Disruption of mitochondria-associated ER membranes: a novel mechanism for high-salt diet-exacerbated hemorrhagic shock-induced lymphatic dysfunction

BACKGROUND: Although high-salt diet (HSD) impairs cardiovascular function, its impact on the prognosis of hemorrhagic shock (HS) has not been elucidated. Impaired mesenteric lymphatic contractility post-HS contributes to an unfavorable prognosis. Since mitochondria-associated endoplasmic reticulum membranes (MAMs) regulate calcium-dependent contraction, we hypothesized that HSD exacerbates HS-induced lymphatic dysfunction by damaging MAM integrity in lymphatic smooth muscle cells (LSMCs). METHODS: Male Wistar rats were fed either a normal diet (ND) or HSD containing 8% NaCl for 8 weeks. A conscious rat model of fixed-pressure HS (40 mmHg for 90 min) with resuscitation was established. The rats were divided into four groups: ND+SS, ND+HS, HSD+SS, and HSD+HS. Additional HS groups were treated with either the IP3R1 inhibitor 2-APB (HSD+HS+2-APB) or the IP3R1 activator CdCl 2 (ND+HS+CdCl 2 ). Survival time and in vivo and ex vivo mesenteric lymphatic contractility were assessed. The ultrastructure and protein expression of MAM were analyzed. RESULTS: HSD significantly increased blood pressure but not body weight and markedly reduced survival time after HS. HSD alone impaired mesenteric lymphatic contractility and exacerbated HS-induced contractile and reactive dysfunction. HS and HSD independently shortened the contact distance and increased the contact coefficient of MAM in LSMCs, with combined exposure producing the most severe disruption. These structural alterations were accompanied by increased protein expression of IP3R1 and VDAC1. Importantly, therapeutic inhibition of MAM with 2-APB in HSD+HS rats improved survival, restored lymphatic contractility, and normalized MAM structure and protein expression. Conversely, pharmacological aggravation of MAM with CdCl 2 in ND+HS rats worsened survival and lymphatic function, paralleling MAM disruption. CONCLUSION: Chronic HSD is a risk factor for poor outcomes after HS, worsening both survival and mesenteric lymphatic function by disrupting MAM integrity in LSMCs. Targeting MAM, exemplified by IP3R1 inhibition, represents a novel therapeutic strategy for mitigating shock-induced lymphatic dysfunction, particularly in salt-sensitive populations.