Renal Pathology in Hemizygous Sickle Cell Mice

Abstract

Transgenic mice have been developed that express exclusively human sickle cell beta hemoglobin and have major pathological features found in humans with sickle cell disease. These mice provide a unique opportunity to investigate the fundamental mechanisms of this disease and to design new strategies to correct the associated genetic defect(s). We found that in breeding males expressing only adult human alpha-globin and sickle beta-globin (homozygous SS mice) with females containing these transgenes plus one copy of the mouse beta-globin gene (hemizygous SS mice) greater than expected numbers of hemizygous offspring were produced than homozygous mice (carrying no mouse beta-globin gene). These hemizygous mice, expressing the human alpha and sickle beta(s) transgenes in combination with mouse beta+/-, were used for our preliminary studies of their renal pathology. No kidney lesions were found in the control (129/Sv) mice, whereas about 50% of the hemizygous SS mice showed mild-to-severe kidney lesions, including glomerulonephritis, cystic atypical hyperplastic tubules, and general nephropathy. Kidneys of some hemizygous mice were normal or showed minimal nephropathy, yet those of the susceptible phenotype developed a mild-to-more-severe form of renal lesions. The tubular epithelium of kidneys of hemizygous mice of the more affected phenotype exhibited increased expression of inducible nitric oxide synthase with an increased 3-nitrotyrosine in close proximity. There was also a stronger immunostaining for vascular cell adhesion molecule-1 in the interstitial capillary cells as well as the tubular epithelial cells of the renal cortex, compared with normal control mice. The occurrence of a high incidence of renal abnormalities in our hemizygous SS mice suggests that these mice may provide a suitable model to study the pathogenesis of nephropathy resulting from altered blood flow and/or insufficient oxygen delivery.

Hemolysis in sickle cell mice causes pulmonary hypertension due to global impairment in nitric oxide bioavailability

“…Right atrial pressures of young adult sickle mice and hemizygotes were not significantly different ( Figure 1A). Although known to have abnormal hematology and kidneys, 41,57 hemizygotes did not differ from wild-type mice in baseline hemodynamics (data not shown). Despite the observed increases in pulmonary artery pressures, the systemic blood pressure did not differ between sickle, hemizygote, and wild-type mice.…”

“…Transplantation also provides additional control animals to compare with the vascular responsiveness of hemizygous mice, which differ from wild-type mice in many respects, including a high hemoglobin oxygen affinity. 41,57 Mice engrafted by 2 1 ⁄2 months after transplantation, with peripheral blood counts identical to the sickle mouse donors and demonstrating more than 90% HbS by hemoglobin electrophoresis. Cardiac catheterization was performed in all mice that survived transplantation, at a similar age as the mice that did not receive transplants.…”

Nitric oxide in gingival crevicular fluid and nitric oxide synthase expression in the gingiva of patients with sickle cell disease

“…SCD is also strongly associated with oxidative stress, increased expression of endothelial cell adhesion molecules, and blood adhesion. Increased iNOS expression and NO production have been observed in the kidneys and the liver in SCD patients [8], in mice [2,3,8,9], and in pigs [4]. During the clinically asymptomatic state, NO bioavailability is reduced in SCD patients due to scavenging of NO by cell-free hemoglobin released from hemolyzed sickle erythrocytes [50] and increased arginase activity [51].…”

“…Increased iNOS expression and a consequent increase in tissue nitrite and nitrate production have been observed in the kidneys and liver of SCD patients [8], mice [2,3,8,9], and pigs [4]. Additionally, it was shown that iNOS inhibition significantly limits tissue ischemia-reperfusion injury in the liver and kidneys [10,11]; however, inhibition of iNOS attenuated ischemia-reperfusion injury in the rat heart [12] and did not affect ischemia-reperfusion injury in the rat lung [13].…”

“…Interactions between abnormal rigid erythrocytes and the vascular wall result in endothelial activation, which may lead to endothelial damage and tissue ischaemia in SCD. Chronic inflammation during both the steady state and vasoocclusive crisis occurs via the action of cytokines and other inflammatory factors [1][2][3][4]. The clinical manifestations of the disease, such as painful crises, anemia, bone necrosis, and leg ulceration, arise due to chronic hemolysis, vaso-occlusion, ischemia, and tissue damage.…”