Cholinergic agonists reduce blood pressure in a mouse model of systemic lupus erythematosus

Abstract

Increased inflammation arising from an abnormal immune response can damage healthy tissue and lead to disease progression. An important example of this is the accumulation of inflammatory mediators in the kidney, which can subsequently lead to hypertension and renal injury. The origin of this inflammation may involve neuro-immune interactions. For example, the novel vagus nerve-to-spleen mechanism known as the "cholinergic anti-inflammatory pathway" controls inflammation upon stimulation. However, if this pathway is dysfunctional, inflammation becomes less regulated and chronic inflammatory diseases such as hypertension may develop. Systemic lupus erythematosus (SLE) is an autoimmune disease with aberrant immune function, increased renal inflammation, and prevalent hypertension. We hypothesized that the cholinergic anti-inflammatory pathway is impaired in SLE and that stimulation of this pathway would protect from the progression of hypertension in SLE mice. Female SLE (NZBWF1) and control (NZW) mice were administered nicotine or vehicle for 7 days (2 mg/kg/day, subcutaneously) in order to stimulate the cholinergic anti-inflammatory pathway at the level of the splenic nicotinic acetylcholine receptor (α7-nAChR). Blood pressure was assessed posttreatment. Nicotine-treated SLE mice did not develop hypertension and this lower blood pressure (compared to saline-treated SLE mice) coincided with lower splenic and renal cortical expression of pro-inflammatory cytokines. These data provide evidence that the cholinergic anti-inflammatory pathway is impaired in SLE In addition, these data suggest that stimulation of the cholinergic anti-inflammatory pathway can protect the kidney by dampening inflammation and therefore prevent the progression of hypertension in the setting of SLE.

Keywords: Cholinergic anti‐inflammatory pathway; hypertension; inflammation; kidney; nicotine; renal injury.

Figure 1

Chronic nicotine infusion increases plasma cotinine levels: Plasma cotinine (ng/mL) assessed by ELISA in control and SLE mice administered saline or nicotine for 7 days. n = 3–4 plasma samples/group; P* versus corresponding saline‐treated; P + versus Control/Nicotine.

Figure 2

Chronic nicotine exposure blunts splenic TNF‐α in female SLE mice: The release of a splenic inflammatory mediator was measured in order to confirm stimulation of the cholinergic anti‐inflammatory pathway at the level of the α7‐nAChR. Protein expression of TNF‐α assessed by Western blot in spleens of control and SLE mice administered saline or nicotine for 7 days. Data are normalized to total protein. n = 4–5 spleens/group; P* versus Control/Saline; P + versus SLE/Saline. TNF, tumor necrosis factor.

Figure 3

Chronic nicotine exposure attenuates the rise in blood pressure and protects from renal injury in female SLE mice: (A) Mean arterial pressure measured in control and SLE mice administered saline or nicotine for 7 days. n = 7–9 animals/group; P* versus Control/Saline; P + versus SLE/Saline; (B) Urinary albumin excretion, an accepted index of renal injury, measured in control and SLE mice administered saline or nicotine for 7 days. n = 7–12 animals/group; P* versus Control/Saline.

Figure 4

Chronic nicotine exposure alters renal inflammatory mediators in female SLE mice (A) Protein expression of TNF‐α assessed by Western blot in the renal cortex of control and SLE mice administered saline or nicotine for 7 days. Data are normalized to total protein. n = 4–5 kidneys/group; (B) Protein expression of TNF‐α assessed by Western blot in the renal medulla of control and SLE mice administered saline or nicotine for 7 days. Data are normalized to total protein. n = 3–4 kidneys/group; (C) Protein expression of the anti‐inflammatory cytokine, interleukin (IL)‐10, assessed by Western blot in the renal cortex of control and SLE mice administered saline or nicotine for 7 days. Data are normalized to total protein. n = 4–5 kidneys/group; P + versus Control/Saline; (D) Protein expression of the anti‐inflammatory cytokine, interleukin (IL)‐10, assessed by Western blot in the renal medulla of control and SLE mice administered saline or nicotine for 7 days. Data are normalized to total protein. n = 3–4 kidneys/group; P* versus corresponding Control; P + versus SLE/Saline. TNF‐α, tumor necrosis factor; SLE, Systemic lupus erythematosus.

Figure 5

Chronic nicotine exposure alters renal cortical MCP‐1 in female SLE mice: Protein expression of dimerized MCP‐1 assessed by Western blot in kidneys of control and SLE mice administered saline or nicotine for 7 days. Data is normalized to total protein. n = 4–5 kidneys/group; P* versus Control/Saline. MCP‐1, monocyte chemoattractant protein, SLE, Systemic lupus erythematosus.

Figure 6

Selective cholinergic agonist (PNU‐282,987) blunts the rise in blood pressure and reduces from renal injury in female SLE mice: (A) Mean arterial pressure measured in control and SLE mice administered vehicle or PNU‐282,987 for 28 days. n = 2–4 animals/group; (B) Proteinuria as measured by Albustix (“grades” calculated as described in the methods) in control and SLE mice administered vehicle or PNU‐282,987 for 28 days. n = 3–5 animals/group; (C) Glomerulosclerosis index in PAS‐stained paraffin embedded kidneys of control and SLE mice administered vehicle or PNU‐292,987 for 28 consecutive days. n = 3–4/group; (D) Representative pictures of PAS‐stained kidneys of control and SLE mice administered vehicle or PNU‐292,987 for 28 consecutive days. SLE, Systemic lupus erythematosus; PAS, periodic acid‐Schiff.