New-onset dermatomyositis following SARS-CoV-2 infection and vaccination: a case-based review.

Dermatomyositis is a rare, type I interferon-driven autoimmune disease, which can affect muscle, skin and internal organs (especially the pulmonary system). In 2021, we have noted an increase in new-onset dermatomyositis compared to the years before the SARS-CoV-2 pandemic in our center. We present four cases of new-onset NXP2 and/or MDA5 positive dermatomyositis shortly after SARS-CoV-2 infection or vaccination. Three cases occurred within days after vaccination with Comirnaty and one case after SARS-CoV-2 infection. All patients required intensive immunosuppressive treatment. MDA5 antibodies could be detected in three patients and NXP2 antibodies were found in two patients (one patient was positive for both antibodies). In this case-based systematic review, we further analyze and discuss the literature on SARS-CoV-2 and associated dermatomyositis. In the literature, sixteen reports (with a total of seventeen patients) of new-onset dermatomyositis in association with a SARS-CoV-2 infection or vaccination were identified. Ten cases occurred after infection and seven after vaccination. All vaccination-associated cases were seen in mRNA vaccines. The reported antibodies included for instance MDA5, NXP2, Mi-2 and TIF1γ. The reviewed literature and our cases suggest that SARS-CoV-2 infection and vaccination may be considered as a potential trigger of interferon-pathway. Consequently, this might serve as a stimulus for the production of dermatomyositis-specific autoantibodies like MDA5 and NXP2 which are closely related to viral defense or viral RNA interaction supporting the concept of infection and vaccination associated dermatomyositis.

Proteasome inhibition activates the mitochondrial pathway of apoptosis in human CD4+ T cells.

We have previously shown that inhibition of the proteolytic activity of the proteasome induces apoptosis and suppresses essential functions of activated human CD4(+) T cells, and we report now the detailed mechanisms of apoptosis following proteasome inhibition in these cells. Here we show that proteasome inhibition by bortezomib activates the mitochondrial pathway of apoptosis in activated CD4(+) T cells by disrupting the equilibrium of pro-apoptotic and anti-apoptotic proteins at the outer mitochondrial membrane (OMM) and by inducing the generation of reactive oxygen species (ROS). Proteasome inhibition leads to accumulation of pro-apoptotic proteins PUMA, Noxa, Bim and p53 at the OMM. This event provokes mitochondrial translocation of activated Bax and Bak homodimers, which induce loss of mitochondrial membrane potential (DeltaPsim). Breakdown of DeltaPsim is followed by rapid release of pro-apoptotic Smac/DIABLO and HtrA2 from mitochondria, whereas release of cytochrome c and AIF is delayed. Cytoplasmic Smac/DIABLO and HtrA2 antagonize IAP-mediated inhibition of partially activated caspases, leading to premature activation of caspase-3 followed by activation of caspase-9. Our data show that proteasome inhibition triggers the mitochondrial pathway of apoptosis by activating mutually independent apoptotic pathways. These results provide novel insights into the mechanisms of apoptosis induced by proteasome inhibition in activated T cells and underscore the future use of proteasome inhibitors for immunosuppression.

Proteasome inhibition suppresses essential immune functions of human CD4+ T cells.

The proteasome constitutes the central proteolytic component of the highly conserved ubiquitin-proteasome system, which is required for the maintenance and regulation of basic cellular processes, including differentiation, proliferation, cell cycling, gene transcription and apoptosis. Here we show that inhibition of proteasomal proteolytic activity by the proteasome inhibitors bortezomib and lactacystin suppresses essential immune functions of human CD4(+) T cells activated by allogeneic dendritic cells (DCs). In activated CD4(+) T cells, proteasome inhibition induces apoptosis accompanied by rapid accumulation and stabilization of the tumour suppressor protein p53. Activated CD4(+) T cells surviving proteasome inhibition undergo inhibition of proliferation by induction of G(1) phase cell-cycle arrest. Induction of G(1) arrest is accompanied by the accumulation of cyclin-dependent kinase inhibitors p21(WAF1/CIP1) and p27(KIP1) and the disappearance of cyclin A, cyclin D2 and proliferating cell nuclear antigen, proteins known to regulate G(1) to S phase cell-cycle transitions. Expression of the activation-associated cell surface receptors CD25, CD28, CD120b and CD134 as well as production of interferon-gamma (IFN-gamma), tumour necrosis factor-alpha (TNF-alpha), interleukin-4 (IL-4) and IL-5 is suppressed in response to proteasome inhibition in CD4(+) T cells activated by DCs. Expression of CD25, IFN-gamma, TNF-alpha, IL-4 and IL-5 is known to be mediated by the transcriptional activity of nuclear factor of activated T cells (NFAT), and we show here that proteasome inhibition suppresses activation and nuclear translocation of NFATc2 in activated CD4(+) T cells. Thus, the proteasome is required for essential immune functions of activated CD4(+) T cells and can be defined as a molecular target for the suppression of deregulated and unwanted T-cell-mediated immune responses.