The retina-specific basigin isoform does not induce IL-6 expression in mouse monocytes.

Purpose: Basigin gene products are positioned on adjacent cell types in the neural retina and are thought to compose a lactate metabolon important for photoreceptor cell function. The Ig0 domain of basigin isoform 1 (basigin-1) is highly conserved throughout evolution, which suggests a conserved function. It has been suggested that the Ig0 domain has proinflammatory properties, and it is hypothesized to interact with basigin isoform 2 (basigin-2) for cell adhesion and lactate metabolon formation. Therefore, the purpose of the present study was to determine whether the Ig0 domain of basigin-1 binds to basigin-2 and whether the region of the domain used for binding is also used to stimulate interleukin-6 (IL-6) expression. Methods: Binding was assessed using recombinant proteins corresponding to the Ig0 domain of basigin-1 and endogenously expressed basigin-2 from mouse neural retina and brain protein lysates. The proinflammatory properties of the Ig0 domain were analyzed with exposure of the recombinant proteins to the mouse monocyte RAW 264.7 cell line and subsequent measurement of the IL-6 concentration in the culture medium via enzyme-linked immunosorbent assay (ELISA). Results: The data indicate that the Ig0 domain interacts with basigin-2 through a region within the amino half of the domain and that the Ig0 domain does not stimulate the expression of IL-6 in mouse cells in vitro. Conclusions: The Ig0 domain of basigin-1 binds to basigin-2 in vitro. In addition, contrary to previous reports, there was no evidence that the Ig0 domain potentiates IL-6 expression in a mouse monocyte cell line in vitro. However, it is possible that the Ig0 domain stimulates the expression of proinflammatory cytokines other than IL-6, or that the potential involvement of the Ig0 domain of basigin-1 in the acute inflammatory response is dependent on species.

Intranasal Carnosine Mitigates α-Synuclein Pathology and Motor Dysfunction in the Thy1-aSyn Mouse Model of Parkinson's Disease.

Parkinson's disease (PD) is a debilitating neurodegenerative disorder. Early symptoms include motor dysfunction and impaired olfaction. Toxic aggregation of α-synuclein (aSyn) in the olfactory bulb (OB) and substantia nigra pars compacta (SNpc) is a hallmark of PD neuropathology. Intranasal (IN) carnosine (2 mg/d for 8 weeks) was previously demonstrated to improve motor behavior and mitochondrial function in Thy1-aSyn mice, a model of PD. The present studies evaluated the efficacy of IN carnosine at a higher dose in slowing progression of motor deficits and aSyn accumulation in Thy1-aSyn mice. After baseline neurobehavioral assessments, IN carnosine was administered (0.0, 2.0, or 4.0 mg/day) to wild-type and Thy1-aSyn mice for 8 weeks. Olfactory and motor behavioral measurements were repeated prior to end point tissue collection. Brain sections were immunostained for aSyn and tyrosine hydroxylase (TH). Immunopositive cells were counted using design-based stereology in the SNpc and OB mitral cell layer (MCL). Behavioral assessments revealed a dose-dependent improvement in motor function with increasing carnosine dose. Thy1-aSyn mice treated with 2.0 or 4.0 mg/d IN carnosine exhibited fewer aSyn-positive (aSyn(+)) cell bodies in the SNpc compared to vehicle-treated mice. Moreover, the number of aSyn(+) cell bodies in carnosine-treated Thy1-aSyn mice was reduced to vehicle-treated wild-type levels in the SNpc. Carnosine treatment did not affect the number of aSyn(+) cell bodies in the OB-MCL or the number of TH(+) cells in the SNpc. In summary, intranasal carnosine treatment decreased aSyn accumulation in the SNpc, which may underlie its mitigation of motor deficits in the Thy1-aSyn mice.