Kidney-targeted inhibition of protein kinase C-α ameliorates nephrotoxic nephritis with restoration of mitochondrial dysfunction

A quantitative review of nanotechnology-based therapeutics for kidney diseases

Kidney-specific nanocarriers offer a targeted approach to enhance therapeutic efficacy and reduce off-target effects in renal treatments. The nanocarriers can achieve organ or cell specificity via passive targeting and active targeting mechanisms. Passive targeting capitalizes on the unique physiological traits of the kidney, with factors like particle size, charge, shape, and material properties enhancing organ specificity. Active targeting, on the other hand, achieves renal specificity through ligand-receptor interactions, modifying nanocarriers with molecules, peptides, or antibodies for receptor-mediated delivery. Nanotechnology-enabled therapy targets diseased kidney tissue by modulating podocytes and immune cells to reduce inflammation and enhance tissue repair, or by inhibiting myofibroblast differentiation to mitigate renal fibrosis. This review summarizes the current reports of the drug delivery systems that have been tested in vivo, identifies the nanocarriers that may preferentially accumulate in the kidney, and quantitatively compares the efficacy of various cargo-carrier combinations to outline optimal strategies and future research directions. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Therapeutic Approaches and Drug Discovery > Emerging Technologies.

Potential implications of protein kinase Cα in pathophysiological conditions and therapeutic interventions

PKCα is a molecule with many functions that play an important role in cell survival and death to maintain cellular homeostasis. Alteration in the normal functioning of PKCα is responsible for the complicated etiology of many pathologies, including cancer, cardiovascular diseases, kidney complications, neurodegenerative diseases, diabetics, and many others. Several studies have been carried out over the years on this kinase's function, and regulation in normal physiology and pathological conditions. A lot of data with antithetical results have therefore accumulated over time to create a complex framework of physiological implications connected to the PKCα function that needs comprehensive elucidation. In light of this information, we critically analyze the multiple roles played by PKCα in basic cellular processes and their molecular mechanism during various pathological conditions. This review further discusses the current approaches to manipulating PKCα signaling amplitude in the patient's favour and proposed PKCα as a therapeutic target to reverse pathological states.

Cellular mechanism of action of forsythiaside for the treatment of diabetic kidney disease

Background: Diabetic kidney disease (DKD) becomes the leading cause of death for end-stage renal disease, whereas the potential mechanism is unclear and effective therapy is still rare. Our study was designed to investigate the cellular mechanism of Forsythiaside against DKD. Materials and Methods: The targets of Forsythiaside and the DKD-related targets were obtained from databases. The overlapping targets in these two sets were regarded as potential targets for alleviation of DKD by Forsythiaside. The targets of diabetic podocytopathy and tubulopathy were also detected to clarify the mechanism of Forsythiaside ameliorating DKD from the cellular level. Results: Our results explored that PRKCA and RHOA were regarded as key therapeutic targets of Forsythiaside with excellent binding affinity for treating DKD podocytopathy. Enrichment analysis suggested the underlying mechanism was mainly focused on the oxidative stress and mTOR signaling pathway. The alleviated effects of Forsythiaside on the reactive oxidative species accumulation and PRKCA and RHOA proteins upregulation in podocytes were also confirmed. Conclusion: The present study elucidates that Forsythiaside exerts potential treatment against DKD which may act directly RHOA and PRKCA target by suppressing the oxidative stress pathway in podocytes. And Forsythiaside could be regarded as one of the candidate drugs dealing with DKD in future experimental or clinical researches.

Novel Drug Delivery Technologies and Targets for Renal Disease

The burden of acute and chronic kidney diseases to the health care system is exacerbated by the high mortality that this disease carries paired with the still limited availability of comprehensive therapies. A reason partially resides in the complexity of the kidney, with multiple potential target cell types and a complex structural environment that complicate strategies to protect and recover renal function after injury. Management of both acute and chronic renal disease, irrespective of the cause, are mainly focused on supportive treatments and renal replacement strategies when needed. Emerging preclinical evidence supports the feasibility of drug delivery technology for the kidney, and recent studies have contributed to building a robust catalog of peptides, proteins, nanoparticles, liposomes, extracellular vesicles, and other carriers that may be fused to therapeutic peptides, proteins, nucleic acids, or small molecule drugs. These fusions can display a precise renal uptake, an enhanced circulating time, and a directed intraorgan biodistribution while protecting their cargo to improve therapeutic efficacy. However, several hurdles that slow the transition towards clinical applications are still in the way, such as solubility, toxicity, and sub-optimal renal targeting. This review will discuss the feasibility and current limitations of drug delivery technologies for the treatment of renal disease, offering an update on their potential and the future directions of these promising strategies.

Epigallocatechin-3-Gallate Allosterically Activates Protein Kinase C-α and Improves the Cognition of Estrogen Deficiency Mice

Protein kinase C (PKC) isozymes play essential roles in biological processes, and activation of PKC is proposed to alleviate the symptoms of a variety of diseases. It would be of great significance to find effective pharmacological modulators of PKC isozymes that can be translated for clinical use. Here, using in vitro activity assay, we demonstrated that green tea extract (-)-epigallocatechin-3-gallate (EGCG) dose-dependently activated PKCα with a half effective concentration (EC50) of 0.49 μM. We also performed surface plasmon resonance analysis and found that EGCG binds PKCα with an equilibrium dissociation constant (K_D) value of 4.11 × 10^-6 mol/L. Further computational flexible docking analysis revealed that EGCG interacted with the catalytic C3-C4 domain of PKCα (PDB: 4RA4) through establishing polar hydrogen bonds with V420, T401, E387, and K368 of PKCα, and the benzene ring group of EGCG hydrophobically interacted with the hydrophobic pocket formed by L345, M470, I479, and V353 of PKCα. Interestingly, the PKCα-selective blocker Ro-32-0432 could compete with EGCG for the same substrate-binding pocket of PKCα. Moreover, we found that EGCG dose-dependently improved the spatial memory, object recognition ability, and hippocampal long-term potentiation of ovariectomized mice, which was offset by Ro-32-0432. Collectively, our findings reveal a novel PKCα agonist and open the way to a new perspective on PKCα pharmacology and the treatment of PKCα-related diseases, including cognitive impairment.

Targeted Drug Delivery Systems for Kidney Diseases

Kidney diseases have gradually become a global health burden. Along with the development of nanotechnology, many hybrids or nanomaterials have been utilized to promote treatment efficiency with negligible side effects. These therapeutic agents have been successfully applied in many fields. In particular, some efforts have also been made to ameliorate the treatment of kidney diseases through targeted delivery nanomaterials. Though most of the delivery systems have not yet been transmitted into clinical use or even still at an early stage, they have shown great potential in carrying immunosuppressants like tacrolimus and triptolide, antioxidants, or siRNAs. Excitingly, some of them have achieved significant treatment effectiveness and reduced systemic side effect in kidney disease animal models. Here, we have reviewed the recent advances and presented nanotherapeutic devices designed for kidney targeted delivery.

N-methyl-d-aspartate receptor hyperfunction contributes to d-serine-mediated renal insufficiency

Glutamate N-methyl-d-aspartate receptor (NMDAR) hyperfunction is known to contribute to acute renal failure due to ischemia-reperfusion and endotoxemia. d-Serine is a coagonist for NMDAR activation, but whether NMDARs play a role in d-serine-mediated nephrotoxicity remains unclear. Here, we demonstrate that NMDAR blockade ameliorated d-serine-induced renal injury. In NMDAR-expressing LLC-PK1 cells, which were used as a proximal tubule model, d-serine but not l-serine induced cytotoxicity in a dose-dependent manner, which was abrogated by the selective NMDAR blockers MK-801 and AP-5. Time-dependent oxidative stress, evidenced by gradually increased superoxide and H2O2 production, was associated with d-serine-mediated cytotoxicity; these reactive oxygen species could be alleviated not only after NMDAR inhibition but also by NADPH oxidase (NOX) inhibition. Activation of protein kinase C (PKC)-δ and PKC-ζ is a downstream signal for NMDAR-mediated NOX activation because PKC inhibition diminishes the NOX activity that is induced by d-serine. Renal injury was further confirmed in male Wistar rats that intraperitoneally received d-serine but not l-serine. Peak changes in glucosuria, proteinuria, and urinary excretion of lactate dehydrogenase and malondialdehyde were found after 24 h of treatment. Persistent tubular damage was observed after 7 days of treatment. Cotreatment with the NMDAR blocker MK-801 for 24 h abolished d-serine-induced functional insufficiency and tubular damage. MK-801 attenuated renal superoxide formation by lowering NOX activity and protein upregulation of NOX4 but not NOX2. These results reveal that NMDAR hyperfunction underlies d-serine-induced renal injury via the effects of NOX4 on triggering oxidative stress.NEW & NOTEWORTHY Ionotropic N-methyl-d-aspartate receptors (NMDARs) are not only present in the nervous system but also expressed in the kidney. Overstimulation of renal NMDARs leads to oxidative stress via the signal pathway of calcium/protein kinase C/NADPH oxidase in d-serine-mediated tubular cell damage. Intervention of NMDAR blockade may prevent acute renal injury caused by d-serine.

Feprazone Ameliorates TNF-α-Induced Loss of Aggrecan via Inhibition of the SOX-4/ADAMTS-5 Signaling Pathway

Background: Arthritis is a cartilage degenerative disease that is mainly induced by the degradation of the cartilage extracellular matrix (ECM), which is found to be regulated by the expression level of a disintegrin and metalloproteinase with thrombospondin motifs 5 (ADAMT-5), an enzyme degrading Aggrecans in the ECM. Feprazone is a classic nonsteroidal anti-inflammatory drug with promising efficacy in arthritis. The present study aims to investigate the protective effect of Feprazone on the degraded Aggrecan in the human chondrocytes induced with tumor necrosis factor-α (TNF-α) and to clarify the underlying mechanism. Methods: To investigate the effect of Feprazone, the CHON-001 chondrocytes were stimulated with TNF-α (10 ng/mL) in the presence or absence of Feprazone (3, 6 μM) for 24 h. Mitochondrial membrane potential was evaluated using the Rhodamine 123 assay. The gene expressions of interleukin-1β (IL-1β), interleukin-8 (IL-8), monocyte chemotactic protein 1 (MCP-1), and ADAMTS-5 in the treated chondrocytes were detected using real-time quantitative polymerase chain reaction (qRT-PCR), and the protein levels of these targets were determined using enzyme-linked immunosorbent assay (ELISA). SOX-4 was knocked down by transfecting the siRNA into the chondrocytes. Western blot analysis was utilized to evaluate the expression levels of SOX-4, Aggrecan, and protein kinase C (PKCα). Results: First, the reduced mitochondrial membrane potential (ΔΨ_m) and secretion of proinflammatory factors (IL-1β, IL-8, and MCP-1) induced by TNF-α were significantly reversed by treatment with Feprazone. Second, the expression of Aggrecan was significantly decreased by stimulation with TNF-α via upregulation of ADAMTS-5 but was dramatically reversed by the introduction of Feprazone. Third, we found that TNF-α elevated the expression of ADAMTS-5 by upregulating SOX-4, which was observed to be related to the activation of PKCα. Lastly, the elevated expression of SOX-4 induced by TNF-α was significantly reversed by Feprazone. Conclusions: Feprazone might ameliorate TNF-α-induced loss of Aggrecan via the inhibition of the SOX-4/ADAMTS-5 signaling pathway.

The mitochondrial-targeted peptide SBT-20 ameliorates inflammation and oxidative stress in chronic renal failure

Chronic renal failure (CRF) is the final outcome of the development of chronic kidney disease with different causes. Although CRF is a common clinical disease, its pathogenesis remains to be improved. SBT-20 belongs to a class of cell-permeable peptides that target the inner mitochondrial membrane, reduce reactive oxygen species (ROS), normalize electron transport chain function, and ATP generation. Our experiment was to evaluate whether SBT-20 affected the oxidative stress and inflammatory process of CRF. The levels of ROS production, mitochondrial membrane potential, NF- κB-p65, TNF-α, Drp1, and mfn2 were measured before and after SBT-20 treatment. We observed that SBT-20 treatment inhibited H2O2-induced mitochondrial ROS production. SBT-20 could also restore the mitochondrial membrane potential and reduce the elevated levels of NF-κB-p65 and TNF-α in HK-2 cells. In vivo, the renal function of CRF mice recovered after treating with SBT-20, the levels of necrotic cells and inflammation decreased, and the morphology of mitochondria recovered. The results showed that SBT-20 had a protective effect on CRF by reducing oxidative stress, inflammation progression via down-regulating of NF-κB-p65, TNF-α, and Drp1 and upregulating of Mfn2. These data support SBT-20 could be used as a potential preparation for CRF.

Protein kinase Cα mediates recovery of renal and mitochondrial functions following acute injury

Previously, we have shown that active protein kinase Cα (PKCα) promotes recovery of mitochondrial function after injury in vitro [Nowak G & Bakajsova D (2012) Am J Physiol Renal Physiol 303, F515-F526]. This study examined whether PKCα regulates recovery of mitochondrial and kidney functions after ischemia-induced acute injury (AKI) in vivo. Markers of kidney injury were increased after bilateral ischemia and returned to normal levels in wild-type (WT) mice. Maximum mitochondrial respiration and activities of respiratory complexes and F_o F₁ -ATPase decreased after ischemia and recovered in WT mice. Reperfusion after ischemia was accompanied by translocation of active PKCα to mitochondria. PKCα deletion reduced mitochondrial respiration and activities of respiratory complex I and F_o F₁ -ATPase in noninjured kidneys, indicating that PKCα is essential in developing fully functional renal mitochondria. These changes in PKCα-deficient mice were accompanied by lower levels of complex I subunits (NDUFA9 and NDUFS3) and the γ-subunit of F_o F₁ -ATPase. Also, lack of PKCα exacerbated ischemia-induced decreases in respiration, complex I and F_o F₁ -ATPase activities, and blocked their recovery after injury, indicating a crucial role of PKCα in promoting mitochondrial recovery after AKI. Further, PKCα deletion exacerbated acetylation and succinylation of key mitochondrial proteins of energy metabolism after ischemia due to decreases in deacetylase and desuccinylase (sirtuin3 and sirtuin5) levels in renal mitochondria. Thus, our data show a novel role for PKCα in regulating levels of mitochondrial sirtuins and acetylation and succinylation of key mitochondrial proteins. We conclude that PKCα deletion: (a) affects renal physiology by decreasing mitochondrial capacity for maximum respiration; (b) blocks recovery of mitochondrial functions, renal morphology, and functions after AKI; and (c) decreases survival after AKI. ENZYMES: Protein kinase C: EC 2.7.11.13; NADH : ubiquinone reductase (H⁺ -translocating; complex I): EC 7.1.1.2; FoF1-ATPase (H⁺ -transporting two-sector ATPase): EC 7.1.2.2; Succinate : ubiquinone oxidoreductase (complex II): EC 1.3.5.1; Ubiquinol : cytochrome-c reductase (complex III): EC 7.1.1.8; Cytochrome c oxidase (complex IV): EC 1.9.3.1; NAD-dependent protein deacetylase sirtuin-3, mitochondrial: EC 2.3.1.286; NAD-dependent protein deacetylase sirtuin-5, mitochondrial: EC 3.5.1.-; Proteinase K (peptidase K): EC 3.4.21.64.

Maternal High Fat Diet and in-Utero Metformin Exposure Significantly Impact upon the Fetal Renal Proteome of Male Mice

There is accumulating evidence for fetal programming of later kidney disease by maternal obesity or associated conditions. We performed a hypothesis-generating study to identify potentially underlying mechanisms. Female mice were randomly split in two groups and fed either a standard diet (SD) or high fat diet (HFD) from weaning until mating and during pregnancy. Half of the dams from both groups were treated with metformin ((M), 380 mg/kg), resulting in four experimental groups (SD, SD-M, HFD, HFD-M). Caesarean section was performed on gestational day 18.5. Fetal kidney tissue was isolated from cryo-slices using laser microdissection methods and a proteomic screen was performed. For single proteins, a fold change ≥1.5 and q-value <0.05 were considered to be statistically significant. Interestingly, HFD versus SD had a larger effect on the proteome of fetal kidneys (56 proteins affected; interaction clusters shown for proteins concerning transcription/translation, mitochondrial processes, eicosanoid metabolism, H2S-synthesis and membrane remodeling) than metformin exposure in either SD (29 proteins affected; clusters shown for proteins involved in transcription/translation) or HFD (6 proteins affected; no cluster). By further analysis, ATP6V1G1, THY1, PRKCA and NDUFB3 were identified as the most promising candidates potentially mediating reprogramming effects of metformin in a maternal high fat diet.

The Effects of Icariin on Enhancing Motor Recovery Through Attenuating Pro-inflammatory Factors and Oxidative Stress via Mitochondrial Apoptotic Pathway in the Mice Model of Spinal Cord Injury

Spinal cord injury (SCI) is a severe medical problem leading to crucial life change. Icariin (ICA) is a natural flavonoid compound extracted from the Chinese herb Epimedium brevicornum which has neuroprotective effects. But little is known about the relationship between ICA and SCI. We hypothesized ICA may enhance motor recovery through attenuating inflammation, oxidative stress and mitochondrial dysfunction. Mice were randomly assigned to sham, SCI, ICA 20 μmol/kg (low dose) and ICA 50 μmol/kg (high dose) groups. And Behavioral, biochemical, molecular biological, immunofluorescent and histological assays were performed. First, ICA enhanced motor recovery greatly at 14, 28, and 42 days and protected spinal cord tissues especially in the high dose group. Meanwhile, ICA decreased the production of interleukin-1 beta, tumor necrosis factor-alpha and inducible nitric oxide synthase at 24 h and 3 days after SCI. The level of mitochondrial reduced glutathione, superoxide dismutase, adenosine triphosphate (ATP), Na⁺-K⁺-ATPase, mitochondrial membrane potential, state III respiration rate and the respiratory control ratio were also significantly increased, while malondialdehyde level and Ca²⁺ concentration were decreased by ICA. Furthermore, ICA decreased the expression of mitochondrial apoptotic proteins at 3 days after SCI. More importantly, transferase UTP nick end labeling (TUNEL) and Nissl staining implied that ICA at a high dose inhibited the neuronal apoptosis after SCI. Our research indicated that early and continuous treatment of ICA at a high dose significantly enhanced motor recovery after SCI through inhibiting pro-inflammatory factors, oxidative stress and neuronal apoptosis via mitochondrial apoptotic pathway.