In newborn brain injury, one cell-death pathway splits in two: one arm summons mitochondrial cleanup, the other causes the damage — in mouse neurons and a neonatal mouse model

Edited by Samael A. Tejada, Founder & Editor-in-Chief

A pathway named for killing cells turns out to moonlight as the call that summons the mitochondrial cleanup crew — and the protein that actually executes the killing is a different one, on the other side of the ledger. For a field shopping for drug targets in newborn brain injury, that fork is the whole story.

What did the injury switch on?

Wu and colleagues modeled ischemia-reperfusion injury with oxygen-glucose deprivation and reperfusion (OGD/Rep) in mouse primary neurons and mouse neuroblastoma Neuro-2a cells. The insult activated necroptosis: phosphorylation of MLKL increased and necrosome components translocated to mitochondria. In parallel, the cells induced mitophagy — upregulation of Parkin and BNIP3, increased mitochondrial conversion of LC3A/B-II, and induction of ClpP, a mitochondrial protease. In a neonatal mouse model of HIE, hypoxia-ischaemia challenge concurrently activated necroptosis and mitophagy pathways in the hippocampus, and spatial transcriptomics revealed region-specific signatures of necroptosis-related mitochondrial stress and mitophagy across hippocampus and cortex. The two programs, in other words, are anatomically and temporally intertwined in the living newborn brain, not just in the dish.

Where exactly is the fork?

The divergence is the paper's core finding. Pharmacological inhibition of RIPK1 or RIPK3 — the kinases at the top of the necroptosis cascade — attenuated the OGD/Rep-induced mitophagy, which means that arm of the pathway promotes the mitochondrial quality-control response: it is, functionally, part of the rescue. MLKL behaves oppositely. Knocking MLKL down enhanced mitophagy while similarly suppressing ClpP induction, and it restored mitochondrial function and morphology. So within one named pathway, the upstream kinases help mitochondria get cleaned up while the downstream executioner contributes to mitochondrial dysfunction. The authors' conclusion is measured: a previously unrecognized divergence within the necroptosis cascade, and a mechanistic rationale for targeting distinct components — not the pathway as a whole — in HIE and related ischemia-reperfusion injuries.

Why does the distinction matter for treatment hunting?

Necroptosis inhibitors are an active drug-development area, and the naive strategy — block the pathway, save the brain — is exactly what this paper complicates. A drug that inhibits RIPK1 or RIPK3 might reduce necroptotic death signaling while simultaneously weakening the mitophagy that clears damaged mitochondria after the injury, potentially trading one harm for another. An MLKL-directed strategy, by contrast, aligned in these models with more cleanup and restored mitochondrial function. None of that is a treatment: the evidence is mouse neurons, a mouse cell line and newborn mice, HIE care today still rests on therapeutic hypothermia and supportive care, and no compound was tested as a therapy here. What the study changes is the map drug hunters draw from — and maps are what the next experiments are built on.

Where the evidence stands

• Established: Hypoxic-ischaemic encephalopathy is a devastating newborn brain injury; necroptosis is a programmed cell-death pathway running through RIPK1, RIPK3 and MLKL; and mitophagy (involving Parkin and BNIP3) is the cell's mitochondrial quality-control cleanup.
• Preliminary: In mouse primary neurons, Neuro-2a cells and a neonatal mouse HIE model (Cell Death & Disease, Nov 3, 2026; DOI 10.1038/s41419-026-09382-w), injury activated necroptosis and mitophagy together; RIPK1/RIPK3 inhibition attenuated mitophagy, while MLKL knockdown enhanced mitophagy and restored mitochondrial function and morphology.
• Absent: Human tissue or patient data, any tested drug or treatment, and any evidence in larger-animal or clinical models of HIE.