Prolonged administration of FTY720 does not cause renal toxicity in mice.

Prevention of allograft rejection without renal toxicity caused by calcineurin-inhibitor immunosuppression is a major goal for transplantation. FTY720 is a synthetic drug that modulates immune responses of transplantation in many animal models. FTY720 modulating mechanisms relate to lymphocyte migration to peripheral lymph nodes instead of inflammatory sites. The drug has no effect on T-cell proliferation or cytokine production, and therefore prevents generalized immunosuppression. However, it is still to be confirmed that FTY720 has no nephrotoxic effects when administered continuously. In the present study FTY720 was administered orally for 21 days to C57BL/6 mice that underwent weekly evaluations. FTY720 (1 mg/kg per day) impaired body weight gain, but had no significant effect on either renal function or structure. Our findings suggest that FTY720 may provide a reasonable add-on therapy in calcineurin-inhibitor-treated transplant recipients.

N-Domain angiotensin I-converting enzyme expression in renal artery of Wistar, Wistar Kyoto, and spontaneously hypertensive rats.

One of the most intriguing features in kidney transplantation is the finding that kidneys from hypertensive rats can transfer arterial hypertension on transplantation into normotensive rats. Some evidence also suggest that, in humans undergoing renal transplantation, the genotype of the donor kidney determines the blood pressure in the recipient. The renin-angiotensin-aldosterone system is the major etiological candidate in hypertension because it plays an important role in the control of cardiovascular homeostasis. Angiotensin-converting enzyme (ACE) cleaves the C-terminal from angiotensin I as well as from bradykinin. Thus, by generating the potent vasoconstrictor angiotensin II and by degrading the vasodepressor bradykinin, ACE is considered to play a role in blood pressure regulation. We have previously described the presence of N-domain ACE in urine of Wistar (W), Wistar Kyoto (WKY), and spontaneously hypertensive rats (SHR), all of which can hydrolyze the vasodilator peptide Angiotensin 1-7 and also the N-Acetyl-Ser-Asp-Lys-Pro, two peptides described as specific for N-domain ACE. These findings suggest that the 90 kd ACE isoform found in urine and in tissues of SHR is a possible genetic marker of hypertension. Based on the fact that the renal artery has an important role in the control of renal blood flow, we evaluated the presence of N-domain ACE in the renal artery of hypertensive and normotensive rats. Using Western blotting techniques on the renal arteries of W and WKY rats, we detected the 190-kd ACE (similar to somatic ACE) and also the 65-kd ACE previously described in urine and renal tissue as N-domain ACE. The 65-kd and 90-kd isoforms of ACE were also detected in renal arteries in SHR rats. Further studies are required to understand the role of 90-kd enzyme described as a possible local marker of hypertension, its contribution in angiotensin catabolism, and whether this abnormal form of the enzyme has any link with the development and transfer of hypertension after transplantation.

Role of substance P in blood pressure regulation in salt-dependent experimental hypertension.

The participation of substance P in the pathogenesis of five models of experimental hypertension, ie, DOCA-salt, subtotal nephrectomy, one-kidney-one clip renovascular, two-kidney-one clip renovascular, and spontaneous hypertension, was evaluated via an acute infusion of a newly synthesized potent, specific nonpeptide antagonist of substance P at the NK-1 receptor, the agent CP 96,345. In conscious unrestrained rats, CP 96,345 induced significant and sustained increases in mean arterial pressure of DOCA-salt, subtotal nephrectomy, and one-kidney-one clip renovascular hypertensive rats but only small and nonsignificant changes in blood pressure of two-kidney-one clip renovascular and spontaneously hypertensive rats. CP 96,345 had no effect on the blood pressure of sham-treated controls and Wistar-Kyoto rats. This NK-1 receptor antagonist did not significantly affect the heart rate of any experimental model studied. The data suggest that endogenous substance P may act as a partial counterregulatory mechanism against vasoconstriction in models of salt-dependent hypertension.

Cardiovascular effects of a specific nonpeptide antagonist of substance P (NK-1) receptor in DOCA-salt hypertension.

The neurotransmitter substance P acts also as a potent vasodilator. Its participation in the pathogenesis of deoxycorticosterone acetate (DOCA)-salt hypertension was evaluated by an acute infusion of a newly synthesized, potent, specific nonpeptide antagonist of substance P at the NK-1 receptor, the agent CP 96,345. In conscious unrestrained rats, CP 96,345 induced significant and sustained increases in mean arterial pressure of DOCA-salt rats but only small, transient, and nonsignificant rises in blood pressure of sham-treated control rats. The rise in blood pressure was not accompanied by changes in heart rate. Maximal blood pressure increase in DOCA-salt rats was 31.7 +/- 14.8 mm Hg. In a second series of experiments, the hemodynamic effects of this antagonist were evaluated under anesthesia in both DOCA-salt and sham-treated control rats by the thermodilution method. During CP 96,345 infusion, sustained increases in cardiac index and stroke volume and decreases in total peripheral resistance were observed in both DOCA-salt and control rats. In DOCA-salt rats, cardiac index rose by 79.4%, while total peripheral resistance fell by 27.9% of the baseline values. In control rats, the changes were smaller (+27.2% and -22.5%, respectively). Stroke volume changed in parallel to cardiac output in both groups. The data suggest that acute blockade of NK-1 receptors increases blood pressure in DOCA-salt rats mainly by an increase in cardiac output. We conclude that endogenous substance P tends to counteract the DOCA-salt-induced elevation of blood pressure by modulating both cardiac output and peripheral resistance.

Role of bradykinin in insulin sensitivity and blood pressure regulation during hyperinsulinemia.

The purpose of these experiments was to determine in normotensive rats the role of endogenous bradykinin, prostaglandins, and nitric oxide in glucose metabolism and blood pressure response to hyperinsulinemia. Normotensive Wistar rats were treated with two different bradykinin antagonists, indomethacin or N omega-nitro-L-arginine methyl ester, concurrently with a euglycemic clamp with insulin infusion rates of 3 or 6 mU/kg per minute. Glucose uptake, steady-state plasma insulin levels, and insulin sensitivity index were determined over 2 hours. Bradykinin inhibition dramatically reduced glucose uptake and insulin sensitivity index during both the lower and higher insulin infusion rates to 30% and 32%, respectively, of values observed in control rats. Inhibition of prostaglandins or nitric oxide did not alter glucose metabolism in these rats. Blood pressure remained unchanged in the control group throughout the clamp but increased significantly in rats submitted to inhibition of bradykinin, prostaglandins, or nitric oxide, suggesting that these vasodilator systems tend to counteract the hypertensive effect of hyperinsulinemia. The counterregulatory component attributable to bradykinin was about twice as great as that attributable to nitric oxide. These findings suggest that insulin infusion in normotensive Wistar rats fails to raise blood pressure because its effects are offset by mobilization of vasodilator mechanisms, such as bradykinin, prostaglandins, and nitric oxide. Bradykinin seems to play the most important homeostatic role under these conditions, because its inhibition significantly reduces insulin sensitivity and allows blood pressure to rise.

Successful treatment of chromoblastomycosis with topical heat therapy.

Four female patients with chromoblastomycosis were completely cured by prolonged topical application of tolerable heat from pocket warmers. The lesions involuted after 2, 3, and 6 months, respectively, in three patients who faithfully followed our strict treatment schedule, in contrast to the fourth patient who performed the topical heat therapy in an irregular manner at home over a 12-month period. In vitro studies showed that the mature colonies of Fonsecaea pedrosoi, isolated from three of the patients, withstood persistent heating at 42.5 degrees C for more than 1 month. This suggested that heat killing of the causative organisms is unlikely to have been the sole reason for the effectiveness of this simple therapeutic modality.

The speckled epidermal nuclear immunofluorescence of mixed connective tissue disease seems to develop as an in vitro phenomenon.

The pathogenesis of speckled epidermal nuclear immunofluorescence in patients with mixed connective tissue disease (MCTD) was studied by reproducing this reaction in guinea-pigs, using serum samples containing high titre antibody to ribonucleoprotein (RNP). Immunofluorescence studies on specimens obtained from guinea-pig skin into which serum samples containing high titre RNP antibody had been injected intradermally, revealed positive epidermal nuclear staining for IgG. This speckled immunofluorescence was demonstrable immediately after injection and remained so for 24 or 48 h. The pattern of fluorescence was similar in all cases, and there was no penetration of RNP antibody through the cell membrane. The epidermal nuclear fluorescence was not detected with sera at a dilution of 1:100 or more. These results provide strong evidence that the epidermal nuclear immunofluorescence observed in patients with high titre antibody to RNP develops as an in vitro phenomenon.