The plasticity of regulatory T cell function

Regulatory T cells (T(regs)) can suppress a wide variety of cell types, in diverse organ sites and inflammatory conditions. Whereas T(regs) possess multiple suppressive mechanisms, the number required for maximal function is unclear. Furthermore, whether any interrelationship or cross-regulatory mechanisms exist to orchestrate and control their utilization is unknown. In this study, we assessed the functional capacity of T(regs) lacking the ability to secrete both IL-10 and IL-35, which individually are required for maximal T(reg) activity. Surprisingly, IL-10/IL-35 double-deficient T(regs) were fully functional in vitro and in vivo. Loss of IL-10 and IL-35 was compensated for by a concurrent increase in cathepsin E (Ctse) expression, enhanced TRAIL (Tnfsf10) expression, and soluble TRAIL release, rendering IL-10/IL-35 double-deficient T(regs) functionally dependent on TRAIL in vitro and in vivo. Lastly, whereas C57BL/6 T(regs) are normally IL-10/IL-35 dependent, BALB/c T(regs), which express high levels of cathepsin E and enhanced TRAIL expression, are partially TRAIL dependent by default. These data reveal that cross-regulatory pathways exist that control the utilization of suppressive mechanisms, thereby providing T(reg) functional plasticity.     

Drug-induced senescence generates chemoresistant stemlike cells with low reactive oxygen species

Tumor recurrence after chemotherapy or radiation remains a major obstacle to successful cancer treatment. A subset of cancer cells, termed cancer stem cells, can elude conventional treatments and eventually regenerate a tumor that is more aggressive. Despite the large number of studies, molecular events that govern the emergence of aggressive therapy-resistant cells with stem cell properties after chemotherapy are poorly defined. The present study provides evidence for the rare escape of tumor cells from drug-induced cell death, after an intermediate stay in a non-cycling senescent stage followed by unstable multiplication characterized by spontaneous cell death. However, some cells appear to escape and generate stable colonies with an aggressive tumor stem cell-like phenotype. These cells displayed higher CD133 and Oct-4 expression. Notably, the drug-selected cells that contained low levels of reactive oxygen species (ROS) also showed an increase in antioxidant enzymes. Consistent with this in vitro experimental data, we observed lower levels of ROS in breast tumors obtained after neoadjuvant chemotherapy compared with samples that did not receive preoperative chemotherapy. These latter tissues also expressed enhanced levels of ROS defenses with enhanced expression of superoxide dismutase. Higher levels of Oct-4 and CD133 were also observed in tumors obtained after neoadjuvant chemotherapy. Further studies provided evidence for the stabilization of Nrf2 due to reduced 26 S proteasome activity and increased p21 association as the driving signaling event that contributes to the transition from a high ROS quiescent state to a low ROS proliferating stage in drug-induced tumor stem cell enrichment.     

Drug delivery: an odyssey of 100 years

Drug delivery has metamorphosed from the concept of a pill to molecular medicine in the past 100 years. Better appreciation and integration of pharmacokinetic and pharmacodynamic principles in design of drug delivery systems has led to improved therapeutic efficacy. A greater understanding of the molecular transport in relation to physico-chemical properties has led to the evolution of a biopharmaceutics classification system, which should be a future road map, governing drug design, development and delivery. While drugs belonging to class I and II will be delivered by established platform technologies, novel delivery strategies will evolve and mature to realize the potential of 'new generation' biotech and non biotech drugs belonging to class III and IV, respectively.     

Diminished transmission of drug resistant HIV-1 variants with reduced replication capacity in a human transmission model

Background

Different patterns of drug resistance are observed in treated and therapy naïve HIV-1 infected populations. Especially the NRTI-related M184I/V variants, which are among the most frequently encountered mutations in treated patients, are underrepresented in the antiretroviral naïve population. M184I/V mutations are known to have a profound effect on viral replication and tend to revert over time in the new host. However it is debated whether a diminished transmission efficacy of HIV variants with a reduced replication capacity can also contribute to the observed discrepancy in genotypic patterns.As dendritic cells (DCs) play a pivotal role in HIV-1 transmission, we used a model containing primary human Langerhans cells (LCs) and DCs to compare the transmission efficacy M184 variants (HIV-M184V/I/T) to HIV wild type (HIV-WT). As control, we used HIV harboring the NNRTI mutation K103N (HIV-K103N) which has a minor effect on replication and is found at a similar prevalence in treated and untreated individuals.

Results

In comparison to HIV-WT, the HIV-M184 variants were less efficiently transmitted to CCR5⁺ Jurkat T cells by both LCs and DCs. The transmission rate of HIV-K103N was slightly reduced to HIV-WT in LCs and even higher than HIV-WT in DCs. Replication experiments in CCR5⁺ Jurkat T cells revealed no apparent differences in replication capacity between the mutant viruses and HIV-WT. However, viral replication in LCs and DCs was in concordance with the transmission results; replication by the HIV-M184 variants was lower than replication by HIV-WT, and the level of replication of HIV-K103N was intermediate for LCs and higher than HIV-WT for DCs.

Conclusions

Our data demonstrate that drug resistant M184-variants display a reduced replication capacity in LCs and DCs which directly impairs their transmission efficacy. As such, diminished transmission efficacy may contribute to the lower prevalence of drug resistant variants in therapy naive individuals.

     

Subclinical inflammation on MRI of hand and foot of anticitrullinated peptide antibody–negative arthralgia patients at risk for rheumatoid arthritis

Introduction

It is known that anticitrullinated peptide antibody (ACPA)–positive rheumatoid arthritis (RA) has a preclinical phase. Whether this phase is also present in ACPA-negative RA is unknown. To determine this, we studied ACPA-negative arthralgia patients who were considered prone to progress to RA for local subclinical inflammation observed on hand and foot magnetic resonance imaging (MRI) scans.

Methods

We studied a total of 64 ACPA-negative patients without clinically detectable arthritis and with arthralgia of the small joints within the previous 1 year. Because of the character of the patients’ symptoms, the rheumatologists considered these patients to be prone to progress to RA. For comparisons, we evaluated 19 healthy, symptom-free controls and 20 ACPA-negative RA patients, who were identified according to the 1987 American Rheumatism Association criteria. All participants underwent MRI of unilateral wrist, metacarpophalangeal and metatarsophalangeal joints. Synovitis and bone marrow oedema (BME) were scored according to the OMERACT rheumatoid arthritis magnetic resonance imaging scoring system, and the scores were summed to yield the ‘MRI inflammation score’. Scores were compared between groups. Among the ACPA-negative arthralgia patients, MRI inflammation scores were related to C-reactive protein (CRP) levels and the tenderness of scanned joints.

Results

MRI inflammation scores increased progressively among the groups of controls and ACPA-negative arthralgia and RA patients (median scores = 0, 1 and 10, respectively; P < 0.001). The MRI inflammation scores of ACPA-negative arthralgia patients were significantly higher than those of controls (P = 0.018). In particular, the synovitis scores were higher in ACPA-negative arthralgia patients (P = 0.046). Among the ACPA-negative arthralgia patients, inflammation was observed predominantly in the wrist (53%). The synovitis scores were associated with CRP levels (P = 0.007) and joint tenderness (P = 0.026). Despite the limited follow-up duration, five patients developed clinically detectable arthritis. These five patients had higher scores for MRI inflammation (P = 0.001), synovitis (P = 0.002) and BME (P = 0.003) compared to the other patients.

Conclusion

Subclinical synovitis was observed in the small joints of ACPA-negative arthralgia patients, and especially in patients whose conditions progressed to clinically detectable arthritis. This finding suggests the presence of a preclinical phase in ACPA-negative RA. Further longitudinal studies of these lesions and patients are required to confirm this hypothesis.     

Brain-specific knockdown of miR-29 results in neuronal cell death and ataxia in mice

Several microRNAs have been implicated in neurogenesis, neuronal differentiation, neurodevelopment, and memory. Development of miRNA-based therapeutics, however, needs tools for effective miRNA modulation, tissue-specific delivery, and in vivo evidence of functional effects following the knockdown of miRNA. Expression of miR-29a is reduced in patients and animal models of several neurodegenerative disorders, including Alzheimer''s disease, Huntington''s disease, and spinocerebellar ataxias. The temporal expression pattern of miR-29b during development also correlates with its protective role in neuronal survival. Here, we report the cellular and behavioral effect of in vivo, brain-specific knockdown of miR-29. We delivered specific anti-miRNAs to the mouse brain using a neurotropic peptide, thus overcoming the blood-brain-barrier and restricting the effect of knockdown to the neuronal cells. Large regions of the hippocampus and cerebellum showed massive cell death, reiterating the role of miR-29 in neuronal survival. The mice showed characteristic features of ataxia, including reduced step length. However, the apoptotic targets of miR-29, such as Puma, Bim, Bak, or Bace1, failed to show expected levels of up-regulation in mice, following knockdown of miR-29. In contrast, another miR-29 target, voltage-dependent anion channel1 (VDAC1), was found to be induced several fold in the hippocampus, cerebellum, and cortex of mice following miRNA knockdown. Partial restoration of apoptosis was achieved by down-regulation of VDAC1 in miR-29 knockdown cells. Our study suggests that regulation of VDAC1 expression by miR-29 is an important determinant of neuronal cell survival in the brain. Loss of miR-29 results in dysregulation of VDAC1, neuronal cell death, and an ataxic phenotype.     

Dynamic Regulation of Host Restriction Factor Expression over the Course of HIV-1 Infection In Vivo

In this study, we investigated the expression levels of host restriction factors in six untreated HIV-1-positive patients over the course of infection. We found that the host restriction factor gene expression profile consistently increased over time and was significantly associated with CD4⁺ T cell activation and viral load. Our data are among the first to demonstrate the dynamic nature of host restriction factors in vivo over time.     

TNF‐α/IFN‐γ synergy amplifies senescence‐associated inflammation and SARS‐CoV‐2 receptor expression via hyper‐activated JAK/STAT1

Older age and underlying conditions such as diabetes/obesity or immunosuppression are leading host risk factors for developing severe complications from COVID‐19 infection. The pathogenesis of COVID‐19‐related cytokine storm, tissue damage, and fibrosis may be interconnected with fundamental aging processes, including dysregulated immune responses and cellular senescence. Here, we examined effects of key cytokines linked to cellular senescence on expression of SARS‐CoV‐2 viral entry receptors. We found exposure of human umbilical vein endothelial cells (HUVECs) to the inflammatory cytokines, TNF‐α + IFN‐γ or a cocktail of TNF‐α + IFN‐γ + IL‐6, increased expression of ACE2/DPP4, accentuated the pro‐inflammatory senescence‐associated secretory phenotype (SASP), and decreased cellular proliferative capacity, consistent with progression towards a cellular senescence‐like state. IL‐6 by itself failed to induce substantial effects on viral entry receptors or SASP‐related genes, while synergy between TNF‐α and IFN‐γ initiated a positive feedback loop via hyper‐activation of the JAK/STAT1 pathway, causing SASP amplification. Breaking the interactive loop between senescence and cytokine secretion with JAK inhibitor ruxolitinib or antiviral drug remdesivir prevented hyper‐inflammation, normalized SARS‐CoV‐2 entry receptor expression, and restored HUVECs proliferative capacity. This loop appears to underlie cytokine‐mediated viral entry receptor activation and links with senescence and hyper‐inflammation.