Out of the Laboratory and Into the Field: Validation of Portable Cell Culture Protocols

Examining systemic inflammation as a pathway linking peer victimization to depressive symptoms in adolescence

BACKGROUND

Adolescents exposed to victimization are at an increased risk for a variety of adverse mental health outcomes, including depressive symptoms. Yet, the biological pathways underlying these associations remain poorly understood. Focusing on within-person processes, we examined whether low-grade systemic inflammation mediated the longitudinal associations between peer victimization and depressive symptoms in adolescence.

METHODS

207 adolescents (at baseline Mage = 12.69 years; SD = 0.49; 43.5% female) participated in a multi-wave longitudinal study, with assessments repeated every 6 months over 1.5 years. At each assessment wave, participants self-reported their peer victimization experiences and depressive symptoms. Dried blood spots were collected at each wave using a finger prick procedure to assay a key marker of low-grade systemic inflammation, interkeukin-6 (IL-6). Data were analyzed using random-intercept cross-lagged panel models.

RESULTS

The cross-lagged paths from IL-6 to depressive symptoms were significant across all models and waves (β12 = .13; β23 = .12; β34 = .08), indicating that when adolescents' levels of low-grade systemic inflammation were above their person-specific average, they reported increased levels of depressive symptoms in the subsequent months. However, no significant cross-lagged within-person associations emerged between peer victimization and either IL-6 or depressive symptoms.

CONCLUSIONS

The findings provide no evidence for the hypothesized mediating role of inflammation in the within-person associations between peer victimization and depressive symptoms. Nevertheless, they extend prior research by indicating that elevated levels of low-grade systemic inflammation predict the development of depressive symptoms in adolescence.

Implementation of a minimally invasive cell culture system to measure the regulation of inflammation in a school-based sample of adolescents

Dysregulated inflammation underlies many human diseases, and measures of responsiveness to activation, and sensitivity to inhibition, provide important information beyond baseline assessments of chronic inflammation. This study implements a simplified cell culture protocol in a school-based setting, using finger stick capillary blood collected from 333 adolescents (age 11.4-15.6 years) incubated with lipopolysaccharide (LPS). Median cytokine responses for IL6, IL1β, and TNFα were 61.9, 26.2, and 11.2 pg/mL, respectively. Samples were also incubated with LPS and glucocorticoid (GC) to measure GC sensitivity. Median responses were reduced in the presence of GC inhibition for IL6 (20.3 pg/mL), IL1β (10.5 pg/mL), and TNFα (3.3 pg/mL). Minimally invasive cell culture protocols provide novel opportunities for measuring inflammatory phenotypes in a wide range of non-clinical settings.

Family Disadvantage, Education, and Health Outcomes Among Black Youths Over a 20-Year Period

Importance

Upward mobility (via educational attainment) is highly valued, but longitudinal associations with mental and physical health among Black youths are less understood.

Objective

To examine associations of childhood family disadvantage and college graduation with adult mental and physical health in Black youths followed up into adulthood.

Design, Setting, and Participants

This longitudinal, prospective cohort study of Black youths from the state of Georgia who were studied for 20 years (ages 11 to 31 years) was conducted between 2001 and 2022. Participants for this study were drawn from the Strong African American Healthy Adults Program. Data analysis was conducted from April 2023 to January 2024.

Exposures

Family economic disadvantage (measured during the adolescent years) and college graduation (indicating upward mobility).

Main Outcomes and Measures

Primary outcomes included mental health, substance use, and physical health. Mental health included a composite of internalizing and disruptive problems (anxiety, depression, anger, aggressive behaviors, and emotional reactivity). Substance use included a composite of smoking, drinking, and drug use. Physical health included metabolic syndrome (MetS) and proinflammatory phenotypes (immune cells mounting exaggerated cytokine responses to bacterial challenge and being insensitive to inhibitory signals from glucocorticoids). Mental and physical health measures were taken at age 31 and during the adolescent years. Linear and logistic regression analyses, as well as mediated moderation analyses, were conducted.

Results

The study population consisted of 329 Black youths (212 women [64%]; 117 men [36%]; mean [SD] age at follow-up, 31 [1] years). Compared with those who did not graduate college, those who graduated from college had 0.14 SD fewer mental health problems (b = -1.377; 95% CI, -2.529 to -0.226; β = -0.137; P = .02) and 0.13 SD lower levels of substance use (b = -0.114; 95% CI, -0.210 to -0.018; β = -0.131; P = .02). Residualized change scores revealed that college graduates showed greater decreases from age 16 to 31 years in mental health problems (b = -1.267; 95% CI, -2.360 to -0.174; β = -0.133; P = .02) and substance use problems (b = -0.116; 95% CI, -0.211 to -0.021; β = -0.136; P = .02). For physical health, significant interactions between childhood family disadvantage and college completion emerged in association with MetS (OR, 1.495; 95% CI, 1.111-2.012; P = .008) and proinflammatory phenotype (b = 0.051; 95% CI, 0.003 to 0.099; β = 0.131; P = .04). Among youths growing up in disadvantaged households, college completion was associated with a 32.6% greater likelihood of MetS (OR, 3.947; 95% CI, 1.003-15.502; P = .049) and 0.59 SD more proinflammatory phenotype (mean difference, 0.249, 95% CI, 0.001 to 0.497; P = .049). Conversely, among those from economically advantaged backgrounds, college completion was correlated with lower MetS and less proinflammatory phenotype. Findings held after controlling for body mass index at age 19 years.

Conclusions and Relevance

In this longitudinal cohort study of Black youths, graduating from college was associated with an adult profile of better mental health but poorer physical health among those from economic disadvantage. These findings suggest that developing interventions that foster healthy outcomes across multiple life domains may be important for ensuring that striving for upward mobility is not accompanied by unintended cardiometabolic risk.

Exposure to parental depression in adolescence and proinflammatory phenotypes 20 years later

Although the biological embedding model of adversity proposes that stressful experiences in childhood create a durable proinflammatory phenotype in immune cells, research to date has relied on study designs that limit our ability to make conclusions about whether the phenotype is long-lasting. The present study leverages an ongoing 20-year investigation of African American youth to test research questions about the extent to which stressors measured in childhood forecast a proinflammatory phenotype in adulthood, as indicated by exaggerated cytokine responses to bacterial stimuli, monocyte insensitivity to inhibitory signals from hydrocortisone, and low-grade inflammation. Parents reported on their depressive symptoms and unsupportive parenting tendencies across youths' adolescence. At age 31, youth participants (now adults) completed a fasting blood draw. Samples were incubated with lipopolysaccharide and doses of hydrocortisone to evaluate proinflammatory processes. Additionally, blood samples were tested for indicators of low-grade inflammation, including IL-6, IL-8, IL-10, and TNF-α, and soluble urokinase plasminogen activator receptor. Analyses revealed that parental depression across youths' adolescence prospectively predicted indicators of proinflammatory phenotypes at age 31. Follow-up analyses suggested that unsupportive parenting mediated these associations. These findings suggest that exposure to parental depression in adolescence leaves an imprint on inflammatory activity that can be observed 20 years later.

Three common assumptions about inflammation, aging, and health that are probably wrong

Chronic inflammation contributes to the onset and progression of cardiovascular disease and other degenerative diseases of aging. But does it have to? This article considers the associations among inflammation, aging, and health through the lens of human population biology and suggests that chronic inflammation is not a normal nor inevitable component of aging. It is commonly assumed that conclusions drawn from research in affluent, industrialized countries can be applied globally; that aging processes leading to morbidity and mortality begin in middle age; and that inflammation is pathological. These foundational assumptions have shifted focus away from inflammation as a beneficial response to infection or injury and toward an understanding of inflammation as chronic, dysregulated, and dangerous. Findings from community-based studies around the world-many conducted in areas with relatively high burdens of infectious disease-challenge these assumptions by documenting substantial variation in levels of inflammation and patterns of association with disease. They also indicate that nutritional, microbial, and psychosocial environments in infancy and childhood play important roles in shaping inflammatory phenotypes and their contributions to diseases of aging. A comparative, developmental, and ecological approach has the potential to generate novel insights into the regulation of inflammation and how it relates to human health over the life course.

Measuring food insecurity: An introduction to tools for human biologists and ecologists

OBJECTIVE

Food insecurity is a significant and growing concern undermining the wellbeing of 30% of the global population. Food in/security is a complex construct consisting of four dimensions: availability, access, utilization, and stability, making it challenging to measure. We provide a toolkit human biologists/ecologists can use to advance research on this topic.

METHODS

We review the strengths and limitations of common tools used to measure food access and utilization, the two dimensions most proximate to people's lived experience, and emphasize tools that provide data needed to best link food security with human biological outcomes. We also discuss methods that provide contextual data human biologists/ecologists will find useful for study design, ensuring instrument validity, and improving data quality.

RESULTS

Food access is principally measured using experience-based instruments that emphasize economic access. Social access, such as food sharing, is under-studied and we recommend using social network analysis to explore this dimension. In terms of utilization, emphasis has been on food choice measured as dietary diversity. Food preparation and intrahousehold distribution, also part of the utilization dimension, are less studied and standardized instruments for measuring both are lacking. The embodiment of food insecurity has focused on child growth, although a growing literature addresses adult mental wellbeing and chronic and infectious disease risk.

CONCLUSIONS

We see the potential to expand outcomes to include reproductive and immune function, physical activity, and the gut microbiome. Human biologists/ecologists are well-positioned to advance understanding of the human health impacts of food insecurity and provide data to support intervention efforts.

A highly sensitive multiplex immunoassay for inflammatory cytokines in dried blood spots

OBJECTIVES

Inflammatory cytokines are key regulators of inflammation, but current measurement approaches require venous blood to quantify low circulating concentrations associated with chronic, low-grade inflammation. This article describes a highly sensitive multiplex immunoassay protocol for the measurement of IL6, IL8, IL10, and TNFα in finger stick dried blood spot (DBS) samples.

METHODS

The protocol uses a multiplex electrochemiluminescent immunoassay platform. The following measures of assay performance were evaluated: reliability (inter-assay percent coefficient of variation; %CV), precision (intra-assay %CV), lower limit of detection (LLD), linearity of dilution, and agreement with results from matched plasma samples.

RESULTS

Analysis of three control samples across the assay range indicated an acceptable level of precision and reliability for each cytokine. Linearity of dilution returned average values that ranged from 104.1 to 127.6% of expected. Lower limits of detection for IL6, IL8, and IL10 were <0.5, and <1.0 pg/ml for TNFα. Level of agreement in results between matched DBS and plasma samples was high for all cytokines except for IL8.

CONCLUSIONS

Finger stick DBS sampling provides a viable alternative to venipuncture for the quantification of IL6, IL10, and TNFα at low concentrations associated with chronic inflammation. The presence of red blood cells may interfere with the quantification of IL8 in DBS. In facilitating blood collection in nonclinical settings this method can advance scientific understandings of how social and ecological contexts shape immune function and health over the life course.