Calcium effects on superoxide dismutase and catalase of the rabbit urinary bladder muscle and mucosa

TFEB activation triggers pexophagy for functional adaptation during oxidative stress under calcium deficient-conditions

BACKGROUND

Calcium is a ubiquitous intracellular messenger that regulates the expression of various genes involved in cell proliferation, differentiation, and motility. The involvement of calcium in diverse metabolic pathways has been suggested. However, the effect of calcium in peroxisomes, which are involved in fatty acid oxidation and scavenges the result reactive oxygen species (ROS), remains elusive. In addition, impaired peroxisomal ROS inhibit the mammalian target of rapamycin complex 1 (mTORC1) and promote autophagy. Under stress, autophagy serves as a protective mechanism to avoid cell death. In response to oxidative stress, lysosomal calcium mediates transcription factor EB (TFEB) activation. However, the impact of calcium on peroxisome function and the mechanisms governing cellular homeostasis to prevent diseases caused by calcium deficiency are currently unknown.

METHODS

To investigate the significance of calcium in peroxisomes and their roles in preserving cellular homeostasis, we established an in-vitro scenario of calcium depletion.

RESULTS

This study demonstrated that calcium deficiency reduces catalase activity, resulting in increased ROS accumulation in peroxisomes. This, in turn, inhibits mTORC1 and induces pexophagy through TFEB activation. However, treatment with the antioxidant N-acetyl-l-cysteine (NAC) and the autophagy inhibitor chloroquine impeded the nuclear translocation of TFEB and attenuated peroxisome degradation.

CONCLUSIONS

Collectively, our study revealed that ROS-mediated TFEB activation triggers pexophagy during calcium deficiency, primarily because of attenuated catalase activity. We posit that calcium plays a significant role in the proper functioning of peroxisomes, critical for fatty-acid oxidation and ROS scavenging in maintaining cellular homeostasis. These findings have important implications for signaling mechanisms in various pathologies, including Zellweger's syndrome and ageing.

Antioxidant status in patients with bladder cancer regarding cancer stage and grade

Objective

The imbalance of antioxidants and pro-oxidants plays a crucial role in the carcinogenesis of bladder cancer (BC). This study aimed to evaluate serum antioxidant status in patients with BC and determine its potential use in the diagnosis and progression potential considerations following histopathological assessment.

Methods

A cross-sectional study included 90 patients with BC, divided into Ta, T1, and T2-T4 stage subgroups, and according to cancer progression potential, into low-grade (LG) and high-grade (HG) subgroups. The control group (CG) included 30 healthy volunteers. Antioxidant status was determined using the spectrophotometric method and standard laboratory tests.

Results

Serum superoxide dismutase activity was significantly higher in BC patients regarding cancer stage in comparison to the CG (p<0.001). Catalase activity was highest in T2-T4 subgroup and was significantly higher compared to the Ta (p<0.01) and T1 (p<0.05) subgroups. Serum albumin level was significantly lower in the BC group compared to the CG (p<0.001). In addition, it was significantly lower in T2-T4 subgroup compared to T1 and Ta subgroups (p<0.01). A significant negative correlation was found between tumor size and serum albumin level only (r=-0.386, p<0.01). Catalase activity was higher in HG subgroup (p=0.009), while bilirubin level was higher in LG subgroup (p=0.035). The optimal cut-off value of catalase activity in differentiating patients with LG and HG BC subgroups was ≥11.96 IU/L, and the specificity and sensitivity were 51.1% and 82.2%, respectively. Bilirubin level, for a calculated optimal cut-off value of ≥11.95 μmol/L, had a specificity of 44.1% and sensitivity of 80.0%.

Conclusion

More invasive stages of BC with greater progression potential are associated with an increase in enzymatic antioxidant activity and a decrease in non-enzymatic antioxidant capacity. It may suggest a possible role of antioxidants in the prediction and monitoring of illness trajectory.

Oxidative stress in the bladder of men with LUTS undergoing open prostatectomy: a pilot study

Purpose:

This study aims to evaluate the link between preoperative parameters and oxidative stress (OS) markers in the bladder wall of men undergoing open prostatectomy.

Materials and Methods:

From July 2014 to August 2016, men aged ≥ 50 years and presenting with LUTS were prospectively enrolled. Preoperative assessment included validated questionnaires (IPSS and OAB - V8), lower urinary tract ultrasound and urodynamics. Bladder biopsies were taken during open prostatectomy for determination of OS markers. Increased OS was defined by increased concentration of malondialdehyde (MDA) and / or decreased concentration of antioxidant enzymes (superoxide dismutase and / or catalase). P<0.05 was regarded as statistically significant.

Results:

Thirty - eight consecutive patients were included. Mean age was 66.36 ± 6.44 years, mean prostate volume was 77.7 ± 20.63 cm3, and mean IPSS was 11.05 ± 8.72 points. MDA concentration was increased in men with severe bladder outlet obstruction (BOO grade V - VI according to the Schaefer's nomogram) in comparison with BOO grade III - IV (p = 0.022). Patients with severe LUTS also had higher MDA concentration when compared to those with mild LUTS (p = 0.031). There was a statistically significant association between increased post - void residual urine (cut off ≥ 50 mL) and not only higher levels of MDA, but also reduced activity of SOD and catalase (p < 0.05).

Conclusions:

This pilot study showed that severity of LUTS and BOO were associated with increased MDA concentration in the bladder wall of men undergoing open prostatectomy. Further studies are still needed to assess the role of non - invasive biomarkers of OS in predicting bladder dysfunction in men with LUTS.

The effect of partial outlet obstruction on calpain and phospholipase-2 activities: analyzed by severity and duration

In an attempt to better understand the two pathways that lead to bladder decompensation following partial obstruction in rabbits one of which is caused by calcium-activated enzymes and the other by oxidative stress, calpain and phospholipase A2 (PLA2) biochemical assays were conducted to see how bladder decompensation is mediated by these two calcium-activated enzymes. Partial outlet obstructions of varying durations (4, 8, and 12 weeks plus controls) were performed on 32 New Zealand white rabbits. The rabbits were also grouped by severity: control, mild, intermediate, and severe. The activities of Calpain and PLA2 on the muscle tissue of the bladders were analyzed. A stronger correlation was seen between activities and severities as opposed to between activities and durations for both PLA2 and calpain. The activity for PLA2 increased dramatically from control to mild and then stayed constant for both intermediate and severe obstructions. Calpain activity increased steadily from control to mild to intermediate to severe. Based on the increase in levels of the calcium-dependent enzymes, it was clearly shown that calcium levels increased in all stages of bladder decompensation most notably with the mild obstructions. Based on previous studies in which nitrotyrosine and dinitrophenol levels did not increase in mildly obstructed rabbits, the calcium overload pathway may predominate in mild decompensation because cells in mildly obstructed bladders are better able to cope with oxidative stress than increased calcium levels.

Effect of severity and duration of bladder outlet obstruction on catalase and superoxide dismutase activity

OBJECTIVES

To study the effects of partial bladder outlet obstruction on the cell's anti-oxidant defense mechanisms, superoxide dismutase and catalase, in order to elucidate how the bladder responds to oxidative stress.

METHODS

Four groups of eight rabbits were subjected to partial bladder outlet obstruction for 4, 8 and 12 weeks. Eight sham rabbits were used as the control group. The bladders were removed under anesthesia, and the muscle and mucosa were separated, frozen and stored at -80°C for analysis. Superoxide dismutase and catalase assays were carried out on these tissues. The groups were also categorized by severity (mild, intermediate and severe) of decompensation, as well as duration.

RESULTS

When separated by duration, catalase activity of the mucosa was significantly higher in the control and the 12-weeks obstructed rabbits. This activity was lower than the control in the 4- and 8-weeks obstructed rabbits. When separated by severity, catalase activity of the mucosa was significantly higher and severely decompensated than the muscle in the controls. When separated by duration or severity, superoxide dismutase activity of the muscle was significantly lower than controls for all obstructed rabbits. The activities of both superoxide dismutase and catalase were significantly reduced in the severely decompensated bladder smooth muscle, but not in the 12-weeks obstructed bladder smooth muscle.

CONCLUSIONS

Partial bladder outlet obstruction has significant effects on the activity of both superoxide dismutase and catalase in the bladder, with variations that are dependent on the severity and duration of the obstruction.