In Vivo Imaging of Enhanced Leukocyte Accumulation in Atherosclerotic Lesions in Humans

Background

Understanding how leukocytes impact atherogenesis contributes critically to our concept of atherosclerosis development and the identification of potential therapeutic targets.

Objectives

The study evaluates an in vivo imaging approach to visualize peripheral blood mononuclear cell (PBMC) accumulation in atherosclerotic lesions of cardiovascular (CV) patients using hybrid single-photon emission computed tomography/computed tomography (SPECT/CT).

Methods

At baseline, CV patients and healthy controls underwent ¹⁸fluorodeoxyglucose positron emission tomography-computed tomography and magnetic resonance imaging to assess arterial wall inflammation and dimensions, respectively. For in vivo trafficking, autologous PBMCs were isolated, labeled with technetium-99m, and visualized 3, 4.5, and 6 h post-infusion with SPECT/CT.

Results

Ten CV patients and 5 healthy controls were included. Patients had an increased arterial wall inflammation (target-to-background ratio [TBR] right carotid 2.00 ± 0.26 in patients vs. 1.51 ± 0.12 in controls; p = 0.022) and atherosclerotic burden (normalized wall index 0.52 ± 0.09 in patients vs. 0.33 ± 0.02 in controls; p = 0.026). Elevated PBMC accumulation in the arterial wall was observed in patients; for the right carotid, the arterial-wall-to-blood ratio (ABR) 4.5 h post-infusion was 2.13 ± 0.35 in patients versus 1.49 ± 0.40 in controls (p = 0.038). In patients, the ABR correlated with the TBR of the corresponding vessel (for the right carotid: r = 0.88; p < 0.001).

Conclusions

PBMC accumulation is markedly enhanced in patients with advanced atherosclerotic lesions and correlates with disease severity. This study provides a noninvasive imaging tool to validate the development and implementation of interventions targeting leukocytes in atherosclerosis.     

On the rise and fall of the apnea−hypopnea index: A historical review and critical appraisal

The publication of “The Sleep Apnea Syndromes” by Guilleminault et al. in the 1970s hallmarked the discovery of a new disease entity involving serious health consequences. Obstructive sleep apnea was shown to be the most important disorder among the sleep apnea syndromes (SAS). In the course of time, it was found that the prevalence of obstructive sleep apnea reached the proportions of a global epidemic, with a major impact on public health, safety and the economy. Early on, a metric was introduced to gauge the seriousness of obstructive sleep apnea, based on the objective measurement of respiratory events during nocturnal sleep. The apnea index and later on the apnea?hypopnea index, being the total count of overnight respiratory events divided by the total sleep time in hours, were embraced as principle measures to establish the diagnosis of obstructive sleep apnea and to rate its severity. The current review summarises the historical evolution of the apnea?hypopnea index, which has been subject to many changes, and has been criticised for not capturing relevant clinical features of obstructive sleep apnea. In fact, the application of the apnea?hypopnea index as a continuous exposure variable is based on assumptions that it represents a disease state of obstructive sleep apnea and that evocative clinical manifestations are invariably caused by obstructive sleep apnea if the apnea?hypopnea index is above diagnostic threshold. A critical appraisal of the extensive literature shows that both assumptions are invalid. This conclusion prompts a reconsideration of the role of the apnea?hypopnea index as the prime diagnostic metric of clinically relevant obstructive sleep apnea.     

Blinded histopathological characterisation of POLE exonuclease domain‐mutant endometrial cancers: sheep in wolf's clothing

Aims

POLE exonuclease domain mutations identify a subset of endometrial cancer (EC) patients with an excellent prognosis. The use of this biomarker has been suggested to refine adjuvant treatment decisions, but the necessary sequencing is not widely performed and is relatively expensive. Therefore, we aimed to identify histopathological and immunohistochemical characteristics to aid in the detection of POLE‐mutant ECs.

Methods and results

Fifty‐one POLE‐mutant endometrioid, 67 POLE‐wild‐type endometrioid and 15 POLE‐wild‐type serous ECs were included (total N = 133). An expert gynaecopathologist, blinded to molecular features, evaluated each case (two or more slides) for 16 morphological characteristics. Immunohistochemistry was performed for p53, p16, MLH1, MSH2, MSH6, and PMS2. POLE‐mutant ECs were characterised by a prominent immune infiltrate: 80% showed peritumoral lymphocytes and 59% showed tumour‐infiltrating lymphocytes, as compared with 43% and 28% of POLE‐wild‐type endometrioid ECs, and 27% and 13% of their serous counterparts (P < 0.01, all comparisons). Of POLE‐mutant ECs, 33% contained tumour giant cells; this proportion was significantly higher than that in POLE‐wild‐type endometrioid ECs (10%; P = 0.003), but not significantly different from that in serous ECs (53%). Serous‐like features were as often (focally) present in POLE‐mutant as in POLE‐wild‐type endometrioid ECs (6–24%, depending on the feature). The majority of POLE‐mutant ECs showed wild‐type p53 (86%), negative/focal p16 (82%) and normal mismatch repair protein expression (90%).

Conclusions

A simple combination of morphological and immunohistochemical characteristics (tumour type, grade, peritumoral lymphocytes, MLH1, and p53 expression) can assist in prescreening for POLE exonuclease domain mutations in EC, increasing the probability of a mutation being detected from 7% to 33%. This facilitates the use of this important prognostic biomarker in routine pathology.     

CYTOTOXICITY BY NONIMMUNE ALLOGENEIC LYMPHOID CELLS : SPECIFIC SUPPRESSION BY ANTIBODY TREATMENT OF THE LYMPHOID CELLS

Nonimmune lymphoid cells were capable of causing cytotoxicity of H-2 incompatible mouse tumor cells in vitro in the presence of PHA, whereas syngeneic cells were not. Semisyngeneic and X-irradiated (1500–3000 R) F₁ hybrid lymphoid cells were cytotoxic for target cells derived from one of the parental strains. In addition, parental nonimmune and X-irradiated lymphoid cells damaged hybrid target cells. It was concluded that one component of cytotoxicity was not related to an induction of a primary immune response in vitro, since F₁ hybrid cells are not capable of reacting immunologically against parental type target cells. It seemed probable that cytotoxicity was caused by target cell confrontation with antigenically and/or structurally incompatible lymphoid cells. This conclusion was strengthened by the demonstration that isoantibodies produced in the target strain and directed against the allogeneic lymphoid cells specifically suppressed cytotoxicity. Isoantibodies reacting against some but not all of the antigenic determinants of the lymphoid cells differentiating them from the target cells did not suppress cytotoxicity. The specific suppression of cytotoxicity by specific isoantibodies against the lymphoid cells support the allogeneic inhibition concept.     

Lethal encephalitis in myeloid differentiation factor 88-deficient mice infected with herpes simplex virus 1

Herpes simplex virus 1 (HSV-1), a large DNA virus from the Herpesviridae family, is the major cause of sporadic lethal encephalitis and blindness in humans. Recent studies have shown the importance of Toll-like receptors (TLRs) in the immune response to HSV-1 infection. Myeloid differentiation factor 88 (MyD88) is a critical adaptor protein that is downstream to mediated TLR activation and is essential for the production of inflammatory cytokines. Here, we studied the relationship between MyD88 and HSV-1 using a purified HSV-1 isolated from a natural oral recurrent human infection. We observed the activation of TLR-2 by HSV-1 in vitro using Chinese hamster ovary cells stably transfected with a reporter gene. Interestingly, we found that only peritoneal macrophages from MyD88-/- mice, but not macrophages from TRL2-/- or from wild-type mice, were unable to produce tumor necrosis factor-alpha in response to HSV-1 exposure. Additionally, although TLR2-/- mice showed no enhanced susceptibility to intranasal infection with HSV-1, MyD88-/- mice were highly susceptible to infection and displayed viral migration to the brain, severe neuropathological signs of encephalitis, and 100% mortality by day 10 after infection. Together, our results suggest that innate resistance to HSV-1 is mediated by MyD88 and may rely on activation of multiple TLRs.