Protective effect of inducible aldo-keto reductases on 4-hydroxynonenal- induced hepatotoxicity

Lipid-derived electrophiles inhibit the function of membrane channels during ferroptosis

The therapeutic targeting of ferroptosis requires full understanding of the molecular mechanism of this regulated cell death pathway. While lipid-derived electrophiles (LDEs), including 4-hydroxy-2-nonenal (4-HNE), are important biomarkers of ferroptosis, a functional role for these highly reactive species in ferroptotic cell death execution has not been established. Here, through mechanistic characterization of LDE-detoxification impairment, we demonstrate that LDEs mediate altered protein function during ferroptosis. Applying live cell fluorescence imaging, we first identified that export of glutathione-LDE-adducts through multidrug resistance-associated protein (MRP) channels is inhibited following exposure to a panel of ferroptosis inducers (FINs) with different modes of action (type I-IV FINs erastin, RSL3, FIN56, and FINO2). This channel inhibition was recreated by both initiation of lipid peroxidation and treatment with 4-HNE. Importantly, treatment with radical-trapping antioxidants prevented impaired LDE-adduct export when working with both FINs and lipid peroxidation initiators but not 4-HNE, pinpointing LDEs as the cause of this inhibited MRP activity observed during ferroptosis. Our findings, when combined with reports of widespread LDE alkylation of key proteins following ferroptosis induction, including MRP1, set a precedent for LDEs as critical mediators of ferroptotic cell damage. Lipid hydroperoxide breakdown to form truncated phospholipids and LDEs may fully explain membrane permeabilization and modified protein function downstream of lipid peroxidation, offering a unified explanation of the molecular cell death mechanism of ferroptosis.

Aldo-keto reductase-7A2 protects against atorvastatin-induced hepatotoxicity via Nrf2 activation

Atorvastatin (ATO), as a cholesterol-lowering drug, was the world's best-selling drug in the early 2000s. However, ATO overdose-induced liver or muscle injury is a threat to many patients, which restricts its application. Previous studies suggest that ATO overdose is accompanied with ROS accumulation and increased lipid peroxidation, which are the leading causes of ATO-induced liver damage. This study is, therefore, carried out to investigate the roles of anti-oxidant pathways and enzymes in protection against ATO-induced hepatotoxicity. Here we show that in ATO-challenged HepG2 cells, the expression levels of transcription factor NFE2L2/Nrf2 (nuclear factor erythroid 2 p45-related factor 2) are significantly upregulated. When Nrf2 is pharmacologically inhibited or genetically inactivated, ATO-induced cytotoxicity is significantly aggravated. Aldo-keto reductase-7A (AKR7A) enzymes, transcriptionally regulated by Nrf2, are important for bioactivation and biodetoxification. Here, we reveal that in response to ATO exposure, mRNA levels of human AKR7A2 are significantly upregulated in HepG2 cells. Furthermore, knockdown of AKR7A2 exacerbates ATO-induced hepatotoxicity, suggesting that AKR7A2 is essential for cellular adaptive response to ATO-induced cell damage. In addition, overexpression of AKR7A2 in HepG2 cells can significantly mitigate ATO-induced cytotoxicity and this process is Nrf2-dependent. Taken together, these findings indicate that Nrf2-mediated AKR7A2 is responsive to high concentrations of ATO and contributes to protection against ATO-induced hepatotoxicity, making it a good candidate for mitigating ATO-induced side effects.

The Impact of Long-Term Hypoxia on the Antioxidant Defense System in the Siberian Frog Rana amurensis

The Siberian frog Rana amurensis has a uniquely high tolerance to hypoxia among amphibians, as it is able to withstand several months underwater with almost no oxygen (0.2 mg/liter) vs. several days for other studied species. Since it was hypothesized that hypoxia actives the antioxidant defense system in hypoxia-tolerant animals, one would expect similar response in R. amurensis. Here, we studied the effect of hypoxia in the Siberian frog based on the transcriptomic data, activities of antioxidant enzyme, and content of low-molecular-weight antioxidants. Exposure to hypoxia upregulated expression of three relevant transcripts (catalase in the brain and two aldo-keto reductases in the liver). The activities of peroxidase in the blood and catalase in the liver were significantly increased, while the activity of glutathione S-transferase in the liver was reduced. The content of low-molecular-weight antioxidants (thiols and ascorbate) in the heart and liver was unaffected. In general, only a few components of the antioxidant defense system were affected by hypoxia, while most remained unchanged. Comparison to other hypoxia-tolerant species suggests species-specific adaptations to hypoxia-related ROS stress.

Role of NRF2 and reactive aldehydes in acute cellular rejection in liver transplant recipients

OBJECTIVE

To evaluate the level of oxidative stress and antioxidative response in the transplanted liver and its role in acute cellular rejection (ACR). Particular attention was paid to ACR diagnosis in patients with hepatitis C (HCV), as histopathological features of ACR and viral disease recurrence overlap.

METHODS

This retrospective study included 40 liver transplant patients who underwent liver transplantation with two consecutive liver biopsies performed during one hospitalization period: 1.) initial biopsy of the donor liver (before implantation) and 2.) indication biopsy (after suspected ACR). Based on the etiology, patients were divided into two groups: 22 patients with alcoholic liver cirrhosis (EtOH group) and 18 patients with hepatitis C cirrhosis (HCV group). We analyzed the presence of acrolein, HNE (4-hydroxynonenal), and the major antioxidant transcription factor NRF2 (nuclear factor erythroid 2-related factor 2) in both biopsies.

RESULTS

The presence of acrolein and HNE in both biopsies indicates increased oxidative stress, while the decrease in these aldehydes in the indication biopsies indicates a decrease in oxidative stress over time, reflecting liver graft recovery. The absence of NRF2 in both biopsies reflects significantly reduced antioxidant protection in patients undergoing liver transplantation.

CONCLUSION

The results support the role of oxidative stress in the pathogenesis of ACR. The presence of acrolein and the absence of HNE in the indication biopsy in patients with ACR could contribute to the diagnosis of ACR in clinical practice when functional antibodies are tested in the clinical setting.

The Specific Binding and Promotion Effect of Azoles on Human Aldo-Keto Reductase 7A2

Human AKR 7A2 broadly participates in the metabolism of a number of exogenous and endogenous compounds. Azoles are a class of clinically widely used antifungal drugs, which are usually metabolized by CYP 3A4, CYP2C19, and CYP1A1, etc. in vivo. The azole-protein interactions that human AKR7A2 participates in remain unreported. In this study, we investigated the effect of the representative azoles (miconazole, econazole, ketoconazole, fluconazole, itraconazole, voriconazole, and posaconazole) on the catalysis of human AKR7A2. The steady-state kinetics study showed that the catalytic efficiency of AKR7A2 enhanced in a dose-dependent manner in the presence of posaconazole, miconazole, fluconazole, and itraconazole, while it had no change in the presence of econazole, ketoconazole, and voriconazole. Biacore assays demonstrated that all seven azoles were able to specifically bind to AKR7A2, among which itraconazole, posaconazole, and voriconazole showed the strongest binding. Blind docking predicted that all azoles were apt to preferentially bind at the entrance of the substrate cavity of AKR7A2. Flexible docking showed that posaconazole, located at the region, can efficiently lower the binding energy of the substrate 2-CBA in the cavity compared to the case of no posaconazole. This study demonstrates that human AKR7A2 can interact with some azole drugs, and it also reveals that the enzyme activity can be regulated by some small molecules. These findings will enable a better understanding of azole-protein interactions.

Association between aldehyde exposure and sex steroid hormones among adults

Exogenous and endogenous exposure to aldehydes is seen worldwide. Aldehydes are closely associated with human diseases, especially reproductive toxicity. However, the effect of aldehyde exposure on sex steroid hormones among adults remains uninvestigated. A total of 851 participants aged over 18 years were included in this cross-sectional analysis based on data from National Health and Nutrition Examination Survey (NHANES) 2013-2014. Serum aldehyde concentrations were quantified following an automated analytical method. Sex steroid hormones including total testosterone, estradiol, and sex hormone binding globulin (SHBG) were detected. Multivariate linear regression models, forest plots, generalized additive model (GAM), and smooth curve fitting analysis were used to assess the associations between quartiles of aldehydes and sex steroid hormones levels after adjusting for potential confounders. Butyraldehyde and propanaldehyde were found to be negatively associated with estradiol and SHBG in females and males, respectively. β values with 95% confidence intervals (95% CIs) were - 20.59 (- 38.30 to - 2.88) for Q2 vs. Q1 of butyraldehyde and - 8.13 (- 14.92 to - 1.33) and - 7.79 (- 14.91 to - 0.67) for Q2 vs. Q1 and Q4 vs. Q1 of propanaldehyde. No significant associations were observed between other aldehydes and sex hormones. In premenopausal women, isopentanaldehyde was inversely associated with serum total testosterone levels (Q4 vs. Q1: OR =  - 7.95, 95% CI: - 15.62 to - 0.27), whereas propanaldehyde was positively associated with serum estradiol concentration (Q3 vs. Q1: β = 28.88, 95% CI: 0.83 to 56.94). Compared with Q1, Q3 of isopentanaldehyde was associated with 3.53 pg/mL higher concentration of estradiol in postmenopausal women (β = 3.53, 95% CI: 0.08 to 6.97). Moreover, in males under 40 years, butyraldehyde and heptanaldehyde were inversely proportional to total testosterone levels and heptanaldehyde and butyraldehyde were negatively associated with estradiol and SHBG. Decreased total testosterone, elevated estradiol, and decreased SHBG levels were found in higher quartiles of benzaldehyde, hexanaldehyde and isopentanaldehyde, and propanaldehyde, respectively, in males aged over 60 years. In male participants aged 40-60 years, only hexanaldehyde was observed to be correlated with higher serum estradiol levels. In conclusion, our current research presented the association between six serum aldehydes and sex hormones. Of note, stratification analyses were conducted in participants with different menopausal statuses and age among males and females. Sex- and age-specific effect of aldehyde exposure on alterations in sex hormone levels were observed. Further studies are warranted to confirm the causal relationship and explore the underlying mechanisms.

Characterization, expression, and function analysis of AKR1A1 gene from yellow catfish (Tachysurus fulvidraco)

Aldehyde reductase (AKR1A1) is a carbonyl detoxification protein in toxic aldehyde removal. In the present study, the full-length cDNA of yellow catfish AKR1A1 (TfAKR1A1) was cloned. As expected, yellow catfish AKR1A1 showed similarities with that of other species. Subsequently, prokaryotic expression vector was constructed and recombinant TfAKR1A1 (rTfAKR1A1) was successfully induced and purified. rTfAKR1A1 exhibited reductive activity to many aldehydes and ketones. To determine whether TfAKR1A1 could confer stress tolerance in vitro, the viability of control and TfAKR1A1 expression E. coli under abiotic stress was compared by spot assay. Results showed that the recombinant strain had better stress resistance under cadmium, hydrogen peroxide, and DL-glyceraldehyde stress. Then, effects of an intraperitoneal injection of rTfAKR1A1 protein on cadmium-induced oxidative stress were evaluated. Results displayed that TfAKR1A1 and Nrf2 expression levels were significantly decreased, CAT and SOD expression levels were significantly increased, BCL-2 and IL-10 expression levels were significantly increased, and caspase3a, NF-κB, and IL-1β expression levels were significantly decreased in protein-injection group. Furthermore, oxidative stress indexes in livers under different protein injection doses were examined by ELISA. Results showed that CAT, SOD, and GSH-Px activities were upregulated, ROS and T-AOC contents were also improved, while MDA content was significantly decreased both in lower and middle dose injection groups. Finally, liver pathological section analysis was performed. Results displayed that liver injury degree in protein-injected groups was lower than that of PBS group under cadmium stress. These results suggested that TfAKR1A1 played important roles in response to cadmium stress in yellow catfish.

Neuroprotective Effects of Withania somnifera on 4-Hydroxynonenal Induced Cell Death in Human Neuroblastoma SH-SY5Y Cells Through ROS Inhibition and Apoptotic Mitochondrial Pathway

The antioxidant, anti-inflammatory, and anticancer activities of Withania somnifera (WS) are known for a long time. This study was aimed to examine whether WS also diminishes 4-hydroxy-trans-2-nonenal (HNE)-induced neurotoxicity in human neuroblastoma (SH-SY5Y) cell line. The cytotoxic response of HNE (0.1-50 μM) and WS (6.25-200 μg/ml) was measured by MTT assay after exposing SH-SY5Y cells for 24 h. Then neuroprotective potential was assessed by exposing the cells to biologically safe concentrations of WS (12.5, 25, and 50 μg/ml) then HNE (50 μM). Results showed a concentration-dependent protective effect of WS at 12.5, 25, and 50 μg/ml against HNE (50 μM) induced cytotoxicity and cell inhibition. Pre-exposure to WS resulted in a strong inhibition of 24, 55 and 83% in malondialdehyde (MDA) level; 5, 27 and 60% in glutathione (GSH) level; 12, 36 and 68% in catalase activity; 11, 33 and 67% in LDH leakage; and 40, 80 and 120% in cellular LDH activity at 12.5, 25, and 50 μg/ml, respectively, induced by 50 μM HNE in SH-SY5Y cells. The HNE-mediated cellular changes (cell shrinkage, rounded bodies, and inhibition of outgrowth) and increased caspase-3 activity were also prevented by WS. The HNE-induced upregulation of proapoptotic markers (p53, caspase-3, and -9, and Bax) and downregulation of antiapoptotic marker Bcl-2 genes were also blocked by pretreatment with WS. Altogether, our findings indicate that WS possesses a protective potential against HNE-induced neurotoxicity.

Overview of AKR1C3: Inhibitor Achievements and Disease Insights

Human aldo-keto reductase family 1 member C3 (AKR1C3) is known as a hormone activity regulator and prostaglandin F (PGF) synthase that regulates the occupancy of hormone receptors and cell proliferation. Because of the overexpression in metabolic diseases and various hormone-dependent and -independent carcinomas, as well as the emergence of clinical drug resistance, an increasing number of studies have investigated AKR1C3 inhibitors. Here, we briefly review the physiological and pathological function of AKR1C3 and then summarize the recent development of selective AKR1C3 inhibitors. We propose our viewpoints on the current problems associated with AKR1C3 inhibitors with the aim of providing a reference for future drug discovery and potential therapeutic perspectives on novel, potent, selective AKR1C3 inhibitors.

An Evaluation of the In Vitro Roles and Mechanisms of Silibinin in Reducing Pyrazinamide- and Isoniazid-Induced Hepatocellular Damage

Tuberculosis remains a significant infectious lung disease that affects millions of patients worldwide. Despite numerous existing drug regimens for tuberculosis, drug-induced liver injury is a major challenge that limits the effectiveness of these therapeutics. Two drugs that form the backbone of the commonly administered quadruple antitubercular regimen, that is, pyrazinamide (PZA) and isoniazid (INH), are associated with such hepatotoxicity. Yet, we lack safe and effective alternatives to the antitubercular regimen. Consequently, current research largely focuses on exploiting the hepatoprotective effect of nutraceutical compounds as complementary therapy. Silibinin, a herbal product widely believed to protect against various liver diseases, potentially provides a useful solution given its hepatoprotective mechanisms. In our study, we identified silibinin’s role in mitigating PZA- and INH-induced hepatotoxicity and elucidated a deeper mechanistic understanding of silibinin’s hepatoprotective ability. Silibinin preserved the viability of human foetal hepatocyte line LO2 when co-administered with 80 mM INH and decreased apoptosis induced by a combination of 40 mM INH and 10 mM PZA by reducing oxidative damage to mitochondria, proteins, and lipids. Taken together, this proof-of-concept forms the rational basis for the further investigation of silibinin’s hepatoprotective effect in subsequent preclinical studies and clinical trials.

Can Medicinal Plants and Bioactive Compounds Combat Lipid Peroxidation Product 4-HNE-Induced Deleterious Effects?

The toxic reactive aldehyde 4-hydroxynonenal (4-HNE) belongs to the advanced lipid peroxidation end products. Accumulation of 4-HNE and formation of 4-HNE adducts induced by redox imbalance participate in several cytotoxic processes, which contribute to the pathogenesis and progression of oxidative stress-related human disorders. Medicinal plants and bioactive natural compounds are suggested to be attractive sources of potential agents to mitigate oxidative stress, but little is known about the therapeutic potentials especially on combating 4-HNE-induced deleterious effects. Of note, some investigations clarify the attenuation of medicinal plants and bioactive compounds on 4-HNE-induced disturbances, but strong evidence is needed that these plants and compounds serve as potent agents in the prevention and treatment of disorders driven by 4-HNE. Therefore, this review highlights the pharmacological basis of these medicinal plants and bioactive compounds to combat 4-HNE-induced deleterious effects in oxidative stress-related disorders, such as neurotoxicity and neurological disorder, eye damage, cardiovascular injury, liver injury, and energy metabolism disorder. In addition, this review briefly discusses with special attention to the strategies for developing potential therapies by future applications of these medicinal plants and bioactive compounds, which will help biological and pharmacological scientists to explore the new vistas of medicinal plants in combating 4-HNE-induced deleterious effects.