Kupffer cells capture transplanted mitochondria to prevent liver injury and inflammation

Author(s):
Avinash Mukkala; Bruna David; Menachem Ailenberg; Jady Liang; Chirag Vaswani; Danielle Karakas; Rachel Goldfarb; William Barbour; Avishai Gasner; Ruoxian Wu; Raluca Petrut; Mirjana Jerkic; Ana Andreazza; Heyu Ni; Claudia dos Santos; Haibo Zhang; Andras Kapus; Paul Kubes; Ori Rotstein

Background:

Liver ischemia/reperfusion (I/R)-induced injury and inflammation is a pathophysiology that is relevant in the clinical contexts of hemorrhagic shock/resuscitation, elective liver surgery and organ transplantation. One common pathogenic event in I/R is mitochondrial dysfunction, characterized by depolarization of the mitochondrial potential, elaboration of reactive free radicals, and the depletion of cellular ATP. Recently, mitochondrial transplantation has emerged as an innovative therapeutic in various animal models of I/R. Complement receptor of the immunoglobulin superfamily (CRIg/VSIG4), is an immunoreceptor which recognizes opsonized bacteria, and has previously been shown to be engaged in anti-inflammatory signaling in I/R.

Hypothesis:

We hypothesized that CRIg/VSIG4 mediates the hepatoprotective effects of MTx in liver I/R.

Methods:

An in vivo murine model of 70% liver I/R was utilized to study the efficacy of MTx, and knockout/transgenic mouse models were used to interrogate the potential mechanism of hepatoprotection.

Results:

We determined that MTx was markedly hepatoprotective in liver I/R, and systemically anti-inflammatory. Moreover, MTx in liver I/R diminished the exudation of neutrophils into the lung alveolar space, and permeation of neutrophils into the liver sinusoids. Using intravital imaging of the in vivo mouse liver sinusoids, we discovered that I/R-subjected Kupffer cells (KCs), rapidly captured transplanted mitochondria, and shortly acidified mitochondria within intracellular lysosomal compartments. Next, to specifically understand the role of KCs, we depleted KCs in the diphtheria toxin inducible Clec4f/iDTR transgenic mouse, induced I/R, and revealed that indeed KCs are necessary for the hepatoprotective and anti-inflammatory effects of MTx. Finally, we induced I/R with or without MTx, in CRIg knockout mice and found that there was both loss of mitochondria capture by Kupffer cells and loss of hepatoprotection. In addition, I/R-subjected CRIg knockout mice showed greater injury and inflammation when transplanted with mitochondria.

Conclusions:

In this manner, we demonstrated that CRIg-dependent capture of mitochondria by I/R-subjected Kupffer cells is a hepatoprotective mechanism for MTx in vivo. These studies identify a novel treatment regimen in liver I/R and a potential molecular/cellular target which exerts the beneficial effects of MTx.