Brain polar phenol content, behavioural and neurochemical effects of Corinthian currant in a rotenone rat model of Parkinson's disease

OBJECTIVE

Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by the loss of nigral dopaminergic neurons, leading to reduced motor control. A contributing factor for the nigrostriatal degeneration is known to be oxidative stress, while antioxidant/anti-inflammatory properties of natural polyphenols have been suggested to show beneficial effects. The present study questioned the potential neuroprotective effects of supplementary diet with Corinthian currant, using a rat rotenone PD model.

METHODS

The alterations in motor activity, brain Corinthian currant polar phenols' accumulation, expression patterns of tyrosine hydroxylase (TH), dopamine transporter (DAT) and brain-derived neurotrophic factor (BDNF) in the nigrostriatal dopaminergic system were determined in rotenone-treated, currant-diet rats and matching controls.

RESULTS

Rotenone treatment resulted in motor deficits and TH expression decreases in the nigrostriatal pathway, exhibiting PD-like behavioural motor and neurochemical phenotypes. Interestingly, 38 days Corinthian currant consumption resulted in differential accumulation of polar phenols in mesencephalon and striatum and had a significant effect on attenuating motor deficits and dopaminergic cell loss in substantia nigra pars compacta. In addition, it induced up-regulation of BDNF expression in the nigrostriatal dopaminergic system.

DISCUSSION

Taken all together, evidence is provided for the potential neuroprotective influences of Corinthian currant consumption, involving the neurotrophic factor BDNF, in rescuing aspects of PD-like phenotype.

Oct-2 is required early in T cell-independent B cell activation for G1 progression and for proliferation

Oct-2, a POU homeodomain protein expressed primarily in B cells, is a powerful transcriptional activator that binds to DNA at sites appropriately placed for major effects on immunoglobulin gene expression. Our examination of B cell development and function in Oct-2 null mice did not support an essential role for Oct-2 early in B cell development. Rather, Oct-2 was required later, when B cells were induced to differentiate to antibody-secreting cells. We show here that Oct-2 is not required for normal immunoglobulin production by mature B lymphocytes. Instead, it is essential for a normal proliferative response to polyclonal mitogens. Responses to signals from activated T cells are unaffected. The requirement for Oct-2 maps to an early activation step in G1, during which B cells make the commitment to progress through the cell cycle and to divide.

A form of immunologic tolerance through impairment of germinal center development

Primary immunization with the T-cell-dependent antigen (4-hydroxy-3-nitrophenyl)acetyl (NP) coupled to human serum albumin results in the development of two pathways of B-cell development, the extrafollicular pathway and the germinal center pathway. Soluble, deaggregated NP-human serum albumin injected before immunization results in a marked diminution of clonable higher-affinity antibody-forming cell precursors--i.e., a form of immunologic tolerance within the secondary B-cell repertoire. We describe here the cellular changes in the spleen that underlie this tolerance. Using multiparameter flow cytometry, we show that tolerant mice develop far fewer NP-binding, peanut agglutinin-positive, or germinal center cells than the control immunized mice; 14 days after challenge control spleens have approximately 2 x 10(5) such cell per spleen, whereas the tolerant mice have approximately 1 x 10(4) cells. Furthermore, we demonstrate by immunohistology a reduction in the number of germinal centers containing lambda-bearing cells, characteristic of the response of C57BL/6 mice to NP. Taken together, these data suggest an impairment of germinal center development in the tolerant mice.

Oct-2, although not required for early B-cell development, is critical for later B-cell maturation and for postnatal survival

Oct-2, a POU homeo domain transcription factor, is believed to stimulate B-cell-restricted expression of immunoglobulin genes through binding sites in immunoglobulin gene promoters and enhancers. To determine whether Oct-2 is required for B-cell development or function, or has other developmental roles, the gene was disrupted by homologous recombination. Oct-2-l- mice develop normally but die within hours of birth for undetermined reasons. Mutants contain normal numbers of B-cell precursors but are somewhat deficient in IgM+ B cells. These B cells have a marked defect in their capacity to secrete immunoglobulin upon mitogenic stimulation in vitro. Thus, Oct-2 is not required for the generation of immunoglobulin-bearing B cells but is crucial for their maturation to immunoglobulin-secreting cells and for another undetermined organismal function.

Soluble antigen profoundly reduces memory B-cell numbers even when given after challenge immunization

The splenic B-cell repertoire of unimmunized C57BL/6 mice can be examined for anti-(4-hydroxy-3-nitrophenyl)acetyl (NP) B cells of relatively high affinity by using a dual strategy. First, limiting numbers of splenocytes are polyclonally activated by Escherichia coli lipopolysaccharide and a mixture of interleukins 2, 4, and 5 in the presence of 3T3 filler cells, thus ensuring that many B-cell clones switch to IgG1 antibody production. Second, an enzyme-linked immunosorbent assay is geared to register only higher-affinity antibody by (i) detecting only bivalent IgG1 antibody and ignoring IgM and (ii) using a lowly substituted NP-conjugated protein as the capture layer. Naive spleens contain very few higher-affinity anti-NP B cells thus defined, but thymus (T)-dependent immunization causes the appearance of approximately 10(5) per spleen within 2 weeks. The development of these clonable anti-NP antibody-forming cell precursors can be virtually eliminated by a single injection of 1 mg of soluble, freshly deaggregated NP2-human serum albumin (HSA). This toleragen works not only if injected prior to challenge immunization, but even if given up to 6 days later. Soluble HSA works partially but not nearly as well as NP2-HSA, suggesting the possibility that the toleragen must act on T and B cells. NP conjugated to irrelevant carriers achieved partial tolerance in only one of four experiments. The studies demonstrate the need for continuing T-cell help throughout the process of memory B-cell generation. They also show that those recently activated T cells involved in this process can be silenced in vivo by soluble toleragen.

Memory cell generation ablated by soluble protein antigen by means of effects on T- and B-lymphocyte compartments

Adult C57BL/6 mice were injected with 100 micrograms of soluble, freshly deaggregated human serum albumin (HSA) to produce partial immunologic tolerance. Uninjected normal control (N) mice contain only approximately 100 B cells in their spleens with the capacity to (i) be activated in vitro into clonal proliferation by Escherichia coli lipopolysaccharide plus interleukins 2, 4, and 5, (ii) form IgG1 as well as IgM antibody, and (iii) display specificity for HSA when only IgG1 is allowed to score in an enzyme-linked immunosorbent assay (ELISA). Such N mice generate approximately 50,000 clonable anti-HSA IgG1 antibody-forming cell precursors in their spleens after T-dependent immunization with HSA absorbed onto alum and given with Bordetella pertussis adjuvant. Mice preinjected with soluble HSA (TOL) generate far fewer anti-HSA IgG1 antibody-forming cell precursors, termed anti-HSA memory cells. Splenocytes were transferred from N or TOL mice into lethally irradiated syngeneic recipients together with syngeneic bone marrow. Whereas N splenocytes generated plentiful memory cells within 2 weeks in antigenically challenged recipients, TOL splenocytes did not. Work with Ly-5 congenic mice ruled out memory cell generation from either the host or the bone marrow inoculum within this limited time. N T cells plus TOL B cells showed consistently lowered memory cell generation. TOL T cells plus N B cells showed an even greater lowering of adoptive memory cell generation. Thus the lowered response capacity of TOL mice resided in the T- and B-cell compartments. Attempts to show a suppressor component within the T-cell population were inconclusive, but a profound defect in capacity to respond to HSA in vitro was exhibited by the CD4+ T cells of TOL mice. B lymphocytes were harvested from T-dependently immunized mice 5 days after challenge, incubated with soluble HSA for 18 hr, and then adoptively transferred together with N T cells. The recently activated B cells were not rendered tolerant by this manipulation. The results argue for a major T-cell component in the process whereby soluble protein antigens ablate affinity maturation and memory cell generation.

Soluble antigen abrogates the appearance of anti-protein IgG1-forming cell precursors during primary immunization

The anti-human serum albumin (HSA) B-cell repertoire of C57BL/6 mice was examined by culturing splenocytes at limiting dilution following polyclonal stimulation with Escherichia coli lipopolysaccharide and a lymphokine mixture. The frequency of anti-HSA precursors was determined before and after immunization with alum-precipitated HSA and 10(9) killed Bordetella pertussis organisms, by submitting clonal supernatants to an ELISA. Anti-HSA IgG1-forming precursors were rare in unimmunized spleens, representing approximately equal to 1 in 500,000 splenocytes or only approximately equal to 100 cells per spleen. Between day 5 and day 7 after immunization, this figure increased to approximately equal to 20,000 cells per spleen. Over the following 3 weeks, there was a progressive increase in the mean optical density generated in the clonal ELISA, presumably due to affinity maturation of the B-cell population. When freshly deaggregated HSA was injected before or even up to 4 days after challenge immunization, the appearance of anti-HSA IgG1-forming cell precursors was largely prevented. The effect was most marked with 5 mg or 1 mg of soluble HSA, but impressive partial effects could be seen with as little as 10 micrograms of HSA if administered before challenge immunization. Most of the few clones seen after the higher doses of the toleragen appeared to make antibody of low affinity. The capacity to influence the B-cell pool by soluble antigen administered just 1-2 days before the sudden appearance of IgG1 precursors argues against the totality of the effect being due to T-cell-mediated suppression and in favor of a direct effect on B cells.