OBJECTIVE: To test the hypothesis that intravenous use of methotrexate associated with lipid nanoemulsions can achieve superior anti-inflammatory effects in the joints of rabbits with antigen-induced arthritis compared with commercial methotrexate. METHODS: Arthritis was induced in New Zealand rabbits sensitized with methylated bovine serum albumin and subsequently intra-articularly injected with the antigen. A nanoemulsion of methotrexate labeled with 3H-cholesteryl ether (4 mg/kg methotrexate) was then intravenously injected into four rabbits to determine the plasma decaying curves and the biodistribution of the methotrexate nanoemulsion by radioactive counting. Additionally, the pharmacokinetics of the methotrexate nanoemulsion were determined by high-pressure liquid chromatography. Twenty-four hours after arthritis induction, the animals were allocated into three groups, with intravenous injection with saline solution (n=9), methotrexate nanoemulsion (0.5 µmol/kg methotrexate, n=7), or commercial methotrexate (0.5 µmol/kg, n=4). The rabbits were sacrificed 24 h afterward. Synovial fluid was then collected for protein leakage and cell content analyses and synovial membranes were collected for histopathological analysis. RESULTS: The methotrexate nanoemulsion was taken up mainly by the liver and the uptake by arthritic joints was two-fold greater than that by control joints. The methotrexate nanoemulsion treatment reduced leukocyte influx into the synovial fluid by nearly 65%; in particular, mononuclear and polymorphonuclear cells were reduced by 47 and 72%, respectively. In contrast, cell influx was unaffected following treatment with commercial methotrexate. Protein leakage into the arthritic knees of the rabbits was also more limited following methotrexate nanoemulsion treatment than following commercial methotrexate treatment. CONCLUSIONS: The intravenous methotrexate nanoemulsion showed anti-inflammatory effects on the synovia of arthritic joints that were clearly superior to the effects of a commercial methotrexate preparation. This result is conceivably due to greater methotrexate uptake by the joints when the drug is associated with a nanoemulsion.

No remodelamento que se segue às sobrecargas de volume não é descrito o aumento de fibrose miocárdica. Após o infarto, entretanto, há hipertrofia do miocárdio remoto com acúmulo de fibrose, particularmente no subendocárdio. Na fístula aorto-cava, tal como no infarto, é possível que a queda da pressão de perfusão coronariana interfira com a fibrose cardíaca. OBJETIVO: Investigar o papel das mudanças hemodinâmicas agudas sobre a fibrose cardíaca na fístula aorto-cava. MÉTODO: Ratos Wistar submetidos a fístula aorto-cava, seguidos por 4 e 8 semanas, constituíram 4 grupos, fístula aorto-cava 4 e fístula aorto-cava 8 (10 ratos cada) e seus respectivos controles (sham-operated controls - Sh), Sh4 e Sh8 (8 ratos cada). A hemodinâmica foi realizada 1 semana após a cirurgia. A hipertrofia e a fibrose foram quantificadas ao final do seguimento pelo diâmetro dos miócitos e pela fração de volume do colágeno. RESULTADOS: Comparados com Sh4 e Sh8, a pressão de pulso, a pressão diastólica final do ventrículo esquerdo e a +dP/dt foram maiores em fístula aorto-cava 4 e fístula aorto-cava 8, enquanto a -dP/dt foi similar. A pressão estimada da perfusão coronariana (mmHg) foi menor em fístula aorto-cava 8 (52,6±4,1) do que em Sh8 (100,8±1,3), mas comparável entre fístula aorto-cava 4 (50,0±8,9) e Sh4 (84,8±2,3). O diâmetro dos miócitos foi maior em fístula aorto-cava 8 e a fibrose intersticial e subendocárdica maior em fístula aorto-cava 4 e fístula aorto-cava 8. Houve correlação inversa e independente da pressão de perfusão coronariana com a fibrose subendocárdica (r²=0,86; p<0,0001) e das pressões sistólica (r²=0,73; p=0,0035) e diastólica final do ventrículo esquerdo (r²=0,55; p=0.0124) com a fibrose intersticial. CONCLUSÃO: A queda precoce da pressão de perfusão coronariana e o aumento das pressões ventriculares após a fístula aorto-cava associam-se com fibrose miocárdica subseqüente.

Left ventricular hypertrophy following volume overload is regarded as an example of cardiac remodeling without increased fibrosis accumulation. However, infarction is associated with increased fibrosis within the noninfarcted, hypertrophied myocardium, particularly in the subendocardial regions. It is conceivable to suppose that, as also occurs postinfarction, low coronary driving pressure may also interfere with accumulation of myocardial fibrosis following aortocaval fistula. PURPOSE: To investigate the role of acute hemodynamic changes in subsequent deposition of cardiac fibrosis in response to aortocaval fistula. METHOD: Aortocaval fistula were created in 4 groups of Wistar rats that were followed over 4 and 8 weeks: aortocaval fistula 4 and aortocaval fistula 8 (10 rats each) and their respective controls (sham-operated controls - Sh), Sh4 and Sh8 (8 rats each). Hemodynamic measurements were performed 1 week after surgery. Hypertrophy and fibrosis were quantified by myocyte diameter and collagen volume fraction at the end of follow up. RESULT: Compared with Sh4 and Sh8, pulse pressure, left ventricular end-diastolic pressure, and +dP/dt were higher in aortocaval fistula 4 and aortocaval fistula 8, but -dP/dt was similar. Coronary driving pressure (mm Hg), used as an estimate of perfusion pressure, was lower in aortocaval fistula 8 (52.6 ± 4.1) than in Sh8 (100.8 ± 1.3), but comparable between aortocaval fistula 4 (50.0 ± 8.9) and Sh4 (84.8 ± 2.3). Myocyte diameter was greater in aortocaval fistula 8, whereas interstitial and subendocardial fibrosis were greater in aortocaval fistula 4 and aortocaval fistula 8. Coronary driving pressure correlated inversely and independently with subendocardial fibrosis (r² = .86, P <.001), whereas left ventricular systolic pressure (r² = 0.73, P = .004) and end-diastolic pressure (r² = 0.55, P = 012) correlated positively and independently with interstitial fibrosis. CONCLUSION: Coronary driving pressure falls and ventricular pressures increase early after aortocaval fistula and are associated with subsequent myocardial fibrosis deposition.