Addressing critical gaps in understanding the in vivo behavior of polyethylene glycol (PEG)-based excipients, this study systematically elucidates the biological fate of methoxy-PEG₆-hydroxyl (M-PEG₆-OH) through comprehensive pharmacokinetic and metabolic investigations in rats. Employing a validated ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) methodology, we reveal distinctive biodistribution characteristics including rapid systemic clearance (Half-life (t 1/2 ) = 1.92 ± 1.16 h) and extensive tissue penetration (Apparent volume of distribution (V d ) = 0.84 ± 0.45 L/kg), suggesting efficient extravascular dissemination. Excretion pathways analysis demonstrated predominant renal elimination, with 59.03 % of the administered dose recovered in urine within 48 h post-IV injection, contrasting with minimal fecal excretion (0.99 %). Quantitative metabolite profiling identified M-PEG₅-CH₂COOH as the oxidative transformation product through terminal hydroxyl modification. The significantly higher relative abundance of metabolites (M-PEG 5 -CH 2 COOH) in urine compared to feces within the same time period provides critical insights into the biotransformation processes and metabolic pathways of the PEG polymer. These findings establish the first systematic evidence of metabolic trajectory and elimination mechanisms for M-PEG-OH, offering vital references for optimizing PEGylated drug delivery systems with enhanced biocompatibility and predictable safety profiles.
NLRP3 inflammasome is activated by diverse stimuli including infections, intracellular and environmental irritants. How NLRP3 senses these unrelated stimuli and what activates NLRP3 remain unknown. Here we report that signal-dependent NLRP3 phase separation initiated its activation, in which the palmitoyltransferase ZDHHC7-mediated tonic NLRP3 palmitoylation and an IDR region in the FISNA domain of NLRP3 play important roles. Moreover, three conserved hydrophobic residues in the IDR critically mediate multivalent weak interactions. NLRP3-activating stimuli including K + efflux and NLRP3-interacting molecules imiquimod, palmitate, and cardiolipin all cause NLRP3 conformational change and induce its phase separation and activation in cells and/or in vitro. Surprisingly, amphiphilic molecules like di-alcohols used to inhibit biomolecular phase separation and chemotherapeutic drugs doxorubicin and paclitaxel activate NLRP3 independently of ZDHHC7 by directly inducing NLRP3 phase separation. Mechanistically, amphiphilic molecules decrease the solubility of both palmitoylated and non-palmitoylated NLRP3 to directly induce its phase separation and activation while NLRP3 palmitoylation reduces its solubility to some extent without activation. Therefore, ZDHHC7-mediated NLRP3 palmitoylation in resting cells licenses its activation by lowering the threshold for NLRP3 phase separation in response to any of the diverse stimuli whereas NLRP3 solubility-reducing molecules like di-alcohols and chemotherapeutic drugs activate NLRP3 directly. The signal-induced NLRP3 phase separation likely provides the simplest and most direct mechanistic basis for NLRP3 activation.
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