Interleukin-6 mediates enhanced thrombus development in cerebral arterioles following a brief period of focal brain ischemia

Baseline Serum Biomarkers of Inflammation and Subsequent Visit-to-Visit Blood Pressure Variability: A Post Hoc Analysis of MESA

BACKGROUND

Higher blood pressure variability (BPV) is associated with the development of major vascular diseases, independent of mean blood pressure. However, despite data indicating that serum inflammatory markers are linked to hypertension, the association between serum inflammatory markers and BPV has not been studied in humans.

METHODS

This is a post hoc analysis of the Multi-Ethnic Study of Atherosclerosis (MESA) study. The study exposure was tertiles of serum level of interleukin-6 (IL-6), C-reactive protein (CRP), d-dimer, plasmin-antiplasmin complex (PAP), fibrinogen antigen, and calibrated Factor VIII (%) at the baseline study visit. The primary outcome was visit-to-visit BPV measured as the residual standard deviation (rSD) of at least 4 study visits (2000-2018). Two logistic regression models were fit to the top tertile of rSD during follow-up: in Model 1, we adjusted for age, sex, and hypertension, and in Model 2, for patient age categories, sex, race/ethnicity, education, hypertension, diabetes, smoking, drinking, body mass index, lipid-lowering medication, and mean systolic blood pressure.

RESULTS

Our analysis included 5,483 patients, with a mean (SD) age of 61.4 (10.0) years, 52.9% female, and 40.7% White. In unadjusted analyses, all markers of inflammation were associated with higher BPV, but after adjustment, only IL-6 retained significance (P < 0.001). The odds ratio for the highest tertile of BPV and IL-6 was 1.49 (95% confidence interval [CI] 1.28-1.74, P < 0.001).

CONCLUSIONS

Baseline serum IL-6 was associated with increased subsequent BPV in a large multiracial cohort. Further investigation is needed to better understand the relationship between chronic inflammation and BPV.

Neuroprotective Effects of Theobromine in permanent bilateral common carotid artery occlusion rat model of cerebral hypoperfusion

Cerebral hypoperfusion (CH) is a common underlying mechanism of dementia disorders linked to aberrations in the neurovascular unit. Hemodynamic disturbances adversely affect cellular energy homeostasis that triggers a sequence of events leading to irrevocable damage to the brain and neurobehavioral discrepancies. Theobromine is a common ingredient of many natural foods consumed by a large population worldwide. Theobromine has shown health benefits in several studies, attributed to regulation of calcium homeostasis, phosphodiesterase, neurotransmission, and neurotrophins. The current study evaluated the neuroprotective potential of theobromine against CH in the permanent bilateral common carotid artery occlusion (BCCAO) prototype. Wistar rats were distributed in Sham-operated (S), S + T100, CH, CH + T50, and CH + T100 groups. Animals received permanent BCCAO or Sham treatment on day 1. Theobromine (50, 100 mg/kg) was given orally in animals subjected to BCCAO for 14 days daily. CH caused neurological deficits (12-point scale), motor dysfunction, and memory impairment in rats. Treatment with theobromine significantly attenuated neurological deficits and improved sensorimotor functions and memory in rats with CH. In biochemistry investigation of the entire brain, findings disclosed reduction in brain oxidative stress, inflammatory intermediaries (tumor necrosis factor-α, interleukin-1β and - 6, nuclear factor-κB), markers of cell demise (lactate dehydrogenase, caspase-3), acetylcholinesterase activity, and improvement in γ-aminobutyric acid quantity in rats that were given theobromine for 14 days daily after CH. Histopathological analysis substantiated attenuation of neurodegenerative changes by theobromine. The findings of this study indicated that theobromine could improve neurological scores, sensorimotor abilities, and memory in CH prototype.

Therapeutic effect of anti-HMGB1 antibody in a mouse model of 4-h middle cerebral artery occlusion: comparison with tissue plasminogen activator

OBJECTIVE

Delayed tissue plasminogen activator (tPA) treatment increases the risk of intracerebral hemorrhage in patients with ischemic stroke. We previously demonstrated that tPA treatment caused hemorrhagic complications in a 4-h middle cerebral artery occlusion (MCAO) mouse model when administered after reperfusion. In the present study, we administered an anti-high mobility group box 1 (αHMGB1) antibody to 4-h MCAO mice to evaluate the usability of αHMGB1 antibody treatment in the delayed phase of ischemia, beyond the therapeutic time window of tPA.

METHODS

αHMGB1 antibody, tPA and control IgG were dissolved in normal saline and administered intravenously into the tail vein of the mice after reperfusion. Infarct volume, hemorrhagic volume, brain swelling, functional outcomes and levels of pro-inflammatory cytokines, such as HMGB1, interleukin (IL)-6 and tumor necrosis factor (TNF)-α, were evaluated 24 h after MCAO.

RESULTS

tPA treatment was not only ineffective but also caused a massive intracerebral hemorrhage. Treatment with αHMGB1 antibody reduced the infarct volume and swelling and ameliorated neurologic impairment and motor coordination without hemorrhagic complications by inhibiting HMGB1 activity. Moreover, the αHMGB1 antibody suppressed pathways of secondary inflammatory responses, such as IL-6 and TNF-α, after cerebral ischemia.

CONCLUSION

These results indicate that αHMGB1 antibody may be therapeutically efficient in the delayed phase of ischemia, where tPA treatment is no longer an eligible option. Treatment with an αHMGB1 antibody may be an effective therapeutic option in patients who exceed the tPA therapeutic time window.

Liver vitronectin release into the bloodstream increases due to reduced vagal muscarinic signaling after cerebral stroke in female mice

Vitronectin (VTN) is a glycoprotein enriched in the blood and activates integrin receptors. VTN blood levels increase only in female mice 24 h after an ischemic stroke and exacerbate brain injury through IL-6-driven inflammation, but the VTN induction mechanism is unknown. Here, a 30 min middle cerebral artery occlusion (MCAO) in female mice induced VTN protein in the liver (normally the main source) in concert with plasma VTN. Male mice were excluded as VTN is not induced after stroke. MCAO also increased plasma VTN levels after de novo expression of VTN in the liver of VTN-/- female mice, using a hepatocyte-specific (SERPINA1) promoter. MCAO did not affect SERPINA1 or VTN mRNA in the liver, brain, or several peripheral organs, or platelet VTN, compared to sham mice. Thus, hepatocytes are the source of stroke-induced increases in plasma VTN, which is independent of transcription. The cholinergic innervation by the parasympathetic vagus nerve is a potential source of brain-liver signaling after stroke. Right-sided vagotomy at the cervical level led to increased plasma VTN levels, suggesting that VTN release is inhibited by vagal tone. Co-culture of hepatocytes with cholinergic neurons or treatment with acetylcholine, but not noradrenaline (sympathetic transmitter), suppressed VTN expression. Hepatocytes have muscarinic receptors and the M1/M3 agonist bethanechol decreased VTN mRNA and protein release in vitro via M1 receptors. Finally, systemic bethanechol treatment blocked stroke-induced plasma VTN. Thus, VTN translation and release are inhibited by muscarinic signaling from the vagus nerve and presents a novel target for lessening detrimental VTN expression.

Impact of Age on Systemic Inflammatory Profile of Patients With ST-Segment-Elevation Myocardial Infarction and Acute Ischemic Stroke

BACKGROUND

Aging is associated with a chronic low-grade inflammatory state. This condition may affect the acute inflammatory response involved in ST-segment-elevation myocardial infarction (STEMI) or acute ischemic stroke (AIS). We sought to compare the profile of a set of circulating inflammatory markers between young and older patients admitted for STEMI or AIS.

METHODS

HIBISCUS-STEMI (Cohort of Patients to Identify Biological and Imaging Markers of Cardiovascular Outcomes in ST Elevation Myocardial Infarction) and HIBISCUS-STROKE (Cohort of Patients to Identify Biological and Imaging Markers of Cardiovascular Outcomes in Stroke) are 2 cohort studies that enrolled patients with STEMI treated with primary percutaneous coronary intervention in the cardiac intensive care unit of Lyon and patients with AIS treated with mechanical thrombectomy in the Lyon Stroke Center, respectively from 2016 to 2019. Patients were classified as older if they were ≥65 years and as young if they were <65 years. In both cohorts, CRP (C-reactive protein), IL (interleukin)-6, IL-8, IL-10, MCP (monocyte chemoattractant protein), sTNF-RI (soluble tumor necrosis factor receptor I), sST2 (soluble form suppression of tumorigenicity 2), and VCAM-1 (vascular cellular adhesion molecule-1) were measured on serum collected at 5 time points using enzyme-linked immunosorbent assay. A multiple logistic regression model was performed to detect an association between area under the curve of circulating inflammatory markers within the first 48 hours and older age.

RESULTS

A total of 260 patients with STEMI and 164 patients with AIS were included. Of them, there were 76 (29%) and 105 (64%) older patients with STEMI and AIS, respectively. Following multivariable analysis, a high area under the curve of IL-6 and sTNF-RI, a low lymphocyte count, and a high neutrophil-lymphocyte ratio at 24 hours were associated with older age in patients with STEMI and AIS.

CONCLUSIONS

Older patients had higher IL-6 and sTFN-RI levels within the first 48 hours associated with a lower lymphocyte count and a higher neutrophil-lymphocyte ratio at 24 hours in both cohorts.

A lower admission level of interleukin-6 is associated with first-pass effect in ischemic stroke patients

BACKGROUND

First-pass effect (FPE) defined as a complete or near-complete reperfusion achieved after a single thrombectomy pass is predictive of favorable outcome in acute ischemic stroke (AIS) patients. We aimed to assess whether admission levels of inflammatory markers are associated with FPE.

METHODS

HIBISCUS-STROKE (CoHort of Patients to Identify Biological and Imaging markerS of CardiovascUlar Outcomes in Stroke) includes AIS patients with large vessel occlusion treated with mechanical thrombectomy following brain MRI. C-reactive protein, interleukin (IL)-6, IL-8, IL-10, monocyte chemoattractant protein-1, soluble tumor necrosis factor receptor I, soluble form suppression of tumorigenicity 2, matrix metalloproteinase-9 (MMP-9), soluble P-selectin, and vascular cellular adhesion molecule-1 were measured in admission sera using an ELISA assay. FPE was defined as a complete or near-complete reperfusion (thrombolysis in cerebral infarction scale (TICI) 2c or 3) after the first pass. A multivariate logistic regression analysis was performed to assess independent factors associated with FPE.

RESULTS

A total of 151 patients were included. Among them, 43 (28.5%) patients had FPE. FPE was associated with low admission levels of IL-6, MMP-9, and platelet count, an older age, lack of hypertension, lack of tandem occlusion, a shorter thrombus length, and a reduced procedural time. Following multivariate analysis, a low admission level of IL-6 was associated with FPE (OR 0.66, 95% CI 0.46 to 0.94). Optimal cut-off of IL-6 level for distinguishing FPE from non-FPE was 3.0 pg/mL (sensitivity 92.3%, specificity 42.3%).

CONCLUSION

A lower admission level of IL-6 is associated with FPE.

Identification of Host Factors Associated with the Development of Equine Herpesvirus Myeloencephalopathy by Transcriptomic Analysis of Peripheral Blood Mononuclear Cells from Horses

Equine herpesvirus-1 is the cause of respiratory disease, abortion, and equine herpesvirus myeloencephalopathy (EHM) in horses worldwide. EHM affects as many as 14% of infected horses and a cell-associated viremia is thought to be central for EHM pathogenesis. While EHM is infrequent in younger horses, up to 70% of aged horses develop EHM. The aging immune system likely contributes to EHM pathogenesis; however, little is known about the host factors associated with clinical EHM. Here, we used the “old mare model” to induce EHM following EHV-1 infection. Peripheral blood mononuclear cells (PBMCs) of horses prior to infection and during viremia were collected and RNA sequencing with differential gene expression was used to compare the transcriptome of horses that did (EHM group) and did not (non-EHM group) develop clinical EHM. Interestingly, horses exhibiting EHM did not show respiratory disease, while non-EHM horses showed significant respiratory disease starting on day 2 post infection. Multiple immune pathways differed in EHM horses in response to EHV-1. These included an upregulation of IL-6 gene expression, a dysregulation of T-cell activation through AP-1 and responses skewed towards a T-helper 2 phenotype. Further, a dysregulation of coagulation and an upregulation of elements in the progesterone response were observed in EHM horses.

Association of Interleukin-6 Levels and Futile Reperfusion After Mechanical Thrombectomy

OBJECTIVE

To assess whether interleukin-6 (IL-6) level is a marker of futile reperfusion in patients with acute ischemic stroke (AIS) with large vessel occlusion treated with mechanical thrombectomy (MT).

METHODS

The Cohort of Patients to Identify Biological and Imaging Markers of Cardiovascular Outcomes in Stroke (HIBISCUS-STROKE) includes patients with AIS treated with MT after MRI. We performed a sequential assessment of IL-6 (admission, 6 hours, 24 hours, 48 hours and 3 months from admission). Among patients with successful reperfusion (Thrombolysis in Cerebral Infarction scale 2b/3), reperfusion was considered effective if 3-month modified Rankin Scale (mRS) score was 0 to 2 and futile if 3-month mRS score was 3 to 6. Our model was adjusted for the main confounding variables.

RESULTS

One hundred sixty-four patients represent the study population. One hundred thirty-three patients had successful reperfusion (81.1%), while in 46 (34.6%), reperfusion was classified as futile. In single-variable analyses, high IL-6 levels at 6, 24, and 48 hours in combination with a higher age, a prestroke mRS score >2, a history of hypertension or diabetes, lack of current smoking, a higher baseline NIH Stroke Scale score, the absence of associated intravenous thrombolysis, an intracranial internal carotid artery or a tandem occlusion, and an increased infarct growth were associated with futile reperfusion. After multivariable analyses, a high IL-6 level at 24 hours (odds ratio 6.15, 95% confidence interval 1.71-22.10) remained associated with futile reperfusion.

CONCLUSIONS

IL-6 is a marker of futile reperfusion in the setting of MT.

Ultrafast Hypothermia Selectively Mitigates the Early Humoral Response After Cardiac Arrest

Background Total liquid ventilation (TLV) has been shown to prevent neurological damage though ultrafast cooling in animal models of cardiac arrest. We investigated whether its neuroprotective effect could be explained by mitigation of early inflammatory events. Methods and Results Rabbits were submitted to 10 minutes of ventricular fibrillation. After resuscitation, they underwent normothermic follow-up (control) or ultrafast cooling by TLV and hypothermia maintenance for 3 hours (TLV). Immune response, survival, and neurological dysfunction were assessed for 3 days. TLV improved neurological recovery and reduced cerebral lesions and leukocyte infiltration as compared with control (eg, neurological dysfunction score=34±6 versus 66±6% at day 1, respectively). TLV also significantly reduced interleukin-6 blood levels during the hypothermic episode (298±303 versus 991±471 pg/mL in TLV versus control at 3 hours after resuscitation, respectively), but not after rewarming (752±563 versus 741±219 pg/mL in TLV versus control at 6 hours after resuscitation, respectively). In vitro assays confirmed the high temperature sensitivity of interleukin-6 secretion. Conversely, TLV did not modify circulating high-mobility group box 1 levels or immune cell recruitment into the peripheral circulation. The link between interleukin-6 early transcripts (<8 hours) and neurological outcome in a subpopulation of the previously described Epo-ACR-02 (High Dose of Erythropoietin Analogue After Cardiac Arrest) trial confirmed the importance of this cytokine at the early stages as compared with delayed stages (>8 hours). Conclusions The neuroprotective effect of hypothermic TLV was associated with a mitigation of humoral interleukin-6 response. A temperature-dependent attenuation of immune cell reactivity during the early phase of the post-cardiac arrest syndrome could explain the potent effect of rapid hypothermia. Registration URL: https://www.clinicaltrials.gov; Unique identifier: NCT00999583.

Animal models of transient ischemic attack: a review

Transient ischemic attack (TIA) is defined as a brief episode of neurological dysfunction caused by focal cerebral ischemia. TIA is a critical early warning signal of stroke. Patients with TIA may have long-term cognitive decline. The pathogenesis and pathological changes of TIA have not been fully elucidated. Animal models can simulate the process of human diseases and are essential tools to investigate injury mechanisms and therapeutic approaches of TIA. Most TIA animal models are based on ischemic stroke models and the definition of TIA. Each model has unique strengths and weaknesses. The establishment of a successful and reliable TIA model should follow three criteria: (1) objective evidence of cerebral arteries occlusion and reperfusion, (2) no permanent neurological deficit, and (3) no acute cerebral infarction. However, experimental animal models are impossible to be completely consistent with human TIA, because TIA itself is a heterogeneous disease. In the present review, the selection of animals, methodological development, and evaluation of cerebral blood flow of animal models of TIA are comprehensively evaluated.

Novel Role of T Cells and IL-6 (Interleukin-6) in Angiotensin II-Induced Microvascular Dysfunction

Hypertension is an established risk factor for subsequent cardiovascular diseases, with Ang II (angiotensin II) playing a major role in mediating thrombotic and inflammatory abnormalities. Although T cells and IL-6 (interleukin-6) play an important role in adaptive immune responses, little is known about their role(s) in the thromboinflammatory responses associated with Ang II. Here we show using intravital microscopy coupled with the light/dye injury model that Rag-1 deficient (Rag-1-/-) and IL-6 deficient (IL-6-/-) mice are afforded protection against Ang II-induced thrombosis. Blocking IL-6 receptors (using CD126 and gp130 antibodies) significantly diminished Ang II-mediated thrombosis and inflammatory cell recruitment in mice. Furthermore, the adoptive transfer of IL-6-/--derived T cells into Rag-1-/- mice failed to accelerate Ang II-induced thrombosis compared with Rag-1-/- mice reconstituted with wild-type-derived T cells, suggesting T cell IL-6 mediates the thrombotic abnormalities associated Ang II hypertension. Interestingly, adoptive transfer of WT T cells into Rag-1-/-/Ang II mice resulted in increased numbers of immature platelets, which constitutes a more active platelet population, that is, prothrombotic and proinflammatory. To translate our in vivo findings, we used clinical samples to demonstrate that IL-6 also predisposes platelets to an interaction with collagen receptors, thereby increasing the propensity for platelets to aggregate and cause thrombosis. In summary, we provide compelling evidence for the involvement of IL-6, IL-6R, and T-cell-dependent IL-6 signaling in Ang II-induced thromboinflammation, which may provide new therapeutic possibilities for drug discovery programs for the management of hypertension.

The mean platelet volume on admission predicts unfavorable stroke outcomes in patients treated with IV thrombolysis

Purpose

The role of biomarkers in the prediction of acute ischemic stroke (AIS) outcome or response to thrombolytic therapy (with recombinant tissue plasminogen activator [rt-PA]) remains limited. The aim of this study was to evaluate whether mean platelet volume (MPV) could predict short-term functional outcome in patients with AIS following rt-PA treatment.

Patients and methods

This was a retrospective analysis of 237 AIS patients (mean age 71.04±0.8 years, 50.6% women) consecutively admitted to a tertiary care center between 2011 and 2015.

Results

The mean MPV in the cohort was 9.8±0.35 fL (lowest tertile <7.29 fL, median 7.29–8.8 fL, and highest tertile >8.8 fL). Patients in the lowest tertile compared to median and highest tertiles were less often dependent (modified Rankin scale [mRS] ≥3) at admission (87.2% vs 96.1% and 96.1%, respectively, P=0.04) and less often had a poor stroke outcome (mRS 4–6) at discharge (28.2% vs 55.3% and 44.7%, P<0.01). However, there was no significant difference between tertiles with regard to AIS etiology, CT (Alberta Stroke Program Early CT) score, frequency of stroke due to large artery occlusion, risk of secondary hemorrhage, and early neurologic deterioration. Multivariable analysis after adjustment for confounders showed that patients in the second and third tertiles had a significantly higher risk of poor stroke outcome (OR =1.9, 95% CI =1.01–4), lack of early improvement (OR =1.91, 95% CI =1.05–3.47), lower chance of good outcome (mRS 0–2; OR =0.38, 95% CI =0.18–0.78), or minor stroke at discharge (OR =0.47, 95% CI =0.26–0.84). Receiver operating characteristic analysis for prediction of poor stroke outcome showed that the optimal cut-off point of MPV was 8.8 fL (area under the curve 0.586 [0.512–0.659], P=0.03) with a sensitivity of 82.7% and a specificity of 43.9%.

Conclusion

Disabling or fatal ischemic stroke in thrombolyzed patients was observed more often in patients with high admission MPV. The prognostic value of MPV was independent of other well-defined individual risk factors.

Effect of Interventional Therapy on IL-1β, IL-6, and Neutrophil-Lymphocyte Ratio (NLR) Levels and Outcomes in Patients with Ischemic Cerebrovascular Disease

Background

This study investigated the clinical effect of interventional therapy in ischemic cerebrovascular disease (ICD).

Material/Methods

A retrospective analysis was performed on 260 ICD patients who were divided into a control group (122 patients, conventional drug treatment) and an observation group (138 patients, interventional therapy plus conventional drug treatment). Enzyme-linked immunosorbent assay was used to examine the expression of IL-1β, IL-6, and NLR. Furthermore, neurological deficit scores and Barthel index scores as well as the correlation of IL-1β, IL-6 and NLR were examined in these 2 groups.

Results

The expression of IL-1β, IL-6, and NLR significantly decreased in both groups after 1 week or 4 weeks of treatment compared with before treatment (P<0.05). Significant differences in neurological impairment scores were detected between these 2 groups after 4 weeks of treatment (P<0.05), and the control group showed higher neurological deficit scores than did the observation group (P<0.05). Barthel index scores were significantly higher after treatment than before treatment in the control and observation group (P<0.05), and the control group had lower Barthel index scores than did the observation group (P<0.05). Pearson correlation analysis showed that IL-1β, IL-6, and NLR expression were positively correlated in ICD patients (P<0.05).

Conclusions

Interventional surgery combined with conventional drug therapy can reduce serum IL-1β and IL-6 levels, decrease neurological impairment, and improve the quality of life of patients. The combined treatment group showed better outcomes than did the group that received the drug alone; therefore, combined therapy is suitable for promoting better clinical outcomes.

Iron Pathophysiology in Stroke

Ischemic and hemorrhagic stroke are the common types of stroke that lead to brain injury neurological deficits and mortality. All forms of stroke remain a serious health issue, and there is little successful development of drugs for treating stroke. Incomplete understanding of stroke pathophysiology is considered the main barrier that limits this research progress. Besides mitochondria and free radical-producing enzymes, labile iron is an important contributor to oxidative stress. Although iron regulation and metabolism in cerebral stroke are not fully understood, much progress has been achieved in recent years. For example, hepcidin has recently been recognized as the principal regulator of systemic iron homeostasis and a bridge between inflammation and iron regulation. This review discusses recent research progress in iron pathophysiology following cerebral stroke, focusing molecular regulation of iron metabolism and potential treatment targets.

Lung injury caused by paraquat poisoning results in increased interleukin-6 and decreased microRNA-146a levels

The aim of the present study was to investigate the expression of microRNA (miR)-146a in the pulmonary macrophages, peripheral blood mononuclear cells and serum of patients with lung injury caused by paraquat poisoning, as well as the underlying mechanism of its regulation in the disease. A total of 26 patients with lung injury caused by paraquat poisoning were included in the present study. In addition, 33 healthy subjects were included as the control group. The expression levels of interleukin (IL)-6 mRNA and miR-146a was determined by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Western blotting was used to measure IL-6 protein expression, while enzyme-linked immunosorbent assay was also performed to determine the secretion of IL-6 protein. A dual-luciferase reporter assay was conducted to examine whether IL-6 mRNA is a direct target of miR-146a. Patients with lung injury caused by paraquat poisoning exhibited higher IL-6 mRNA and protein levels as compared with those in healthy subjects. In addition, miR-146a expression in patients with paraquat poisoning-induced lung injury was significantly reduced in comparison with that in healthy subjects. Notably, the overexpression of miR-146a by mimic transfection downregulated the expression of IL-6 in pulmonary macrophages. The results of dual-luciferase reporter assay demonstrated that IL-6 mRNA was a direct target of miR-146a. Therefore, the present study demonstrated that increased expression of IL-6 in patients with lung injury caused by paraquat poisoning is associated with decreased expression of miR-146a. Furthermore, miR-146a may regulate the occurrence and immune response of lung injury caused by paraquat poisoning and this process is possibly achieved via IL-6, an important cytokine that mediates inflammation.

Granzyme A in Human Platelets Regulates the Synthesis of Proinflammatory Cytokines by Monocytes in Aging

Dysregulated inflammation is implicated in the pathobiology of aging, yet platelet-leukocyte interactions and downstream cytokine synthesis in aging remains poorly understood. Platelets and monocytes were isolated from healthy younger (age <45, n = 37) and older (age ≥65, n = 30) adults and incubated together under autologous and nonautologous conditions. Synthesis of inflammatory cytokines by monocytes, alone or in the presence of platelets, was examined. Next-generation RNA-sequencing allowed for unbiased profiling of the platelet transcriptome in aging. Basal IL-8 and MCP-1 synthesis by monocytes alone did not differ between older and younger adults. However, in the presence of autologous platelets, monocytes from older adults synthesized greater IL-8 (41 ± 5 versus 9 ± 2 ng/ml, p < 0.0001) and MCP-1 (867 ± 150 versus 216 ± 36 ng/ml, p < 0.0001) than younger adults. Platelets from older adults were sufficient for upregulating the synthesis of inflammatory cytokines by monocytes. Using RNA-sequencing of platelets followed by validation via RT-PCR and immunoblot, we discovered that granzyme A (GrmA), a serine protease not previously identified in human platelets, increases with aging (∼9-fold versus younger adults, p < 0.05) and governs increased IL-8 and MCP-1 synthesis through TLR4 and caspase-1. Inhibiting GrmA reduced excessive IL-8 and MCP-1 synthesis in aging to levels similar to younger adults. In summary, human aging is associated with changes in the platelet transcriptome and proteome. GrmA is present and bioactive in human platelets, is higher in older adults, and controls the synthesis of inflammatory cytokines by monocytes. Alterations in the platelet molecular signature and signaling to monocytes may contribute to dysregulated inflammatory syndromes in older adults.