS

DR rat model was constructed treated with Ad-CFTR. Hematoxylin and Eosin (HE) staining was applied for testing the thickness of each layer of retinal tissues. Enzyme-linked immunosorbent assay (ELISA) was used to determine levels of serum inflammatory cytokines and contents of oxidative stress related genes in rats. Terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end labeling (TUNEL) staining was used to detect retinal cell apoptosis, and western blotting to measure the expression of MAPK/NF-κB pathway-related proteins in retinal tissues.

RESULTS

Our experiment revealed the remarkable decrease of CFTR protein in retinal tissues of DR rats. DR rats had decreased body weight and increased blood glucose level, with decreased thickness of total retinal thickness (TRT), outer nuclear layer and outer plexiform layer (ONL + OPL), inner nuclear layer (INL), and inner plexiform layer (IPL). Besides, DR rats were apparently up-regulated in the expression of pro-inflammatory cytokines, with increased malondial dehyde (MDA), p-ERK1/2/ERK1/2 and p-JNK1/2/JNK1/2 expressions, decreased superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activity in retinal tissues, as well as up-regulated p65 protein in nucleus and down-regulated p65 protein in cytoplasm. DR rats treated with Ad-CFTR were effectively improved regarding the above parameters except body weight and blood glucose.

CONCLUSIONS

CFTR can inhibit MAPK/NF-κB signaling pathway to ameliorate inflammatory response and oxidative stress-induced injury of DR rats, thereby reducing retinal cell apoptosis and playing a protective role in retina.

Mechanisms of 15-Epi-LXA4-Mediated HO-1 in Cytoprotection Following Inflammatory Injury

INTRODUCTION

Heme oxygenase-1 (HO-1) is a protective protein in oxidative stress response. LXA4 is an "inflammatory braking signal" that is widely studied at present. The purpose of this study was to elucidate that LXA4 can protect cells by inducing HO-1 in human pulmonary microvascular endothelial cells (HPMECs) as in vitro model to explain acute lung injury after severe acute pancreatitis.

METHODS

This study was performed in two parts: (1) To investigate the mechanisms of lipoxin A4-induced HO-1 expression in vitro, the study subjects were divided into four groups: a control group, LXA4 group (50 ng/mL LXA4), inhibitor group (50 ng/mL LXA4 + 20 μM LY294002 or 50 ng/mL LXA4 + 2 nmol/mL Bis II), and agonist group (50 ng/mL insulin-like growth factor 1, PMA). Western blotting was used to detect the expression of p-Akt, Akt, protein kinase C (PKC), p-Nrf2, Nrf2, and Keap1, and the location of Nrf2 was detected using immunofluorescence. The activation of antioxidant responsive element induced by Nrf2 was detected using Electrophoretic Mobility Shift Assay and (2) to investigate the cytoprotection of HO-1 induced by LXA4 in vitro, the subjects were divided into four groups: a control group, tumor necrosis factor α (TNF-α) group (50 ng/mL), LXA4 group (50 ng/mL TNF-α + 50 ng/mL LXA4), and Zinc protoporphyrin IX group (pretreated with 0.5 μM Zinc protoporphyrin IXfor 12 h, followed by 50 ng/mL TNF-α + 50 ng/mL LXA4). BCECF/AM-labeled THP-1 cells were used to analyze the adhesion of HPMECs, and a mitochondrial membrane potential assay kit with JC-1 was used to analyze the apoptosis of HPMECs.

RESULTS

In part one, (1) LXA4 upregulated the expression of HO-1 in a dose-dependent manner and (2) LXA4 activated the PI3K/Akt and PKC pathways and modulated the phosphorylation and subsequent depolymerization of Nrf2 from Keap1, promoting the translocation of Nrf2 to the nucleus. In part two, (1) LXA4 reversed the changes in mitochondrial membrane potential to alleviate apoptosis in HPMECs and (2) LXA4 attenuated the adhesion of HPMECs induced by TNF-α.

CONCLUSIONS

LXA4 can activate the PI3K/Akt and PKC pathways and induce the phosphorylation of Nrf2, resulting in the upregulation of HO-1. In addition, LXA4 alleviates adhesion and protects mitochondrial function by upregulating the expression of HO-1, which exerts cytoprotection in severe acute pancreatitis-induced lung injury.

Adipose-Derived Mesenchymal Stem Cells Alleviate Hypertrophic Scar by Inhibiting Bioactivity and Inducing Apoptosis in Hypertrophic Scar Fibroblasts

Background: As a fibrotic disease with a high incidence, the pathogenesis of hypertrophic scarring is still not fully understood, and the treatment of this disease is also challenging. In recent years, human adipose-derived mesenchymal stem cells (AD-MSCs) have been considered an effective treatment for hypertrophic scars. This study mainly explored whether the therapeutic effect of AD-MSCs on hypertrophic scars is associated with oxidative-stress-related proteins. Methods: AD-MSCs were isolated from adipose tissues and characterized through flow cytometry and a differentiation test. Afterwards, coculture, cell proliferation, apoptosis, and migration were detected. Western blotting and a quantitative real-time polymerase chain reaction (qRT-PCR) were used to detect oxidative stress-related genes and protein expression in hypertrophic scar fibroblasts (HSFs). Flow cytometry was used to detect reactive oxygen species (ROS). A nude mouse animal model was established; the effect of AD-MSCs on hypertrophic scars was observed; and hematoxylin and eosin staining, Masson's staining, and immunofluorescence staining were performed. Furthermore, the content of oxidative-stress-related proteins, including nuclear factor erythroid-2-related factor 2 (Nrf2), heme oxygenase 1 (HO-1), B-cell lymphoma 2(Bcl2), Bcl2-associated X(BAX) and caspase 3, was detected. Results: Our results showed that AD-MSCs inhibited HSFs' proliferation and migration and promoted apoptosis. Moreover, after coculture, the expression of antioxidant enzymes, including HO-1, in HSFs decreased; the content of reactive oxygen species increased; and the expression of Nrf2 decreased significantly. In animal experiments, we found that, at 14 days after injection of AD-MSCs into human hypertrophic scar tissue blocks that were transplanted onto the dorsum of nude mice, the weight of the tissue blocks decreased significantly. Hematoxylin and eosin staining and Masson's staining demonstrated a rearrangement of collagen fibers. We also found that Nrf2 and antioxidant enzymes decreased significantly, while apoptotic cells increased after AD-MSC treatment. Conclusions: Our results demonstrated that AD-MSCs efficiently cured hypertrophic scars by promoting the apoptosis of HSFs and by inhibiting their proliferation and migration, which may be related to the inhibition of Nrf2 expression in HSFs, suggesting that AD-MSCs may provide an alternative therapeutic approach for the treatment of hypertrophic scars.

Exposure to Heated Tobacco Products Aerosol Causes Acute Stress Responses in the Lung of Mouse

In the present study, we evaluated the acute response of mice exposed to IQOS aerosol, a brand-name heated tobacco product (HTP), in the lung tissue. First, the thiobarbituric acid-reactive substances (TBA-RS) value was measured as an index to assess oxidative stress, and a significant increase was observed after exposure, followed by a significant increase in the total lung GSH concentration. The stress responses induced by IQOS aerosols was then analyzed by focusing on the changes in Nrf2 and ATF4, which are transcription factors that induce the expression of genes involved in GSH biosynthesis or metabolism. Although Nrf2 activation was not observed, significant accumulation of ATF4 in the nuclear fraction was noted three hours after exposure to IQOS aerosols. Upon an examination of changes in factors in the GSH biosynthetic system, a significant increase in cystine concentration in the lung tissue was measured, and an increase in xCT expression level was observed in the cell membrane fraction three-six hours after IQOS exposure. Furthermore, characteristic changes in HO-1, a stress-response protein regulated by ATF4, was discovered six hours after IQOS exposure. Moreover, analysis of the upstream ATF4 regulatory system revealed that phosphorylation of eIF2α was enhanced in the lung cytoplasmic fraction three hours after exposure to IQOS aerosols. These findings suggest that ER stress might be induced as an early response to IQOS aerosol exposure, accompanied by the activation of the eIF2α-ATF4 axis. These intracellular changes have also been reported after exposure to combustible cigarette smoke. Thus, the acute response found in the lungs of mice in the present study demonstrate that the inhalation of aerosols from IQOS elicits a biological response similar to that of combustible cigarette smoke. In conclusion, our results provide evidence that the biological effects of HTPs, such as IQOS, cannot be ignored in the lungs.

Identification of Heme Oxygenase-1 as a Putative DNA-Binding Protein

Heme oxygenase-1 (HO-1) is a rate-limiting enzyme in degrading heme into biliverdin and iron. HO-1 can also enter the nucleus and regulate gene transcription independent of its enzymatic activity. Whether HO-1 can alter gene expression through direct binding to target DNA remains unclear. Here, we performed HO-1 CHIP-seq and then employed 3D structural modeling to reveal putative HO-1 DNA binding domains. We identified three probable DNA binding domains on HO-1. Using the Proteinarium, we identified several genes as the most highly connected nodes in the interactome among the HO-1 gene binding targets. We further demonstrated that HO-1 modulates the expression of these key genes using Hmox1 deficient cells. Finally, mutation of four conserved amino acids (E215, I211, E201, and Q27) within HO-1 DNA binding domain 1 significantly increased expression of Gtpbp3 and Eif1 genes that were identified within the top 10 binding hits normalized by gene length predicted to bind this domain. Based on these data, we conclude that HO-1 protein is a putative DNA binding protein, and regulates targeted gene expression. This provides the foundation for developing specific inhibitors or activators targeting HO-1 DNA binding domains to modulate targeted gene expression and corresponding cellular function.

Heme Oxygenase-1 as Therapeutic Target for Diabetic Foot Ulcers

A diabetic foot ulcer (DFU) is one of the major complications of diabetes. Wound healing under diabetic conditions is often impaired. This is in part due to the excessive oxidative stress, prolonged inflammation, immune cell dysfunction, delayed re-epithelialization, and decreased angiogenesis present at the wound site. As a result of these multifactorial impaired healing pathways, it has been difficult to develop effective therapeutic strategies for DFU. Heme oxygenase-1 (HO-1) is the rate-limiting enzyme in heme degradation generating carbon monoxide (CO), biliverdin (BV) which is converted into bilirubin (BR), and iron. HO-1 is a potent antioxidant. It can act as an anti-inflammatory, proliferative, angiogenic and cytoprotective enzyme. Due to its biological functions, HO-1 plays a very important role in wound healing, in part mediated through the biologically active end products generated by its enzymatic activity, particularly CO, BV, and BR. Therapeutic strategies involving the activation of HO-1, or the topical application of its biologically active end products are important in diabetic wound healing. Therefore, HO-1 is an attractive therapeutic target for DFU treatment. This review will provide an overview and discussion of the importance of HO-1 as a therapeutic target for diabetic wound healing.

Prevention of Oxidative Damage in Spinal Cord Ischemia Upon Aortic Surgery: First-In-Human Results of Shock Wave Therapy Prove Safety and Feasibility

Background Spinal cord ischemia (SCI) remains a devastating complication after aortic dissection or repair. A primary hypoxic damage is followed by a secondary damage resulting in further cellular loss via apoptosis. Affected patients have a poor prognosis and limited therapeutic options. Shock wave therapy (SWT) improves functional outcome, neuronal degeneration and survival in murine spinal cord injury. In this first-in-human study we treated 5 patients with spinal cord ischemia with SWT aiming to prove safety and feasibility. Methods and Results Human neurons were subjected to ischemic injury with subsequent SWT. Reactive oxygen species and cellular apoptosis were quantified using flow cytometry. Signaling of the antioxidative transcription factor NRF2 (nuclear factor erythroid 2-related factor 2) and immune receptor Toll-like receptor 3 (TLR3) were analyzed. To assess whether SWT act via a conserved mechanism, transgenic tlr3^-/- zebrafish created via CRISPR/Cas9 were subjected to spinal cord injury. To translate our findings into a clinical setting, 5 patients with SCI underwent SWT. Baseline analysis and follow-up (6 months) included assessment of American Spinal Cord Injury Association (ASIA) impairment scale, evaluation of Spinal Cord Independence Measure score and World Health Organization Quality of Life questionnaire. SWT reduced the number of reactive oxygen species positive cells and apoptosis upon ischemia via induction of the antioxidative factor nuclear factor erythroid 2-related factor 2. Inhibition or deletion of tlr3 impaired axonal growth after spinal cord lesion in zebrafish, whereas tlr3 stimulation enhanced spinal regeneration. In a first-in-human study, we treated 5 patients with SCI using SWT (mean age, 65.3 years). Four patients presented with acute aortic dissection (80%), 2 of them exhibited preoperative neurological symptoms (40%). Impairment was ASIA A in 1 patient (20%), ASIA B in 3 patients (60%), and ASIA D in 1 patient (20%) at baseline. At follow-up, 2 patients were graded as ASIA A (40%) and 3 patients as ASIA B (60%). Spinal cord independence measure score showed significant improvement. Examination of World Health Organization Quality of Life questionnaires revealed increased scores at follow-up. Conclusions SWT reduces oxidative damage upon SCI via immune receptor TLR3. The first-in-human application proved safety and feasibility in patients with SCI. SWT could therefore become a powerful regenerative treatment option for this devastating injury.

The loss of pancreatic islet NADPH oxidase (NOX)2 improves islet transplantation

Islet transplantation is a promising treatment strategy for type 1 diabetes mellitus (T1DM) patients. However, oxidative stress-induced graft failure due to an insufficient revascularization is a major problem of this therapeutic approach. NADPH oxidase (NOX)2 is an important producer of reactive oxygen species (ROS) and several studies have already reported that this enzyme plays a crucial role in the endocrine function and viability of β-cells. Therefore, we hypothesized that targeting islet NOX2 improves the outcome of islet transplantation. To test this, we analyzed the cellular composition and viability of isolated wild-type (WT) and Nox2-/- islets by immunohistochemistry as well as different viability assays. Ex vivo, the effect of Nox2 deficiency on superoxide production, endocrine function and anti-oxidant protein expression was studied under hypoxic conditions. In vivo, we transplanted WT and Nox2-/- islets into mouse dorsal skinfold chambers and under the kidney capsule of diabetic mice to assess their revascularization and endocrine function, respectively. We found that the loss of NOX2 does not affect the cellular composition and viability of isolated islets. However, decreased superoxide production, higher glucose-stimulated insulin secretion as well as expression of nuclear factor erythroid 2-related factor (Nrf)2, heme oxygenase (HO)-1 and superoxide dismutase 1 (SOD1) was detected in hypoxic Nox2-/- islets when compared to WT islets. Moreover, we detected an early revascularization, a higher take rate and restoration of normoglycemia in diabetic mice transplanted with Nox2-/- islets. These findings indicate that the suppression of NOX2 activity represents a promising therapeutic strategy to improve engraftment and function of isolated islets.

The different facets of heme-oxygenase 1 in innate and adaptive immunity

Heme oxygenase (HO) enzymes are responsible for the main oxidative step in heme degradation, generating equimolar amounts of free iron, biliverdin and carbon monoxide. HO-1 is induced as a crucial stress response protein, playing protective roles in physiologic and pathological conditions, due to its antioxidant, anti-apoptotic and anti-inflammatory effects. The mechanisms behind HO-1-mediated protection are being explored by different studies, affecting cell fate through multiple ways, such as reduction in intracellular levels of heme and ROS, transcriptional regulation, and through its byproducts generation. In this review we focus on the interplay between HO-1 and immune-related signaling pathways, which culminate in the activation of transcription factors important in immune responses and inflammation. We also discuss the dual interaction of HO-1 and inflammatory mediators that govern resolution and tissue damage. We highlight the dichotomy of HO-1 in innate and adaptive immune cells development and activation in different disease contexts. Finally, we address different known anti-inflammatory pharmaceuticals that are now being described to modulate HO-1, and the possible contribution of HO-1 in their anti-inflammatory effects.

In vitro 5-Fluorouracil resistance produces enhanced photodynamic therapy damage in SCC and tumor resistance in BCC

Non-melanoma skin cancer (NMSC) is the most common malignancy worldwide, with rising incidence in the recent years. It includes basal cell carcinoma (BCC), and squamous cell carcinoma (SCC). Several non-invasive therapies have been developed for its treatment such as topical 5-Fluorouracil (5FU) and photodynamic therapy (PDT), among others. Despite both are appropriated for NMSC treatment, recurrence cases have been reported. To prevent this, in this work we explore the potential of the combination of PDT and 5FU to treat SCC and BCC. First we evaluate the efficacy of PDT in cells resistant to 5FU. For this purpose, we use SCC-13 and CSZ-1 cells, obtained from a human SCC and a murine BCC, respectively. We first induced 5FU resistance in these cell lines by repeated treatments with the drug and then, the efficacy to PDT was evaluated. The results obtained indicated that SCC-5FU resistant cells were sensible to PDT administration, whereas BCC-5FU resistant cells were also resistant to PDT. The observed responses in both cell lines are in concordance to Protoporphyrin IX (PpIX) and reactive oxygen species (ROS) levels produced after the incubation with MAL and subsequent light exposure. The obtained data support the fact that PDT seems to be an appropriate therapeutic option to be administered after 5FU resistance in SCC. However, PDT would not be a choice therapy for resistant BCC cells to 5FU.

Effect of Thymoquinone on Renal Damage Induced by Hyperlipidemia in LDL Receptor-Deficient (LDL-R-/-) Mice

Hyperlipidemia is a well-established risk factor for kidney injury, which can lead to chronic kidney disease (CKD). Thymoquinone (TQ) is one of the most active ingredients in Nigella sativa seeds. It has various beneficial properties, including antioxidant and anti-inflammatory activities. TQ also exerts positive effects on doxorubicin- (DOX-) induced nephropathy and ischemia-reperfusion-induced kidney injury in rats. Therefore, in this study, we investigated the possible protective effects of TQ against kidney injury in low-density lipoprotein receptor-deficient (LDL-R^-/^-) mice. Eight-week-old male LDL-R^-/^- mice were randomly divided into the following three groups: normal diet (ND group), high-fat diet (HFD group), and HFD combined with TQ (HFD+TQ group). The mice were fed the same diet for eight weeks. After eight weeks, we performed serological analysis of the mice in all three groups. We histologically analyzed the kidney tissue and also investigated the expression of proinflammatory cytokines in the kidney tissue. Metabolic characteristics, including total cholesterol (TC), low-density lipoprotein-cholesterol (LDL-C), and creatinine (CRE) levels, were lower in the LDL-R^-/^- HFD+TQ mice than in the HFD mice. Periodic acid-Schiff (PAS) and Masson's trichrome staining revealed excessive lipid deposition and collagen accumulation in the kidneys of the LDL-R^-/^- HFD mice, which were significantly reduced in the LDL-R^-/^- HFD+TQ mice. Furthermore, macrophages and levels of proinflammatory cytokines were lower in the kidney tissues of the LDL-R^-/^- HFD+TQ mice than in those of the LDL-R^-/^- HFD mice. Moreover, profibrosis- and oxidative stress-related protein expression was lower in the kidney tissues of the LDL-R^-/^- HFD+TQ mice than in those of the LDL-R^-/^- HFD mice. These results indicate that TQ may be a potential therapeutic agent for kidney damage caused by hyperlipidemia.

The Nuclear Translocation of Heme Oxygenase-1 in Human Diseases

Heme oxygenase-1 (HO-1) is a rate-limiting enzyme in the degradation of heme to generate carbon monoxide (CO), free iron and biliverdin, which could then be converted to bilirubin by biliverdin reductase. HO-1 exhibits cytoprotective effects of anti-apoptosis, anti-oxidation, and anti-inflammation via these byproducts generated during the above process. In the last few years, despite the canonical function of HO-1 and possible biological significance of its byproducts, a noncanonical function, through which HO-1 exhibits functions in diseases independent of its enzyme activity, also has been reported. In this review, the noncanonical functions of HO-1 and its translocation in other subcellular compartments are summarized. More importantly, we emphasize the critical role of HO-1 nuclear translocation in human diseases. Intriguingly, this translocation was linked to tumorigenesis and tumor progression in lung, prostate, head, and neck squamous cell carcinomas and chronic myeloid leukemia. Given the importance of HO-1 nuclear translocation in human diseases, nuclear HO-1 as a novel target might be attractive for the prevention and treatment of human diseases.

Therapeutic implication of carbon monoxide in drug resistant cancers

Drug resistance is the major obstacle that undermines effective cancer treatment. Recently, the application of gas signaling molecules, e.g., carbon monoxide (CO), in overcoming drug resistance has gained significant attention. Growing evidence showed that CO could inhibit mitochondria respiratory effect and glycolysis, two major ATP production pathways in cancer cells, and suppress angiogenesis and inhibit the activity of cystathionine β-synthase that is important in regulating cancer cells homeostasis, leading to synergistic effects when combined with cisplatin, doxorubicin, or phototherapy, etc. in certain resistant cancer cells. In the current review, we attempted to have a summary of these research conducted in the past decade using CO in treating drug resistant cancers, and have a detailed interpretation of the underlying mechanisms. The critical challenges will be discussed and potential solutions will also be provided. The information collected in this work will hopefully evoke more effects in using CO for the treatment of drug resistant cancers.

Heme Oxygenase-1 Protects Hair Cells From Gentamicin-Induced Death

Gentamicin ototoxicity can generate free radicals within the inner ear, leading to permanent damage to sensory hair cells (HCs) and eventually hearing loss. The following study examined the alterations of oxidative damage-related genes in the cochlea and important molecules responsible for oxidation following gentamicin injury in vitro. The RT² Profiler polymerase chain reaction (PCR) array was used to screen candidate targets for treatment to prevent hearing loss caused by gentamicin. We found that during gentamicin-induced death in HCs, Heme oxygenase-1 (HO-1) had a high fold change in the HCs of the cochlea. Moreover, the use of CoPPIX to induce HO-1 inhibited gentamicin-induced HC death, while HO-1 inhibitors ZnPPIX after CoPPIX reversed this process. Furthermore, the inhibitors of NF-E2-related factor-2 (Nrf2) reduced the expression of HO-1 and inhibited the protective effect of HO-1 after gentamicin, thus suggesting that the Nrf2/HO-1 axis might regulate gentamicin-associated ototoxicity. We further demonstrated that induction of HO-1 up-regulated the expression of Nrf2 in both cochlear and HEI-OC1 cells. In summary, these findings indicated that HO-1 protects HCs from gentamicin by up-regulating its expression in HCs and interacting with Nrf2 to inhibit reactive oxygen species (ROS).

Induction of Heme Oxygenase-1 by 15d-Prostaglandin J2 Mediated via a ROS-Dependent Sp1 and AP-1 Cascade Suppresses Lipopolysaccharide-Triggered Interleukin-6 Expression in Mouse Brain Microvascular Endothelial Cells

Heme oxygenase-1 (HO-1) has been shown to exert antioxidant, anti-inflammatory, and anti-apoptotic effects in various types of cells. Therefore, the induction of HO-1 is an excellent rationale for the development of protective drugs. 15-Deoxy-Δ^12,14-prostaglandin J₂ (15d-PGJ₂) can modulate the expression of antioxidant defense proteins and be beneficial for neuroinflammation. Brain endothelial cells play an important role in the pathophysiology of brain disorders. Whether 15d-PGJ₂ can induce HO-1 expression and protect against the inflammatory responses in mouse brain microvascular endothelial (bEnd.3) cells remains unclear. Here, we reveal that 15d-PGJ₂ stimulated HO-1 protein and mRNA expression in a time- and concentration-dependent manner in bEnd.3 cells, which was attenuated by diphenyleneiodonium chloride (DPI) and MitoTempo. Thus, activation of NADPH oxidase (NOX)- and mitochondria-derived reactive oxygen species (ROS) mediated 15d-PGJ₂-induced HO-1 expression. ROS generation could cause phosphorylation of protein kinase C (PKC)δ, leading to HO-1 expression, which was suppressed by Rottlerin (selective inhibitor PKCδ), DPI, and MitoTempo. We further demonstrated that phosphorylation of c-Jun N-terminal kinase (JNK)1/2 participated in 15d-PGJ₂-upregulated HO-1 expression, which was blocked by SP600125 or Rottlerin. Moreover, 15d-PGJ₂-induced HO-1 expression was mediated through the activation of c-Jun (a subunit of activator protein 1 (AP-1)) and specificity protein 1 (Sp1), leading to their interaction with the HO-1 promoter, revealed by chromatin immunoprecipitation assay, which was attenuated by SP600125, Mithramycin A, or Tanshinone II A. We further verified the anti-inflammatory effect of HO-1 expression. Our results showed that 15d-PGJ₂-induced HO-1 could mitigate the lipopolysaccharide-triggered interleukin-6 expression and secretion, as measured by an ELISA assay kit. These results suggest that 15d-PGJ₂-induced HO-1 expression is mediated through the activation of NOX- and mitochondria-derived ROS-dependent PKCδ/JNK1/2/Sp1 and the AP-1 signaling pathway and protects against inflammatory responses in bEnd.3 cells.

Non-canonical vs. Canonical Functions of Heme Oxygenase-1 in Cancer

Heme oxygenase-1 (HO-1) is a critical stress-responsive enzyme that has antioxidant and anti-inflammatory functions. HO-1 catalyzes heme degradation, which gives rise to the formation of carbon monoxide (CO), biliverdin, and iron. The upregulation of HO-1 under pathological conditions associated with cellular stress represents an important cytoprotective defense mechanism by virtue of the anti-oxidant properties of the bilirubin and the anti-inflammatory effect of the CO produced. The same mechanism is hijacked by premalignant and cancerous cells. In recent years, however, there has been accumulating evidence supporting that the upregulation of HO-1 promotes cancer progression, independently of its catalytic activity. Such non-canonical functions of HO-1 are associated with its interaction with other proteins, particularly transcription factors. HO-1 also undergoes post-translational modifications that influence its stability, functional activity, cellular translocation, etc. HO-1 is normally present in the endoplasmic reticulum, but distinct subcellular localizations, especially in the nucleus, are observed in multiple cancers. The nuclear HO-1 modulates the activation of various transcription factors, which does not appear to be mediated by carbon monoxide and iron. This commentary summarizes the non-canonical functions of HO-1 in the context of cancer growth and progression and underlying regulatory mechanisms.

Non-canonical vs. Canonical Functions of Heme Oxygenase-1 in Cancer

Heme oxygenase-1 (HO-1) is a critical stress-responsive enzyme that has antioxidant and anti-inflammatory functions. HO-1 catalyzes heme degradation, which gives rise to the formation of carbon monoxide (CO), biliverdin, and iron. The upregulation of HO-1 under pathological conditions associated with cellular stress represents an important cytoprotective defense mechanism by virtue of the anti-oxidant properties of the bilirubin and the anti-inflammatory effect of the CO produced. The same mechanism is hijacked by premalignant and cancerous cells. In recent years, however, there has been accumulating evidence supporting that the upregulation of HO-1 promotes cancer progression, independently of its catalytic activity. Such non-canonical functions of HO-1 are associated with its interaction with other proteins, particularly transcription factors. HO-1 also undergoes post-translational modifications that influence its stability, functional activity, cellular translocation, etc. HO-1 is normally present in the endoplasmic reticulum, but distinct subcellular localizations, especially in the nucleus, are observed in multiple cancers. The nuclear HO-1 modulates the activation of various transcription factors, which does not appear to be mediated by carbon monoxide and iron. This commentary summarizes the non-canonical functions of HO-1 in the context of cancer growth and progression and underlying regulatory mechanisms.

Cyclophosphamide Induces the Ferroptosis of Tumor Cells Through Heme Oxygenase-1

Ferroptosis has been implicated in the therapeutic responses of various types of tumors. Cyclophosphamide (CTX), one of the most successful antitumor agents, is widely used to treat both hematopoietic and solid tumors. In this study, we revealed the ferroptosis pathway targeted by CTX treatment in tumor cells and clarified its mechanisms. Cell viability was remarkably suppressed by CTX, accompanied by the accumulation of intracellular iron and reactive oxygen species (ROS), reduced glutathione levels, deformed mitochondria and a loss of the mitochondrial membrane potential. These effects were impeded by the ferroptosis inhibitors ferrostatin-1 (Fer1) and deferoxamine (DFO). Moreover, CTX treatment obviously upregulated nuclear factor E2 related factor 2 (NRF2) and heme oxygenase-1 (HMOX-1) expression. Additionally, the HMOX-1 inducer Hemin notably enhanced CTX-mediated tumor inhibition in vitro and in vivo through a mechanism that involved interfering with the ferroptosis process. Therefore, our findings indicated ferroptosis induction by CTX through the activation of the NRF2/HMOX-1 pathway, which might provide a potential strategy for tumor chemotherapy.

Methyltransferase like 7B is a potential therapeutic target for reversing EGFR-TKIs resistance in lung adenocarcinoma

BACKGROUND

Identification of potential novel targets for reversing resistance to Epidermal Growth Factor Receptor (EGFR)-tyrosine kinase inhibitors (EGFR-TKIs) holds great promise for the treatment of relapsed lung adenocarcinoma (LUAD). In the present study, we aim to investigate the role of methyltransferase-like 7B (METTL7B) in inducing EGFR-TKIs resistance in LUAD and whether it could be a therapeutic target for reversing the resistance.

METHODS

METTL7B-overexpressed LUAD cell lines, gefitinib and osimertinib-resistant Cell-Derived tumor Xenograft (CDX) and Patient-Derived tumor Xenograft (PDX) mouse models were employed to evaluate the role of METTL7B in TKIs resistance. Ultraperformance liquid chromatography-tandem mass spectrometer (UPLC-MS/MS) was used to identify the metabolites regulated by METTL7B. Methylated RNA immunoprecipitation (MeRIP)-qPCR analysis was performed to measure the N⁶-methyladenosine (m⁶A) status of mRNA of METTL7B targeted genes. Gold nanocluster-assisted delivery of siRNA targeting METTL7B (GNC-siMETTL7B) was applied to evaluate the effect of METTL7B in TKIs resistance.

RESULTS

Increased expression of METTL7B was found in TKIs-resistant LUAD cells and overexpression of METTL7B in LUAD cells induced TKIs resistance both in vitro and in vivo. Activated ROS-metabolism was identified in METTL7B-overexpressed LUAD cells, accompanied with upregulated protein level of GPX4, HMOX1 and SOD1 and their enzymatic activities. Globally elevated m⁶A levels were found in METTL7B-overexpressed LUAD cells, which was reduced by knock-down of METTL7B. METTL7B induced m⁶A modification of GPX4, HMOX1 and SOD1 mRNA. Knock-down of METTL7B by siRNA re-sensitized LUAD cells to gefitinib and osimertinib both in vitro and in vivo.

CONCLUSIONS

This study uncovered a new critical link in METTL7B, glutathione metabolism and drug resistance. Our findings demonstrated that METTL7B inhibitors could be used for reversing TKIs resistance in LUAD patients.

Redox modulation by plant polyphenols targeting vitagenes for chemoprevention and therapy: Relevance to novel anti-cancer interventions and mini-brain organoid technology

The scientific community, recently, has focused notable attention on the chemopreventive and therapeutic effects of dietary polyphenols for human health. Emerging evidence demonstrates that polyphenols, flavonoids and vitamins counteract and neutralize genetic and environmental stressors, particularly oxidative stress and inflammatory process closely connected to cancer initiation, promotion and progression. Interestingly, polyphenols can exert antioxidant or pro-oxidant cytotoxic effects depending on their endogenous concentration. Notably, polyphenols at high dose act as pro-oxidants in a wide type of cancer cells by inhibiting Nrf2 pathway and the expression of antioxidant vitagenes, such as NAD(P)H-quinone oxidoreductase (NQO1), glutathione transferase (GT), GPx, heme oxygenase-1 (HO-1), sirtuin-1 (Sirt1) and thioredoxin (Trx) system which play an essential role in the metabolism of reactive oxygen species (ROS), detoxification of xenobiotics and inhibition of cancer progression, by inducing apoptosis and cell cycle arrest according to the hormesis approach. Importantly, mutagenesis of Nrf2 pathway can exacerbate its "dark side" role, representing a crucial event in the initiation stage of carcinogenesis. Herein, we review the hormetic effects of polyphenols and nanoincapsulated-polyphenols in chemoprevention and treatment of brain tumors via activation or inhibition of Nrf2/vitagenes to suppress carcinogenesis in the early stages, and thus inhibit its progression. Lastly, we discuss innovative preclinical approaches through mini-brain tumor organoids to study human carcinogenesis, from basic cancer research to clinical practice, as promising tools to recapitulate the arrangement of structural neuronal tissues and biological functions of the human brain, as well as test drug toxicity and drive personalized and precision medicine in brain cancer.

Nutrition, Immunology, and Kidney: Looking Beyond the Horizons

PURPOSE OF REVIEW

Chronic kidney disease (CKD) is epidemic throughout the word. Despite various novel therapeutic opportunities, CKD is still associated with high morbidity and mortality. In CKD, patient's chronic inflammation is frequent and related with adverse outcomes. Both innate and adaptive immunity are dysfunctional in CKD. Therefore, it is plausible to interfere with dysfunctional immunity in these patients. In the current review, we present the updated experimental and clinical data summarizing the effects of nutritional interventions including natural products and dietary supplements on immune dysfunction in the context of CKD.

RECENT FINDINGS

Nutritional interventions including natural products and dietary supplements (e.g., curcumin, sulforaphane, resistant starch, anthocyanin, chrysin, short chain fatty acids, fish oil resistant starch) slow down the inflammation by at least 6 mechanisms: (i) decrease nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB); (ii) decrease NLR family pyrin domain containing 3 (NLRP3); (iii) decrease interleukin-1 (IL-1), decrease interleukin-6 (IL-6) secretion; (iv) decrease polymorphonuclear priming); (v) promote anti-inflammatory pathways (nuclear factor-erythroid factor 2-related factor 2 (NFR2); (vi) increase T regulatory (Tregs) cells). Natural products and dietary supplements may provide benefit in terms of kidney health. By modulation of nutritional intake, progression of CKD may be delayed.

Effects of Heme Oxygenase-1 on c-Kit-Positive Cardiac Cells

Heme oxygenase-1 (HO-1) is one of the most powerful cytoprotective proteins known. The goal of this study was to explore the effects of HO-1 in c-kit-positive cardiac cells (CPCs). Lin^NEG/c-kit^POS CPCs were isolated and expanded from wild-type (WT), HO-1 transgenic (TG), or HO-1 knockout (KO) mouse hearts. Compared with WT CPCs, cell proliferation was significantly increased in HO-1^TG CPCs and decreased in HO-1^KO CPCs. HO-1^TG CPCs also exhibited a marked increase in new DNA synthesis during the S-phase of cell division, not only under normoxia (21% O₂) but after severe hypoxia (1% O₂ for 16 h). These properties of HO-1^TG CPCs were associated with nuclear translocation (and thus activation) of Nrf2, a key transcription factor that regulates antioxidant genes, and increased protein expression of Ec-SOD, the only extracellular antioxidant enzyme. These data demonstrate that HO-1 upregulates Ec-SOD in CPCs and suggest that this occurs via activation of Nrf2, which thus is potentially involved in the crosstalk between two antioxidants, HO-1 in cytoplasm and Ec-SOD in extracellular matrix. Overexpression of HO-1 in CPCs may improve the survival and reparative ability of CPCs after transplantation and thus may have potential clinical application to increase efficacy of cell therapy.

Heme Oxygenase 1 in Vertebrates: Friend and Foe

HO-1 is the inducible form of the enzyme heme-oxygenase. HO-1 catalyzes heme breakdown, reducing the levels of this important oxidant molecule and generating antioxidant, anti-inflammatory, and anti-apoptotic byproducts. Thus, HO-1 has been described as an important stress response mechanism during both physiologic and pathological processes. Interestingly, some findings are demonstrating that uncontrolled levels of HO-1 byproducts can be associated with cell death and tissue destruction as well. Furthermore, HO-1 can be located in the nucleus, influencing gene transcription, cellular proliferation, and DNA repair. Here, we will discuss several studies that approach HO-1 effects as a protective or detrimental mechanism in different pathological conditions. In this sense, as the major organs of vertebrates will deal specifically with distinct types of stresses, we discuss the HO-1 role in each of them, exposing the contradictions associated with HO-1 expression after different insults and circumstances.

Roburic acid attenuates osteoclastogenesis and bone resorption by targeting RANKL-induced intracellular signaling pathways

Excessive activity of osteoclasts contributes to skeletal diseases such as osteoporosis and osteolysis. However, current drugs targeting osteoclast have various deficiencies, placing natural compounds as substitutions of great potential. Roburic acid (RA) is a triterpenoid exacted from Radix Gentianae Macrophyllae, which exhibits inhibitory effects on inflammation and oxidation. By employing an in vitro osteoclastogenesis model, this study investigates the effects and mechanisms of RA on intracellular signaling induced by receptor activator of nuclear factor-κB ligand (RANKL). As expected, RA at a concentration scope from 1 to 10 μM dampened the osteoclast differentiation of bone marrow macrophages (BMMs) but without cell toxicity. Interestingly, RA showed no effect on osteoblastogenesis in vitro. Furthermore, RA mitigated F-actin ring formation, hydroxyapatite resorption, and gene expression in osteoclasts. Mechanistically, RA suppressed TNF receptor-associated factor 6 (TRAF6), the crucial adaptor protein following RANKL-RANK binding. On the one hand, RA downregulated the nuclear factor-κB (NF-κB) activity, extracellular regulated protein kinases (ERK) phosphorylation, and calcium oscillations. On the other hand, RA upregulated the antioxidative response element (ARE) response and the protein expression of heme oxygenase (HO)-1. These upstream alterations eventually led to the suppression of the nuclear factor of activated T cells 1 (NFATc1) activity and the expression of proteins involved in osteoclastogenesis and bone resorption. Furthermore, by using an ovariectomized (OVX) mice model, RA was found to have therapeutic effects against bone loss. On account of these findings, RA could be used to restrain osteoclasts for treating osteoporosis and other osteolytic diseases.

Forensic significance of intracardiac heme oxygenase-1 expression in acute myocardial ischemia

Heme oxygenase-1 (HO-1), an inducible stress-response protein, exerts anti-oxidant and anti-apoptotic effects. However, its significance in forensic diagnosis of acute ischemic heart diseases (AIHD) such as myocardial infarction (MI) is still unknown. We examined the immunohistochemical expression of HO-1 in the heart samples to discuss their forensic significance to determine acute cardiac ischemia. The heart samples were obtained from 23 AIHD cases and 33 non-AIHD cases as controls. HO-1 positive signals in cardiomyocyte nuclear were detected in 78.2% of AIHD cases, however, that were detected in only 24.2% control cases with statistical difference between AIHD and non-AIHD groups. In contrast to HO-1 protein expression, there was no significant difference in the appearance of myoglobin pallor regions and leukocyte infiltration in the hearts between AIHD and non-AIHD groups. From the viewpoints of forensic pathology, intracardiac HO-1 expression would be considered a valuable marker to diagnose AIHD as the cause of death.

The non-canonical effects of heme oxygenase-1, a classical fighter against oxidative stress

The role of heme oxygenase-1 in resisting oxidative stress and cell protection has always been a hot research topic. With the continuous deepening of research, in addition to directly regulating redox by catalyzing the degradation of heme, HO-1 protein also participates in the gene expression level in a great diversity of methods, thereby initiating cell defense. Particularly the non-canonical nuclear-localized HO-1 and HO-1 protein interactions play the role of a warrior against oxidative stress. Besides, HO-1 may be a promising marker for disease prediction and detection in many clinical trials. Especially for malignant diseases, there may be new advances in the treatment of HO-1 by regulating abnormal ROS and metabolic signaling. The purpose of this review is to systematically sort out and describe several aspects of research to facilitate further detailed mechanism research and clinical application promotion in the future.

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The different subcellular localizations ofHO-1 implies that it has special functions.

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Nuclear HO-1 plays an indispensable role in gene regulation and other aspects.

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The interactions between HO-1 and others provide the possibility to participate in vital physiological processes.

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HO-1 may become a potential disease assessment marker.

Heme Oxygenase-1 at the Nexus of Endothelial Cell Fate Decision Under Oxidative Stress

Endothelial cells (ECs) form the inner lining of blood vessels and are central to sensing chemical perturbations that can lead to oxidative stress. The degree of stress is correlated with divergent phenotypes such as quiescence, cell death, or senescence. Each possible cell fate is relevant for a different aspect of endothelial function, and hence, the regulation of cell fate decisions is critically important in maintaining vascular health. This study examined the oxidative stress response (OSR) in human ECs at the boundary of cell survival and death through longitudinal measurements, including cellular, gene expression, and perturbation measurements. 0.5 mM hydrogen peroxide (HP) produced significant oxidative stress, placed the cell at this junction, and provided a model to study the effectors of cell fate. The use of systematic perturbations and high-throughput measurements provide insights into multiple regimes of the stress response. Using a systems approach, we decipher molecular mechanisms across these regimes. Significantly, our study shows that heme oxygenase-1 (HMOX1) acts as a gatekeeper of cell fate decisions. Specifically, HP treatment of HMOX1 knockdown cells reversed the gene expression of about 51% of 2,892 differentially expressed genes when treated with HP alone, affecting a variety of cellular processes, including anti-oxidant response, inflammation, DNA injury and repair, cell cycle and growth, mitochondrial stress, metabolic stress, and autophagy. Further analysis revealed that these switched genes were highly enriched in three spatial locations viz., cell surface, mitochondria, and nucleus. In particular, it revealed the novel roles of HMOX1 on cell surface receptors EGFR and IGFR, mitochondrial ETCs (MTND3, MTATP6), and epigenetic regulation through chromatin modifiers (KDM6A, RBBP5, and PPM1D) and long non-coding RNA (lncRNAs) in orchestrating the cell fate at the boundary of cell survival and death. These novel aspects suggest that HMOX1 can influence transcriptional and epigenetic modulations to orchestrate OSR affecting cell fate decisions.

In silico Characterization of the Heme Oxygenase 1 From Bottlenose Dolphin (Tursiops truncatus): Evidence of Changes in the Active Site and Purifying Selection

Cetacea is a clade well-adapted to the aquatic lifestyle, with diverse adaptations and physiological responses, as well as a robust antioxidant defense system. Serious injuries caused by boats and fishing nets are common in bottlenose dolphins (Tursiops truncatus); however, these animals do not show signs of serious infections. Evidence suggests an adaptive response to tissue damage and associated infections in cetaceans. Heme oxygenase (HO) is a cytoprotective protein that participates in the anti-inflammatory response. HO catalyzes the first step in the oxidative degradation of the heme group. Various stimuli, including inflammatory mediators, regulate the inducible HO-1 isoform. This study aims to characterize HO-1 of the bottlenose dolphin in silico and compare its structure to the terrestrial mammal protein. Upstream HO-1 sequence of the bottlenose dolphin was obtained from NCBI and Ensemble databases, and the gene structure was determined using bioinformatics tools. Five exons and four introns were identified, and proximal regulatory elements were detected in the upstream region. The presence of 10 α-helices, three 310 helices, the heme group lodged between the proximal and distal helices, and a histidine-25 in the proximal helix serving as a ligand to the heme group were inferred for T. truncatus. Amino acid sequence alignment suggests HO-1 is a conserved protein. The HO-1 "fingerprint" and histidine-25 appear to be fully conserved among all species analyzed. Evidence of positive selection within an α-helix configuration without changes in protein configuration and evidence of purifying selection were found, indicating evolutionary conservation of the coding sequence structure.