Microglia serve as the principal immune cells of the central nervous system, maintaining brain homeostasis by exerting immunosurveillance and clearance of misfolded proteins, pathogens, and cellular debris [
37]. In AD, resident resting microglia are activated and migrate to regions of Aβ plaques to facilitate their clearance. TUS has been demonstrated to enhance the phagocytic activity of microglia to clear Aβ deposits [
22,
38]. Corroborating these findings, our in vivo and in vitro results revealed a significantly higher ratio of recruited microglia to Aβ plaque phagocytosis within the US-treated group (Figs.
4 and
6), suggesting an enhanced capacity for Aβ clearance. Importantly, TUS intervention did not significantly alter the expression of key genes in the amyloidogenic pathway, including the rate-limiting enzymes BACE1 and PSEN1 (Fig. S4). These results indicate that the observed plaque reduction was driven primarily by enhanced clearance mechanisms rather than suppressed production. Additionally, microglia are mechanosensitive cells capable of responding to alterations in the extracellular mechanical milieu [
39]. Previous studies indicate that tissue stiffness is elevated in Aβ plaque-associated regions, accompanied by a selective up-regulation of the mechanosensitive ion channel Piezo1 in associated microglia [
40]. Acoustic radiation force generated by ultrasound has been demonstrated to modulate the activity of such mechanosensitive channels [
41]. Furthermore, research suggests that ultrasound may directly excite neurons by inducing nanoscale cavitation events within the lipid bilayer of the cell membrane, even in the absence of microbubbles [
42]. In the present study, the mechanical index (MI) of the ultrasound applied was maintained below 1.9, a threshold considered sufficient to avoid significant inertial cavitation [
43]. Given the only mild intracranial temperature rise observed in our experiments (Fig. S3a), we propose that the primary bio-effective component of TUS under our conditions likely stems from its nonthermal mechanical force—specifically, acoustic radiation force—rather than from thermal or cavitation effects. This acoustic force may directly activate mechanosensitive molecules such as Piezo1 on the microglial membrane, thereby initiating downstream intracellular signaling that ultimately drives morphological remodeling, immune activation, and enhanced phagocytic function. Moreover, chronic activation of microglia results in the release of pro-inflammatory cytokines and chemokines that induce neuroinflammation, thereby exacerbating AD progression [
44].
RIPK1 is a multidomain serine/threonine kinase characterized by an N-terminal kinase domain, a C-terminal death domain, and an intermediary domain connecting the 2 [
45,
46]. Immunofluorescence staining of human AD postmortem cortical samples revealed a significant increase in
RIPK1, which positively correlated with the pathological progression of the disease [
47]. Moreover, elevated levels of
RIPK1 were observed in AD mouse models, with prominent expression in microglia in both murine and human brains [
29]. These findings were confirmed in this study (Figs. S6 and S7). A previous study revealed that
RIPK1 activation is crucial in microglia-mediated neuroinflammation linked to neurological disorders [
48]. Within
TNF-α signaling,
RIPK1 amplifies the inflammatory response by assembling a pivotal complex with partners like tumor necrosis factor receptor-associated death domain protein (TRADD) and tumor necrosis factor receptor associated factor 2 (TRAF2). This assembly is essential for
NF-κB pathway activation, which in turn drives the production of pro-inflammatory cytokines [
26,
27]. Given its role in driving neuroinflammatory and degenerative processes,
RIPK1 therefore emerges as a compelling target for AD intervention. Inhibition of
RIPK1 through pharmacological and genetic means has been confirmed to lower Aβ plaque and inflammatory cytokine within APP/PS1 mice, resulting in improved memory deficits. Furthermore,
RIPK1 inhibition could facilitate the breakdown of Aβ by microglia in vitro [
29]. Our findings indicated that TUS significantly down-regulated both
RIPK1 and phosphorylated
RIPK1 in the hippocampus of AD mice, thereby inhibiting the
NF-κB signaling pathway, which likely constitutes the alleviation of neuroinflammation (Fig.
5 and Fig. S6). Additionally, in our in vitro study, the regulatory effect of TUS on
RIPK1 in microglia was identified (Fig.
6). Importantly, this effect appears to be context dependent. As shown in Fig. S8, the same US applied to BV2 cells in the absence of Aβ did not significantly alter
RIPK1 expression or the release of key inflammatory cytokines. This contrast suggests that TUS does not intrinsically modulate microglial inflammatory signaling, but rather, its regulatory action on the
RIPK1/
NF-κB pathway is specifically engaged within the AD pathological milieu, likely in response to Aβ burden. Moreover,
RIPK1-induced necroptosis has been demonstrated to activate immune cells and enhance inflammatory responses [
49]. Its inhibition has been found to reduce neuroinflammation and improve both pathological and cognitive functions in AD [
29,
50]. Our integrated in vivo and in vitro findings revealed the inhibitory effect of TUS on necrotic apoptotic proteins (Figs.
5 and
6), which may contribute to the alleviation of neuroinflammation in AD and support the recovery of cognitive function.