Yuichi Hori

siRNA-Based Therapy Ameliorates Glomerulonephritis

RNA interference by short interfering RNAs (siRNAs) holds promise as a therapeutic strategy, but use of siRNAs in vivo remains limited. Here, we developed a system to target delivery of siRNAs to glomeruli via poly(ethylene glycol)-poly(l-lysine)-based vehicles. The siRNA/nanocarrier complex was approximately 10 to 20 nm in diameter, a size that would allow it to move across the fenestrated endothelium to access to the mesangium. After intraperitoneal injection of fluorescence-labeled siRNA/nanocarrier complexes, we detected siRNAs in the blood circulation for a prolonged time. Repeated intraperitoneal administration of a mitogen-activated protein kinase 1 (MAPK1) siRNA/nanocarrier complex suppressed glomerular MAPK1 mRNA and protein expression in a mouse model of glomerulonephritis; this improved kidney function, reduced proteinuria, and ameliorated glomerular sclerosis. Furthermore, this therapy reduced the expression of the profibrotic markers TGF-beta1, plasminogen activator inhibitor-1, and fibronectin. In conclusion, we successfully silenced intraglomerular genes with siRNA using nanocarriers. This technique could aid the investigation of molecular mechanisms of renal disease and has potential as a molecular therapy of glomerular diseases.

Impact of irbesartan, an angiotensin receptor blocker, on uric acid level and oxidative stress in high-risk hypertension patients

Hyperuricemia is a known cardiovascular risk factor. The angiotensin II receptor blocker (ARB) losartan is known to decrease serum uric acid (UA) level. A recent in vitro study demonstrated a strong interaction between irbesartan and UA transporters that exceeded that of losartan. The purpose of the present study was to evaluate the hypouricemic effect of irbesartan in a clinical setting. A total of 40 high-risk hypertensive outpatients with coronary artery disease, cerebrovascular disease and/or diabetes complications who were taking ARBs other than irbesartan and losartan were enrolled in this study. After a 4-week control period, the patients’ prescribed ARBs were exchanged for an equivalent dose of irbesartan. We assessed blood pressure, heart rate, serum UA level, parameters of lipid and glucose metabolism, cardiac and renal function and inflammatory and oxidative stress markers in blood samples taken immediately before the initiation of irbesartan treatment and again after 12 weeks of treatment. All 40 recruited patients were followed (31 men and 9 women, mean age: 68 years) without any dropouts. During the 12 weeks of irbesartan treatment, no significant changes in blood pressure, heart rate, parameters of lipid or glucose metabolism or other biomarkers of cardiac function, renal function, or inflammation were observed. However, UA level (5.9±1.6 to 5.5±1.6 mg ml−1, P=0.028) and the oxidative stress marker derivative reactive oxygen metabolites (dROMs) (354±83 to 310±65 U.CARR, P<0.001) were significantly lower at 12 weeks of treatment compared with before treatment. These results suggest that irbesartan has beneficial effects on hyperuricemia and oxidative stress.

Limitation of the bandpass filter in preventing oversensing of pectoral myopotentials over the long-term follow-up

A 60‐year‐old male experienced an inappropriate shock from an implantable cardioverter‐defibrillator (ICD) because of oversensing of pectoral myopotentials. Battery depletion was also observed, and a generator change was performed. A single‐chamber ICD (VENTAK PRIZM II 1860) was changed to a new ICD (INCEPTA VR F161). The myopotentials were clearly eliminated by the difference in the band pass filter (PRIZM; 21‐171 Hz, INCEPTA; 20‐85 Hz), but unfortunately, new noise was documented 4 years later. The utility of the bandpass filter for preventing oversensing of myopotentials was observed, but the limitation of its use for long‐term follow‐up was also indicated.

273 GLOMERULAR-TARGETED MOLECULAR THERAPY USING TYROSINE HYDROXYLASE SIRNAS AMELIORATES GLOMERULAR DAMAGE IN DOCA-SALT HYPERTENSIVE RATS

Background: Renal sympathetic nerve plays an important role in progress of hypertension and kidney injury. Thus, we examined the protective effect of glomeruli-specific inhibition of tyrosine hydroxylase (TH), an enzyme upper stream in catecholamine synthesis, in glomeruar injury of hypertension models, using TH siRNAs. Design and methods: Deoxycorticosterone acetate (DOCA)-salt rats (uninephrectomized, DOCA- administraterd, and high-salt (8.0%) diet-fed for 3 weeks), which showed sympathoexcitation, were treated with TH or scrambled siRNAs. SiRNAs were administered systemically by using blockcopolymers composed of polyethylene glycol-poly (L-lysine) (PEG-PLL) vehicle, naming PIC nanocarrier 1. And we used uninephrectomized rats without DOCA and high-salt diet as a control. Results: DOCA-salt rats showed increased arterial pressure, albuminuria, glomerular sclerosis and tubulointerstitial injury compared with control rats. In DOCA-salt rats, glomerular expression of TH was increased and its expression was suppressed after administration of TH siRNAs. TH siRNAs ameliorated albuminuria, glomerular sclerosis without affecting arterial pressure and tubulointerstitial injury. However, srambled siRNAs/PIC nanocarriers did not influence these parameters, which confirmed that PIC nanocarriers itself did not affect renal pathogenesis. Conclusions: Glomerular sympathetic nerve may contribute to progress of glomerular injury. SiRNAs delivery system using PIC nanocarrier can be a potential tool for molecular therapy of glomerular diseases. References:Hideki Shimizu, Yuichi Hori,Shinya Kaname, Koei Yamada, Nobuhiro Nishiyama, Satoru Matsumoto, Kanjiro Miyata, Makoto Oba, Akira Yamada, Kazunori Kataoka, Toshiro Fujita: siRNA-Based Therapy Ameliorates Glomerulonephritis. J Am Soc Nephrol 21: 622–633, 2010