Structural and Functional Alterations of MAMs and Their Immunomodulatory Roles in Sepsis-Induced Lung Injury.

BACKGROUND

Sepsis-induced acute lung injury (SI-ALI) is a major cause of morbidity and mortality among septic patients. Recent evidence highlights the role of mitochondria-associated membranes (MAMs)-specialized contact sites between the endoplasmic reticulum (ER) and mitochondria-in regulating calcium signaling, lipid metabolism, energy homeostasis, and immune responses. Structural and functional alterations of MAMs are increasingly recognized as critical contributors to the pathogenesis of SI-ALI.

OBJECTIVES

This review aims to summarize the structural and functional characteristics of MAMs, elucidate their alterations and immunoregulatory roles in sepsis-induced lung injury, and discuss potential therapeutic strategies targeting MAMs to mitigate pulmonary damage.

METHODS

A comprehensive literature review was conducted using recent studies focused on the molecular structure, signaling mechanisms, and pathological changes of MAMs in sepsis and related inflammatory diseases. Emphasis was placed on calcium signaling, mitochondrial dysfunction, oxidative stress, and inflammasome activation.

RESULTS

MAMs maintain close ER-mitochondria contacts (10-30 nm) through key proteins such as inositol 1,4,5-trisphosphate receptor (IP3R), glucose-regulated protein 75 (GRP75), voltage-dependent anion channel (VDAC), and mitofusin-2 (MFN2). During sepsis, oxidative stress and inflammatory cytokines disrupt these contacts, leading to impaired calcium transfer, mitochondrial dysfunction, and energy deficiency. Dysregulated MAMs promote NLR family pyrin domain containing 3 (NLRP3) inflammasome activation, excessive reactive oxygen species (ROS) production, and mitochondrial DNA (mtDNA) release, thereby amplifying inflammatory cascades and immune cell apoptosis. Therapeutic strategies that restore MAM integrity-such as upregulating MFN2, activating ER autophagy, or modulating calcium transport proteins-have shown potential to attenuate lung injury by improving mitochondrial metabolism and reducing oxidative stress.

CONCLUSIONS

MAMs play essential roles in maintaining intracellular homeostasis and immune balance. Their structural and functional disruption contributes significantly to the progression of SI-ALI. Targeting MAMs offers promising therapeutic opportunities for preventing and treating sepsis-induced lung injury, although further mechanistic and clinical studies are warranted to translate these findings into practice.