Sympathetic Enhancement of Memory T-Cell Homing and Hypertension Sensitization.

RATIONALE: Effector memory T lymphocytes (TEM cells) exacerbate hypertension in response to repeated hypertensive stimuli. These cells reside in the bone marrow for prolonged periods and can be reactivated on reexposure to the hypertensive stimulus. OBJECTIVE: Because hypertension is associated with increased sympathetic outflow to the bone marrow, we hypothesized that sympathetic nerves regulate accumulation and reactivation of bone marrow-residing hypertension-specific TEM cells. METHODS AND RESULTS: Using unilateral superior cervical ganglionectomy in wild-type C57BL/6 mice, we showed that sympathetic nerves create a bone marrow environment that supports residence of hypertension-specific CD8+ T cells. These cells, defined by their proliferative response on coculture with dendritic cells from Ang (angiotensin) II-infused mice, were reduced in denervated compared with innervated bone of Ang II-infused mice. Adoptively transferred CD8+ T cells from Ang II-infused mice preferentially homed to innervated compared with denervated bone. In contrast, ovalbumin responsive T cells from OT-I mice did not exhibit this preferential homing. Increasing superior cervical ganglion activity by activating Gq-coupled designer receptor exclusively activated by designer drug augmented CD8+ TEM bone marrow accumulation. Adoptive transfer studies using mice lacking ß2AR (ß2 adrenergic receptors) indicate that ß2AR in the bone marrow niche, rather than T-cell ß2AR is critical for TEM cell homing. Inhibition of global sympathetic outflow using Gi-coupled DREADD (designer receptor exclusively activated by designer drug) injected into the rostral ventrolateral medulla or treatment with a ß2AR antagonist reduced hypertension-specific CD8+ TEM cells in the bone marrow and reduced the hypertensive response to a subsequent response to low dose Ang II. CONCLUSIONS: Sympathetic nerves contribute to the homing and survival of hypertension-specific TEM cells in the bone marrow after they are formed in hypertension. Inhibition of sympathetic nerve activity and ß2AR blockade reduces these cells and prevents the blood pressure elevation and renal inflammation on reexposure to hypertension stimuli.

Excessive cholecalciferol supplementation increases kidney dysfunction associated with intrarenal artery calcification in obese insulin-resistant mice.

Diabetes mellitus accelerates vascular calcification (VC) and increases the risk of end-stage renal disease (ESRD). Nevertheless, the impact of VC in renal disease progression in type 2 diabetes mellitus (T2DM) is poorly understood. We addressed the effect of VC and mechanisms involved in renal dysfunction in a murine model of insulin resistance and obesity (ob/ob), comparing with their healthy littermates (C57BL/6). We analyzed VC and renal function in both mouse strains after challenging them with Vitamin D3 (VitD3). Although VitD3 similarly increased serum calcium and induced bone disease in both strains, 24-hour urine volume and creatinine pronouncedly decreased only in ob/ob mice. Moreover, ob/ob increased urinary albumin/creatinine ratio (ACR), indicating kidney dysfunction. In parallel, ob/ob developed extensive intrarenal VC after VitD3. Coincidently with increased intrarenal vascular mineralization, our results demonstrated that Bone Morphogenetic Protein-2 (BMP-2) was highly expressed in these arteries exclusively in ob/ob. These data depict a greater susceptibility of ob/ob mice to develop renal disease after VitD3 in comparison to paired C57BL/6. In conclusion, this study unfolds novel mechanisms of progressive renal dysfunction in diabetes mellitus (DM) after VitD3 in vivo associated with increased intrarenal VC and highlights possible harmful effects of long-term supplementation of VitD3 in this population.

Central EP3 (E Prostanoid 3) Receptors Mediate Salt-Sensitive Hypertension and Immune Activation.

We recently identified a pathway underlying immune activation in hypertension. Proteins oxidatively modified by reactive isoLG (isolevuglandin) accumulate in dendritic cells (DCs). PGE2 (Prostaglandin E2) has been implicated in the inflammation associated with hypertension. We hypothesized that PGE2 via its EP (E prostanoid) 3 receptor contributes to DC activation in hypertension. EP3-/- mice and wild-type littermates were exposed to sequential hypertensive stimuli involving an initial 2-week exposure to the nitric oxide synthase inhibitor Nω-nitro-L-arginine methyl ester hydrochloride in drinking water, followed by a 2-week washout period, and a subsequent 4% high-salt diet for 3 weeks. In wild-type mice, this protocol increased systolic pressure from 123±2 to 148±8 mm Hg (P<0.05). This was associated with marked renal inflammation and a striking accumulation of isoLG adducts in splenic DCs. However, the increases in blood pressure, renal T-cell infiltration, and DC isoLG formation were completely prevented in EP3-/- mice. Similar protective effects were also observed in wild-type mice that received intracerebroventricular injection of a lentiviral vector encoding shRNA targeting the EP3 receptor. Further, in vitro experiments indicated that PGE2 also acts directly on DCs via its EP1 receptors to stimulate intracellular isoLG formation. Together, these findings provide new insight into how EP receptors in both the central nervous system and peripherally on DCs promote inflammation in salt-induced hypertension.

A high-fat diet increases interleukin-3 and granulocyte colony-stimulating factor production by bone marrow cells and triggers bone marrow hyperplasia and neutrophilia in Wistar rats.

It is well established that the excessive consumption of a high-fat diet (HFD) results in overweight, obesity and an increase in leptin concentrations, which triggers a chronic inflammatory condition that is associated with a high white blood cell count. Two-month-old male Wistar rats were fed a control (CON) diet or an HFD for 12 weeks. After this period, hemogram, myelogram and biochemical parameters were evaluated along with the cell cycle and the percentage of CD34(+) cells in the bone marrow as well as cell proliferation and differentiation assays and the production of stem cell factor, interleukin 3 (IL-3), granulocyte colony-stimulating factor (G-CSF) and granulocyte macrophage colony-stimulating factor (GM-CSF). The HFD animals exhibited leukocytosis and neutrophilia with increased C-reactive protein, leptin, cholesterol and triglyceride concentrations. In the HFD group, the bone marrow revealed myeloid hyperplasia, especially of the granulocytic compartment with a higher percentage of CD34(+) cells and a higher percentage of cells in the G2/S/M cell cycle phases. In addition, the HFD bone marrow cells had a higher capacity to proliferate and differentiate into granulocytic cells in an in vitro system and a higher capacity to produce IL-3 and G-CSF. These data led us to infer that the HFD induces leukocytosis and neutrophilia suggesting alterations in hematopoiesis system modulation.