LCZ696 (sacubitril/valsartan) protects against cyclophosphamide-induced nephrotoxicity in adult male rats: Up-regulation of Apelin-13/ACE2, miR-200, and down-regulation of TGF-β/SMAD 2/3 and miR-192

The Protective Effects of Saxagliptin and Cilostazol in an Experimental Model of Cyclophosphamide-Induced Nephrotoxicity in Rats: Targeting iNOS/NF-kB and Nrf-2/HO-1 Pathways

Cyclophosphamide (CYP) is an extensively used immunosuppressive drug and chemotherapeutic agent for various malignancies. Nevertheless, its use is limited due to adverse effects, including nephrotoxicity. Saxagliptin is a DPP4 inhibitor, while cilostazol serves as an antiplatelet agent. Their nephroprotective effects arise from antioxidant and anti-inflammatory properties. This study investigated the potential protective effects of Saxagliptin and Cilostazol in rats with kidney damage induced by CYP. Five equal groups of 50 male Wistar rats were randomly categorised as Group I (Control group), Group II: CYP untreated nephrotoxicity-induced group, Group III: Nephrotoxicity-induced group treated with saxagliptin, Group IV: Nephrotoxicity-induced group treated with cilostazol, and Group V: Nephrotoxicity-induced group treated with saxagliptin and cilostazol. Renal tissues and blood samples were collected for biochemical analysis of urea, creatinine, and acute kidney injury biomarkers, including Kim-1 and NGAL. Additionally, oxidative stress and inflammatory biomarkers such as GSH, MDA, TNF-α and IL-1β were assessed, along with gene expression of Nrf-2/HO-1 and NF-kB. Immunohistochemical analysis of iNOS, and histopathological study were also conducted. Saxagliptin and cilostazol ameliorated the nephrotoxicity induced by CYP, as indicated by improvements in urea, creatinine, and acute kidney injury biomarkers Kim-1 and NGAL. Furthermore, there was a decrease in oxidative stress via the upregulation of Nrf-2/HO-1, increased levels of GSH, downregulation of MDA and decreased inflammation via the downregulation of TNF-α, IL-1β and iNOS/NF-kB. The combination of saxagliptin and cilostazol demonstrated a significant improvement compared to using each agent individually. The combination of Saxagliptin/Cilostazol is superior to monotherapy by either of each alone in preventing CYP-induced nephrotoxicity.

Protective effect of valsartan alone and in combination with neprilysin inhibitor (valsartan + sacubitril) against hepatic ischemia-reperfusion injury: targeting angiotensin II receptor-neprilysin and modulating SMAD-4/NF-κβ/JNK pathways in rats

Ischemia-reperfusion injury (IRI) is a common pathogenic situation that arises throughout all liver surgeries, including liver transplants. We aimed to compare the preventive effects of valsartan (VST) against valsartan + sacubitril (LCZ696) on hepatic injury caused by IRI. A total of thirty-six male Westar albino rats were split into six groups randomly: sham, IRI, VST + IRI, LCZ696 + IRI, VST, and LCZ696. The medicines were given orally for 10 days in a row. Hepatic tissues and blood were examined through histopathological imaging and immunohistochemical detection of hepatic SMAD-4 protein expression plus serum aminotransferase (ALT, AST) and gamma-glutamyl transferase (GGT) levels. Angiotensin II, aldosterone, and plasma renin activity were evaluated in rat serum. Liver tissue homogenate was utilized to assess reduced glutathione (GSH), myeloperoxidase (MPO), malondialdehyde (MDA), and total nitric oxide (NOx) levels. Pro-inflammatory indicators, tumor necrosis factor-alpha (TNF-α), and interleukin-1β (IL-1β), moreover with apoptosis indicators, BCL2-associated X protein (Bax), B-cell lymphoma 2 (Bcl-2), and galactine-9 (GAL9) proteins plus caspase-3, were measured in hepatic tissue homogenate. Hepatic endothelin-1 and neprilysin activity were evaluated. Western blot was done for c-Jun N-terminal kinase (JNK-7) plus nuclear factor-kappa B (NF-κβ) expressions. The study revealed that VST and LCZ696 pretreatment showed significant restoration of liver injury, correction of oxidative profile, and inhibition in the angiotensin II receptor-neprilysin pathway. Inflammatory mediators and apoptosis were significantly inhibited. The expression of SMAD-4, JNK-7, and NF-κβ proteins was notably diminished. The improvement in hepatic architecture supports these histopathological results. In conclusion, LCZ696 possesses a potentially significant protective effect against liver IRI superior to VST alone.

Protective effects of herbal compounds against cyclophosphamide-induced organ toxicity: a pathway-centered approach

Cyclophosphamide is a key component of numerous chemotherapeutic protocols, demonstrating broad-spectrum efficacy against various malignancies and non-cancerous conditions. This review examines CPM's metabolic pathways, therapeutic applications, and its resulting organ-specific toxicities. Despite its clinical benefits in treating nephrotic syndrome, encephalomyelitis, breast cancer, ovarian cancer, and other diseases, CPM is associated with significant adverse effects on the kidneys, liver, heart, lungs, and intestines. The discussion delves into the molecular mechanisms underlying these toxicities, highlighting dysregulation in key signaling pathways, including Nrf2, NF-κB, MAPK/ERK, and AKT. In addressing these challenges, recent studies have identified various herbal drugs and phytochemicals capable of mitigating CPM-induced toxicity. Notable compounds such as cinnamaldehyde, baicalin, quercetin, and curcumin have demonstrated protective effects. Integrating these herbal formulations with CPM therapy is proposed to enhance patient safety and treatment efficacy. This review underscores the influence of CPM on apoptosis and inflammation pathways, which lead to alterations in organ-specific biomarkers. Phytochemicals may exert protective effects by restoring disrupted signaling pathways and normalizing altered biomarkers. The compilation of phytochemicals presented in this review serves as a valuable resource for researchers exploring other herbal products with potential protective effects against CPM toxicity. A significant gap in the current literature is the lack of clinical trials evaluating phytochemicals that mitigate CPM toxicity in vivo. Rigorous clinical studies are necessary to establish the efficacy and safety of herbal formulations in cancer treatment. Such research will clarify the role of natural remedies in complementing conventional therapies, ultimately improving patient outcomes.

LCZ696, an angiotensin receptor-neprilysin inhibitor, ameliorates epithelial-mesenchymal transition of peritoneal mesothelial cells and M2 macrophage polarization

AIMS

To investigate the effects and mechanisms of LCZ696, an angiotensin receptor-neprilysin inhibitor (ARNI), on epithelial-mesenchymal transition (EMT) of peritoneal mesothelial cells and on macrophage M2 polarization.

METHODS

We examined the effects of LCZ696 in a 4.25% high glucose peritoneal dialysis fluid (PDF)-induced peritoneal fibrosis (PF) mouse model, and explored the mechanisms of LCZ696 on human peritoneal mesothelial cells (HPMCs) stimulated by TGF-β1 (5 ng/mL) and on Raw264.7 cells stimulated by IL-4 (10 ng/mL). To further elucidate the mechanism, we treated HPMCs with the conditioned medium of Raw264.7 cells.

RESULTS

LCZ696 effectively improved PF and inhibited the process of EMT in PDF mice. In vitro, LCZ696 also significantly alleviated the EMT of TGF-β1 induced HPMCs, although there was no statistically significant difference when compared to the Valsartan treatment group. Moreover, LCZ696 ameliorates the increased expression of Snail and Slug, two nuclear transcription factors that drive the EMT. Mechanistically, TGF-β1 increased the expression of TGFβRI, p-Smad3, p-PDGFRβ and p-EGFR, while treatment with LCZ696 abrogated the activation of TGF-β/Smad3, PDGFRβ and EGFR signaling pathways. Additionally, exposure of Raw264.7 to IL-4 results in increasing expression of Arginase-1, CD163 and p-STAT6. Treatment with LCZ696 inhibited IL-4-elicited M2 macrophage polarization by inactivating the STAT6 signaling pathway. Furthermore, we observed that LCZ696 inhibits EMT by blocking TGF-β1 secretion from M2 macrophages.

CONCLUSION

Our study demonstrated that LCZ696 improves PF and ameliorates TGF-β1-induced EMT of HPMCs by blocking TGF-β/Smad3, PDGFRβ and EGFR pathways. Meanwhile, LCZ696 also inhibits M2 macrophage polarization by regulating STAT6 pathway.

LMK-235 suppresses osteoclastogenesis and promotes osteoblastogenesis by inhibiting HDAC4

Osteoblasts and osteoclasts play an important role in maintaining the structural integrity of bone tissue, in which osteoclasts degrade bone structure and osteoblasts restore bone tissue. The imbalance of osteoblast and osteoclast function can lead to many bone-related diseases, such as osteoporosis and inflammatory osteolysis. The drug that can both promote bone formation and inhibit bone loss will be able to treat those diseases. In this study, it was found that LMK-235, an selective HDAC4/5 inhibitor, inhibited the differentiation and maturation of osteoclasts by regulating NF-κB and p-Smad2/3 signaling pathways via inhibition of HDAC4. At the same time, we found that LMK-235 promoted osteoblast mineralization by upregulating Runx2 expression via inhibition of HDAC4. In vivo, LMK-235 was able to alleviate lipopolysaccharide (LPS)-induced calvarial osteolysis and promote the repair of bone defects. Taken together, LMK-235 suppresses osteoclast differentiation and promotes osteoblast formation by inhibiting HDAC4. This may provide a valuable treatment for bone diseases caused by abnormal osteoclast bone resorption and osteoblast bone regeneration.

Modulation of keap-1/Nrf2/HO-1 and NF-ĸb/caspase-3 signaling pathways by dihydromyricetin ameliorates sodium valproate-induced liver injury

Nuclear factor erythroid factor 2 (Nrf2) is the key regulatory of the antioxidant response elements. Also, Nrf2 interacts with nuclear factor kappa B (NF-ĸB) to inhibit subsequent inflammatory cascade. Activation of Nrf2 signaling ameliorates drug-induced liver injury. Sodium valproate (SVP) is an anti-epilepsy drug with a hepatotoxic adverse effect that restricts its clinical use. In this study, coadministration of Dihydromyricetin (DHM), a natural flavonoid, with SVP to rats upregulated gene expression of Nrf2 and its downstream gene, heme oxygenase 1 (HO-1), while suppressed the Nrf2 repressor, Keap-1. Additionally, DHM led to downregulation of proinflammatory factors in liver tissues, including NF-ĸB, interleukin 1 beta (IL-1β), and tumor necrosis factor alpha (TNF-α). This was accompanied by a decrease in the proapoptotic protein (cleaved caspase-3) expression level. Furthermore, biochemical and histopathological studies showed that DHM treatment improved liver function and lipid profile while decreased inflammatory cell infiltration, congestion, and hepatocellular damage. According to our knowledge, prior research has not examined the protective effect of DHM on the liver injury induced by SVP. Consequently, this study provides DHM as a promising herbal medication that, when used with SVP, can prevent its induced hepatotoxicity owing to its potential anti-oxidative, anti-inflammatory, and anti-apoptotic properties.

Protective effects of microbial biosurfactants produced by Bacillus halotolerans and Candida parapsilosis on bleomycin-induced pulmonary fibrosis in mice: Impact of antioxidant, anti-inflammatory and anti-fibrotic properties via TGF-β1/Smad-3 pathway and miRNA-326

Idiopathic pulmonary fibrosis (IPF) is an irreversible disease which considered the most fatal pulmonary fibrosis. Pulmonary toxicity including IPF is the most severe adverse effect of bleomycin, the chemotherapeutic agent. Based on the fact that, exogenous surfactants could induce alveolar stabilization in many lung diseases, the aim of this study was to explore the effects of low cost biosurfactants, surfactin (SUR) and sophorolipids (SLs), against bleomycin-induced pulmonary fibrosis in mice due to their antioxidant, and anti-inflammatory properties. Surfactin and sophorolipids were produced by microbial conversion of frying oil and potato peel wastes using Bacillus halotolerans and Candida parapsilosis respectively. These biosurfactants were identified by FTIR, 1H NMR, and LC-MS/MS spectra. C57BL/6 mice were administered the produced biosurfactants daily at oral dose of 200 mg kg-1 one day after the first bleomycin dose (35 U/kg). We evaluated four study groups: Control, Bleomycin, Bleomycin+SUR, Bleomycin+SLs. After 30 days, lungs from each mouse were sampled for oxidative stress, ELISA, Western blot, histopathological, immunohistochemical analyses. Our results showed that the produced SUR and SLs reduced pulmonary oxidative stress and inflammatory response in the lungs of bleomycin induced mice as they suppressed SOD, CAT, and GST activities also reduced NF-κβ, TNF-α, and CD68 levels. Furthermore, biosurfactants suppressed the expression of TGF-β1, Smad-3, and p-JNK fibrotic signaling pathway in pulmonary tissues. Histologically, SUR and SLs protected against lung ECM deposition caused by bleomycin administration. Biosurfactants produced from microbial sources can inhibit the induced inflammatory and fibrotic responses in bleomycin-induced pulmonary fibrosis.

Nephroprotective Effect of Bergapten Against Cyclophosphamide-Mediated Renal Stress, Inflammation, and Fibrosis in Wistar Rats: Probable Role of NF-kB and TGF-β1 Signaling Molecules

Cyclophosphamide (CPM) is a well-established antineoplastic drug with marked clinical outcomes in various types of cancers. Despite being a promising drug, its use is associated with significant renal toxicity and often limits its use, leading to compromised clinical outcomes. Therefore, this study explored the renal protective effect of bergapten (BGP), a natural bioactive compound that showed marked antioxidant, anti-inflammatory, anticancer, and neuroprotective effects. Till now, BGP has not been studied for its renal protective effect in an in vivo model. Animals were divided into control, toxic, BGP-3, BGP-10, and BGP Per se. The control group was treated with normal saline for 2 weeks. To the toxic group, CPM 200 mg/kg was given on day 7 as i.p. To BGP-3, 10, and Per se, BGP-3 and 10 mg/kg, ip was given 2 weeks with a single shot of CPM 200 day 7. To the Per se group, only BGP 10 mg/kg, ip was given from day 1 to day 14. After 14 days, animals were sacrificed, and kidneys were removed and studied for the markers of oxidative stress, inflammation, renal injury, renal fibrosis, and renal damage using biochemical, histopathological, and immunohistochemical studies. We found that BGP-10 effectively reversed the damage toward normal, whereas BGP-3 failed to exhibit a significant renal protective effect. We conclude that bergapten could be a potential renal protective drug, and hence, more detailed cellular molecular-based studies are needed to bring this drug from the bench to the bedside.

Protective effect of novel angiotensin receptor neprilysin inhibitor S086 on target organ injury in spontaneously hypertensive rats

BACKGROUND

Hypertension is a clinical syndrome characterized by elevated systemic arterial blood pressure associated with injury to the heart, kidney, brain, and other organs. Angiotensin receptor neprilysin inhibitors (ARNi), including angiotensin receptor blockers (ARBs) and neprilysin inhibitors (NEPi), have been shown to be safe and effective at reducing blood pressure and alleviating development of target organ injury. This study was used to develop S086 as a novel ARNi and conducted preclinical studies in animal models to evaluate the protective effects of S086 on target organs.

METHODS

This study used a 14-month-old spontaneously hypertensive rat (SHR) model to evaluate the protective effects of S086 on the cardiovascular system and organs such as heart and kidney by blood pressure monitoring, urine and blood examination, pathological examination, and immunological index detection.

RESULTS

After administering S086 orally to the SHR, their blood pressure and levels of renal injury indicators such as serum creatinine and urinary microalbumin were reduced, and myocardial cell necrosis and cardiac fibrosis of the heart were significantly improved. In addition, there were also significantly improvements in the histological lesions of blood vessels and the kidneys.

CONCLUSIONS

The findings showed that S086 effectively reduced the blood pressure of SHR and had effects on alleviating development of heart, blood vessels and kidney.

The mechanistic interplay between Nrf-2, NF-κB/MAPK, caspase-dependent apoptosis, and autophagy in the hepatoprotective effects of Sophorolipids produced by microbial conversion of banana peels using Saccharomyces cerevisiae against doxorubicin-induced hepatotoxicity in rats

BACKGROUND

Doxorubicin (DOX) is a well-known chemotherapeutic agent which causes serious adverse effects due to multiple organ damage, including cardiotoxicity, nephrotoxicity, neurotoxicity, and hepatotoxicity. The mechanism of DOX-induced organ toxicity might be attributed to oxidative stress (OS) and, consequently, activation of inflammatory signaling pathways, apoptosis, and blockage of autophagy. Sophorolipids (SLs) as a glycolipid type of biosurfactants, are natural products that have unique properties and a wide range of applications attributed to their antioxidant and anti-inflammatory properties.

AIMS

Production of low-cost SLs from Saccharomyces cerevisiae grown on banana peels and investigating their possible protective effects against DOX-induced hepatotoxicity.

MAIN METHODS

The yeast was locally isolated and molecularly identified, then the yielded SLs were characterized by FTIR, 1H NMR and LC-MS/MS spectra. Posteriorly, thirty-two male Wistar rats were randomly divided into four groups; control (oral saline), SLs (200 mg/kg, p.o), DOX (10 mg/kg; i.p.), and SL + DOX (200 mg/kg p.o.,10 mg/kg; i.p., respectively). Liver function tests (LFTs), oxidative stress, inflammatory, apoptosis as well as autophagy markers were investigated.

KEY FINDINGS

SLs were produced with a yield of 49.04% and treatment with SLs improved LFTs, enhanced Nrf2 and suppressed NF-κB, IL-6, IL-1β, p38, caspase 3 and Bax/Bcl2 ratio in addition to promotion of autophagy when compared to DOX group.

SIGNIFICANCE

Our results revealed a novel promising protective effect of SLs against DOX-induced hepatotoxicity in rats.

Evaluating the protective role of trimetazidine versus nano-trimetazidine in amelioration of bilateral renal ischemia/reperfusion induced neuro-degeneration: Implications of ERK1/2, JNK and Galectin-3 /NF-κB/TNF-α/HMGB-1 signaling

BACKGROUND

Renal ischemia/reperfusion (I/R) is a primary culprit of acute kidney injury. Neurodegeneration can result from I/R, but the mechanisms are still challenging. We studied the implications of bilateral renal I/R on brain and potential involvement of the oxidative stress (OS) driven extracellular signal-regulated kinase1/2, c-Jun N-terminal kinase (ERK1/2, JNK) and Galectin-3 (Gal-3)/nuclear factor Kappa B (NF-қB)/tumor necrosis factor-alpha (TNF-α), high mobility group box-1 (HMGB-1), and caspase-3 paths upregulation. We tested the impact of Nano-trimetazidine (Nano-TMZ) on these pathways being a target of its neuroprotective effects.

METHODS

Study groups; Sham, I/R, TMZ+I/R, and Nano-TMZ+I/R. Kidney functions, cognition, hippocampal OS markers, Gal-3, NF-қB, p65 and HMGB-1 gene expression, TNF-α level, t-JNK/p-JNK and t-ERK/p-ERK proteins, caspase-3, glial fibrillary acidic protein (GFAP) and ionized calcium binding protein-1 (Iba-1) were assessed.

RESULTS

Nano-TMZ averted renal I/R-induced hippocampal impairment by virtue of its anti: oxidative, inflammatory, and apoptotic properties.

CONCLUSION

Nano-TMZ is more than anti-ischemic.

LCZ696 attenuates sepsis-induced liver dysfunction in rats; the role of oxidative stress, apoptosis, and JNK1/2-P38 signaling pathways

AIM

Sepsis is a serious inflammatory response to infection with an annual incidence rate of >48 million cases and 11 million fatalities worldwide. Furthermore, sepsis remains the world's fifth-greatest cause of death. For the first time, the current study aims to evaluate the possible hepatoprotective benefits of LCZ696, a combination of an angiotensin receptor blocker (valsartan) and a neprilysin inhibitor prodrug (sacubitril), on cecal ligation and puncture (CLP)-induced sepsis in rats.

MAIN METHODS

CLP was employed to induce sepsis. Hepatic malondialdehyde (MDA), reduced glutathione (GSH), superoxide dismutase (SOD), interleukin-6 (IL-6), IL-1β, tumor necrosis factor-alpha (TNF-α), and caspase 3 were assessed using ELISA. Serum alanine transaminase (ALT) and aspartate transaminase (AST) were also measured. Western blot assay was used to determine the expression of JNK1/2 and P38 proteins. The histology of liver tissues was also examined.

KEY FINDINGS

CLP resulted in significant elevation of AST, ALT, MDA, IL-6, IL-1β, TNF-α, and caspase 3 levels, and up-regulation of p/t JNK1/2, and p/t P38 proteins, as compared to the sham group. However, level of GSH, and SOD activity were reduced in CLP group. LCZ696 significantly improved all the previously mentioned biochemical and histological abnormalities better than using valsartan alone.

SIGNIFICANCE

LCZ696 substantially ameliorated CLP-induced liver damage, compared to valsartan, by reducing proinflammatory mediators, inhibiting the JNK1/2 and P38 signaling pathway, and attenuating apoptosis.

A biochemical, theoretical and immunohistochemical study comparing the therapeutic efficacy of curcumin and taurine on T-2 toxin induced hepatotoxicity in rats

Introduction: Foodborne trichothecene T-2 Toxin, is a highly toxic metabolite produced by Fusarium species contaminating animal and human food, causing multiple organ failure and health hazards. T-2 toxins induce hepatotoxicity via oxidative stress causing hepatocytes cytotoxicity and genotoxicity. In this study, curcumin and taurine were investigated and compared as antioxidants against T-2-provoked hepatotoxicity. Methods: Wistar rats were administrated T-2 toxin sublethal oral dose (0.1 mg/kg) for 2 months, followed by curcumin (80 mg/kg) and taurine (50 mg/kg) for 3 weeks. Biochemical assessment of liver enzymes, lipid profiles, thiobarbituric acid reactive substances (TBARs), AFU, TNF-α, total glutathione, molecular docking, histological and immunohistochemical markers for anti-transforming growth factor-β1 (TGFβ1), double-strand DNA damage (H2AX), regeneration (KI67) and apoptosis (Active caspase3) were done. Results and Discussion: Compared to T-2 toxin, curcumin and taurine treatment significantly ameliorated hepatoxicity as; hemoglobin, hematocrit and glutathione, hepatic glycogen, and KI-67 immune-reactive hepatocytes were significantly increased. Although, liver enzymes, inflammation, fibrosis, TGFβ1 immunoexpressing and H2AX and active caspase 3 positive hepatocytes were significantly decreased. Noteworthy, curcumin's therapeutic effect was superior to taurine by histomorphometry parameters. Furthermore, molecular docking of the structural influence of curcumin and taurine on the DNA sequence showed curcumin's higher binding affinity than taurine. Conclusion: Both curcumin and taurine ameliorated T-2 induced hepatotoxicity as strong antioxidative agents with more effectiveness for curcumin.

Exogenous Apelin-13 Administration Ameliorates Cyclophosphamide- Induced Oxidative Stress, Inflammation, and Apoptosis in Rat Lungs

BACKGROUND

Apelin-13 is an endogenous adipocytokine known for its antioxidant, antiinflammatory, and antiapoptotic properties.

OBJECTIVE

We aimed to investigate the possible protective effects of exogenous Apelin-13 administration on oxidative stress, inflammation, and apoptosis induced by the cytotoxic agent cyclophosphamide (CP) in the lungs.

METHODS

Twenty-four male Wistar albino rats were divided into four groups: Control (saline), CP (200 mg/kg), Apelin-13 (10 μg/kg/day), and CP+Apelin-13. CP was administered as a single dose on the fifth day, and apelin-13 was administered intraperitoneally for five days. Total oxidant status (TOS), total antioxidant status (TAS), and lipid peroxidation were determined with spectrophotometry, TNFα and IL1β were determined with ELISA, APJ, Sirt1, NF-κB, and p53 mRNA expressions were determined with qRT-PCR, cytochrome (Cyt) C and caspase-3 protein expressions were studied with western blotting in lung tissues. The oxidative stress index (OSI) was also calculated. Furthermore, serum surfactant protein-D (SP-D) and Krebs von den Lungen-6 (KL-6) levels were measured with ELISA.

RESULTS

Compared to the control group, TOS, OSI, lipid peroxidation, TNFα, IL1β, cyt C, caspase-3, APJ, NF-κB, and p53 were higher, and Sirt1 was lower in the lung tissue of rats in the CP group. Serum KL-6 and SP-D levels were higher in the CP group. Co-administration of CP with Apelin-13 completely reversed the changes induced by CP administration.

CONCLUSION

Exogenous Apelin-13 treatment protected lung tissue against injury by inhibiting cyclophosphamide-induced oxidative stress, inflammation, and apoptosis. This protective effect of apelin-13 was accompanied by upregulation of the Sirt1 and downregulation of NF-κB/p53 in the lungs.