Research

The research focus areas in the Moeckel lab are centered on the cellular biology of regeneration from cell injury and its role in preventing AKI progression to chronic kidney disease (CKD):

1. Cell survival and regeneration mechanisms after ischemic/hypoxic injury: the focus is on the role of autophagy and mitochondrial regeneration in preventing cell death mechanisms.
2. The role of impaired autophagy in progression of chronic kidney disease (CKD): the pleiotropic cytokines MIF and D-DT induce autophagy-mediated repair mechanisms which enhance recovery from injury and prevent progression of tubular atrophy and interstitial fibrosis.
3. Cell-cell interaction between intrinsic progenitor cells and tubular epithelial cells: Damage-associated molecular profiles (DAMPS) stimulate signaling pathways and cytokine excretion in progenitor cells, such as the medullary interstitial cells (MICs), which mediate cell regeneration and repair and prevent progression of fibrosis.

Macrophage migration inhibitory factor (MIF) is an inflammatory and stress-regulating cytokine that has been shown to protect the heart from ischaemia-reperfusion injury by attenuating myocyte oxidative stress, reducing infarct size and preserving cardiac function. MIF-2/D-DT shares 34% sequence identity with MIF and also has been shown to be cytoprotective in ischaemia-reperfusion injury in various cell types. Both MIF and MIF-2/D-DT signal through the cognate MIF cytokine superfamily receptor CD74 to which MIF-2/D-DT is a more selective agonist. CD74 is a transmembrane glycoprotein that regulates cell proliferation, cell survival and secretion of inflammatory mediators in a variety of cells. MIF-2/D-DT binding to CD74 protects heart and liver tissue from ischemia/reperfusion injury. Previous studies have shown that MIF acts through the phosphatidylinositol 3-kinase (PI3K)-RAC- serine/threonine protein kinase (Akt) signaling pathway to promote cellular resistance to ischemia, hypoxia and glucose deprivation in mesenchymal stem cells (MSC). This stimulation of the PI3K-Akt pathway by MIF was CD74-dependent. Stimulation of this signaling pathway by MIF rescues mesenchymal stem cells from DOXO-induced cell senescence.

A recent study in our lab has shown a cytoprotective effect of MIF-2/D-DT treatment in a mouse ischemia-reperfusion model in vivo and also in hypoxic mouse proximal tubule cells in vitro. This study showed that MIF-2/D-DT treatment induces autophagy by activating of eIF2α, which stimulates expression of the ATF4 transcription factor and known driver of autophagosome formation. Phosphorylation of eIF2α and subsequent stimulation of ATF4 expression are part of the unfolded protein response (UPR). The UPR enhances protein folding capacity in the ER and eliminates unfolded/misfolded proteins to maintain ER homeostasis under cell stress conditions. The UPR is mediated by three main stress sensors located in the ER membrane including ATF6, PERK and IRE1. While PERK activation initiates eIF2 and ATF4 responses, activation of IRE1 controls the expression of the transcription factor XBP1, a key effector of the UPR in mammalian cells, which regulates gene expression to maintain ER function. XBP1 activation leads to upregulation of genes related to quality control of protein folding. These mechanisms have the potential to ameliorate the tissue damage caused by severe ischemic injury.

The morphology of mitochondria is under constant change due to ongoing fission and fusion processes and is a fundamental requirement for normal mitochondrial function. Despite the obvious importance of mitochondrial dynamics in cell homeostasis, the physiological role of mitochondrial fusion in cell survival is still poorly understood. The human p62 protein performs a variety of functions including targeting proteins to autophagy. A recent study showed that p62-mediated mitochondrial clustering suppresses cell death. Optic atrophy 1 (OPA1) is a dynamin-related GTPase that is responsible for fusion of the inner and outer mitochondrial membrane following injury. While mice lacking OPA1 die at an early embryonic state, point mutations in OPA1 lead to dominant optic atrophy in humans. A recent study has shown that cell stress stimulates mitochondria to form a highly interconnected network, called stress-induced mitochondrial hyper-fusion (SIMH), which confers resistance upon stressed cells. The study further showed that OPA1 was required to mediate this pro-survival response against different cell stresses. We observed that MIF-2/D-DT treated human kidney cells showed ultrastructural evidence of mitochondrial hyper-fusion and repair.

Students and post-docs in my lab are exposed to a wide variety of physiologic, biochemical, cell biological, molecular and cell biology experimental protocols as well as different transgenic and knock-out technologies to generate animal models for tubular injury regeneration. Moreover, the student will be exposed to human kidney biopsy material in an attempt to correlate findings in the animal and cell culture models with actual pathological mechanisms in patient kidney biopsy tissue.