Necrosis by Sodium Overload (NECSO)

1.1 Mechanism Overview

Necrosis by sodium overload (NECSO) represents a novel metal/ion‑dependent regulated cell death driven by disrupted intracellular Na⁺ homeostasis, which is characterized by osmotic collapse, energy exhaustion and secondary ionic toxicity triggered by aberrant sodium accumulation. Under physiological conditions, cells maintain intracellular Na⁺ homeostasis via Na⁺/K⁺‑ATPase, Na⁺/H⁺ exchanger 1 (NHE1), voltage‑gated sodium channels (Nav), transient receptor potential channel TRPM4 and other transporters. Abnormal activation or impairment of these ion regulatory systems triggers sustained Na⁺ influx and elevates cytoplasmic Na⁺ concentrations. This forces Na⁺/K⁺‑ATPase to continuously consume ATP to sustain ionic gradients, eventually resulting in severe energy depletion. Once sodium accumulation exceeds cellular buffering capacity, osmotic equilibrium collapses, massive water influx occurs, leading to cellular swelling, organelle distension and disrupted plasma membrane integrity, presenting typical necrotic morphological features.

Meanwhile, sodium overload provokes secondary Ca²⁺ influx via reverse‑mode operation of the Na⁺/Ca²⁺ exchanger (NCX), aggravating mitochondrial Ca²⁺ burden, loss of mitochondrial membrane potential, reactive oxygen species (ROS) accumulation and mitochondrial functional failure. Furthermore, Na⁺‑mediated cellular stress initiates lysosomal injury and inflammatory signaling cascades, including CTSB release, NLRP3 inflammasome activation and GSDMD‑dependent pore formation, which further amplify cell lysis and inflammatory responses. Accordingly, the execution cascade of NECSO can be summarized as: disrupted Na⁺ homeostasis → ATP depletion → osmotic collapse → secondary Ca²⁺ overload → mitochondrial damage → inflammatory necrosis.

NECSO Mechanism Diagram. Necrosis by sodium overload (NECSO) is initiated by massive Na⁺ influx and disrupted sodium homeostasis, triggering ATP depletion and osmotic collapse. Subsequently, Na⁺/Ca²⁺ exchanger (NCX)‑mediated calcium overload, mitochondrial dysfunction and amplified inflammatory signaling cascades occur, ultimately leading to necrotic plasma membrane rupture.

1.2 Target List

Mechanism Module	Target (Gene/Protein)	Full Name	Biological Function	Mechanism in Na⁺‑dependent Cell Death	Research Value / Detection Index
Na⁺ Overload (Core Event)	TRPM4	Transient receptor potential melastatin 4	Calcium‑activated non‑selective cation channel mediating Na⁺ influx	Excessive activation promotes Na⁺ entry and intracellular Na⁺ accumulation	Marker of Na⁺ influx activation
	Nav1.5 (SCN5A)	Sodium voltage‑gated channel alpha subunit 5	Voltage‑gated sodium channel responsible for Na⁺ transport	Increased sodium channel activity contributes to Na⁺ overload	Indicator of sodium channel activation
	NHE1 (SLC9A1)	Sodium/hydrogen exchanger 1	Exchanges intracellular H⁺ for extracellular Na⁺ to regulate intracellular pH	Enhanced Na⁺/H⁺ exchange increases intracellular Na⁺ accumulation	Marker of Na⁺ influx regulation
	Na⁺/K⁺‑ATPase (ATP1A1)	Sodium/potassium‑transporting ATPase alpha‑1 subunit	Maintains Na⁺ and K⁺ gradients through ATP‑dependent ion transport	Initially compensates for Na⁺ overload by promoting Na⁺ extrusion, but fails during late‑stage injury	Indicator of Na⁺ homeostasis disruption
Energy Metabolic Collapse	ATP5A	ATP synthase F1 subunit alpha	Catalyzes ATP synthesis through oxidative phosphorylation	Mitochondrial dysfunction reduces ATP production capacity	Marker of mitochondrial energy failure
	p‑AMPK	Phosphorylated AMP‑activated protein kinase	Energy stress sensor regulating metabolic adaptation	Activated during ATP depletion and cellular energy crisis	Energy stress indicator
	COX4	Cytochrome c oxidase subunit 4	Component of mitochondrial respiratory Complex IV involved in oxygen consumption	Impaired respiratory chain decreases oxidative phosphorylation efficiency	Respiratory chain damage marker
	NDUFS1	NADH dehydrogenase [ubiquinone] Fe‑S protein 1	Core component of mitochondrial Complex I involved in electron transfer	Dysfunction disrupts electron transport and mitochondrial respiration	Complex I functional marker
Na⁺‑Ca²⁺ Coupled Injury	NCX1 (SLC8A1)	Sodium/calcium exchanger 1	Exchanges intracellular Ca²⁺ and extracellular Na⁺ to regulate calcium homeostasis	Reverse‑mode activation promotes Ca²⁺ influx and secondary calcium overload	Marker of Na⁺/Ca²⁺ exchange dysfunction
	SERCA2	Sarco/endoplasmic reticulum Ca²⁺‑ATPase 2	Pumps Ca²⁺ into the endoplasmic reticulum and maintains Ca²⁺ homeostasis	Reduced activity contributes to intracellular Ca²⁺ accumulation	Calcium homeostasis marker
Mitochondrial Injury	JC‑1 / TMRE	Mitochondrial membrane potential fluorescent probes	Detect mitochondrial membrane potential (ΔΨm)	Na⁺ overload induces mitochondrial depolarization and dysfunction	Detection of mitochondrial membrane potential loss
	ROS / MitoSOX	Reactive oxygen species / mitochondrial superoxide indicator	Detect mitochondrial oxidative stress	Mitochondrial dysfunction increases ROS production	Oxidative stress indicator
	HMOX1	Heme oxygenase 1	Antioxidant enzyme involved in cellular stress response	Activated as a protective response to oxidative stress	Oxidative stress response marker
	NQO1	NAD(P)H quinone dehydrogenase 1	Antioxidant and detoxification enzyme	Reflects activation of cellular antioxidant defense	Antioxidant response marker
	TOM20	Translocase of outer mitochondrial membrane 20	Mediates mitochondrial protein import and reflects mitochondrial integrity	Altered distribution indicates mitochondrial structural damage	Mitochondrial integrity marker
	COX4	Cytochrome c oxidase subunit 4	Maintains respiratory Complex IV function	Reduced expression reflects mitochondrial respiratory injury	Mitochondrial damage marker
Osmotic Collapse (NECSO Hallmark Event)	Cell swelling	Cellular volume expansion	Morphological consequence of ionic imbalance	Na⁺ accumulation drives osmotic water influx and cellular swelling	Hallmark morphological feature
	PI uptake	Propidium iodide uptake	Detects loss of membrane integrity	Increased membrane permeability occurs during terminal necrotic damage	Cell death validation marker
	LDH release	Lactate dehydrogenase release	Reflects plasma membrane rupture	Indicates terminal necrotic membrane damage	Necrotic cell death marker
Lysosomal Damage	CTSB	Cathepsin B	Lysosomal cysteine protease involved in protein degradation	Lysosomal injury causes CTSB release and amplifies cell death signaling	Marker of lysosomal membrane damage
Inflammatory Amplification	NLRP3	NLR family pyrin domain containing 3	Forms inflammasome complexes in response to cellular stress	Activation promotes inflammatory cell death signaling	Inflammasome activation marker
	Caspase‑1	Cysteine‑aspartic acid protease 1	Inflammatory caspase responsible for IL‑1β/IL‑18 maturation	Activation promotes inflammatory amplification	Marker of inflammasome activation
	GSDMD‑N	Gasdermin D N‑terminal domain	Forms membrane pores after GSDMD cleavage	Mediates membrane rupture and inflammatory cell death execution	Pyroptosis‑like execution marker
DAMP Release / Terminal Necrosis	HMGB1	High mobility group box 1 protein	Nuclear DNA‑binding protein released during necrotic cell death	Release indicates inflammatory necrosis and DAMP signaling	DAMP release marker
	IL‑1β	Interleukin‑1 beta	Pro‑inflammatory cytokine	Increased secretion reflects inflammatory activation	Inflammatory output marker
	IL‑18	Interleukin‑18	Cytokine involved in immune activation	Released during inflammasome‑associated cell death	Inflammatory cytokine marker

1.3 Application Scheme

Judgement Purpose	Recommended Marker Panel
Na⁺ overload	Na⁺ probe + TRPM4 + NHE1
Disrupted ion homeostasis	Na⁺/K⁺‑ATPase + NCX1
Secondary Ca²⁺ injury	Ca²⁺ probe + NCX1
Mitochondrial damage	ROS + ΔΨm + COX4/ATP5A
Necrosis occurrence	LDH + PI + HMGB1
Inflammatory amplification	NLRP3 + GSDMD‑N

1.4 References

1. Hu H, Chen Z, Li Y, Peng J, Cao J, Zhou H, Wang M, Du Y, Wu H, Zhao H, Huang S, Yu D, Liu M, Shevchenko OV, Matveeva NY, Yang Y, Huang K, Lv D, Min J, Chen L, Wang F. Metal‑dependent regulated cell death: Molecular architecture and translational frontiers. Imeta. 2026 Jul 6;5(3):e70141. doi: 10.1002/imt2.70141. PMID: 42491529; PMCID: PMC13377419.