Reno- and hepato-protective effect of allopurinol after renal ischemia/reperfusion injury: Crosstalk between xanthine oxidase and peroxisome proliferator-activated receptor gamma signaling

Renal ischemia/reperfusion (I/R) is a common cause of acute kidney injury and remote liver damage is an ultimate negative outcome. Current treatments for I/R typically involve the use of antioxidants and anti-inflammatory to protect against oxidative stress and inflammation. Xanthine oxidase (XO) and PPAR-γ contribute to renal I/R-induced oxidative stress; however, the crosstalk between the two pathways remains unexplored. In the present study, we report that XO inhibitor, allopurinol (ALP), protects kidney and liver after renal I/R by PPAR-γ activation. Rats with renal I/R showed reduced kidney and liver functions, increased XO, and decreased PPAR-γ. ALP increased PPAR-γ expression and improved liver and kidney functions. ALP also reduced inflammation and nitrosative stress indicated by reduction in TNF-α, iNOS, nitric oxide (NO), and peroxynitrite formation. Interestingly, rats co-treated with PPAR-γ inhibitor, BADGE, and ALP showed diminished beneficial effect on renal and kidney functions, inflammation, and nitrosative stress. This data suggests that downregulation of PPAR-γ contributes to nitrosative stress and inflammation in renal I/R and the use of ALP reverses this effect by increasing PPAR-γ expression. In conclusion, this study highlights the potential therapeutic value of ALP and suggests targeting XO-PPAR-γ pathway as a promising strategy for preventing I/R injury.

Reno-protective effect of mangiferin against methotrexate-induced kidney damage in male rats: PPARγ-mediated antioxidant activity

Methotrexate (MTX) is an immunosuppressant used for the treatment of cancer and autoimmune diseases. MTX has a major adverse effect, acute kidney injury, which limits its use. Mangiferin (MF) is a natural bioactive xanthonoid used as a traditional herbal supplement to boost the immune system due to its potent anti-inflammatory and antioxidant activity. The present study evaluates the protective effect of MF against MTX-induced kidney damage. Male Wistar rats received MTX to induce nephrotoxicity or were pretreated with MF for 10 constitutive days before MTX administration. MF dose-dependently improved renal functions of MTX-treated rats and this activity was correlated with increased renal expression of PPARγ, a well-known transcriptional regulator of the immune response. Pretreating rats with PPARγ inhibitor, BADGE, reduced the reno-protective activity of MF. Furthermore, MF treatment significantly reduced MTX-induced upregulation of the pro-inflammatory (NFκB, interleukin-1ß, TNF-α, and COX-2), oxidative stress (Nrf-2, hemoxygenase-1, glutathione, and malondialdehyde), and nitrosative stress (nitric oxide and iNOS) markers in the kidney. Importantly, BADGE treatment significantly reduced the anti-inflammatory and antioxidant activity of MF. Therefore, our data suggest that the reno-protective effect of MF against MTX-induced nephrotoxicity is due to inhibition of inflammation and oxidative stress in a PPAR-γ-dependent manner.

Radionuclide lung imaging in respiratory decompression sickness: potential role in the diagnosis and evaluation of hyperbaric therapy

Of the more than 3.5 million trained divers in the United States, many will experience various illnesses specific to divers. Most of these illnesses are related to the changes in absolute pressure that divers experience while diving. During and after ascent, a diver is at risk for decompression sickness and pulmonary barotrauma. A very rare casualty is pulmonary decompression sickness from immersion. This is a literature review and case report of a young woman with acute respiratory decompression sickness who had defects on perfusion lung imaging after a diving accident and after hyperbaric oxygen therapy. However, the perfusion defects reverted to normal in less than 24 hours. Possible explanations for the changes in the appearances of the scans are offered and discussed. This case report shows the potential utility of lung scanning in the diagnostic examination of these patients and the evaluation of the adequacy of treatment with hyperbaric oxygen therapy. A greater use of ventilation-perfusion lung scans in the treatment of such patients may establish its role more definitely.

Technetium-99m sestamibi uptake in a maxillary brown tumor

Brown tumors have been reported to take up TI-201 when dual-tracer parathyroid scintigraphy using TI-201 and Tc-99m pertechnetate was performed. With the change to the more favorable Tc-99m sestamibi parathyroid scanning, similar phenomena of tracer uptake in brown tumors have been reported. The authors describe a 44-year-old man with a left maxillary swelling. Laboratory investigations revealed elevated parathyroid hormone levels. Computed tomography of the head showed a left maxillary expansile mass. Subsequently, a Tc-99m sestamibi scan was performed to rule out a parathyroid adenoma. Left inferior parathyroid retention of the tracer was seen, indicating a parathyroid adenoma. An incidental finding was the uptake of Tc-99m MIBI in the left maxillary brown tumor. This case suggests the utility and possible specificity of Tc-99m MIBI uptake in diagnosing brown tumors.

Potential pitfall in parathyroid sestamibi imaging resulting from a cardiac pacemaker

A 47-year-old woman with a history of end-stage renal disease and hyperparathyroidism after total parathyroidectomy had Tc-99m sestamibi imaging to identify possible ectopic parathyroid tissue. This study was prompted by increasing calcium and parathyroid hormone levels after several years of taking calcium supplements necessitated by a surgically induced hypoparathyroid state and end-stage renal disease. The scan showed persistent linear activity in the upper right mediastinum in delayed images, after washout of the thyroid had occurred. Because of the unusual configuration of this finding, investigation of the patient's clinical history and other imaging studies was undertaken. The authors concluded that the unusual mediastinal uptake was not hyperactive parathyroid tissue, but rather was attributed to the presence of central venous pacemaker wires. Thus, this case illustrates a potential pitfall in parathyroid sestamibi imaging, the uptake of which may increase in the presence of a cardiac pacemaker, and it emphasizes the importance of correlative imaging.