Inflammation and Late-Life Depression: Unraveling the Complex Relationship and Potential Therapeutic Strategies

The origins of late-life depression are multifaceted and remain challenging to fully understand. While the traditional monoamine neurotransmitter hypothesis provides some insights, it falls short in explaining the disease's onset and progression, leaving treatments often less than optimal. There is an emergent need to uncover new underlying mechanisms. Among these, the "inflammation hypothesis" has been gaining traction in scientific discussions regarding late-life depression. There is compelling evidence linking inflammation processes to the emergence of this form of depression. This review delves into the nuanced relationship between inflammation and late-life depression, emphasizing the pivotal role and implications of inflammation in its pathogenesis. Changes in Ca2+ homeostasis, cytokine levels, brainderived neurotrophic factor (BDNF), white cell ratios, and the involvement of the NOD-, LRR-, and Pyrin domain-containing protein 3 (NLRP3) inflammasome have all been suggested as potential biomarkers that tie inflammation to late-life depression. Furthermore, factors such as aging-induced DNA damage, oxidative stress, mitochondrial impairments, disruptions in the hypothalamic-pituitary-adrenal axis, activated microglia and associated neuroinflammation, as well as the gut-brain axis dynamics, could serve as bridges between inflammation and depression. Deepening our understanding of these connections could usher in innovative anti-inflammatory treatments and strategies for late- life depression.