Goji Berry Polysaccharides Shield Stressed Neurons by Restoring Ribosomal Protein RPLP1

Polysaccharides extracted from the goji berry, a fruit long used in traditional Chinese medicine, appear to protect laboratory-grown neurons from the kind of damage that follows a stroke, and the protection seems to hinge on a single ribosomal protein. In a new in vitro study published in Scientific Reports, researchers report that lycium barbarum polysaccharides, known as LBP, reduced apoptosis in mouse hippocampal neurons exposed to an ischemia-reperfusion-like environment, while simultaneously restoring levels of ribosomal protein lateral stalk subunit P1, or RPLP1, a component of the ribosome that was suppressed by the injury. The work was conducted entirely in cell culture, so the findings are preliminary laboratory observations rather than demonstrated clinical benefits.

The research team, led by Na Shao, Boya Ma, Yi Li, Xu Wang and Yarui Du, built a simplified model of ischemic stroke in dishes rather than in animals. They first exposed BV2 microglial cells, an immortalized mouse microglial cell line, to a inflammatory activation protocol: 24 hours of treatment with lipopolysaccharide, a bacterial molecule that drives pro-inflammatory activation, followed by eight hours of oxygen-glucose deprivation, a standard laboratory technique that starves cells of oxygen and glucose to mimic the interruption of blood supply. The researchers selected the eight-hour deprivation window based on preliminary tests showing that it triggered effective inflammatory secretion without causing massive microglial death, leaving roughly 72 percent of the BV2 cells viable. After the deprivation period, the cells recovered for 24 hours in normal culture conditions, and the inflammatory factors they released into the medium were collected, filtered and stored as a standardized insult for the next stage of the experiment.

That inflammatory supernatant was then applied to HT-22 cells, an immortalized mouse hippocampal neuronal cell line, at concentrations of 10, 25, 50 and 75 percent. The researchers screened the doses and settled on 25 percent supernatant combined with 100 micrograms per milliliter of LBP as the optimal intervention conditions for their formal experiments, concentrations chosen from prior screening data to be effective without being toxic. Before combining treatments, the team also tested LBP alone on healthy neurons at concentrations ranging from 10 micrograms per milliliter up to 1 milligram per milliliter over 72 hours, using a metabolic viability assay to identify the maximum non-cytotoxic dose. This dose-finding step matters because a protective compound that harms healthy cells would be of limited use, and the screening established that the chosen LBP concentration did not suppress the growth of unstressed neurons.

With the model established, the first set of results concerned cell proliferation and survival. In the CCK-8 viability assay, neurons exposed to the oxygen-glucose deprivation and reoxygenation conditions, abbreviated OGD/R, showed a significant drop in viability compared with normal controls, at a statistical threshold of P less than 0.01. Adding LBP significantly raised viability back up in the injured cultures. EdU staining, which labels cells that are actively synthesizing DNA, told the same story: the number of proliferating neurons fell sharply after the insult and was substantially restored by LBP treatment. These were measured observations in a cell line, not evidence of tissue recovery in a brain, but they established that the polysaccharide had a measurable effect on neuronal growth under the modeled ischemic conditions.

Apoptosis, the programmed cell death pathway that neurons activate under severe stress, was examined next with two complementary techniques. Flow cytometry using Annexin-V and propidium iodide double staining, which distinguishes viable, early apoptotic, late apoptotic and necrotic cells by the state of their membranes, showed that the proportion of apoptotic neurons rose significantly after OGD/R exposure at P less than 0.001, and that LBP treatment cut that proportion significantly at P less than 0.01. Western blot analysis of apoptosis-related proteins corroborated the flow cytometry. The anti-apoptotic protein Bcl-2 was reduced by the insult, while the pro-apoptotic proteins Bax, cleaved caspase-3 and cleaved PARP-1, molecular markers of the cell-death machinery being actively executed, were all elevated. LBP treatment shifted this balance back toward survival, increasing Bcl-2 and lowering the cleaved, activated forms of caspase-3 and PARP-1, again at P less than 0.01. All experiments were repeated in at least three independent biological replicates.

The central novelty of the study lies in what happened to RPLP1. This protein is an indispensable subunit of the ribosomal stalk complex, the lateral structure on the ribosome that is central to protein synthesis and to cellular stress responses. The researchers measured RPLP1 at the messenger RNA level by RT-qPCR, at the protein level by western blot, and visually by immunofluorescence microscopy. All three methods agreed: OGD/R injury downregulated RPLP1 significantly at both mRNA and protein levels, at P less than 0.001, and LBP treatment partially restored it at P less than 0.01. Immunofluorescence showed strong RPLP1 signal in healthy neurons, a markedly diminished signal after the insult, and a partial recovery with LBP, though the restored level did not fully reach that of normal controls. Notably, LBP alone did not change basal RPLP1 expression in unstressed neurons, suggesting the compound acts on the injury-induced loss rather than simply pushing expression upward regardless of context.

To test whether RPLP1 was merely a bystander or actually required for the protection, the team used lentiviral short hairpin RNA to knock down RPLP1 in the neurons, verifying the reduction by western blot. When RPLP1-deficient neurons were subjected to the OGD/R insult alongside LBP treatment, the protective effect largely collapsed. Flow cytometry showed a significantly higher proportion of apoptotic cells in the knockdown group compared with neurons carrying a control lentivirus, at P less than 0.01, and the protein markers moved in the same direction: Bcl-2 fell, while Bax, cleaved caspase-3 and cleaved PARP-1 rose. The authors interpret this as evidence that RPLP1 is an indispensable mediator of LBP’s anti-apoptotic activity, a conclusion that is well supported within the limits of this cell culture system, though it does not establish that the same relationship holds in living brain tissue.

The study also turned to autophagy, the cellular recycling process that can become excessive and destructive under ischemic stress. In the injured neurons, the autophagy marker LC3-II was elevated and the cargo receptor p62 was depleted, a pattern the authors describe as excessive autophagic activation. LBP reversed both changes, and a tandem fluorescent mRFP-GFP-LC3 assay confirmed the effect visually, with the number of autophagic puncta rising after the insult and falling with LBP treatment. The insult also upregulated the autophagy protein ATG5 while suppressing RPLP1, and LBP rescued both. A co-immunoprecipitation experiment added a physical dimension to the story: the binding between RPLP1 and p62 weakened under OGD/R conditions and was restored by LBP, hinting that the ribosomal protein participates in regulating autophagic flux through its interaction with p62.

Downstream of these events, the researchers traced the PI3K/Akt/mTOR signaling cascade, a master pathway governing cell metabolism, proliferation and survival. Western blots showed that OGD/R exposure markedly suppressed the phosphorylation of Akt and mTOR at P less than 0.001, and that LBP restored the phosphorylation of both at P less than 0.01. To probe causality within this pathway, the team added a PI3K agonist to the LBP-treated injured cultures. The agonist further elevated Akt and mTOR phosphorylation, further increased RPLP1 expression, and further reduced LC3-II and cleaved caspase-3, at P less than 0.05. Taken together, the authors propose a model in which LBP upregulates RPLP1, which supports activation of the PI3K/Akt/mTOR cascade, which in turn restrains excessive autophagy and apoptosis. The authors themselves note an important caveat: they have not yet performed molecular docking or target-binding experiments to verify any direct physical binding between LBP and the relevant proteins, so the mechanism remains a correlation-based model rather than a demonstrated direct interaction.

The limitations of the work are clearly acknowledged by the research team and are worth keeping in view. Every experiment was performed in immortalized cell lines under simplified culture conditions, and the authors state that in vivo animal experiments will be needed to verify the regulatory mechanisms in a living system, where the ischemic microenvironment involves crosstalk among many cell types that a single neuronal culture cannot recapitulate. Future directions they identify include evaluating the pharmacokinetics and bioavailability of LBP, testing efficacy in established animal stroke models, assessing adverse reactions and defining a safe and effective dose range before any translational step, and exploring whether other signaling axes, such as the MAPK cascade, also participate. Within those boundaries, the study adds a specific and testable idea to stroke research: that preserving ribosomal protein RPLP1 and the PI3K/Akt/mTOR pathway it influences may help neurons withstand ischemic stress, and that polysaccharides from a two-thousand-year-old medicinal fruit may offer a route to doing so.

Subject of Research: Neuroprotective effects of lycium barbarum polysaccharides on ischemia-reperfused neurons via RPLP1 regulation

Article Title: Lycium barbarum polysaccharides protect ischemic brain injury through regulating RPLP1 expression on ischemia-reperfusion nerve cells

Article References: Shao, N., Ma, B., Li, Y., Wang, X., & Du, Y. (2026). Lycium barbarum polysaccharides protect ischemic brain injury through regulating RPLP1 expression on ischemia-reperfusion nerve cells. Scientific Reports, 16(1), Article 34419. https://doi.org/10.1038/s41598-026-63504-0

Image Credits: AI Generated

DOI: 10.1038/s41598-026-63504-0

Keywords: ischemic stroke, lycium barbarum polysaccharides, goji berry, RPLP1, neuroprotection, apoptosis, autophagy, PI3K/Akt/mTOR, oxygen-glucose deprivation, HT-22 neurons, in vitro study, ribosomal protein