Adalimumab regulates intracellular TNFα production in patients with rheumatoid arthritis

Introduction

Adalimumab is a fully human anti–tumor necrosis factor α (anti-TNFα) monoclonal antibody that specifically blocks the interaction of TNFα with its receptors. It binds both soluble and transmembrane TNFα. We hypothesized that blocking these TNFα signals regulates the altered TNFα production in rheumatoid arthritis (RA) patients.

Methods

We compared, by flow cytometry, Toll-like receptor induction levels of membrane and intracellular TNFα in monocytes (iTNFα + CD14+ cells) from 12 patients before and after adalimumab treatment with those from 5 healthy donors.

Results

Before starting the treatment, the percentage of iTNFα+ CD14+ cells in the RA patients was significantly lower than that in healthy donors (mean ± SEM = 33.16 ± 4.82% vs 66.51 ± 2.4%, P < 0.001). When we added in vitro TNFα to healthy donor culture cells, levels of iTNFα+ CD14+ cells decreased, suggesting that the TNFα signal was responsible for the iTNFα+ CD14+ cell downregulation observed in the RA patients. After 2, 6 and 12 adalimumab injections, we observed significant blocking of membrane and soluble TNFα and a progressive increase in iTNFα+ CD14+ cells in ten patients with a good to moderate response as defined by the European League Against Rheumatism (EULAR) criteria. Levels of iTNFα+ CD14+ cells after 12 injections in these 10 patients were comparable to levels in healthy donors. In two patients, iTNFα+ CD14+ cell upregulation was not observed, and their EULAR-defined responses had not improved. The first patient developed antiadalimumab antibodies, explaining why adalimumab was not able to block membrane and soluble TNFα. In the second patient, adalimumab was discontinued because of adverse effects, which led to a decrease in iTNFα+ CD14+ cells to levels measured before treatment.

Conclusions

Our findings suggest that adalimumab treatment in RA patients can return iTNFα levels to those of healthy donors. This effect was not observed in the presence of neutralizing antiadalimumab antibodies.

Functional consequences of platelet binding to T lymphocytes in inflammation

Expression of the scavenger receptor CD36 on lymphocytes is intriguing. We observed that a minor subpopulation of lymphocytes expressed CD36 on the cell surface. We investigated the source of CD36 and also the proliferation and cytokine production of these CD36(+) CD4(+) lymphocytes. Flow cytometry analysis and immunofluorescence microscopy showed that CD36(+) platelets were responsible for CD36 detection on lymphocytes. CD36 was then used as a tool to characterize lymphocytes with bound platelets. Activation-induced proliferation was lower in CD4(+) lymphocytes with bound platelets than lymphocytes without bound platelets. IL-17 and IFN-γ production was also reduced in lymphocytes with bound platelets. We then studied the presence of CD36(+) CD4(+) lymphocytes in RA patients. We observed that the percentage of CD4(+) lymphocytes with bound platelets was higher on RA patients than in healthy donors. RA patients with higher titers of anti-CCP, RF levels, and cardiovascular risk index presented a lower percentage of CD4(+) lymphocytes with bound platelets. These patients also had higher IL-17 and IFN-γ production. These results suggest that platelet-binding modifies lymphocyte function. This binding could be a regulatory mechanism in RA that confers a less severe phenotype.

The stromal-vascular fraction of adipose tissue contributes to major differences between subcutaneous and visceral fat depots

Adipose tissue represents a complex tissue both in terms of its cellular composition, as it includes mature adipocytes and the various cell types comprising the stromal-vascular fraction (SVF), and in relation to the distinct biochemical, morphological and functional characteristics according to its anatomical location. Herein, we have characterized the proteomic profile of both mature adipocyte and SVF from human visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) fat depots in order to unveil differences in the expression of proteins which may underlie the distinct association of VAT and SAT to several pathologies. Specifically, 24 proteins were observed to be differentially expressed between SAT SVF versus VAT SVF from lean individuals. Immunoblotting and RT-PCR analysis confirmed the differential regulation of the nuclear envelope proteins lamin A/C, the membrane-cytoskeletal linker ezrin and the enzyme involved in retinoic acid production, aldehyde dehydrogenase 1A2, in the two fat depots. In sum, the observation that proteins with important cell functions are differentially distributed between VAT and SAT and their characterization as components of SVF or mature adipocytes pave the way for future research on the molecular basis underlying diverse adipose tissue-related pathologies such as metabolic syndrome or lipodystrophy.