Significance Solid tumors contain large numbers of immune cells, including monocytes and monocyte-derived macrophages that promote tumor progression. During tumor development, monocytes accumulate in the spleen. However, the influence of spleen cells on tumor growth remains controversial. Here, we used novel methods for tracking intertissue migration and monitoring hematopoiesis to show that during tumor development the bone marrow dramatically accelerates production of monocytes, rapidly transferring many of these newly formed cells to a reservoir in the spleen. However, these spleen monocytes are less able than their bone marrow counterparts to enter the tumor and make only a minor contribution to the tumor-infiltrating monocyte population. These findings clarify the roles of the spleen and bone marrow in cancer development.

Abstract-Angiotensin-converting enzyme inhibitors and angiotensin AT 1 receptor blockers reduce myocardial ischemiareperfusion injury via bradykinin B 2 receptor-and angiotensin AT 2 receptor-mediated mechanisms. The renin inhibitor aliskiren increases cardiac tissue kallikrein and bradykinin levels. In the present study, we investigated the effect of aliskiren on myocardial ischemia-reperfusion injury and the roles of B 2 and AT 2 receptors in this effect. Female SpragueDawley rats were treated with aliskiren (10 mg/kg per day) and valsartan (30 mg/kg per day), alone or in combination, together with the B 2 receptor antagonist icatibant (0.5 mg/kg per day) or the AT 2 receptor antagonist PD123319 (30 mg/ kg per day), for 4 weeks before myocardial ischemia-reperfusion injury. Aliskiren increased cardiac bradykinin levels and attenuated valsartan-induced increases in plasma angiotensin II levels. In vehicle-treated rats, myocardial infarct size (% area at risk, mean±SEM, n=7-13) was 43±3%. This was reduced to a similar extent by aliskiren, valsartan, and their combination to 24±3%, 25±3%, and 22±2%, respectively. Icatibant reversed the cardioprotective effects of aliskiren and the combination of aliskiren plus valsartan, but not valsartan alone, indicating that valsartan-induced cardioprotection was not mediated by the B 2 receptor. PD123319 reversed the cardioprotective effects of aliskiren, valsartan, and the combination of aliskiren plus valsartan. Aliskiren protects the heart from myocardial ischemia-reperfusion injury via a B 2 receptor-and AT 2 receptor-mediated mechanism, whereas cardioprotection by valsartan is mediated via the AT 2 receptor. In addition, aliskiren attenuates valsartan-induced increases in angiotensin II levels, thus preventing AT 2 receptor-mediated cardioprotection by valsartan. MethodsDetailed methods are provided in the online-only Data Supplement. Results Effects of Drug Treatment on Systolic BloodPressure, Body Weight, Heart Weight/Body Weight Ratio, and Mean Arterial Blood Pressure During I/R Injury Systolic blood pressure (SBP) of the 12 groups of rats during the 4-week treatment period before I/R injury is shown in the Table. In the present study, we used doses of aliskiren (10 mg/kg per day SC) and valsartan (30 mg/kg per day PO) that have little effect on blood pressure in normotensive Sprague-Dawley rats. Neither aliskiren nor valsartan caused any change in SBP during the 4 weeks (Table). However, SBP in rats receiving the combination of aliskiren plus valsartan was less than that in vehicle-treated rats. In contrast, SBP in rats receiving the B 2 receptor antagonist icatibant (0.5 mg/kg per day SC) alone was higher than that of vehicle-treated rats. Rats treated with aliskiren, valsartan, and the combination of aliskiren plus valsartan had lower SBP during combined treatment with icatibant than that of rats treated with icatibant alone. Treatment with the AT 2 receptor antagonist PD123319 (30 mg/kg per day SC) alone did not affect blood pressure. During combined treatment w...

To investigate the cause of salt sensitivity in a normotensive animal model, we treated rats with a low-dose of the nitric oxide synthase inhibitor, L-NAME, that does not elevate blood pressure per se or induce kidney fibrosis. A high salt diet increased the circulating blood volume both in L-NAMEtreated and nontreated animals for the first 24 hours. Thereafter, the blood volume increase persisted only in the L-NAME-treated rats. Blood pressure was higher in the L-NAMEtreated group from the start of high salt diet exposure. Within the first 24 hours of salt loading, the L-NAME treated animals failed to show vasodilation and maintained high systemic vascular resistance in response to blood volume expansion. After four weeks on the high salt diet, the slope of the pressure-natriuresis curve was blunted in the L-NAME-treated group. An increase in natriuresis was observed after treatment with hydrochlorothiazide, but not amiloride, a change observed in parallel with increased phosphorylated sodium-chloride cotransporter (NCC). In contrast, a change in blood pressure was not observed in L-NAME-treated NCCdeficient mice fed a high salt diet. Moreover, direct L-NAMEinduced NCC activation was demonstrated in cells of the mouse distal convoluted tubule. The vasodilatator, sodium nitroprusside, downregulated phosphorylated NCC expression. The effect of L-NAME on phosphorylated NCC was blocked by both the SPAK inhibitor STOCK2S-26016 and the superoxide dismutase mimetic TEMPO which also attenuated salt-induced hypertension. These results suggest that the initiation of salt sensitivity in normotensive rodents could be due to hyporeactivity of the vasculature and that maintaining blood pressure could result in a high circulating volume due to inappropriate NCC activity in the low-dose L-NAME model. Thus, even slightly impaired nitric oxide production may be important in salt sensitivity regulation in healthy rodents.