ß-Adrenoceptor Blockade Moderates Neuroinflammation in Male and Female EAE Rats and Abrogates Sexual Dimorphisms in the Major Neuroinflammatory Pathways by Being More Efficient in Males.

Our previous studies showed more severe experimental autoimmune encephalomyelitis (EAE) in male compared with female adult rats, and moderating effect of propranolol-induced ß-adrenoceptor blockade on EAE in females, the effect associated with transcriptional stimulation of Nrf2/HO-1 axis in spinal cord microglia. This study examined putative sexual dimorphism in propranolol action on EAE severity. Propranolol treatment beginning from the onset of clinical EAE mitigated EAE severity in rats of both sexes, but to a greater extent in males exhibiting higher noradrenaline levels and myeloid cell ß2-adrenoceptor expression in spinal cord. This correlated with more prominent stimulatory effects of propranolol not only on CX3CL1/CX3CR1/Nrf2/HO-1 cascade, but also on Stat3/Socs3 signaling axis in spinal cord microglia/myeloid cells (mirrored in the decreased Stat3 and the increased Socs3 expression) from male rats compared with their female counterparts. Propranolol diminished the frequency of activated cells among microglia, increased their phagocyting/endocyting capacity, and shifted cytokine secretory profile of microglia/blood-borne myeloid cells towards an anti-inflammatory/neuroprotective phenotype. Additionally, it downregulated the expression of chemokines (CCL2, CCL19/21) driving T-cell/monocyte trafficking into spinal cord. Consequently, in propranolol-treated rats fewer activated CD4+ T cells and IL-17+ T cells, including CD4+IL17+ cells coexpressing IFN-γ/GM-CSF, were recovered from spinal cord of propranolol-treated rats compared with sex-matched saline-injected controls. All the effects of propranolol were more prominent in males. The study as a whole disclosed that sexual dimorphism in multiple molecular mechanisms implicated in EAE development may be responsible for greater severity of EAE in male rats and sexually dimorphic action of substances affecting them. Propranolol moderated EAE severity more effectively in male rats, exhibiting greater spinal cord noradrenaline (NA) levels and myeloid cell ß2-adrenoceptor (ß2-AR) expression than females. Propranolol affected CX3CR1/Nrf2/HO-1 and Stat3/Socs3 signaling axes in myeloid cells, favored their anti-inflammatory/neuroprotective phenotype and, consequently, reduced Th cell reactivation and differentiation into highly pathogenic IL-17/IFN-γ/GM-CSF-producing cells.

Ageing Affects Thymopoiesis and Experimental Autoimmune Encephalomyelitis Development in a Strain-Dependent Manner.

INTRODUCTION: Considering significance of mechanisms of central tolerance for development of autoimmune diseases, including experimental autoimmune encephalomyelitis (EAE), and suppressive influence of circulating proinflammatory cytokines and alterations in brain-thymus communication, characteristic for the central nervous system (CNS) autoimmune diseases, on thymopoiesis, the study interogated putative strain-based thymus-related specificities relevant for the opposite effects of ageing on susceptibility of Dark Agouti (DA) and Albino Oxford (AO) rats to EAE. METHODS: Quantitative and qualitative changes in thymopoiesis including underlying mechanisms were examined using flow cytometry and RT-qPCR quantification of mRNAs for molecules relevant for integrity of stroma and T-cell development, respectively. RESULTS: With ageing, differently from DA rats, in AO rats the surface density of CD90, a negative regulator of selection threshold, on thymocytes undergoing lineage commitment was upregulated (consistent with TGF-ß expression downregulation), whereas the generation of natural CD4+CD25+Foxp3+ regulatory T cells (nTregs) was impaired reflecting differences in thymic expression of cytokines supporting their development. Additionally, specifically in old AO rats, in whom EAE development depends on IL-17-producing CD8+ T cells, their thymic differentiation was augmented, reflecting augmented thymic IL-4 expression. In turn, differently from old DA rats developing self-limiting EAE, in age-matched AO rats developing EAE of prolonged duration, EAE development led to impaired generation of nTregs and accumulation of proinflammatory, cytotoxic CD28-CD4+ T cells in the periphery. DISCUSSION: The study indicates that strain differences in age-related changes in the efficacy of central tolerance, in addition to enhanced thymic generation of CD8+ T cells prone to differentiate into IL-17-producing cells, could partly explain the opposite effect of ageing on DA and AO rat susceptibility to EAE induction. Additionally, it suggested that EAE development leading to a less efficient thymic output of CD4+ cells and nTregs in old AO rats than their DA counterparts could contribute to prolonged EAE duration in AO compared with DA rats. CONCLUSION: The study warns to caution when designing therapeutic interventions to enhance thymic activity in genetically diverse populations, e.g., humans, and interpreting their outcomes. Furthermore, it indicates that CNS autoimmune pathology may additionally worsen thymic involution and age-related immune changes.

Propranolol diminished severity of rat EAE by enhancing immunoregulatory/protective properties of spinal cord microglia.

Sympathetic dysfunction is suggested to contribute to development of multiple sclerosis and experimental autoimmune encephalomyelitis (EAE) alike. Considering important role of microglia in development/resolution of neuroinflammation, contribution of noradrenaline, the key sympathetic end-point mediator, in modulation of microglial phenotypic and functional properties in rat EAE model was examined. The study showed that noradrenaline acting in neurocrine and autocrine/paracrine way might influence microglia during EAE. Propranolol treatment over the effector phase moderated EAE course. This was associated with the increased proportion of microglia expressing CX3CR1, the key molecule in their immunomodulatory/neuroprotective action, and upregulation of CX3CR1 downstream Nrf2 gene. This correlated with the increased heme oxygenase-1 (HO-1) expression and phagocytic capacity of microglia, and their phenotypic changes mirrored in increased proportion of CD163- and CD83-expressing cells. The enhanced HO-1 expression was linked with the decreased proportion of microglial cells expressing IL-1ß and IL-23, and possibly IL-6, followed by increased proportion of IL-10-expressing microglia, and downregulated MCP-1/CCL2 expression. Consistently, spinal cord infiltration with blood-borne myeloid and CD4+ T cells, as well as CD4+ T-cell reactivation/proliferation and differentiation into highly pathogenic IL-17+ cells co-producing IFN-γ and GM-CSF were decreased in propranolol-treated rats compared with saline-injected controls. The in vitro investigations of the effects of noradrenaline on microglia showed that noradrenaline through ß-adrenoceptor may influence Nrf2 expression also via CX3CR1-independent route. The study suggests ß-adrenoceptor-mediated neuroinflammation-promoting role of noradrenaline in EAE via modulation of microglial Nrf2 expression, and thereby forms the basis for further translational pharmacological research to improve multiple sclerosis therapy.

Age and sex determine CD4+ T cell stimulatory and polarizing capacity of rat splenic dendritic cells.

The study investigated influence of sex and age on splenic myeloid dendritic cells (DCs) from Dark Agouti rats. Freshly isolated DCs from young males exhibited less mature phenotype and greater endocytic capacity compared with those from age-matched females. Upon LPS stimulation in vitro they were less potent in stimulating allogeneic CD4+ cells in mixed leukocyte reaction (MLR), due to lower expression of MHC II, and greater NO and IL-10 production. In accordance with higher TGF-ß production, young male rat DCs were less potent in stimulating IL-17 production in MLR than those from young females. Irrespective of sex, endocytic capacity and responsiveness of DCs to LPS stimulation in culture, judging by their allostimulatory capacity in MLR decreased with age, reflecting decline in MHC II surface density followed by their greater NO production; the effects more prominent in females. Additionally, compared with LPS-stimulated DCs from young rats, those from sex-matched aged rats were more potent in stimulating IL-10 production in MLR, whereas capacity of DCs from aged female and male rats to stimulate IL-17 production remained unaltered and decreased, respectively. This reflected age-related shift in IL-6/TGF-ß production level ratio in LPS-stimulated DC cultures towards TGF-ß, and sex-specific age-related remodeling CD4+ cell cytokine pathways. Additionally, compared with LPS-stimulated DCs from young rats, those cells from sex-matched aged rats were less potent in stimulating IFN-γ production in MLR, the effect particularly prominent in MLRs encompassing male rat DCs. The study showed that stimulatory and polarizing capacity of DCs depends on rat sex and age.

Noradrenaline through ß-adrenoceptor contributes to sexual dimorphism in primary CD4+ T-cell response in DA rat EAE model?

Males exhibit stronger sympathetic nervous system (SNS) activity, but weaker primary CD4+ T-cell (auto)immune responses. To test the role of catecholamines, major end-point SNS mediators, in this dimorphism, influence of propranolol (ß-adrenoceptor blocker) on mitogen/neuroantigen-stimulated CD4+ T cells from female and male EAE rat draining lymph node (dLN) cell cultures was examined. Male rat dLNs exhibited higher noradrenaline concentration and frequency of ß2-adrenoceptor-expressing CD4+ T lymphocytes and antigen presenting cells. Propranolol, irrespective of exogenous noradrenaline presence, more prominently augmented IL-2 production and proliferation of CD4+ lymphocytes in male than female rat dLN cell cultures. In neuroantigen-stimulated dLN cells of both sexes propranolol increased IL-1ß and IL-23/p19 expression and IL-17+ CD4+ cell frequency, but enhanced IL-17 production only in male rat CD4+ lymphocytes, thereby abrogating sexual dimorphism in IL-17 concentration observed in propranolol-free cultures. Thus, ß-adrenoceptor-mediated signalling may contribute to sex bias in rat IL-17-producing cell secretory capacity.

Sexual dimorphism in Th17/Treg axis in lymph nodes draining inflamed joints in rats with collagen-induced arthritis.

Collagen type II-induced arthritis (CIA) in Dark Agouti rats, a model of rheumatoid arthritis (RA), reproduces sexual dimorphism in the incidence and severity of the human disease. Th17 cells are central in the induction/propagation of autoimmune inflammation in CIA and RA. To assess mechanisms underlying this dimorphism in CIA rats, in lymph nodes draining inflamed joints and adjacent tissues (dLNs) from CIA rats of both sexes Th17/CD25+Foxp3+CD4+ T-regulatory cell (Treg) ratio, Th17 cell redifferentiation in functionally distinct subsets and Treg transdifferentiation into IL-17-producing cells (exTregs) were examined. In female rats (developing more severe CIA than their male counterparts) the higher frequency of all Th17 cells (reflecting partly their greater proliferation), followed by the higher frequency of highly pathogenic IFN-γ/GM-CSF-co-producing cells, but lower frequency of less pathogenic/immunoregulatory IL-10-producing cells among them was found. Additionally, compared with male rats, in female rats the lower frequency of Tregs was observed. Moreover, Tregs from female rats exhibited diminished proliferative and suppressive capacity (judging by PD-1 expression) and enhanced conversion into IL-17-producing cells. Given that TGF-ß concentration was comparable in collagen-type II-stimulated dLN cell cultures from female and male rats, the shift in Th17/Treg ratio followed by augmented Th17 cell redifferentiation into IFN-γ/GM-CSF-co-producing cells and Treg transdifferentiation into IL-17-producing cells in female rats was associated with increased concentration of IL-6 in female rat dLN cell cultures, and the higher frequency of IL-1ß- and IL-23-producing cells among their dLN cells. The lower frequency of IL-10-producing B cells, presumably B regulatory cells (Bregs) could also contribute to the shift in Th17/Treg ratio in female rat compared with male rat dLNs. Consistently, the lower expression of IL-35 (the cytokine promoting Treg expansion directly and indirectly, by favoring Breg expansion and conversion into IL-10/IL-35-producing cells) in female rat dLN cells was detected. Thus, the study identified putative cellular and molecular substrates of the sexual dimorphism in the immunopathogenesis and clinical outcome of CIA and suggested mechanisms to be targeted in females to improve control of Th17 response, and consequently clinical outcome of CIA, and possibly RA.

Influence of aging on germinal centre reaction and antibody response to inactivated influenza virus antigens in mice: sex-based differences.

The study examined sex-specificities in age-related changes in BALB/c mice IgG antibody responses to immunisation with trivalent inactivated split-virus influenza bulk. Aging diminished the total serum IgG antibody responses to H1N1 and H3N2 and B influenza virus antigens in mice of both sexes, but they remained greater in aged females. This sex difference in aged mice correlated with the greater post-immunisation increase in the frequency of spleen germinal centre (GC) B cells and more favourable T follicular regulatory (Tfr)/GC B cell ratio, as Tfr cells are suggested to control antibody production through suppression of glycolysis. The greater post-immunisation GC B cell response in aged females compared with males correlated with the greater proliferation of B cells and CD4+ cells in splenocyte cultures from aged females restimulated with inactivated split-virus influenza from the bulk. To support the greater post-immunisation increase in the frequency GC B cell in aged females was more favourable Tfr/T follicular helper (Tfh) cell ratio. Additionally, compared with aged males, in age-matched females the greater avidity of serum IgG antibodies was found. However, in aged females IgG2a/IgG1 antibody ratio, reflecting spleen Th1/Th2 cytokine balance, was shifted towards IgG1 when compared with age-matched male mice. This shift was ascribed to a more prominent decline in the titres of functionally important IgG2a antibodies in females with aging. The study suggest that biological sex should be considered as a variable in designing strategies to manipulate with immune outcome of immunisation in aged animals, and possibly, at very long distance, humans.

Sexual dimorphism in rat thymic involution: a correlation with thymic oxidative status and inflammation.

The study investigated mechanisms underlying sex differences in thymic involution in Dark Agouti rats. Adverse effects of aging on thymus were more pronounced in males than in females. Thymi from old males exhibited more prominent: (i) fibro-adipose degeneration which correlated with greater intensity of thymic oxidative stress and enhanced thymic TGF-ß and IL-6 expression and (ii) decline in thymopoiesis, as suggested by the number of the most mature CD4+CD8-/CD4-CD8+ single positive (SP) TCRαßhigh thymocytes. The greater accumulation of adipose tissue in old male thymus was linked with greater age-related increase in thymic expression of PPARγ and STAT3, a transcription factor regulating the expression of PPARγ downstream genes, in male than in female rats. In aged thymi of both sexes the early CD4-CD8- double negative (DN) stage of thymocyte development was affected, so relative accumulation of the least mature CD45RC+CD2- cells followed by decreased frequency of their DN and CD4+CD8+ double positive (DP) TCRαß- descendants was observed. Additionally, in old males, because of the increased thymic expression of Nur77, a nuclear receptor involved in negative selection, and decreased CD90 (a negative regulator of thymocyte selection threshold) MFI on DP TCRαßint thymocytes, less efficient positive/more efficient negative selection was found. Moreover, in male rats, thymocyte post-selection differentiation/maturation was skewed towards CD4-CD8+ SP TCRαßhigh cells compared with age-matched females, reflecting, at least partly, greater IL-15 expression in their thymi. The study indicated mechanisms underlying sex-based differences in age-related thymic changes and consequently necessity of sex-specific approaches in designing strategies to rejuvenate thymus.

Propranolol Impairs Primary Immune Responses in Rat Experimental Autoimmune Encephalomyelitis.

OBJECTIVE: We examined the effect of ß-adrenoceptor (AR) blockade in the preclinical phase of experimental autoimmune encephalomyelitis (EAE), the most commonly used model of multiple sclerosis, on the development of primary CD4+ T-cell responses in draining lymph nodes (dLNs). METHODS: CD11b+ cell migration to dLNs, CD4+ T-cell activation/proliferation, and IL-17+ CD4+ (Th17) cell numbers in dLN and spinal cord (SC) were examined in male and female Dark Agouti rats using flow cytometry analysis. RESULTS: Irrespective of sex, in propranolol-treated (PT) rats, migration of CD11b+ antigen-presenting cells from the site of immunization to dLNs was impaired compared with saline-treated controls and consequently the frequency of all CD11b+ cells in dLNs and activated cells among them, too. This correlated with decreased expression of CCL19/21 transcripts in dLNs. Consistently, the frequency of activated/proliferating cells among dLN CD4+ T cells was reduced in PT rats. Additionally, propranolol reduced the number of Th17 cells in dLNs and SC. Consistently, male and female PT rats exhibited a decreased incidence of EAE and prolonged duration of the asymptomatic disease phase. CONCLUSION: This study suggests that sympathetic dysregulation is involved in the outbreak of clinical EAE.

Natural killer cells as participants in pathogenesis of rat experimental autoimmune encephalomyelitis (EAE): lessons from research on rats with distinct age and strain.

Natural killer (NK) cells, influencing dendritic cell (DC)-mediated CD4+ lymphocyte priming in draining lymph nodes (dLNs) and controlling spinal cord (SC) infiltration with encephalitogenic CD4+T lymphocytes, modulate EAE (multiple sclerosis model). This study examined their putative contribution to age-related differences in EAE development in Dark Agouti (DA) (exhibiting age-related decrease in EAE susceptibility) and Albino Oxford (AO) (becoming susceptible to EAE with aging) rats. Aging increased NK cell number in dLNs from rats of both strains. In AO rats, but not in DA ones, it also increased the numbers of IFN-γ-producing NK cells (important for DC activation) and activated/matured DCs, thereby increasing activated/matured DC/conventional Foxp3-CD4+ cell ratio and activated CD25+Foxp3-CD4+ cell number. Aging in DA rats diminished activated/matured DC/conventional Foxp3-CD4+ cell ratio and activated Foxp3-CD4+ cell number. However, MBP-stimulated CD4+ cell proliferation did not differ in dLN cell cultures from young and aged AO rats (as more favorable activated/matured DC/Foxp3-CD4+ cell ratio was abrogated by lower intrinsic CD4+ cell proliferative capacity and a greater regulatory CD25+Foxp3+CD4+ lymphocyte frequency), but was lower in those from aged compared with young DA rats. At SC level, aging shifted Foxp3-CD4+/cytotoxic CX3CR1+ NK cell ratio towards the former in AO rats, so it was less favorable in aged AO rats exhibiting prolonged neurological deficit compared with their DA counterparts. The study showed strain and age differences in number of IFN-γ-producing NK cells in EAE rat dLNs, and suggested that their pathogenetic relevance depends on frequency and/or activity of other cells involved in CD4+ T cell (auto)immune response.

Collagen-induced arthritis in Dark Agouti rats as a model for study of immunological sexual dimorphisms in the human disease.

Collagen-induced arthritis (CIA) is a frequently used animal model of rheumatoid arthritis, human autoimmune disease that exhibits clear sex bias in incidence and clinical course. Female Dark Agouti rats immunized for CIA showed also greater incidence and higher arthritic score than their male counterparts. The study investigated sex differences in mechanisms controlling the primary immune responses in draining lymph nodes (dLNs), as a factor contributing to this dimorphism. The higher frequencies of CD4 + CD25 + Foxp3- cells, presumably activated effector T (Teff) cells, and IL-17+, IFN-γ + and IL-17 + IFN-γ + T cells were found in female compared with male rat dLNs. However, the frequency of CD4 + CD25 + Foxp3+ T regulatory cells (Treg) did not differ between sexes. Thus, CD4+ Teff cells/Treg ratio, and IL-17+ T cells/Treg and IFN-γ + T cells/Treg ratios were higher in female than in male rats, and among them was found lower frequency of PD-1+ cells. This suggested less efficient control of (auto)immune Th1/Th17 cell responses in female rat dLNs. On the contrary, the frequency of IL-4+ T cells was lower in female than in male rat dLNs. Consistently, the ratio of serum levels of collagen-specific IgG2a (IFN-γ-dependent, with an important pathogenic role in CIA) and IgG1 (IL-4-dependent) was shifted towards IgG2a in female compared with male rats. As a whole, the study suggests that sexual dimorphism in the control of T cell activation/polarization could contribute to sex bias in the susceptibility to CIA. Moreover, the study advises the use of animals of both sexes in the preclinical testing of new drugs for rheumatoid arthritis.

Sex bias in mouse humoral immune response to influenza vaccine depends on the vaccine type.

The study explored influence of biological sex on development of humoral immune response to seasonal trivalent whole inactivated virus (WIV) and split virus (SV) influenza vaccines in outbred Swiss mouse model. To this end, mice of both sexes were immunized with WIV (WIV mice) and SV vaccines (SV mice) and examined for specific antibody response. Irrespective of sex, total IgG and neutralizing antibody responses to distinct virus strains were weaker in SV than in WIV mice. In WIV mice of both sexes, irrespective of strain specificity, IgG isotype response was dominated by IgG2a antibodies, while in SV mice nearly equal representation of IgG2a and IgG1 antibodies was found. The analyses of sex differences showed higher titers of H1N1-specific and both H1N1- and H3N2-specific total IgG and neutralizing antibodies in female WIV and SV mice, respectively. Additionally, sexual dimorphism in IgG subclass profile depended on vaccine type. Specifically, compared with males, in females WIV shifted IgG2a/IgG1 antibody ratio towards IgG2a isotype on the account of weaker IgG1 response, whereas in SV mice, irrespective of virus strain, IgG2a and IgG1 isotypes were equally represented in both sexes. These findings indicate the vaccine type-dependent sex bias in antibody response to inactivated influenza vaccines.

Sex Difference in Oxidative Stress Parameters in Spinal Cord of Rats with Experimental Autoimmune Encephalomyelitis: Relation to Neurological Deficit.

The study examined (a) whether there is sex difference in spinal cord and plasma oxidative stress profiles in Dark Agouti rats immunised for experimental autoimmune encephalomyelitis (EAE), the principal experimental model of multiple sclerosis, and (b) whether there is correlation between the oxidative stress in spinal cord and neurological deficit. Regardless of rat sex, with the disease development xanthine oxidase (XO) activity and inducible nitric oxide synthase (iNOS) mRNA expression increased in spinal cord, whereas glutathione levels decreased. This was accompanied by the rise in spinal cord malondialdehyde level. On the other hand, with EAE development superoxide dismutase (SOD) activity decreased, while O2- concentration increased only in spinal cord of male rats. Consequently, SOD activity was lower, whereas O2- concentration was higher in spinal cord of male rats with clinically manifested EAE. XO activity and iNOS mRNA expression were also elevated in their spinal cord. Consistently, in the effector phase of EAE the concentration of advanced oxidation protein product (AOPP) was higher in spinal cord of male rats, which exhibit more severe neurological deficit than their female counterparts. In as much as data obtained in the experimental models could be translated to humans, the findings may be relevant for designing sex-specific antioxidant therapeutic strategies. Furthermore, the study indicated that the increased pro-oxidant-antioxidant balance in plasma may be an early indicator of EAE development. Moreover, it showed that plasma AOPP level may indicate not only actual activity of the disease, but also serve to predict severity of its course.

Sex and age as determinants of rat T-cell phenotypic characteristics: influence of peripubertal gonadectomy.

The study examined the influence of age, sex and peripubertal gonadectomy on a set of T-cell phenotypic parameters. Rats of both sexes were gonadectomised at the age of 1 month and peripheral blood and spleen T lymphocytes from non-gonadectomised and gonadectomised 3- and 11-month-old rats were examined for the expression of differentiation/activation (CD90/CD45RC) and immunoregulatory markers. Peripheral blood T lymphocytes from non-gonadectomised rats showed age-dependent sexual dimorphisms in (1) total count (lower in female than male 11-month-old rats); (2) CD4+:CD8 + cell ratio (higher in female than male rats of both ages); (3) the proportion of recent thymic emigrants in CD8 + T cells (lower in female than male 3-month-old rats) and (4) the proportions of mature naïve and memory/activated cells (irrespective of age, the proportion of naïve cells was higher, whereas that of memory/activated cells was lower in females). Gonadectomy influenced magnitudes or direction of these sex differences. Additionally, sex differences in peripheral blood T-lymphocyte parameters did not fully correspond to those observed in T-splenocyte parameters, suggesting the compartment-specific regulation of the major T-cell subpopulations' and their subsets' composition. Furthermore, there was no sexual dimorphism in the proportion of either CD25 + Foxp3 + cells among CD4 + or CD161+ (NKT) cells within CD8 + T lymphocytes. However, there was gonadal hormone-independent age-associated sexual dimorphism in the proportion of CD161 + cells (NKT cells) in CD8 + T splenocytes. Overall, the study revealed age-dependent variations in sexual dimorphisms in T-cell parameters relevant for immune response efficacy and showed that they are T-cell compartment-specific and partly gonadal hormone-related.

Sex as a determinant of age-related changes in rat spinal cord inflammation-oxidation state.

To close the gap in our knowledge of sex influence on age-related changes in inflammation-oxidation state in spinal cord (SC) relevant to inflammation/oxidative-stress associated neuropathologies, 2-3 month-old (young) and 18-20 month-old (old) rats, exhibiting increased level of IL-6, a commonly used marker of inflamm-aging, were examined for inflammatory/redox status, and the underlying regulatory networks' molecules expression. With age, rat SC microglia became sensitized ("primed"), while SC tissue shifted towards mild inflammatory state, with increased levels of proinflammatory IL-1ß (key marker of microglial systemic inflammation-induced neurotoxicity), which was more prominent in males. This, most likely, reflected age- and sex-related impairment in the expression of CX3CR1, the receptor for fractalkine (CX3CL1), the soluble factor which regulates microglial activation and diminishes production of IL-1ß (central for fractalkine neuroprotection). Considering that (i) age-related changes in SC IL-1ß expression were not followed by complementary changes in SC IL-6 expression, and (ii) the reversal in the direction of the sex bias in circulating IL-6 level and SC IL-1ß expression, it seems obvious that there are tissue-specific differences in the proinflammatory cytokine profile. Additionally, old male rat SC exhibited greater oxidative damage than female, reflecting, most likely, their lower capacity to maintain the pro-oxidant-antioxidant balance. In conclusion, these findings, apart from highlighting the significance of sex for age-associated changes in SC inflammation-oxidation, may be relevant for understating sex differences in human inflammation/oxidative-stress related SC diseases, and consequently, for optimizing their prevention/therapy.

Aging affects the responsiveness of rat peritoneal macrophages to GM-CSF and IL-4.

Macrophages undergo significant functional alterations during aging. The aim of the present study was to investigate changes of rat macrophage functions and response to M1/M2 polarization signals with age. Therefore, resident and thioglycollate-elicited peritoneal macrophages from young (3-month-old) and aged (18-19-month-old) rats were tested for phagocytic capacity and ability to secrete inflammatory mediators following in vitro stimulation with LPS and GM-CSF, and IL-4, prototypic stimulators for classically (M1) and alternatively activated (M2) macrophages, respectively. Aging increased the frequency of monocyte-derived (CCR7+ CD68+) and the most mature (CD163+ CD68+) macrophages within resident and thioglycollate-elicited peritoneal macrophages, respectively. The ability to phagocyte zymosan of none of these two cell subsets was affected by either LPS and GM-CSF or IL-4. The upregulated production of IL-1ß, IL-6 and IL-10 and downregulated that of TGF-ß was observed in response to LPS in resident and thioglycollate-elicited macrophages from rats of both ages. GM-CSF elevated production of IL-1ß and IL-6 in resident macrophages from aged rats and in thioglycollate-elicited macrophages from young rats. Unexpectedly, IL-4 augmented production of proinflammatory mediators, IL-1ß and IL-6, in resident macrophages from aged rats. In both resident and thioglycollate-elicited macrophages aging decreased NO/urea ratio, whereas LPS but not GM-SCF, shifted this ratio toward NO in the macrophages from animals of both ages. Conversely, IL-4 reduced NO/urea ratio in resident and thioglycollate-elicited macrophages from young rats only. In conclusion, our study showed that aging diminished GM-CSF-triggered polarization of elicited macrophages and caused paradoxical IL-4-driven polarization of resident macrophages toward proinflammatory M1 phenotype. This age-related deregulation of macrophage inflammatory mediator secretion and phagocytosis in response to M1/M2 activators may lead to the deficient control of infectious and/or inflammatory diseases in advanced age.

Male rats develop more severe experimental autoimmune encephalomyelitis than female rats: sexual dimorphism and diergism at the spinal cord level.

Compared with females, male Dark Agouti (DA) rats immunized for experimental autoimmune encephalomyelitis (EAE) with rat spinal cord homogenate in complete Freund's adjuvant (CFA) exhibited lower incidence of the disease, but the maximal neurological deficit was greater in the animals that developed the disease. Consistently, at the peak of the disease greater number of reactivated CD4+CD134+CD45RC- T lymphocytes was retrieved from male rat spinal cord. Their microglia/macrophages were more activated and produced greater amount of prototypic proinflammatory cytokines in vitro. Additionally, oppositely to the expression of mRNAs for IL-12/p35, IL-10 and IL-27/p28, the expression of mRNA for IL-23/p19 was upregulated in male rat spinal cord mononuclear cells. Consequently, the IL-17+:IFN-γ+ cell ratio within T lymphocytes from their spinal cord was skewed towards IL-17+ cells. Within this subpopulation, the IL-17+IFN-γ+:IL-17+IL-10+ cell ratio was shifted towards IL-17+IFN-γ+ cells, which have prominent tissue damaging capacity. This was associated with an upregulated expression of mRNAs for IL-1ß and IL-6, but downregulated TGF-ß mRNA expression in male rat spinal cord mononuclear cells. The enhanced GM-CSF mRNA expression in these cells supported the greater pathogenicity of IL-17+ T lymphocytes infiltrating male spinal cord. In the inductive phase of the disease, contrary to the draining lymph node, in the spinal cord the frequency of CD134+ cells among CD4+ T lymphocytes and the frequency of IL-17+ cells among T lymphocytes were greater in male than in female rats. This most likely reflected an enhanced transmigration of mononuclear cells into the spinal cord (judging by the lesser spinal cord CXCL12 mRNA expression), the greater frequency of activated microglia/macrophages and the increased expression of mRNAs for Th17 polarizing cytokines in male rat spinal cord mononuclear cells. Collectively, the results showed cellular and molecular mechanisms underlying the target organ specific sexual dimorphism in the T lymphocyte-dependent immune/inflammatory response, and suggested a substantial role for the target organ in shaping the sexually dimorphic clinical outcome of EAE.

Aging diminishes the resistance of AO rats to EAE: putative role of enhanced generation of GM-CSF Expressing CD4+ T cells in aged rats.

BACKGROUND: Aging influences immune response and susceptibility to EAE in a strain specific manner. The study was designed to examine influence of aging on EAE induction in Albino Oxford (AO) rats. RESULTS: Differently from 3-month-old (young) rats, which were resistant to EAE induction, the majority of aged (24-26-month-old) rats developed mild chronic form of EAE. On 16(th) day post-immunization, when in aged rats the neurological deficit reached plateau, more mononuclear cells, including CD4+ T lymphocytes was retrieved from spinal cord of aged than young rats. The frequencies of IL-17+ and GM-CSF+ cells within spinal cord infiltrating CD4+ lymphocytes were greater in aged rats. To their increased frequency contributed the expansion of GM-CSF + IL-17 + IFN-γ+ cells, which are highly pathogenic in mice. The expression of the cytokines (IL-1ß and IL-23/p19) driving GM-CSF + IL-17 + IFN-γ + cell differentiation in mice was also augmented in aged rat spinal cord mononuclear cells. Additionally, in aged rat spinal cord the expansion of GM-CSF + IL-17-IFN-γ- CD4+ T lymphocytes was found. Consistently, the expression of mRNAs for IL-3, the cytokine exhibiting the same expression pattern as GM-CSF, and IL-7, the cytokine driving differentiation of GM-CSF + IL-17-IFN-γ- CD4 + lymphocytes in mice, was upregulated in aged rat spinal cord mononuclear cells, and the tissue, respectively. This was in accordance with the enhanced generation of the brain antigen-specific GM-CSF+ CD4+ lymphocytes in aged rat draining lymph nodes, as suggested by (i) the higher frequency of GM-CSF+ cells (reflecting the expansion of IL-17-IFN-γ- cells) within their CD4+ lymphocytes and (ii) the upregulated GM-CSF and IL-3 mRNA expression in fresh CD4+ lymphocytes and MBP-stimulated draining lymph node cells and IL-7 mRNA in lymph node tissue from aged rats. In agreement with the upregulated GM-CSF expression in aged rats, strikingly more CD11b + CD45(int) (activated microglia) and CD45(hi) (mainly proinflammatory dendritic cells and macrophages) cells was retrieved from aged than young rat spinal cord. Besides, expression of mRNA for SOCS1, a negative regulator of proinflammatory cytokine expression in innate immunity cells, was downregulated in aged rat spinal cord mononuclear cells. CONCLUSIONS: The study revealed that aging may overcome genetic resistance to EAE, and indicated the cellular and molecular mechanisms contributing to this phenomenon in AO rats.

Aging oppositely affects TNF-α and IL-10 production by macrophages from different rat strains.

Altered functions of macrophages with aging contribute to impairment of both innate and adaptive immunity in the elderly. The present study aimed to examine strain specificity of age-related changes in the phenotypic and functional characteristics of macrophages from DA and AO rats, which differ in average life span. Resident peritoneal macrophages from young (10-12 weeks old) and aged (98-104 weeks old) rats were tested for: (a) the surface expression of TLR4 and CD14; (b) the basal and LPS-induced production of TNF-α and IL-10; and (c) the basal and LPS-induced activity of iNOS and arginase, by measuring the levels of NO and urea, respectively, in the culture supernatants. Aging elevated TLR4 macrophage surface density in rats of both strains. Conversely, the age-related decrease in the surface density of CD14 co-receptor was detected only on macrophages from aged DA rats. Accordingly, with aging in DA rats, contrary to AO rats, upon LPS-stimulation both TNF-α and IL-10 levels decreased in culture supernatants. However, in rats of both strains TNF-α stimulation index (LPS-induced over basal production) remained stable with aging, but it was significantly greater in AO rats. Furthermore, with aging, IL-10 stimulation index decreased and increased in DA and AO rats, respectively. Age-related shift in urea stimulation index complied with the changes of IL-10 stimulation index during aging. In conclusion, the study suggests that the preserved ability of macrophages from aged AO rats to synthesize not only proinflammatory TNF-α, but also immunoregulatory IL-10 cytokine most likely contributes to their longer average life compared with DA rats.

Androgens contribute to age-associated changes in peripheral T-cell homeostasis acting in a thymus-independent way.

OBJECTIVE: Considering a causal role of androgens in thymic involution, age-related remodeling of peripheral T-cell compartments in the absence of testicular hormones was evaluated. METHODS: Rats were orchidectomized (ORX) at the age of 1 month, and T-peripheral blood lymphocytes (PBLs) and splenocytes from young (75-day-old) and aged (24-month-old) rats were examined for differentiation/activation and immunoregulatory marker expression. RESULTS: In ORX rats, following the initial rise, the counts of CD4+ and CD8+ PBLs diminished with aging. This reflected the decline in thymic export as shown by recent thymic emigrant (RTE) enumeration. Orchidectomy increased the count of both of the major T-splenocyte subsets in young rats, and they (differently from controls) remained stable with aging. The CD4+:CD8+ T-splenocyte ratio in ORX rats shifted towards CD4+ cells compared to age-matched controls. Although in the major T-cell subsets in the blood and spleen from aged ORX rats the numbers of RTEs were comparable to the corresponding values in age-matched controls, the numbers of mature naïve and memory/activated cells substantially differed. Compared with age-matched controls, in aged ORX rats the numbers of CD4+ mature naïve PBLs and splenocytes were reduced, whereas those of CD4+ memory/activated cells (predictive of early mortality) were increased. Additionally, in spleens from aged ORX rats, despite unaltered thymic export, CD4+CD25+FoxP3+ and natural killer T cell counts were greater than in age-matched controls. CONCLUSION: (i) Age-related decline in thymopoietic efficacy is not dependent on androgen presence, and (ii) androgens are involved in the maintenance of peripheral T-cell (particularly CD4+ cell) homeostasis during aging.