Angiotensin II type 1 receptor expression in two cases of juxtaglomerular cell tumor: correlation to negative feedback of renin secretion by angiotensin II

[Advance in Research of Angiotensin II and Its Receptor and Malignant Tumor]

Angiotensin AngII, a linear small peptide,which is composed of eight amino acids, is the main effectors of renin-angiotensin systen (Renin-angiotensin system, RAS). AngII, a main biopolypeptide of the RAS, has important pathophysiologic in effects participating in cardiac hypertrophy, vascular cell proproliferation, inflammation and tissue remodeling through G-protein-coupled receptors. In recent years, Ang II can promote tumor cell proliferation, tumor vessel formation and inhibit the differentiation of the tumor cells. This suggests that inhibit the production of AngII or block its effect is expected to become a new measure for the treatment of malignant tumors. This article reviews the advances in research on the relationship between AngII and its receptor and malignant tumor in recent years.

[Case of juxtaglomerular cell tumor (reninoma) treated with laparoscopic partial nephrectomy]

We report a case of a 22-year-old male with juxtaglomerular cell tumor treated with laparoscopic partial nephrectomy. He was referred to our hospital with hypertension, high concentration of plasma renin activity (PRA) and renal mass. Dynamic enhanced computed tomography showed 17-mm weak contrast-enhancing tumor at the upper pole of the left kidney. Renin suppression and stimulation test revealed autonomous renin secretion although renal venous sampling failed to show significant difference in the PRA between the right and left renal vein. We performed laparoscopic left partial nephrectomy. The histological diagnosis was juxtaglomerular cell tumor. After the operation, his blood pressure and PRA were immediately normalized. Juxtaglomerular cell tumor is an important renal tumor as a curable cause of secondary hypertension.

Deficiency of angiotensin type 2 receptor rescues obesity but not hypertension induced by overexpression of angiotensinogen in adipose tissue

Increased angiotensinogen (AGT) production by white adipose tissue has been related to not only obesity but also hypertension. Several studies have highlighted the importance of the angiotensin II type 2 receptor (AT2) in the regulation of blood pressure and fat mass, but the relevance of this transporter in a physiopathological model of increased AGT production, as it occurs in obesity, has not yet been investigated. We used transgenic mice that display either a deletion of AT2 (AT2 KO), an overexpression of AGT (OVEX), or both compound mutants (KOVEX). Results demonstrated that adipocyte hypertrophy and increased lipogenic gene expression induced by adipose AGT overproduction was rescued by deletion of AT2. In line with AGT overexpression, KOVEX and OVEX mice have similar increased plasma AGT levels. However, KOVEX mice display a higher blood pressure than OVEX mice. In kidney, renin expression was clearly reduced in OVEX mice, and its expression was normalized in KOVEX mice. Taken together, we demonstrated that the loss of AT2 expression was sufficient to rescue obesity induced by adipose tissue AGT overexpression and confirmed the necessary role of AT2 for the onset of obesity in this model. Furthermore, despite a reduction of adipose mass in KOVEX, AT2 deficiency caused increased renin production, further worsening the hypertension caused by AGT overexpression.

Angiotensin Subtype-2 Receptors Inhibit Renin Biosynthesis and Angiotensin II Formation

Renin is regulated by angiotensin subtype 1 (AT1) receptor, but it is unknown whether angiotensin subtype 2 (AT2) receptor contributes to this regulation. We hypothesized that AT2 receptors inhibit angiotensin II (Ang II) through inhibition of renin biosynthesis. We monitored changes in renal Ang II, renin mRNA and protein expression, and plasma renin concentration (PRC) in response to renal cortical administration of the AT1 receptor blocker valsartan or the AT2 receptor blocker PD 123319 (PD) in conscious rats administered low sodium intake (LS). Renal interstitial Ang II increased by 47-fold in response to LS and increased further in response to valsartan or PD by 67-fold and 61-fold from normal sodium diet (NS) and by 41% and 29% from LS, respectively. Renin mRNA increased 63% during LS, and either valsartan or PD increased it further by 600% and 250% from NS and 538% and 187% from LS, respectively. Similarly, renal renin content and PRC increased in response to LS and increased further in response to combined LS and valsartan or PD administration. Immunostaining for renal renin protein demonstrated an increase in its expression in juxtaglomular and tubular cells during LS and increased further during AT1 or AT2 receptor blockade. These data demonstrate for the first time to our knowledge that AT2 receptors regulate the renin-angiotensin system activity via inhibition of renin synthesis.

Angiotensin II type 1 receptor mRNA and its protein expression in human pancreatic cancer cell lines

OBJECTIVE

The incidence of pancreatic cancer is increasing in China, and in many patients the surrounding lymphatics have already been invaded and there is blood-borne metastasis at the time of diagnosis. Additionally, pancreatic cancer is largely refractory to conventional therapies. Therefore, to improve its prognosis, it is important to resolve the problem of its growth. Angiotensin II type 1 receptor (AT1) stimulates the growth and angiogenesis of pancreatic cancer and a selective AT1 antagonist could inhibit these effects. The present study aimed to investigate the expression of AT1 in pancreatic cancer cell lines to provide the theoretical basis for its treatment.

METHODS

The pancreatic cancer cell lines were SW1990, PaTu8988s and PANC-1. RT-PCR was used to detect the AT1 mRNA expression, and ABC immunocytochemical staining and SDS-PAGE were used to detect the expression of AT1 protein.

RESULTS

Both AT1 mRNA and protein were expressed in all three cell lines. The AT1 protein was found on the cell membrane and in the cytoplasm of these cells. The AT1 protein (44 x 10(3)) was also demonstrated by SDS-PAGE.

CONCLUSION

The results suggest that AT1 plays an important role in the growth of pancreatic cancer and its inhibition may be a therapeutic strategy.

AT1 angiotensin II receptor mediates intracellular calcium mobilization in normal and cancerous breast cells in primary culture

Angiotensin II (Ang II) increases intracellular calcium concentration ([Ca2+]i) in both normal and cancerous human breast cells in primary culture. Maximal [Ca2+]i increase is obtained using 100nM Ang II in both cell types; in cancerous breast cells, [Ca2+]i increase (delta[Ca2+]i) is 135+/-10nM, while in normal breast cells it reaches 65+/-5 nM (P<0.0001). In both cell types, Ang II evokes a Ca2+ transient peak mediated by thapsigargin (TG) sensitive stores; neither Ca2+ entry through L-type membrane channels or capacitative Ca2+ entry are involved. Type I Ang II receptor subtype (AT1) mediates Ang II-dependent [Ca2+]i increase, since losartan, an AT1 inhibitor, blunted [Ca2+]i increase induced by Ang II in a dose-dependent manner, while CGP 4221A, an AT2 inhibitor, does not. Phospholipase C (PLC) is involved in this signaling mechanism, as U73122, a PLC inhibitor, decreases Ang II-dependent [Ca2+]i transient peak in a dose-dependent mode.Thus, the present study provides new information about Ca2+ signaling pathways mediated through AT1 in breast cells in which no data were yet available.

Juxtaglomerular cell tumor: a clinicopathologic study of four cases and review of the literature

We studied 4 new cases of juxtaglomerular cell tumor and compared their morphologic and immunohistochemicalfeatures with 2 renal hemangiopericytomas and 5 cutaneous glomus tumors. The juxtaglomerular tumors were resectedfrom 2 males and 2 females (mean age at diagnosis, 23 years). Three patients manifested with severe hypertension. Tumors ranged from 2.2 to 8.0 cm and were well circumscribed. The tumors consisted of solid sheets and nodules of variably sized tumor cells with round, oval, and spindled nuclei alternating with edematous microcystic foci. Nuclear atypia, present in all tumors, was a prominent feature in 2. Mitotic activity was not identified. All cases showed hemorrhage, numerous mast cells, and thick-walled blood vessels. Unusual features included coagulative tumor necrosis, a hemangiopericytoma-like vascular pattern, and hyalinized stroma. All tumors were immunoreactive for CD34 and actin. Ultrastructural analysis revealed the presence of rhomboid-shaped renin protogranules. Patients were treated by partial or radical nephrectomy and followed up for 14 to 48 months. There were no recurrences or metastases. The characteristic clinical and morphologic features of juxtaglomerular cell tumor permit distinction from renal hemangiopericytoma and other renal tumors.

Dynamic computer tomography is useful in the differential diagnosis of juxtaglomerular cell tumor and renal cell carcinoma

We compared dynamic computer tomographic CT images of 3 cases of juxtaglomerular (JG) cell tumor with those of 8 cases of renal cell carcinoma (RCC). The JG cell tumor was visualized as a low- to high-density area in case 1, a low-density area in case 2, and a low- to iso-density area in case 3 before contrast enhancement. None of the JG cell tumors were stained during the early phase (1 min), but all were stained moderately during the late phase (5 min) after contrast enhancement. Although all cases of RCC were visualized as a low- to iso-density area before contrast enhancement, they were intensely stained during the early phase with significant washout during the late phase. The present results suggest that the dynamic CT scan is useful in the differential diagnosis of the JG cell tumor and RCC.