TERF2/TRF2 is a pleiotropic telomeric protein that plays a crucial role in tumor formation and progression through several telomere-dependent and -independent mechanisms. Here, we uncovered a novel function for this protein in regulating the macroautophagic/autophagic process upon different stimuli. By using both biochemical and cell biology approaches, we found that TERF2 binds to the non-histone chromatin-associated protein HMGB1, and this interaction is functional to the nuclear/cytoplasmic protein localization. Specifically, silencing of TERF2 alters the redox status of the cells, further exacerbated upon EBSS nutrient starvation, promoting the cytosolic translocation and the autophagic activity of HMGB1. Conversely, overexpression of wild-type TERF2, but not the mutant unable to bind HMGB1, negatively affects the cytosolic translocation of HMGB1, counteracting the stimulatory effect of EBSS starvation. Moreover, genetic depletion of HMGB1 or treatment with inflachromene, a specific inhibitor of its cytosolic translocation, completely abolished the pro-autophagic activity of TERF2 silencing. In conclusion, our data highlighted a novel mechanism through which TERF2 modulates the autophagic process, thus demonstrating the key role of the telomeric protein in regulating a process that is fundamental, under both physiological and pathological conditions, in defining the fate of the cells.Abbreviations: ALs: autolysosomes; ALT: alternative lengthening of telomeres; ATG: autophagy related; ATM: ATM serine/threonine kinase; CQ: Chloroquine; DCFDA: 2',7'-dichlorofluorescein diacetate; DDR: DNA damage response; DHE: dihydroethidium; EBSS: Earle's balanced salt solution; FACS: fluorescence-activated cell sorting; GFP: green fluorescent protein; EGFP: enhanced green fluorescent protein; GSH: reduced glutathione; GSSG: oxidized glutathione; HMGB1: high mobility group box 1; ICM: inflachromene; IF: immunofluorescence; IP: immunoprecipitation; NAC: N-acetyl-L-cysteine; NHEJ: non-homologous end joining; PLA: proximity ligation assay; RFP: red fluorescent protein; ROS: reactive oxygen species; TIF: telomere-induced foci; TERF2/TRF2: telomeric repeat binding factor 2.

HMGB1 is a ubiquitous non-histone protein, which biological effects depend on its expression and subcellular location. Inside the nucleus, HMGB1 is engaged in many DNA events such as DNA repair, transcription and telomere maintenance. HMGB1 has been reported to bind preferentially to bent DNA as well as to noncanonical DNA structures like 4-way junctions and, more recently, to G-quadruplexes. These are four-stranded conformations of nucleic acids involved in important cellular processes, including telomere maintenance. In this frame, G-quadruplex recognition by specific proteins represents a key event to modulate physiological or pathological pathways. Herein, to get insights into the telomeric G-quadruplex DNA recognition by HMGB1, we performed detailed biophysical studies complemented with biological analyses. The obtained results provided information about the molecular determinants for the interaction and showed that the structural variability of human telomeric G-quadruplex DNA may have significant implications in HMGB1 recognition. The biological data identified HMGB1 as a telomere-associated protein in both telomerase-positive and -negative tumor cells and showed that HMGB1 gene silencing in such cells induces telomere DNA damage foci. Altogether, these findings provide a deeper understanding of telomeric G-quadruplex recognition by HMGB1 and suggest that this protein could actually represent a new target for cancer therapy.

The high mobility group box (HMGB) 1 protein, one of the most abundant nuclear non-histone proteins has been known for its inhibitory effect on repair of DNA damaged by the antitumor drug cisplatin. Here, we report the first results that link HMGB1 to repair of cisplatin-treated DNA at nucleosome level. Experiments were carried out with three types of reconstituted nucleosomes strongly positioned on the damaged DNA: linker DNA containing nucleosomes (centrally and end-positioned) and core particles. The highest repair synthesis was registered with end-positioned nucleosomes, two and three times more efficient than that with centrally positioned nucleosomes and core particles, respectively. HMGB1 inhibited repair of linker DNA containing nucleosomes more efficiently than that of core particles. Just the opposite was the effect of the in vivo acetylated HMGB1: stronger repair inhibition was obtained with core particles. No inhibition was observed with HMGB1 lacking the acidic tail. Binding of HMGB1 proteins to different nucleosomes was also analysed. HMGB1 bound preferentially to damage nucleosomes containing linker DNA, while the binding of the acetylated protein was linker independent. We show that both the repair of cisplatin-damaged nucleosomes and its inhibition by HMGB1 are nucleosome position-dependent events which are accomplished via the acidic tail and modulated by acetylation.

Caspase-11, a cytosolic endotoxin (lipopolysaccharide: LPS) receptor, mediates pyroptosis, a lytic form of cell death. Caspase-11-dependent pyroptosis mediates lethality in endotoxemia, but it is unclear how LPS is delivered into the cytosol for the activation of caspase-11. Here we discovered that hepatocyte-released high mobility group box 1 (HMGB1) was required for caspase-11-dependent pyroptosis and lethality in endotoxemia and bacterial sepsis. Mechanistically, hepatocyte-released HMGB1 bound LPS and targeted its internalization into the lysosomes of macrophages and endothelial cells via the receptor for advanced glycation end-products (RAGE). Subsequently, HMGB1 permeabilized the phospholipid bilayer in the acidic environment of lysosomes. This resulted in LPS leakage into the cytosol and caspase-11 activation. Depletion of hepatocyte HMGB1, inhibition of hepatocyte HMGB1 release, neutralizing extracellular HMGB1, or RAGE deficiency prevented caspase-11-dependent pyroptosis and death in endotoxemia and bacterial sepsis. These findings indicate that HMGB1 interacts with LPS to mediate caspase-11-dependent pyroptosis in lethal sepsis.

Recently, High Mobility Group Box1 (HMGB1) protein has been reported as an inflammatory cytokine present in all nucleated cells with crucial role in the genesis and promotion of cancer. No HMGB1 protein mice model and its active site details are available to validate mice in vivo experiments. Here, for the first time we have reported in silico mice HMGB1 model using human HMGB1 template. Prepared HMGB1 secondary structure showed 6-α helices, 5-β turns, 2-γ turns with 67% α-helices, 32% coil and 9% turn without β-sheet, and classified as α-class protein. Ramachandran plot analysis showed 98.2% and 92.3% residues lies in favoured region, verified by RAMPAGE and PDBsum server respectively. Cancer atlas of HMGB1 protein showed up-regulated expression of HMGB1 gene in different cancer, proved by CAB (CAB005873) and HPA-antibody (HPA003506) in silico. HMGB1 protein showed interaction with different biologically important inflammatory protein as depicted in STRING result.Prominent active site has residues Tyr78Ile79Pro80-81Lys82Gly83vGlu84Thr85Lys86-88Phe89Lys90Asp91Pro92Asn93Tyr162Lys165 with 310 Å3 site volume.Interacting residues of CGA-HMGB1 docked complex were ILE79PRO80-81LYS82GLY83GLU84LYS86-88PHE89Arg163Ala164LYS165Gly166 with docking score 3872 and surface area 412.6. CGA-conformer C3950 showed best docking than CGA and conformer-ZINC03947476, iso-chlorogenic acid and cischlorogenic acid. HMGB1 mice model could be a good therapeutic target for anti-cancerous drugs.

Neutrophil extracellular traps (NETs) are produced through ejection of genomic DNA by neutrophils into extracellular space and serve as a weapon to fight against pathogens. Neutrophil elastase, a serine protease loaded on NETs, attacks and kills pathogens, while extracellular high-mobility-group-box-1 (HMGB1) protein serves as a danger signal to other cells. How the action of these factors is coordinated as part of the innate immune response is not fully understood. In this article, using biochemical and biophysical approaches, we demonstrate that DNA mediates specific proteolysis of HMGB1 by neutrophil elastase and that the proteolytic processing remarkably enhances binding activities of extracellular HMGB1. Through the DNA-mediated proteolysis of HMGB1 by neutrophil elastase, the negatively charged segment containing D/E repeats is removed from HMGB1. This proteolytic removal of the C-terminal tail causes a substantial increase in binding activities of HMGB1 because the D/E repeats are crucial for dynamic autoinhibition via electrostatic interactions. Our data on the oxidized HMGB1 (i.e., 'disulfide HMGB1') protein show that the truncation substantially increases HMGB1's affinities for the toll-like receptor TLR4•MD-2 complex, DNA G-quadruplex, and the Holliday junction DNA structure. The DNA-mediated proteolysis of HMGB1 by neutrophil elastase in NETs may promote the function of extracellular HMGB1 as a damage-associated molecular pattern that triggers the innate immune response of nearby cells.

Viruses hijack host proteins to promote infection and dampen host defenses. Adenovirus encodes the multifunctional protein VII that serves both to compact viral genomes inside the virion and disrupt host chromatin. Protein VII binds the abundant nuclear protein high mobility group box 1 (HMGB1) and sequesters HMGB1 in chromatin. HMGB1 is an abundant host nuclear protein that can also be released from infected cells as an alarmin to amplify inflammatory responses. By sequestering HMGB1, protein VII prevents its release, thus inhibiting downstream inflammatory signaling. However, the consequences of this chromatin sequestration on host transcription are unknown. Here, we employ bacterial two-hybrid interaction assays and human cell culture to interrogate the mechanism of the protein VII-HMGB1 interaction. HMGB1 contains two DNA binding domains, the A- and B-boxes, that bend DNA to promote transcription factor binding while the C-terminal tail regulates this interaction. We demonstrate that protein VII interacts directly with the A-box of HMGB1, an interaction that is inhibited by the HMGB1 C-terminal tail. By cellular fractionation, we show that protein VII renders A-box containing constructs insoluble, thereby acting to prevent their release from cells. This sequestration is not dependent on HMGB1's ability to bind DNA but does require post-translational modifications on protein VII. Importantly, we demonstrate that protein VII inhibits expression of interferon β, in an HMGB1-dependent manner, but does not affect transcription of downstream interferon-stimulated genes. Together, our results demonstrate that protein VII specifically harnesses HMGB1 through its A-box domain to depress the innate immune response and promote infection.

Sodium/iodide symporter (NIS)-mediated iodide uptake plays an important physiological role in regulating thyroid gland function, as well as in diagnosing and treating Graves' disease and thyroid cancer. High-mobility group box 1 (HMGB1), a highly conserved nuclear protein, is a positive regulator of autophagy conferring resistance to chemotherapy, radiotherapy and immunotherapy in cancer cells. Here the authors intended to identify the role of HMGB1 in Hank's balanced salt solution (HBSS)-induced autophagy, explore NIS protein degradation through a autophagy-lysosome pathway in thyroid cancer cells and elucidate the possible molecular mechanisms.

A purified system comprised of MutSalpha, MutLalpha, exonuclease 1 (Exo1), and replication protein A (RPA) (in the absence or presence of HMGB1) supports 5'-directed mismatch-provoked excision that terminates after mismatch removal. MutLalpha is not essential for this reaction but enhances excision termination, although the basis of this effect has been uncertain. One model attributes the primary termination function in this system to RPA, with MutLalpha functioning in a secondary capacity by suppressing Exo1 hydrolysis of mismatch-free DNA (Genschel, J., and Modrich, P. (2003) Mol. Cell 12, 1077-1086). A second invokes MutLalpha as the primary effector of excision termination (Zhang, Y., Yuan, F., Presnell, S. R., Tian, K., Gao, Y., Tomkinson, A. E., Gu, L., and Li, G. M. (2005) Cell 122, 693-705). In the latter model, RPA provides a secondary termination function, but together with HMGB1, also participates in earlier steps of the reaction. To distinguish between these models, we have reanalyzed the functions of MutLalpha, RPA, and HMGB1 in 5'-directed mismatch-provoked excision using purified components as well as mammalian cell extracts. Analysis of extracts derived from A2780/AD cells, which are devoid of MutLalpha but nevertheless support 5'-directed mismatch repair, has demonstrated that 5'-directed excision terminates normally in the absence of MutLalpha. Experiments using purified components confirm a primary role for RPA in terminating excision by MutSalpha-activated Exo1 but are inconsistent with direct participation of MutLalpha in this process. While HMGB1 attenuates excision by activated Exo1, this effect is distinct from that mediated by RPA. Assay of extracts derived from HMGB1(+/+) and HMGB1(-/-) mouse embryo fibroblast cells indicates that HMGB1 is not essential for mismatch repair.

Heat-shock protein 27 (Hsp27) is a member of the small heat shock protein family that has been reported to protect cells against pro-inflammatory stresses. High mobility group box 1 (HMGB1) is a proinflammatory cytokine associated with death from sepsis and other inflammatory diseases. After being acetylated by CREB-binding protein (CBP), the transcriptional adaptor and acetyltransferase, HMGB1 translocates from the nucleus to the cytoplasm. In the present study, we investigated the effects of Hsp27 on HMGB1 translocation from the nucleus to the cytoplasm in THP-1 cells. We found that Hsp27 phosphorylation decreased LPS-induced HMGB1 acetylation and translocation from the nucleus to the cytoplasm, as well as its release from THP-1 cells. The study further showed that cytosolic non-phosphorylated Hsp27 enhanced CBP ubiquitination and degradation in LPS-unstimulated cells, which suggested that Hsp27 maintained suitable CBP levels under normal physiological conditions. After LPS stimulation, Hsp27 was phosphorylated at serine residues 15/78 and translocated from the cytoplasm into the nucleus. Consequently, LPS stimulation increased CBP levels and promoted its translocation into the nucleus. In the nucleus, Hsp27 bound to CBP and suppressed CBP acetyltransferase activity and the subsequent CBP-dependent acetylation of HMGB1. Taken together, our data demonstrated that cytosolic non-phosphorylated Hsp27 enhanced the ubiquitin-mediated degradation of CBP, while phosphorylated Hsp27 inhibited CBP acetyltransferase activity in the nucleus. By regulating CBP, Hsp27 maintained cell homeostasis and inhibited excessive inflammatory response.

Hmgb1 belongs to a family of structure-specific DNA binding proteins with DNA chaperone-like properties that mediate chromatin remodeling in a wide range of nuclear processes including regulation of transcription, DNA repair, genome stability, and stress response. A diurnal oscillation of Hmgb1 at the protein level occurs in rat retinal photoreceptor cells and to a lesser extent in bipolar neurons. Expression of Hmgb1 was least at night at Zeitgeber time (ZT) 18 and maximal in the middle of the lights-on period (ZT6). Since rhythmic expression of Hmgb1 protein in photoreceptors continued in complete darkness, it is likely under control of a circadian clock. Within photoreceptor nuclei, Hmgb1 colocalized with acetylated histone H3, a marker of euchromatin. Outside the nucleus a distinct smaller-sized isoform of Hmgb1 was present in photoreceptor inner segments and bound to a membrane fraction with characteristics of endoplasmic reticulum membranes. The rhythmic expression of Hmgb1 protein may underlie the circadian change in chromatin remodeling in addition to histone acetylation.

Extracellular high mobility group box 1 protein  (HMGB1) serves a central role in inflammation as a transporter protein, which binds other immune-activating molecules that are endocytosed via the receptor for advanced glycation end-products (RAGE). These pro-inflammatory complexes are targeted to the endolysosomal compartment, where HMGB1 permeabilizes the lysosomes. This enables HMGB1-partner molecules to avoid degradation, to leak into the cytosol, and to reach cognate immune-activating sensors. Lipopolysaccharide (LPS) requires this pathway to generate pyroptosis by accessing its key cytosolic receptors, murine caspase 11, or the human caspases 4 and 5. This lytic, pro-inflammatory cell death plays a fundamental pathogenic role in gram-negative sepsis. The aim of the study was to identify molecules inhibiting HMGB1 or HMGB1/LPS cellular internalization.

The deposition of amyloid-beta (Aβ) through the cleavage of amyloid-beta precursor protein (APP) is a biomarker of Alzheimer's disease (AD). This study used QIAGEN Ingenuity Pathway Analysis (IPA) to conduct meta-analysis on the molecular mechanisms by which methamphetamine (METH) impacts AD through modulating the expression of APP. All the molecules affected by METH and APP were collected from the QIAGEN Knowledge Base (QKB); 78 overlapping molecules were identified. Upon simulation of METH exposure using the "Molecule Activity Predictor" feature, eight molecules were found to be affected by METH and exhibited activation relationships on APP expression at a confidence of p = 0.000453 (Z-score = 3.51, two-tailed). Core Analysis of these eight molecules identified High Mobility Group Box protein 1 (HMGB1) signaling pathway among the top 5 canonical pathways with most overlap with the 8-molecule dataset. Simulated METH exposure increased APP expression through HMGB1 at a confidence of p < 0.00001 (Z-score = 7.64, two-tailed). HMGB1 is a pathogenic hallmark in AD progression. It not only increases the production of inflammatory mediators, but also mediates the disruption of the blood-brain barrier. Our analyses suggest the involvement of HMGB1 signaling pathway in METH-induced modulation of APP as a potential casual factor of AD.

Liquid-liquid phase separation (LLPS) of G-quadruplex (GQ) is involved in many crucial cellular processes, while the quadruplex-folding and their functions are typically modulated by specific DNA-binding proteins. However, the regulatory mechanism of binding proteins, particularly the well-folded proteins, on the LLPS of GQs is largely unknown. Here, we investigated the effect of HMGB1 on the condensation of a G-quadruplex of KRAS promoter (GQKRAS). The results show that these two rigid macro-biomolecules undergo co-condensation through a mutual promotion manner, while neither of them can form LLPS alone. Fluidity measurements confirm that the liquid-like droplets are highly dynamic. HMGB1 facilitates and stabilizes the quadruplex folding of GQKRAS, and this process enhances their co-condensation. The KRAS promoter DNA retains quadruplex folding in the droplets; interference with the GQ-folding disrupts the co-condensation of GQKRAS/HMGB1. Mechanistic studies reveal that electrostatic interaction is a key driving force of the interaction and co-condensation of GQKRAS/HMGB1; meanwhile, the recognition of two macro-biomolecules plays a crucial role in this process. This result indicates that the phase separation of GQs can be modulated by DNA binding proteins, and this process could also be an efficient way to recruit specific DNA binding proteins.

Inflammation is associated with protein accumulation in IBM, but precise mechanisms are elusive. The "alarmin" HMGB1 is upregulated in muscle inflammation. Its receptor RAGE is crucial for β-amyloid-associated neurodegeneration. Relevant signaling via HMGB1/RAGE is expected in IBM pathology. By real-time-PCR, mRNA-expression levels of HMGB1 and RAGE were upregulated in muscle biopsies of patients with IBM and PM, but not in muscular dystrophy or non-myopathic controls. By immunohistochemistry, both molecules displayed the highest signal in IBM, where they distinctly co-localized to intra-fiber accumulations of β-amyloid and neurofilament/tau. In these fibers, identification of phosphorylated Erk suggested that relevant downstream activation is present upon HMGB1 signaling via RAGE. Protein expressions of HMGB1, RAGE, Erk and phosphorylated Erk were confirmed by Western blot. In a well established cell-culture model for pro-inflammatory cell-stress, exposure of human muscle-cells to IL-1β+IFN-γ induced cytoplasmic translocation of HMGB1 and subsequent release as evidenced by ELISA. Upregulation of RAGE on the cell surface was demonstrated by immunocytochemistry and flow-cytometry. Recombinant HMGB1 was equally potent as IL-1β+IFN-γ in causing amyloid-accumulation and cell-death, and both were abrogated by the HMGB1-blocker BoxA. The findings strengthen the concept of unique interactions between degenerative and inflammatory mechanisms and suggest that HMGB1/RAGE signaling is a critical pathway in IBM pathology.

Autophagy clears long-lived proteins and dysfunctional organelles and generates substrates for adenosine triphosphate production during periods of starvation and other types of cellular stress. Here we show that high mobility group box 1 (HMGB1), a chromatin-associated nuclear protein and extracellular damage-associated molecular pattern molecule, is a critical regulator of autophagy. Stimuli that enhance reactive oxygen species promote cytosolic translocation of HMGB1 and thereby enhance autophagic flux. HMGB1 directly interacts with the autophagy protein Beclin1 displacing Bcl-2. Mutation of cysteine 106 (C106), but not the vicinal C23 and C45, of HMGB1 promotes cytosolic localization and sustained autophagy. Pharmacological inhibition of HMGB1 cytoplasmic translocation by agents such as ethyl pyruvate limits starvation-induced autophagy. Moreover, the intramolecular disulfide bridge (C23/45) of HMGB1 is required for binding to Beclin1 and sustaining autophagy. Thus, endogenous HMGB1 is a critical pro-autophagic protein that enhances cell survival and limits programmed apoptotic cell death.

The high-mobility group box 1 (HMGB1) protein has a central role in immunological antitumour defense. Here we show that natural killer cell-derived HMGB1 directly eliminates cancer cells by triggering metabolic cell death. HMGB1 allosterically inhibits the tetrameric pyruvate kinase isoform M2, thus blocking glucose-driven aerobic respiration. This results in a rapid metabolic shift forcing cells to rely solely on glycolysis for the maintenance of energy production. Cancer cells can acquire resistance to HMGB1 by increasing glycolysis using the dimeric form of PKM2, and employing glutaminolysis. Consistently, we observe an increase in the expression of a key enzyme of glutaminolysis, malic enzyme 1, in advanced colon cancer. Moreover, pharmaceutical inhibition of glutaminolysis sensitizes tumour cells to HMGB1 providing a basis for a therapeutic strategy for treating cancer.

The high mobility group box (HMGB) 1 protein is a very abundant and conserved protein that is implicated in many key cellular events but its functions within the nucleus remain elusive. The role of this protein in replication of closed circular DNA containing a eukaryotic origin of replication has been studied in vitro by using native and recombinant HMGB1 as well as various modified HMGB1 preparations such as truncated protein, lacking its C-terminal tail, in vivo acetylated protein, and recombinant HMGB1 phosphorylated in vitro by protein kinase C (PKC). Native HMGB1 extracted from tumour cells inhibits replication and this effect is reduced upon acetylation and completely abolished upon removal of the acidic C-terminal tail. Recombinant HMGB1, however, fails to inhibit replication but it acquires such a property following in vitro phosphorylation by PKC.

Mammalian homologue of high mobility group box chromatin protein (HMGB) 1 was identified and cloned from human parasites, Schistosoma mansoni and S. haematobium. Sequence analyses showed that the parasite HMGB1s has 35-40% identity to human and rodent HMGB1s, and 33% identity to Caenorhabditis elegans HMGB1. Parasite HMGB1s also contains an A box and B box domain similar to mammalian HMGB1, however, it lacks the C-terminal tail that is present in mammalian HMGB1s. Analysis of the expression of HMGB1 in various life cycle stages of S. mansoni reveal S. mansoni HMGB1 (SmHMGB1) as a stage-specific protein, expressed abundantly in egg and adult female stages and at moderate levels in skin-stage schistosomula. Significant levels of SmHMGB1 were also present in excretory secretions of egg stages. Subsequent characterization studies showed that SmHMGB1 is a potent inducer of pro-inflammatory cytokines such as TNFalpha, IL-1Ralpha, IL-2Ralpha, IL-6, IL-13, IL-13Ralpha1, IL-15 and MIP-1alpha from mouse peritoneal macrophages. Pro-inflammatory activity, especially production of TNFalpha-inducing activity, appears to be a function of the B box domain protein. This was confirmed by both real-time reverse transcription PCR and by cytokine ELISA. Thus, results presented in this study suggest that SmHMGB1 may be a key molecule in the development of host inflammatory immune responses associated with schistosomiasis.

During sepsis, the alarmin HMGB1 is released from tissues and promotes systemic inflammation that results in multi-organ damage, with the kidney particularly susceptible to injury. The severity of inflammation and pro-damage signaling mediated by HMGB1 appears to be dependent on the alarmin's redox state. Therefore, we examined HMGB1 redox in kidney cells during sepsis. Using intravital microscopy, CellROX labeling of kidneys in live mice indicated increased ROS generation in the kidney perivascular endothelium and tubules during lipopolysaccharide (LPS)-induced sepsis. Subsequent CellROX and MitoSOX labeling of LPS-stressed endothelial and kidney proximal tubule cells demonstrated increased ROS generation in these cells as sepsis worsens. Consequently, HMGB1 oxidation increased in the cytoplasm of kidney cells during its translocation from the nucleus to the circulation, with the degree of oxidation dependent on the severity of sepsis, as measured in in vivo mouse samples using a thiol assay and mass spectrometry (LC-MS/MS). The greater the oxidation of HMGB1, the greater the ability of the alarmin to stimulate pro-inflammatory cyto-/chemokine release (measured by Luminex Multiplex) and alter mitochondrial ATP generation (Luminescent ATP Detection Assay). Administration of glutathione and thioredoxin inhibitors to cell cultures enhanced HMGB1 oxidation during sepsis in endothelial and proximal tubule cells, respectively. In conclusion, as sepsis worsens, ROS generation and HMGB1 oxidation increases in kidney cells, which enhances HMGB1's pro-inflammatory signaling. Conversely, the glutathione and thioredoxin systems work to maintain the protein in its reduced state.