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Heme oxygenase-1 (HO1, Hmox1 ) degrades excess heme and is considered an anti-oxidative and anti-inflammatory enzyme. Our previous studies in Hmox1 knockout mice revealed the induction of interferon-stimulated genes (ISGs) in all cell types analyzed, despite unchanged interferon production. Here, we sought to determine whether this induction is driven by intrinsic cellular mechanisms or extrinsic cues at the organismal level, and to identify the pathway underlying HO1-dependent ISG regulation. To this end, we analyzed how ISG expression changes in cultured cells exposed to stressors typical of Hmox1 knockout mice. Using murine wild-type and Hmox1 -deficient (Hmox1 KO) fibroblasts, we found that under control conditions, the expression of most tested ISGs was independent of cellular HO1 status. We next examined the effects of extrinsic stressors, including hemolytic, oxidative, genotoxic, and replication stress, proinflammatory TNFα, and endogenous heme overload. TNFα, which is upregulated in Hmox1 knockout mice, was the sole and universal inducer of ISGs in both wild-type and Hmox1 KO fibroblasts. Unexpectedly, the response of Hmox1 KO cells to exogenous TNFα was weakened, likely due to impaired NF-κB activity and reduced nuclear retention of the p65 subunit. A similar decrease we observed for STAT1. Additionally, the presence of the TREX1 exonuclease in the nucleus pointed to compromised nuclear envelope integrity in HO-deficient cells. Notably, HO1 colocalizes with PARP1, a protein involved in envelope maintenance and regulation of cytoplasmic-nuclear transport. Inhibition of PARP1 with olaparib dampened TNFα-induced nuclear accumulation of p65 and STAT1 in wild-type cells, but not in Hmox1 KO counterparts. In summary, the inflammation observed in Hmox1 -deficient mice appears to be the main cell-extrinsic driver of ISG induction in vivo. Despite this, the inflammatory response to exogenous TNFα is intrinsically attenuated in Hmox1 KO cells, likely due to decreased nuclear retention of NF-κB and STAT1.

G-quadruplexes (G4) are stacked nucleic acid structures that are stabilized by heme. In cells, they affect DNA replication and gene transcription. They are unwound by several helicases but the composition of the repair complex and its heme sensitivity are unclear. We found that the accumulation of G-quadruplexes is affected by heme oxygenase-1 (Hmox1) expression, but in a cell-type-specific manner: hematopoietic stem cells (HSCs) from Hmox1−/− mice have upregulated expressions of G4-unwinding helicases (e.g., Brip1, Pif1) and show weaker staining for G-quadruplexes, whereas Hmox1-deficient murine induced pluripotent stem cells (iPSCs), despite the upregulation of helicases, have more G-quadruplexes, especially after exposure to exogenous heme. Using iPSCs expressing only nuclear or only cytoplasmic forms of Hmox1, we found that nuclear localization promotes G4 removal. We demonstrated that the proximity ligation assay (PLA) can detect cellular co-localization of G-quadruplexes with helicases, as well as with HMOX1, suggesting the potential role of HMOX1 in G4 modifications. However, this colocalization does not mean a direct interaction was detectable using the immunoprecipitation assay. Therefore, we concluded that HMOX1 influences G4 accumulation, but rather as one of the proteins regulating the heme availability, not as a rate-limiting factor. It is noteworthy that cellular G4–protein colocalizations can be quantitatively analyzed using PLA, even in rare cells.

Heme oxygenase-1 (HO1, Hmox1) degrades excess heme and is considered an anti-oxidative and anti-inflammatory enzyme. Our previous studies in Hmox1 knockout mice revealed induction of interferon-stimulated genes (ISGs) in all cell types analyzed, despite unchanged interferon production. Here, we sought to identify the pathway underlying HO1-dependent ISG regulation and determine how ISG expression changes in cultured cells in response to stressors typical of Hmox1-deficient mice. Using murine wild-type and Hmox1-deficient (KO-Hmox1) fibroblasts, we showed that in cells cultured under control conditions, the expression of most of the tested ISGs was independent of cellular HO1 status. We then analyzed the effect of extrinsic stressors: hemolytic, oxidative, genotoxic, and replication stress, proinflammatory TNFalpha, and endogenous heme overload. TNFalpha (upregulated in Hmox1 knockout mice) was the sole and universal ISG inducer in both wild-type and KO-Hmox1 fibroblasts. Unexpectedly, the response of KO-Hmox1 cells to exogenous TNFalpha was weakened, probably due to impaired NF-kappaB activity and reduced p65 nuclear retention. A similar decrease we observed for STAT1. Additionally, the presence of TREX1 exonuclease in the nucleus indicated impaired nuclear envelope integrity. Noteworthy, HO1 colocalizes with PARP1, a protein regulating cytoplasmic-nuclear transport. Olaparib-mediated PARP1 inhibition abolished TNAalpha-induced nuclear accumulation of p65 and STAT1 in wild-type cells, but not in KO-Hmox1 counterparts. In summary, the inflammation typical of Hmox1-deficient mice appears to be a major inducer of ISGs in vivo. Despite this, the inflammatory response to exogenous TNFalpha is attenuated in KO-Hmox1 cells, likely due to decreased nuclear retention of NF-kappaB and STAT1.Competing Interest StatementThe authors have declared no competing interest.

Test artifacts, resembling real machine parts, allow for quantitative evaluation of system performance and provide insight into individual errors, aiding in improvement and standardization of additive manufacturing. The article provides a comprehensive overview of existing test artifacts, categorized based on geometric features and the material used. Various measurement techniques such as stylus profilometry and computed tomography are employed to assess these artifacts. It is also shown that the selective laser melting (SLM) technology and titanium alloys are prevalent in artifact creation. Specific artifact categories include slits, angular aspects, length parameters, variable surfaces, and others, each accompanied by examples from research literature, highlighting diverse artifact designs and their intended applications. The paper critically discusses the main problems with existing geometries. It underscores the importance of user-friendly and unambiguous artifacts for dimensional control, particularly in surface metrology. Furthermore, it anticipates the continued growth of metrological verification in future manufacturing environments, emphasizing the need for precise and reliable measurement results to support decision-making under production conditions.