MRI-guided pulsed focused ultrasound (pFUS) combined with systemic infusion of ultrasound contrast agent microbubbles (MB) causes localized blood-brain barrier (BBB) disruption that is currently being advocated for increasing drug or gene delivery in neurological diseases. The mechanical acoustic cavitation effects of opening the BBB by low-intensity pFUS+MB, as evidenced by contrast-enhanced MRI, resulted in an immediate damage-associated molecular pattern (DAMP) response including elevations in heat-shock protein 70, IL-1, IL-18, and TNFα indicative of a sterile inflammatory response (SIR) in the parenchyma. Concurrent with DAMP presentation, significant elevations in proinflammatory, antiinflammatory, and trophic factors along with neurotrophic and neurogenesis factors were detected; these elevations lasted 24 h. Transcriptomic analysis of sonicated brain supported the proteomic findings and indicated that the SIR was facilitated through the induction of the NFκB pathway. Histological evaluation demonstrated increased albumin in the parenchyma that cleared by 24 h along with TUNEL + neurons, activated astrocytes, microglia, and increased cell adhesion molecules in the vasculature. Infusion of fluorescent beads 3 d before pFUS+MB revealed the infiltration of CD68 + macrophages at 6 d postsonication, as is consistent with an innate immune response. pFUS+MB is being considered as part of a noninvasive adjuvant treatment for malignancy or neurodegenerative diseases. These results demonstrate that pFUS+MB induces an SIR compatible with ischemia or mild traumatic brain injury. Further investigation will be required before this approach can be widely implemented in clinical trials.pulsed focused ultrasound | microbubbles | blood-brain barrier | sterile inflammation | magnetic resonance imaging T he temporal proteomic profile in response to blood-brain barrier disruption (BBBD) consists of molecular features that are common across noninfectious insults such as ischemia, trauma, or autoimmune diseases (1-7). The main purpose of the bloodbrain barrier (BBB) is to maintain homeostasis, preventing the passive crossing of cells and molecules that could induce inflammation or damage to cells. The BBB consists of specialized endothelial cells connected through various tight junction proteins (TJP), astrocyte endplates, and a basement membrane. These components form part of the neurovascular unit (NVU) that is comprised of vessels, pericytes, microglia, astrocytes, and neurons along with the extracellular matrix (1,3,4,8). BBBD secondary to ischemia or trauma leads to increases in endothelial caveolae and down-regulation of TJP, transcytosis of plasma proteins (i.e., albumin), and vasogenic edema (1,6,(8)(9)(10)(11). The presence of albumin in the parenchyma following BBBD can activate astrocytes and microglia and induce the production of cytokines, chemokines, and trophic factors (CCTFs) and cell adhesion molecules (CAMs) as observed with a sterile inflammatory response (SIR) to injury (12-15). The release of CCTFs and inte...