Exploring the in vitro potential of bioactive compounds in relation to age-related immune dysfunction

The aging process is a complex and multifaceted phenomenon influenced by a combination of genetic, environmental, and behavioural factors. A major challenge of aging is the heightened frailty and increased risk of age-related diseases, including cardiovascular, neurological, metabolic, and cognitive disorders. Central to the aging process are two interconnected mechanisms: inflamm-aging and immunosenescence, which play critical roles in the progression of these conditions. Inflamm-aging refers to a chronic, low-grade inflammation that develops with age. Immunosenescence is a progressive decline in immune system function, making the body more vulnerable to infections and less capable of efficiently responding to new threats. Both phenomena are closely interconnected and contribute to the progressive loss of the immune system’s ability to respond effectively to immunological challenges, including vaccination. Consequently, older individuals are more vulnerable to infectious diseases and potential adverse events related to immunisation, highlighting the importance of identifying strategies aimed at improving immune responses in advanced age.This PhD thesis explores strategies involving natural compounds as geroprotectors, which may slow, halt, or even reverse the biological processes of aging. Another key approach focuses on targeting molecular pathways linked to the immune-inflammatory response associated with aging, aiming to mitigate or reverse this physiological process. The primary goal of this study is to expand our understanding of natural compounds that could slow aging and reduce the impact of immune-related changes associated with aging.Among the many molecules capable of modulating key aging markers, some substances contained in natural products like Rhus coriaria Linn (known as sumac) or found in olive tree products, such as those derived from the fruits and leaves of Olea europaea Linn, are of great interest and will be discussed in this thesis.Sumac, a plant often considered invasive in southern Italy, is widespread across the Mediterranean basin and has long been valued for its organoleptic and health-promoting properties. Traditionally used as a powdered spice in both culinary and medicinal practices since ancient times, it remains a staple in Middle Eastern cuisine. However, recently, its nutraceutical potential has garnered increasing attention. This promising aspect will be a central focus of future research, as detailed in the section on future perspectives in this thesis.Oleuropein and oleocanthal, two polyphenolic compounds isolated from Olea europaea Linn, have attracted significant attention for their potential health benefits and influence several molecular pathways that are implicated in inflammation and oxidative stress. Oleuropein and oleocanthal are believed to modulate mechanisms linked to immune system function, and oxi-inflammation, all of which play critical roles in age-related cellular damage and disease. Their effects on these pathways make them promising candidates for potentially slowing the progression of age-related conditions related to immune dysfunction. Considering their potential action on the main trait of immune aging, the immunomodulatory potential of oleuropein and oleocanthal on immune cell populations obtained from healthy subjects was evaluated. Specifically, it has been evaluated the anti-inflammatory and antioxidant effects of oleuropein in Peripheral Blood Mononuclear Cells (PBMCs) derived from subjects divided into two age groups (young adults, 21-35 years, and older adults over 60 years) who received influenza vaccination. The cells were stimulated with viral peptides and treated with oleuropein, either alone or in combination with the p38-mitogen-activated protein kinase inhibitor BIRB 796, to evaluate their potential as additives in influenza vaccine formulations. The goal was to reduce the baseline inflammatory and oxidative state characteristic of older adults (oxi-inflamm-aging), thereby minimizing potential vaccine-related side effects in this population. Cytokines-producing T cells have been determined through flow cytometry, while the oxidative status was evaluated with a fluorometric assay. This was correlated with the evaluation of the immunophenotype by flow cytometry and antibody response in subjects undergoing vaccination, to study the possible effects of aging on cellular and humoral immune responses. With the same main objective, the modulatory action of oleocanthal was evaluated on the differentiation, activation, and functionality of monocyte-derived dendritic cells obtained from PBMCs of healthy subjects. Oleocanthal activity was also tested on monocyte-derived dendritic cells induced to mature with Lipopolysaccharide of Escherichia Coli. The results obtained suggest the potential of these compounds in regulating the immune response, which could be applied in the development of new vaccine formulations or immune-based therapies to be administered to the older population.The articles presented in this thesis represent a selection related to the experimental project pursued during the three years of the doctoral programme. The remainder of the scientific activity is summarised at the end of this work and includes the evaluation of the molecular and immunological mechanisms related to longevity and healthy aging.