Ultrastructural Examination of Glomerular and Tubular Changes in Renal Allografts with Acute Rejection

Sirolimus-induced isometric tubular vacuolization: a new sirolimus histopathologic manifestation

The clinical and pathological experience with sirolimus is limited at this time. In this study, we report severe isometric vacuolization of the proximal tubules after sirolimus therapy in two kidney transplant patients. Patient 1 is a hepatitis C virus-positive, 30-year-old African American man who had end-stage renal disease (ESRD) of unknown etiology. Patient 2 is a 62-year-old white woman with ESRD due to unknown etiology. Both patients were initially placed on tacrolimus, mycophenolic acid, and prednisone immunosuppressive therapy. These patients were switched to sirolimus at 1 and 5 month posttransplant, respectively, due to the development of new-onset hyperglycemia and an elevated serum creatinine. Both patients presented with acute renal failure and high sirolimus levels at 5 years (patient 1) and 10 months posttransplant (patient 2). Biopsies of their kidney transplants showed widespread isometric tubular cytoplasmic vacuolization and severe arterial hyalinosis. Acute renal insufficiency improved after sirolimus dose reduction. In this case report, we introduce a new morphological appearance after sirolimus therapy of isometric cytoplasmic vacuolization of the renal tubules and severe arterial hyalinosis, similar to that seen in calcineurin inhibitor induced tubular toxicity.

Nitric oxide: new evidence for novel therapeutic indications

BACKGROUND

Nitric oxide (NO) deficiency is implicated in many pathophysiological processes in mammals. NO is a ubiquitous molecule involved in multiple cellular functions. Uncontrolled or inappropriate production of NO may lead to several disease states including septic shock, rheumatoid and inflammatory arthropathies, and expansion of cerebral damage after stroke. However, to date, there are no therapeutic agents available that can overcome these conditions. Similarly, underproduction of NO by NO synthase or enhanced breakdown of NO also leads to diseases such as hypertension, ischemic conditions, pre-eclampsia, premature delivery, among others. NO donor therapies are indicated in these conditions.

RESULTS

Nitroglycerin and nitrates (NO donors) have been used as therapeutic agents for the past century, particularly to treat vascular disease, and the only significant adverse effects are headaches. NO donors are highly cost-effective and have beneficial effects in multiple body systems. When the body cannot generate NO via NO synthase or due to rapid turnover leading to inadequate amounts of NO available for biological homeostasis, administration of exogenous NO, or prolongation of the actions of endogenous NO, are practical ways to supplement NO.

CONCLUSION

Recipients of such therapy include patients with angina pectoris, coronary artery disease, hypertension, osteoporosis, gastrointestinal motility disorders, pregnancy-related disorders including premature delivery, pre-eclampsia, vulvodynia, and erectile dysfunction in men. Postmenopausal NO deficiency is rectified with hormone replacement therapy, which enhances local production of NO. Declining local NO production secondary to estrogen deficiency in postmenopausal women and perhaps in older men could be one of the reasons for age-related increased incidences of cardiovascular events and sexual dysfunction. Thus, in addition to supplementation of NO compounds in acute situations like alleviating angina and erectile dysfunction, chronic NO therapy is cost-effective in decreasing cardiovascular events, and improving the urogenital system and skeletal health.