Quantitative Immunohistochemistry to Measure Regional Expression of Nurr1 in the Brain and the Effect of the Nurr1 Heterozygous Genotype

Abstract

The transcription factor Nurr1 is a member of the steroid hormone nuclear receptor superfamily. Ablation of Nurr1 expression arrests mesencephalic dopamine neuron differentiation while attenuation of Nurr1 in the subiculum and hippocampus impairs learning and memory. Additionally, reduced Nurr1 expression has been reported in patients with Parkinson’s disease and Alzheimer’s disease. In order to better understand the overall function of Nurr1 in the brain, quantitative immunohistochemistry was used to measure cellular Nurr1 protein expression, across Nurr1 immunoreactive neuronal populations. Additionally, neuronal Nurr1 expression levels were compared between different brain regions in wild-type mice (+/+) and Nurr1 heterozygous mice (+/−). Regional Nurr1 protein was also investigated at various time points after a seizure induced by pentylenetetrazol (PTZ). Nurr1 protein is expressed in various regions throughout the brain, however, a wide range of Nurr1 expression levels were observed among various neuronal populations. Neurons in the parietal and temporal cortex (secondary somatosensory, insular, auditory, and temporal association cortex) had the highest relative Nurr1 expression (100%) followed closely by the claustrum/dorsal endopiriform cortex (85%) and then subiculum (76%). Lower Nurr1 protein levels were found in neurons in the substantia nigra pars compacta and ventral tegmental area (39%) followed by CA1 (25%) and CA3 (19%) of the hippocampus. Additionally, in the parietal and temporal cortex, two distinct populations of high and medium Nurr1 expressing neurons were observed. Comparisons between +/− and +/+ mice revealed Nurr1 protein was reduced in +/− mice by 27% in the parietal/temporal cortex, 49% in the claustrum/dorsal endopiriform cortex, 25% in the subiculum, 33% in substantia nigra pars compacta, 22% in ventral tegmental area, and 21% in CA1 region of the hippocampus. Based on these data, regional mechanisms appear to exist which can compensate for a loss of a Nurr1 allele. Following a single PTZ-induced seizure, Nurr1 protein in the dentate gyrus peaked around 2 h and returned to baseline by 8 h. Since altered Nurr1 expression has been implicated in neurologic disorders and Nurr1 agonists have showed protective effects, understanding regional protein expression of Nurr1, therefore, is necessary to understand how changes in Nurr1 expression can alter brain function.

Developmental Patterning and Neurogenetic Gradients of Nurr1 Positive Neurons in the Rat Claustrum and Lateral Cortex

“…Even high levels of neuronal activity induced by epileptic seizures did not lead to significant changes of Nurr1 expression in the early postnatal rat brain ( Crispino et al, 1998 ). In later postnatal stages and in adult animals seizure induced changes in Nurr1 expression levels were mainly detected in the hippocampus ( Xing et al, 1997 ; Crispino et al, 1998 ; Kummari et al, 2021 ). Clearly, further studies are needed to understand the relation of neuronal activity and Nurr1 expression in the mammalian forebrain.…”

Medicinal Chemistry and Chemical Biology of Nurr1 Modulators: An Emerging Strategy in Neurodegeneration

“…Nurr1 is mainly expressed in the central nervous system (CNS) . The highest expression levels are found in neurons of the parietal and temporal cortex, the claustrum/dorsal endopiriform cortex, and subiculum . Despite relatively low Nurr1 levels, a critical role of Nurr1 was shown in dopaminergic neurons of the substantia nigra pars compacta and area tegmentalis ventralis. − As a crucial regulator of dopaminergic neuron development and survival, Nurr1 is expressed from early prenatal development to adulthood. − In astrocytes, microglial cells, and other immune cells such as macrophages, Nurr1 is constitutively expressed or induced as an anti-inflammatory response. − It can also be induced in smooth muscle cells and endothelial cells and has anti-atherogenic effects together with Nur77 .…”

“…The highest expression levels are found in neurons of the parietal and temporal cortex, the claustrum/dorsal endopiriform cortex, and subiculum . Despite relatively low Nurr1 levels, a critical role of Nurr1 was shown in dopaminergic neurons of the substantia nigra pars compacta and area tegmentalis ventralis. − As a crucial regulator of dopaminergic neuron development and survival, Nurr1 is expressed from early prenatal development to adulthood. − In astrocytes, microglial cells, and other immune cells such as macrophages, Nurr1 is constitutively expressed or induced as an anti-inflammatory response. − It can also be induced in smooth muscle cells and endothelial cells and has anti-atherogenic effects together with Nur77 . In liver, Nurr1 is induced by cAMP and together with Nur77 and NOR-1 affects glucose utilization and cholesterol and lipid homeostasis. , Nurr1 is, therefore, thought to be involved in metabolic diseases, inflammatory arthritis, attention deficit hyperactivity disorder, and various types of cancer .…”

“…135 The highest expression levels are found in neurons of the parietal and temporal cortex, the claustrum/dorsal endopiriform cortex, and subiculum. 131 Despite relatively low Nurr1 levels, a critical role of Nurr1 was shown in dopaminergic neurons of the substantia nigra pars compacta and area tegmentalis ventralis. 131−134 As a crucial regulator of dopaminergic neuron development and survival, Nurr1 is expressed from early prenatal development to adulthood.…”

Developmental pathways linked to the vulnerability of adult midbrain dopaminergic neurons to neurodegeneration

“…NURR1, a TF belonging to the nuclear hormone receptors and member of the 4A subfamily lacking known ligands (thus “orphan”), has attracted considerable attention because of its involvement in the specification of the mDA neuron phenotype during development and its anti-inflammatory properties ( Decressac et al, 2013 ; Dong et al, 2016 ). NURR1 is widely expressed in the adult rodent brain, including the SNc and VTA ( Zetterström et al, 1996 ; Kummari et al, 2021 ). In the healthy human brain, NURR1 was detected in virtually all mDA neurons at young adult age, but NURR1 as well as TH expression declined significantly in these neurons during aging ( Chu et al, 2002 ).…”