Reduced basal and lipopolysaccharide-stimulated adenosine A1 receptor expression in the brain of nuclear factor-κB p50−/− mice

Abstract

Adenosine promotes cytoprotection under conditions of infection, ischemic preconditioning and oxidative stress. Previous studies from our laboratory indicate that the expression of the adenosine A1 receptor (A1AR) is induced by oxidative stress via activation of nuclear factor (NF)-kappaB. The prototypic transcription factor is composed of homo- or heterodimers of p50 and p65 subunits. To determine the role of NF-kappaB in the regulation of the A1AR in vivo, we compared the A1AR RNA and protein levels in the brains of mice lacking the p50 subunit of NF-kappaB (p50-/- mice) and age-matched B6129PF2/J (F2) controls. Radioligand binding assays in the cortex revealed a significantly lower number of A(1)AR (maximal binding capacity, Bmax) in the cortex of p50-/- mice (151+/-62 fmol/mg protein) versus 479+/-181 fmol/mg protein in the F2 (N=5 per strain, P<0.05), but no change in the equilibrium dissociation constant. Similar reductions in A1AR were measured in the hippocampus, brain stem and hypothalamus and in peripheral tissues, such as the adrenal gland, kidney and spleen. Estimation of the A1AR following purification by antibody affinity columns also indicated reduced A1AR in the p50-/- mice cortex, as compared with the F2 mice. A1AR immunocytochemistry indicates distinct neuronal labeling in the F2 cortex, which was substantially reduced in similar sections obtained from p50-/- mice. The p50-/- mice expressed lower levels of A1AR mRNA than F2 mice, as determined by real time PCR. Quantitation of the A1AR transducing G proteins by Western blotting show significantly less Galphai3, no change in Galphai1, but higher levels of Galphao and Gbeta in the cortices of p50-/-, as compared with F2 mice. Administration of bacterial lipopolysaccharide (LPS), an activator of NF-kappaB, increased A1AR expression in the cortices of F2 mice but not p50-/- mice. Cortical neurons cultures prepared from p50-/- mice showed a greater degree of apoptosis, compared with neurons from F2 mice. Activation of the A1AR reduced apoptosis with greater efficacy in cultures from F2 than p50-/- mice. Taken together, these data support a role for NF-kappaB in determining both the basal and LPS-stimulated A1AR expression in vivo which could contribute to neuronal survival.

Expression of striatal adenosine and dopamine receptors in mice deficient in the p50 subunit of NF-κB

“…1). The p65 protein was detected in both strains, and did not change significantly when the lanes were normalized to the levels of β-actin in this or our previous study (Jhaveri et al 2007). …”

“…Accordingly, the lack of the p50 subunit will remove the suppression of A 2A AR transcription mediated by the p50/p50 homodimer. Although the p50 protein was undetectable in striata from p50 -/-mice as compared with F2 mice, p65 protein did not change significantly when the lanes were normalized to the levels of β-actin in this and our previous study (Jhaveri et al, 2007). An alternative possibility is that the changes in receptor proteins are correlated with but not directly caused by a loss of NFκB function.…”

Effect of Diabetes/Hyperglycemia on the Rat Retinal Adenosinergic System

“…It has been shown in several reports that different agents and conditions can stimulate A 1 AR expression in an NF-κB-dependent manner [24]–[26]. NF-κB, a transcription factor with putative binding sites found in all adenosine receptor genes [27], was shown to be regulated by TNF-α in several cell types, including retinal cells [28], revealing a possible relationship between the high levels of TNF-α present in hyperglycemic conditions [4] and the increased levels of A 1 AR detected under the same conditions.…”

Adenosine A1 receptor antagonist, L-97-1, improves survival and protects the kidney in a rat model of cecal ligation and puncture induced sepsis

“…Adenosine A 1 receptors are coupled via a pertussis toxin-sensitive inhibitory G protein to a number of different intracellular signaling pathways and effector systems, including adenylate cyclase, phospholipase A 2 , phospholipase C, potassium channels, calcium channels, and protein kinase C (Wilson et al, 2009). Adenosine A 1 receptors are upregulated by hypoxia, stress, ischemia/reperfusion, lipopolysaccharide, and inflammation, including in the heart, brain, and kidney (Blackburn et al, 2009; Funakoshi et al, 2007; Jhaveri et al, 2007; Nie et al, 1998). …”