A Dual Role of Heme Oxygenase-1 in Angiotensin II-Induced Abdominal Aortic Aneurysm in the Normolipidemic Mice.

Abdominal aortic aneurysm (AAA) bears a high risk of rupture and sudden death of the patient. The pathogenic mechanisms of AAA remain elusive, and surgical intervention represents the only treatment option. Heme oxygenase-1 (HO-1), a heme degrading enzyme, is induced in AAA, both in mice and humans. HO-1 was reported to mitigate AAA development in an angiotensin II (AngII)-induced model of AAA in hyperlipidemic ApoE-/- mice. Since the role of hyperlipidaemia in the pathogenesis of AAA remains controversial, we aimed to evaluate the significance of HO-1 in the development and progression of AAA in normolipidemic animals. The experiments were performed in HO-1-deficient mice and their wild-type counterparts. We demonstrated in non-hypercholesterolemic mice that the high-dose of AngII leads to the efficient formation of AAA, which is attenuated by HO-1 deficiency. Yet, if formed, they are significantly more prone to rupture upon HO-1 shortage. Differential susceptibility to AAA formation does not rely on enhanced inflammatory response or oxidative stress. AAA-resistant mice are characterized by an increase in regulators of aortic remodeling and angiotensin receptor-2 expression, significant medial thickening, and delayed blood pressure elevation in response to AngII. To conclude, we unveil a dual role of HO-1 deficiency in AAA in normolipidemic mice, where it protects against AAA development, but exacerbates the state of formed AAA.

Simvastatin Attenuates Abdominal Aortic Aneurysm Formation Favoured by Lack of Nrf2 Transcriptional Activity.

Surgical intervention is currently the only option for an abdominal aortic aneurysm (AAA), preventing its rupture and sudden death of a patient. Therefore, it is crucial to determine the pathogenic mechanisms of this disease for the development of effective pharmacological therapies. Oxidative stress is said to be one of the pivotal factors in the pathogenesis of AAAs. Thus, we aimed to evaluate the significance of nuclear factor erythroid 2-related factor 2 (Nrf2) transcriptional activity in the development of AAA and to verify if simvastatin, administered as pre- and cotreatment, may counteract this structural malformation. Experiments were performed on mice with inhibited transcriptional activity of Nrf2 (tKO) and wild-type (WT) counterparts. We used a model of angiotensin II- (AngII-) induced AAA, combined with a fat-enriched diet. Mice were administered with AngII or saline for up to 28 days via osmotic minipumps. Simvastatin administration was started 7 days before the osmotic pump placement and then continued until the end of the experiment. We found that Nrf2 inactivation increased the risk of development and rupture of AAA. Importantly, these effects were reversed by simvastatin in tKO mice, but not in WT. The abrupt blood pressure rise induced by AngII was mitigated in simvastatin-treated animals regardless of the genotype. Simvastatin-affected parameters that differed between the healthy structure of the aorta and aneurysmal tissue included immune cell infiltration of the aortic wall, VCAM1 mRNA and protein level, extracellular matrix degradation, TGF-ß1 mRNA level, and ERK phosphorylation, but neither oxidative stress nor the level of Angiotensin II Type 1 Receptor (AT1R). Taken together, the inhibition of Nrf2 transcriptional activity facilitates AAA formation in mice, which can be prevented by simvastatin. It suggests that statin treatment of patients with hypercholesterolemia might have not only a beneficial effect in terms of controlling atherosclerosis but also potential AAA prevention.

Keap1 governs ageing-induced protein aggregation in endothelial cells.

The breach of proteostasis, leading to the accumulation of protein aggregates, is a hallmark of ageing and age-associated disorders, up to now well-established in neurodegeneration. Few studies have addressed the issue of dysfunctional cell response to protein deposition also for the cardiovascular system. However, the molecular basis of proteostasis decline in vascular cells, as well as its relation to ageing, are not understood. Recent studies have indicated the associations of Nrf2 transcription factor, the critical modulator of cellular stress-response, with ageing and premature senescence. In this report, we outline the significance of protein aggregation in physiological and premature ageing of murine and human endothelial cells (ECs). Our study shows that aged donor-derived and prematurely senescent Nrf2-deficient primary human ECs, but not those overexpressing dominant-negative Nrf2, exhibit increased accumulation of protein aggregates. Such phenotype is also found in the aortas of aged mice and young Nrf2 tKO mice. Ageing-related loss of proteostasis in ECs depends on Keap1, well-known repressor of Nrf2, recently perceived as a key independent regulator of EC function and protein S-nitrosation (SNO). Deposition of protein aggregates in ECs is associated with impaired autophagy. It can be counteracted by Keap1 depletion, S-nitrosothiol reductant or rapamycin treatment. Our results show that Keap1:Nrf2 protein balance and Keap1-dependent SNO predominate Nrf2 transcriptional activity-driven mechanisms in governing proteostasis in ageing ECs.

Murine Bone Marrow Mesenchymal Stromal Cells Respond Efficiently to Oxidative Stress Despite the Low Level of Heme Oxygenases 1 and 2.

AIMS: Mesenchymal stromal cells (MSCs) are heterogeneous cells from adult tissues that are able to differentiate in vitro into adipocytes, osteoblasts, or chondrocytes. Such cells are widely studied in regenerative medicine. However, the success of cellular therapy depends on the cell survival. Heme oxygenase-1 (HO-1, encoded by the Hmox1 gene), an enzyme converting heme to biliverdin, carbon monoxide, and Fe2+, is cytoprotective and can affect stem cell performance. Therefore, our study aimed at assessing whether Hmox1 is critical for survival and functions of murine bone marrow MSCs. RESULTS: Both MSC Hmox1+/+ and Hmox1-/- showed similar phenotype, differentiation capacities, and production of cytokines or growth factors. Hmox1+/+ and Hmox1-/- cells showed similar survival in response to 50 µmol/L hemin even in increased glucose concentration, conditions that were unfavorable for Hmox1-/- bone marrow-derived proangiogenic cells (BDMC). Hmox1+/+ MSCs but not fibroblasts retained low ROS levels even after prolonged incubation with 50 µmol/L hemin, although both cell types have a comparable Hmox1 expression and similarly increase its levels in response to hemin. MSCs Hmox1-/- treated with hemin efficiently induced expression of a vast panel of antioxidant genes, especially enzymes of the glutathione pathway. Innovation and Conclusion: Hmox1 overexpression is a popular strategy to enhance viability and performance of MSCs after the transplantation. However, murine MSCs Hmox1-/- do not differ from wild-type MSCs in phenotype and functions. MSC Hmox1-/- show better resistance to hemin than fibroblasts and BDMCs and rapidly react to the stress by upregulation of quintessential genes in antioxidant response. Antioxid. Redox Signal. 00, 000-000.

Curcumin enhances the cytogenotoxic effect of etoposide in leukemia cells through induction of reactive oxygen species.

Curcumin may exert a more selective cytotoxic effect in tumor cells with elevated levels of free radicals. Here, we investigated whether curcumin can modulate etoposide action in myeloid leukemia cells and in normal cells of hematopoietic origin. HL-60 cell line, normal myeloid progenitor cluster of differentiation (CD)-34(+) cells, and granulocytes were incubated for 4 or 24 hours at different concentrations of curcumin and/or etoposide. Brown Norway rats with acute myeloid leukemia (BNML) were used to prove the influence of curcumin on etoposide action in vivo. Rats were treated with curcumin for 23 days and etoposide was administered for the final 3 days of the experiment. Curcumin synergistically potentiated the cytotoxic effect of etoposide, and it intensified apoptosis and phosphorylation of the histone H2AX induced by this cytostatic drug in leukemic HL-60 cells. In contrast, curcumin did not significantly modify etoposide-induced cytotoxicity and H2AX phosphorylation in normal CD34(+) cells and granulocytes. Curcumin modified the cytotoxic action of etoposide in HL-60 cells through intensification of free radical production because preincubation with N-acetyl-l-cysteine (NAC) significantly reduced the cytotoxic effect of curcumin itself and a combination of two compounds. In contrast, NAC did not decrease the cytotoxic effect of etoposide. Thus, oxidative stress plays a greater role in the cytotoxic effect of curcumin than that of etoposide in HL-60 cells. In vitro results were confirmed in a BNML model. Pretreatment with curcumin enhanced the antileukemic activity of etoposide in BNML rats (1.57-fold tumor reduction versus etoposide alone; P<0.05) and induced apoptosis of BNML cells more efficiently than etoposide alone (1.54-fold change versus etoposide alone; P<0.05), but this treatment protected nonleukemic B-cells from apoptosis. Thus, curcumin can increase the antileukemic effect of etoposide through reactive oxygen species in sensitive myeloid leukemia cells, and it is harmless to normal human cells.